Adrenal Support by Bluebonnet Targeted Choice

POSSIBLY EFFECTIVE

• Anxiety. Small clinical studies suggest that oral ashwagandha might reduce anxiety. Details: One small clinical study in postal workers reporting moderate or severe anxiety shows that taking ashwagandha root (Swiss Herbals) 300 mg twice daily for 12 weeks, in combination with standard psychotherapy interventions, including dietary counseling, deep breathing exercise instruction, and a multivitamin, reduces anxiety scores when compared with standard psychotherapy interventions and placebo (19271). Additionally, two small clinical studies in adults with mild to moderate anxiety, depression, or stress show that taking a specific ashwagandha root extract standardized to contain 2.5% withanolides (Shagandha, Sabinsa Corp.) 500 mg with piperine 5 mg daily for 60-90 days reduces anxiety symptoms and perceived stress and improves sleep and quality of life when compared with placebo (113608,113609). However, another clinical study in young adults shows that taking a specific ashwagandha root and leaf extract (NooGandha, Specnova LLC) 225 mg or 400 mg daily for 30 days does not improve anxiety, stress, and depression scores when compared with placebo (107370).
• Generalized anxiety disorder (GAD). Oral ashwagandha may modestly improve symptoms of anxiety in patients with GAD. Details: Clinical practice guidelines from the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) provisionally recommend ashwagandha root extract at doses of 300-600 mg, standardized to 5% withanolides, daily as monotherapy or adjunctive therapy in patients with GAD. This recommendation is based on a review of three preliminary clinical trials with consistent results (110318). Two of these studies are described below. A small clinical trial in patients with GAD who are taking selective serotonin reuptake inhibitors (SSRIs) shows that taking ashwagandha 1 gram daily for 6 weeks reduces symptoms of anxiety by 48%, compared with a 27% reduction in patients taking placebo. Furthermore, by the end of treatment, 72% of patients taking ashwagandha were determined to have mild symptoms of GAD, compared with only 32% of those taking placebo (102687). Another preliminary clinical trial in patients aged 16 years and older with GAD shows that taking ashwagandha root powder granules 4 grams three times daily for 60 days moderately improves anxious mood in 58% of patients, compared with no moderate improvement in the placebo group. Mild improvement occurred in 82% of patients in the placebo group and 40% of patients in the ashwagandha group (90654).
• Insomnia. Oral ashwagandha may modestly improve sleep in patients with insomnia or non-restorative sleep. Details: A small meta-analysis in patients with insomnia and healthy patients shows that taking a specific ashwagandha root extract (KSM-66, Ixoreal Biomed) 250-600 mg daily or a specific root and leaf extract (Shoden, Arjuna Natural) 120 mg daily for 6-12 weeks modestly improves overall sleep, as well as sleep quality, sleep latency, total sleep time, wake time after sleep onset, and sleep efficiency, when compared with placebo. Effects were more pronounced in those with insomnia, with doses of at least 600 mg daily, and with treatment durations of at least 8 weeks (106784). These findings may be limited by heterogeneity of the included studies. In patients with non-restorative sleep, clinical research shows that taking a specific ashwagandha extract (Shoden, Arjuna Natural Private Ltd) 125 mg daily for 6 weeks increases sleep quality by 72%, compared with an improvement of 29% in patients taking placebo. Small to moderate improvements also occurred in total sleep time, sleep latency, and number of times awake (103476).
• Stress. Oral ashwagandha seems to help reduce stress and may also reduce stress-related weight gain. Details: A meta-analysis of seven small clinical studies in healthy adults, patients with chronic stress, or patients with psychiatric conditions shows that taking ashwagandha 240-1000 mg daily for 8-12 weeks improves stress when compared with placebo (109587). Clinical studies, some of which are included in the meta-analysis mentioned above, evaluating adults with chronic stress show that taking specific ashwagandha root extracts 240 mg daily (Shoden, Arjuna Natural Ltd.), 300 mg twice daily (KSM-66, Ixoreal Biomed), or 500 mg daily (Shagandha, Sabinsa Corp.) with piperine 5 mg for 60 days, or a specific slow-release capsule containing ashwagandha root extract (Prolanza) 300 mg daily for 90 days reduces perceived stress and cortisol levels when compared with baseline and placebo (90652,95617,101816,102682,107371,113608). Additionally, a small clinical study in adults with stress and a related comorbidity, such as anxiety or depression, shows that taking ashwagandha root and leaf extract (Sensoril, Kerry Group) 125-500 mg orally daily for 8 weeks improves stress scores in a dose-dependent manner when compared with placebo (114112). In contrast, a moderate-sized study in adults with overweight or mild obesity with moderate-to-high levels of stress and fatigue shows that taking ashwagandha root extract (Witholytin, Verdure Sciences Inc) 200 mg twice daily for 12 weeks reduces stress when compared to baseline, but not when compared with placebo (113611).In healthy college students, clinical research also shows that taking ashwagandha root extract 350 mg twice daily for 30 days improves qualitative perceptions of stress management, but not stress scores, when compared with placebo (109589,109590). Other clinical research shows that taking ashwagandha root extract 500 mg twice daily may prevent stress-related weight gain when compared with placebo (95617).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Aging. A small clinical study suggests that oral ashwagandha may modestly improve well-being, sleep, and alertness in elderly patients. Details: A small clinical trial in individuals aged 65-80 years shows that taking ashwagandha root extract (KSM-66, Ixoreal Biomed) 600 mg daily for 12 weeks improves overall well-being, sleep quality, and mental alertness by small to moderate amounts when compared with placebo (102684).
• Androgenic alopecia. It is unclear if topical ashwagandha is beneficial for androgenic alopecia. Details: A small clinical study in adults with mild to moderate hair loss, including androgenic alopecia, shows that applying ashwagandha root extract serum (KSM-66, Ixoreal Biomed) 1-2 drops to the scalp daily for 75 days reduces hair shedding and increases hair density, growth, and thickness when compared with placebo (113613).
• Antipsychotic-induced metabolic side effects. It is unclear if ashwagandha is beneficial for attenuating the metabolic side effects of antipsychotic agents. Details: One preliminary clinical trial shows that taking a specific ashwagandha extract (Cap Strelaxin, M/s Pharmanza Herbal Pvt. Ltd.) 400 mg three times daily for one month reduces serum triglycerides by 12% and fasting blood glucose by 15% when compared with baseline levels. Patients were taking atypical antipsychotics and had modestly elevated triglycerides and fasting blood glucose levels at baseline (90649). The validity of these findings is limited by the lack of a comparator group.
• Asthma. Although there has been interest in using oral ashwagandha for asthma, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Athletic performance. It is unclear if ashwagandha is beneficial for improving athletic performance. Details: A meta-analysis of four small clinical trials shows that taking ashwagandha increases aerobic capacity in athletes and non-athletes based on the measurement of maximum oxygen consumption. Effective doses ranged from 500-1000 mg daily for up to 12 weeks (102683). Another meta-analysis shows that taking ashwagandha in doses of 120-1250 mg daily, as a single dose or divided twice daily, for up to 6 months seems to improve muscle strength, speed, time to exhaustion, recovery time, and cardiorespiratory fitness in athletes and non-athletes (105824). However, the validity of this analysis is reduced by the lack of a control group, the varied training levels of the subjects, and the wide range of outcomes assessed. More research is needed to determine whether taking ashwagandha can improve athletic performance.
• Attention deficit-hyperactivity disorder (ADHD). Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In a preliminary clinical trial, children with ADHD were given a combination herbal extract formula (Nurture & Clarity), containing ashwagandha, white peony root, gotu kola, blue-green algae, bacopa, and sage, 3 mL three times daily for 4 months. Measures of attention, cognition, and impulse control improved significantly in children receiving ashwagandha when compared with placebo (19272). The dose of ashwagandha in the combination product was not reported, and the effect of ashwagandha alone in ADHD is unclear.
• Back pain. Although there has been interest in using oral or topical ashwagandha for back pain, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Bipolar disorder. It is unclear if oral ashwagandha is beneficial for improving cognitive function in adults with bipolar disorder. Details: Clinical research shows that taking ashwagandha extract (Sensoril, Natreon, Inc.) 250 mg daily for 1 week and then 250 mg twice daily for 7 weeks, improves some, but not all, measures of cognition by a small-to-moderate amount when compared with placebo (90653).
• Bronchitis. Although there has been interest in using oral ashwagandha for bronchitis, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Cerebellar ataxia. It is unclear if oral ashwagandha is beneficial for improving balance in patients with cerebellar ataxia. Details: A small, open-label study evaluating ashwagandha 500 mg three times daily in combination with Ayurvedic therapy for one month showed improvement in balance indices in subjects with cerebellar ataxia when compared with baseline (19273). The validity of this finding is limited by the lack of a comparator group. Additionally, it is unclear if this effect is due to ashwagandha, other ingredients, or the combination.
• Chemotherapy-related fatigue. Evidence is limited to one small clinical study in patients with breast cancer. Details: In preliminary clinical research in patients with breast cancer, taking ashwagandha powdered root extract 2 grams (Himalaya Drug Co) three times daily through six cycles of chemotherapy decreases chemotherapy-related fatigue when compared with no treatment. Fatigue scores were 16% to 52% higher in the control group when compared to the ashwagandha group (90651).
• Chronic obstructive pulmonary disease (COPD). It is unclear if oral ashwagandha is beneficial in patients with COPD. Details: A small clinical study in patients with stable COPD shows that taking ashwagandha root extract 250 mg twice daily for 12 weeks, along with conventional therapy, improves measures of lung function and exercise tolerance, but not quality of life, when compared with conventional therapy alone (109588).
• Cognitive function. Although there has been interest in using oral ashwagandha for cognitive function, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Constipation. Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in adults with constipation shows that taking a combination product containing ashwagandha root and ambrette fruit extracts 300 mg or 500 mg daily for 14 days improves bowel movement frequency and abdominal, rectal, and stool symptoms when compared with placebo (112114). Additionally, a moderate-sized clinical study in adults with functional constipation shows that using the same combination of ashwagandha and ambrette 300 mg or 500 mg daily for 60 days moderately improves constipation symptom scores and bowel movement scores when compared with placebo (114115). It is unclear if these effects are due to ashwagandha, ambrette, or the combination.
• Coronavirus disease 2019 (COVID-19). Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults hospitalized with COVID-19 shows that taking a specific combination product, (Artovid-20, Bioved Pharmaceuticals) containing ashwagandha, ginger, turmeric, and Boswellia, 1,776 mg orally twice daily for 14 days shortens the duration of symptoms by 0.9 days when compared with placebo. Taking the combination product also modestly reduced the severity ratings of some symptoms, such as sore throat and cough, however, these improvements are unlikely to be clinically relevant (109899). Another small clinical study in adults with mild to moderate COVID-19 shows that taking ashwagandha 500 mg and ginger 1000 mg twice daily for 15 days reduces time to recovery by around 6 days and increases the rate of clinical cure 14-fold and 2.6-fold at days 5 and 7, respectively, when compared with a control. However, taking this combination does not appear to improve the proportion of patients with a negative COVID-19 test, viral clearance, serum antibodies, chest findings, or disease progression when compared with control (112094). The validity of these findings is limited by a lack of blinding, and the study may have been inadequately powered to detect a difference between groups. Other clinical research in adults hospitalized with mild to moderate COVID-19 shows that taking a specific combination product (Coroprotect) containing ashwagandha, pomegranate, turmeric, bacopa, licorice, and other ingredients, twice daily for 10 days improved cough, breathlessness, and fatigue symptoms when compared with placebo (114114). It is unclear if any effects are due to ashwagandha, other ingredients, or the combination.
• Depression. It is unclear if oral ashwagandha is beneficial for depression. Details: A small clinical study in adults with mild to moderate depression, anxiety, or stress shows that taking a specific ashwagandha root extract standardized to contain 2.5% withanolides (Shagandha, Sabinsa) 500 mg with piperine 5 mg daily for 90 days reduces the severity of depressive symptoms, improves sleep and quality of life, and increases serum serotonin levels when compared with placebo (113609).
• Diabetes. It is unclear if oral ashwagandha is beneficial for type 2 diabetes. Details: In patients with type 2 diabetes, preliminary clinical research shows that ashwagandha 3 grams daily for 30 days decreases blood glucose to a degree similar to oral hypoglycemic drugs (19274). However, this study did not compare ashwagandha directly to a group taking oral hypoglycemic drugs.
• Fatigue. It is unclear if oral ashwagandha is beneficial for fatigue. Details: A moderate-sized clinical study in adults with overweight or obesity and moderate-to-high levels of fatigue and stress shows that taking ashwagandha root extract (Witholytin, Verdure Sciences Inc.) 200 mg twice daily for 12 weeks reduces self-reported fatigue when compared with placebo (113611).
• Fibromyalgia. Although there has been interest in using oral ashwagandha for fibromyalgia, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Hiccups. Although there has been interest in using oral ashwagandha for hiccups, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Hypercholesterolemia. It is unclear if ashwagandha is beneficial for hypercholesterolemia. Details: A very small clinical study in subjects with hypercholesterolemia shows that ashwagandha 3 grams daily for 30 days decreases serum cholesterol, triglyceride, low-density lipoprotein (LDL) cholesterol, and very low-density lipoprotein (VLDL) cholesterol levels when compared with baseline (19274). The validity of these findings is limited by the lack of a comparator group.
• Hypothyroidism. It is unclear if ashwagandha is beneficial for hypothyroidism. Details: Preliminary clinical research in adults with subclinical hypothyroidism shows that taking a specific ashwagandha root extract (KSM-66, Ixoreal Biomed) 300 mg twice daily for 8 weeks increases triiodothyronine (T3) and thyroxine (T4) levels by 42% and 20%, respectively, and reduces serum TSH levels by 17% from baseline. These changes are significant when compared with placebo (97292). However, the effects of ashwagandha on thyroid hormone levels in patients with overt hypothyroidism, or in patients taking prescription thyroid hormones, is unknown.
• Infertility. Although there has been interest in using oral ashwagandha for infertility in females, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Male infertility. It is unclear if oral ashwagandha is beneficial for male infertility. Details: Preliminary clinical research in males with infertility shows that taking ashwagandha root powder for approximately 3 months modestly improves hormone levels, as well as sperm count and motility, when compared with baseline (19275,90650). The validity of these findings is limited by the lack of a comparator group. One study used a specific ashwagandha root extract (KSM-66 Ashwagandha, Ixoreal Biomed) 225 mg three times daily; another study provided doses of 5 grams daily (19275,90650).
• Menopausal symptoms. Oral ashwagandha may be beneficial for menopausal symptoms. Details: A small clinical study in healthy adults in perimenopause shows that taking a specific ashwagandha root extract (KSM-66, Ixoreal Biomed) 300 mg twice daily for 8 weeks improves menopausal symptom severity by 24%, compared with 11% in those receiving placebo. Quality of life and hot flashes also were improved in those taking ashwagandha (106785).
• Obsessive-compulsive disorder (OCD). It is unclear if ashwagandha is beneficial for OCD. Details: Preliminary clinical research shows that taking ashwagandha root extract 120 mg after meals for 6 weeks, in conjunction with prescribed selective-serotonin reuptake inhibitors (SSRIs), might reduce OCD symptom severity when compared with prescribed SSRIs alone. The dose was initiated at 30 mg daily and increased by 30 mg every 4 days. Although OCD scores were significantly reduced when compared with placebo, it should be noted that scores were already significantly lower in the placebo group at baseline (95618).
• Osteoarthritis. Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In patients with osteoarthritis, taking a specific combination supplement, containing ashwagandha 450 mg, Ayurvedic zinc complex 50 mg, guggul 100 mg, and turmeric 50 mg (Articulin-F) two capsules three times daily for 3 months reduces symptoms of pain and swelling when compared with placebo. However, there were no radiological improvements (19276). It is unclear if this effect is due to ashwagandha, other ingredients, or the combination.
• Parkinson disease. Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In patients with Parkinson disease, a small clinical study shows that taking a product containing ashwagandha 14.5 grams, cowhage 4.5 grams, Hyoscyamus reticulantus 0.75 grams, and Sida cordifolia 14.5 grams in lukewarm milk twice daily for 56 days improves symptoms like tremor, stiffness, and cramps when compared with baseline. The therapy followed 28 days of cleansing or eliminative therapy using Ayurvedic remedies (6899). The validity of these findings is limited by the lack of a comparator group. Also, it is unclear if these effects are due to ashwagandha, other ingredients, or the combination. Cowhage contains levodopa, which may contribute to any benefit seen with this combination product.
• Psychological well-being. It is unclear if oral ashwagandha is beneficial for improving psychological well-being in college students. Details: A small clinical study in healthy college students shows that taking ashwagandha root extract 350 mg twice daily for 30 days improves perceptions of well-being, including improvements in energy, mental clarity, food cravings, and sleep quality, when compared with placebo. Qualitative analysis also suggests these students had improvements in stress management, but stress scores were not reduced when compared with placebo (109589,109590).
• Rheumatoid arthritis (RA). It is unclear if ashwagandha is beneficial for improving symptoms of RA. Details: Preliminary clinical research shows that taking ashwagandha powder 5 grams twice daily for 3 weeks, followed by 4 weeks of sidh makardhwaj (a mixture of gold, mercury, and sulfur) 100 mg with honey daily, modestly improves symptoms in about 50% of males and 60% of females with RA when compared with baseline (95620). The lack of a control group limits the validity of this finding. Additionally, the effect of ashwagandha powder alone is unclear.
• Sexual dysfunction. Small clinical studies suggest that oral ashwagandha root extract may help improve sexual arousal and sexual desire in some females and males with sexual dysfunction. Details: Two, small clinical studies in adult females with sexual dysfunction show that taking ashwagandha root extract (KSM-66, Ixoreal Biomed) 300 mg twice daily with food for 8 weeks in conjunction with or without counseling increases the number of successful sexual encounters and improves orgasms, satisfaction, lubrication, and arousal when compared with placebo or counseling alone (95619,110492). Also, a small clinical study in adult males with low sexual desire shows that taking the same ashwagandha root extract 300 mg twice daily after meals for 8 weeks improves subjective sexual functioning scores, including measures of sexual arousal, sexual desire, sexual behavior, and orgasm, when compared with placebo (109586).
• Smoking cessation. Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in adults with a history of smoking 5 or more cigarettes daily for at least 3 years shows that taking a specific combination product containing ashwagandha 100 mg, Indian gooseberry, tribulus, bacopa, Albizia lebbeck, licorice, clove, ginger, cowhage, holy basil, and turmeric (Smotect, Smotect India) daily for 3 months reduces the number of cigarettes smoked daily and levels of alveolar carbon monoxide and carboxyhemoglobin but does not improve lung capacity when compared with placebo (112115). It is unclear if these effects are due to ashwagandha, other ingredients, or the combination.
• Tuberculosis. Although there has been interest in using oral ashwagandha for tuberculosis, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Vitiligo. Although there has been interest in using oral ashwagandha for vitiligo, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Wrinkled skin. It is unclear if topical ashwagandha is beneficial in individuals with wrinkled skin. Details: A small clinical study in healthy adults with photoaged skin shows that applying ashwagandha root extract 8% lotion daily for 60 days improves physician-rated scores for skin wrinkles, hydration, brightness, tone, and pigmentation and improves other measures of skin elasticity and hydration when compared with placebo. However, changes in melanin content did not differ between treatment groups (111538).
• Wound healing. Although there has been interest in using topical ashwagandha for healing of skin ulcers and skin sores, there is insufficient reliable information about the clinical effects of ashwagandha for this condition. More evidence is needed to rate ashwagandha for these uses.

(Read more about ASHWAGANDHA)

POSSIBLY INEFFECTIVE

• Athletic performance. Taking cordyceps orally does not seem to improve athletic performance in adults. Details: One small clinical study in endurance-trained cyclists shows that taking a specific mycelial fermentation product of cordyceps (CordyMax Cs-4) 3.15 grams daily for 5 weeks does not improve endurance time trials or aerobic capacity when compared with placebo (12095). Another small study in healthy elderly adults shows that taking the same cordyceps preparation (CordyMax Cs-4) 3 grams daily for 12 weeks does not improve exercise performance when compared with placebo (46120). Research also shows that taking combination products containing cordyceps and other ingredients does not improve athletic performance when compared with control. These products have combined cordyceps (CordyMax Cs-4) 1000 mg with rhodiola 300 mg (46091) or cordyceps (CordyMax Cs-4) 2000 mg with roseroot 600 mg (Optygen, First Endurance) (15573); liquid and powdered cordyceps formulations with reishi mushroom, shiitake mushroom, bamboo, and honey (Fohow oral liquid and Fohow lingzhi capsules, FOHOW Technology Investment Group Co. Ltd.) (98686); and cordyceps (form unknown) 1.2 grams with a 930 mg mixture of extracts of ashwagandha root, green tea leaf, rhodiola root, and astragalus root (Shroom Tech Sport, Onnit Labs) (105079).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Arrhythmia. Although there is interest in using oral cordyceps for arrhythmia, there is insufficient reliable information about the clinical effects of cordyceps for this condition.
• Asthma. Oral cordyceps has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in children with asthma shows that a 619 mg capsule containing equal weights of the dried aqueous extracts of cordyceps, astragalus, skullcap, Radix stemonae, and Bulbus fritillariae daily for 6 months does not reduce the need for medication or improve symptoms when compared with placebo (32935).
• Autoimmune thyroiditis. Oral cordyceps has only been evaluated in combination with other treatmentss; its effect when used alone is unclear. Details: A meta-analysis of low-quality clinical studies in China in patients with Hashimoto's thyroiditis shows that taking cordyceps up to 9 grams daily for up to 28 weeks in addition to a low-iodine diet or levothyroxine decreases circulating thyroid antibody levels including thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) when compared with a low-iodine diet or levothyroxine treatment alone. In the subgroup of patients with hypothyroidism, taking cordyceps with levothyroxine increases free thyroxine (FT4) but does not affect free triiodothyronine (FT3) or thyroid-stimulating hormone (TSH) levels when compared with levothyroxine alone. (113622).
• Chronic kidney disease (CKD). Small clinical studies suggest that oral cordyceps may modestly improve biomarkers in some patients with CKD. Details: A meta-analysis of clinical research in patients in China with CKD shows that taking cordyceps 0.6-2 grams orally three times daily, along with standard treatment, seems to decrease serum creatinine levels by 0.6 mg/dL and increase creatinine clearance by 9.2 mL/min when compared with standard treatment alone (92829). Another meta-analysis of clinical studies in patients in China with diabetic kidney disease shows that taking cordyceps 0.5-2 grams orally three times daily along with angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB) decreases blood urea nitrogen by 2 mg/dL and decreases serum creatinine levels by 0.1 mg/dL when compared with ACEI/ARB treatment alone (92830). Most individual studies in these analyses used Bailing (Cs-C-Q80) or Jinshuibao (Cs-4), fermented cordyceps mycelial products (92829,92830). Both of these analyses are limited by the low methodological quality and short duration (usually 1-6 months) of most of the included studies.
• Chronic obstructive pulmonary disease (COPD). Preliminary clinical studies suggest that oral cordyceps may modestly improve symptoms of COPD. Details: A meta-analysis of preliminary clinical research in patients with moderate or severe COPD shows that taking cordyceps alone or as part of a formulation containing other products for up to 12 months improves lung function and reduces the incidence of an acute exacerbation by a small amount. Also, the distance walked in 6 minutes is increased by about 45 meters, which was considered clinically meaningful. Most individual studies in this analysis used Bailing (Cs-C-Q80) or Jinshuibao (Cs-4), fermented cordyceps mycelial products, in combination with conventional treatments with conventional treatments alone (109705). This analysis is limited by the low methodological quality of the included studies.
• Contrast induced nephropathy. Small clinical studies suggest that oral cordyceps may modestly reduce contrast induced nephropathy. Details: A preliminary clinical study in patients with diabetic nephropathy shows that taking a specific cordyceps mycelial product (Corbrin; CS-C-Q80) 2-3 grams orally three times daily for 3 days before and after angiography reduces the risk of contrast induced nephropathy by about 48% to 66% when compared to standard treatment (92827). However, other preliminary clinical research in patients with stable angina pectoris shows that taking the same cordyceps product 3 grams orally three times daily for 3 days before and after angioplasty does not decrease the prevalence of contrast induced nephropathy when compared to standard therapy (92826). Reasons for these discrepancies are not clear but may relate to the small size and heterogenous populations in these studies.
• Diabetic nephropathy. Early research suggests that oral cordyceps may modestly improve kidney function in patients with diabetic kidney disease. Details: A meta-analysis of low to moderate quality clinical research in patients with diabetic kidney disease shows that taking cordyceps as adjunctive therapy to angiotensin-converting enzyme inhibitors or angiotensin receptor blockers for 2-24 weeks modestly improves kidney function when compared to these medications alone. Kidney function was based on markers such as blood creatinine and urea nitrogen, as well as urinary albumin and total protein. There were also modest improvements in systolic and diastolic blood pressure, triglycerides, and low-density lipoprotein (LDL) cholesterol. There was no effect on glycemic indices. The effect of cordyceps on disease progression or cardiovascular events is unclear (111903).
• Cough. Although there is interest in using oral cordyceps for cough, there is insufficient reliable information about the clinical effects of cordyceps for this purpose.
• Fatigue. Although there is interest in using oral cordyceps for fatigue, there is insufficient reliable information about the clinical effects of cordyceps for this purpose.
• Hepatitis B. Although there is interest in using oral cordyceps for hepatitis B, there is insufficient reliable information about the clinical effects of cordyceps for this condition.
• Hypercholesterolemia. Although there is interest in using oral cordyceps for hypercholesterolemia, there is insufficient reliable information about the clinical effects of cordyceps for this condition.
• Kidney failure. Small clinical studies suggest that oral cordyceps may improve inflammatory markers in patients on hemodialysis. Details: A meta-analysis of small clinical trials in patients in China on hemodialysis suggests that adding cordyceps to standard treatment does not seem to improve serum creatinine levels but may improve certain markers of inflammation, such as C-reactive protein, when compared with placebo. Most individual studies in this analysis used Bailing (Cs-C-Q80) or Jinshuibao (Cs-4), fermented cordyceps mycelial products (105076).
• Kidney transplant. Small clinical studies suggest that oral cordyceps is no better than standard treatment in patients with kidney transplant. Details: A meta-analysis of 4 heterogeneous clinical trials evaluating patients in China immediately post-kidney transplant or patients with complications post-kidney transplant suggests that adding cordyceps to standard therapy with cyclosporine and steroids is no better than adding azathioprine 50-150 mg for improving overall survival or graft survival or reducing rejection risk. However, there was a non-significant trend to reduced risk of graft rejection in the cordyceps group (95905). A higher quality systematic review, which determined the available studies were too heterogeneous to pool together in a meta-analysis, suggests that adding cordyceps 3-6 grams to standard therapy daily is no better than azathioprine or cyclosporine for improving organ rejection, kidney function, or survival in patients after kidney transplant (92828). All individual studies in these analyses used Bailing (Cs-C-Q80) fermented cordyceps mycelial product (95905,92828).
• Sexual dysfunction. It is unclear if oral cordyceps is beneficial in patients with sexual dysfunction. Details: Preliminary clinical research shows that taking a specific mycelial fermentation product of cordyceps (CordyMax Cs-4) approximately 3 grams daily for 40 days can improve symptoms of hyposexuality in 66% of patients, compared with 32% of patients taking natural cordyceps and 24% of patients taking placebo (46145).
• Tinnitus. Although there is interest in using oral cordyceps for tinnitus, there is insufficient reliable information about the clinical effects of cordyceps for this condition. More evidence is needed to rate cordyceps for these uses.

(Read more about CORDYCEPS)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Aging. Although there has been interest in using oral holy basil for aging, there is insufficient reliable information about the clinical effects of holy basil for this purpose.
• Asthma. Although there has been interest in using oral holy basil for asthma, there is insufficient reliable information about the clinical effects of holy basil for this condition.
• Dental plaque. Small clinical studies suggest that topical use of holy basil mouthwash, gel, or toothpaste may modestly reduce the severity of dental plaque. Details: Small clinical studies in patients with mild to moderate dental plaque or gingivitis shows that using 10 mL of a mouthwash containing holy basil leaf extract 4% twice daily for 30 days reduces plaque severity by about 17% to 28% when compared with baseline (91570,103621). In one study, this effect was significant when compared with a placebo mouthwash and similar to a mouthwash containing chlorhexidine 0.12% (91570), whereas the other study did not conduct comparisons between study groups (103621). A small clinical study in patients with chronic gingivitis shows that applying holy basil extract 2% gel as a gingival massage twice daily for 30 days reduces plaque severity when compared with baseline (110030). The validity of this finding is limited by the lack of statistical comparison to the other study groups. Also, a small clinical trial in children 14-15 years of age shows that brushing with toothpaste containing holy basil leaf extract 4% twice daily for 3 weeks reduces plaque severity when compared with placebo, with similar improvements when compared with a fluorinated toothpaste (104183). Holy basil has also been evaluated in combination with other ingredients. A small study shows that rinsing with 10 mL of a solution containing tea tree oil, clove, and holy basil (0.2% to 0.3% of each), for 30 seconds twice daily for 21 days, reduces plaque formation by 64%. This reduction is similar to a 72% reduction seen in the active control group using a mouth rinse containing thymol, eucalyptol, menthol, and methyl salicylate (91446).
• Diabetes. Small clinical studies suggest that oral holy basil may modestly improve glycemic control in patients with diabetes. Details: One small clinical trial in adults with type 2 diabetes shows that taking holy basil dried leaf powder 2.5 grams daily for 4 weeks decreases fasting and postprandial blood glucose by 18%, compared with a 7% reduction in those taking placebo (12242). Another small clinical study in patients with type 2 diabetes shows that taking holy basil 250 mg twice daily in combination with glyburide 5 mg daily for 3 months reduces fasting blood glucose by 16%, postprandial blood glucose by 13%, and glycated hemoglobin (HbA1c) levels by 18% when compared with glyburide alone (91571).
• Dyspepsia. Although there has been interest in using oral holy basil for dyspepsia, there is insufficient reliable information about the clinical effects of holy basil for this purpose.
• Generalized anxiety disorder (GAD). It is unclear if oral holy basil is beneficial in patients with GAD. Details: One small, uncontrolled clinical study in patients with GAD shows that taking holy basil leaf extract 500 mg twice daily following meals for 60 days reduces anxiety and associated symptoms of stress and depression when compared to baseline (19575). The validity of these findings is limited by a lack of control group.
• Gingivitis. Small clinical studies suggest that topical use of holy basil mouthwash or toothpaste may modestly improve gingivitis. Details: Small clinical studies in patients with mild to moderate dental plaque or gingivitis shows that using 10 mL of a mouthwash containing holy basil leaf extract 4% twice daily for 30 days reduces gingivitis by about 23% to 40% when compared with baseline (91570,103621). In one study, these effects were significant when compared with placebo mouthwash and similar to those of a mouthwash containing chlorhexidine 0.12% (91570), whereas the other study did not conduct statistical comparisons between study groups (103621). A small clinical trial in children 14-15 years of age shows that brushing with toothpaste containing holy basil leaf extract 4% twice daily for 3 weeks reduces the severity of gingivitis when compared with placebo, with similar improvements when compared with a fluorinated toothpaste (104183). However, a small clinical study in patients with chronic gingivitis shows that applying holy basil leaf extract 2% gel as a gingival massage twice daily for 30 days does not reduce gingivitis severity when compared with baseline (110030). Holy basil has also been evaluated in combination with other ingredients. A small clinical study shows that rinsing with 10 mL of a solution containing tea tree oil, clove, and holy basil (0.2% to 0.3% of each), for 30 seconds twice daily for 21 days, reduces gum inflammation by 76%. This reduction is similar to a 70% reduction seen in the active control group using a mouth rinse containing thymol, eucalyptol, menthol, and methyl salicylate (91446).
• Headache. Although there has been interest in using oral holy basil for headache, there is insufficient reliable information about the clinical effects of holy basil for this purpose.
• Hepatitis. Although there has been interest in using oral holy basil for hepatitis, there is insufficient reliable information about the clinical effects of holy basil for this condition.
• Hypercholesterolemia. Although there has been interest in using oral holy basil for hypercholesterolemia, there is insufficient reliable information about the clinical effects of holy basil for this purpose.
• Hypertension. Although there has been interest in using oral holy basil for hypertension, there is insufficient reliable information about the clinical effects of holy basil for this purpose.
• Insect repellent. Although there has been interest in using topical holy basil as an insect repellent, there is insufficient reliable information about the clinical effects of holy basil for this purpose.
• Insomnia. It is unclear if oral holy basil is beneficial for sleep problems. Details: A moderate-sized clinical study in adults with stress and sleep problems (i.e., unrefreshing sleep or difficulty falling or staying asleep) shows that taking holy basil 125 mg twice daily for 8 weeks does not improve patient-reported or wearable tracker scores related to sleep when compared with placebo (112416). However, the interpretation of these results is limited by self-reported outcomes and use of a non-validated measurement tool for sleep (i.e., Fitbit device).
• Obesity. It is unclear if oral holy basil is beneficial in overweight or obese patients. Details: One small clinical study in individuals with overweight or obesity shows that taking holy basil extract 250 mg twice daily for 8 weeks slightly reduces body weight and improves levels of triglycerides or low-density lipoprotein (LDL) cholesterol and certain glycemic indices when compared to baseline, but not when compared with no treatment. Holy basil extract also did not improve liver enzymes when compared to baseline or with no treatment (96944).
• Oral submucous fibrosis. It is unclear if topical holy basil paste is beneficial for oral submucous fibrosis. Details: A moderate-sized clinical study in adults with oral submucous fibrosis conducted in India shows that applying a paste containing holy basil extract 250 mg intraorally twice daily for 1 month modestly improves mouth opening scores and patient-reported burning sensation at the 3 month follow up when compared to baseline (112424). However, the validity of these findings is limited by poor methodology and lack of a comparator group.
• Respiratory tract infections. Although there has been interest in using oral holy basil for respiratory tract infections, including bronchitis, common cold, influenza, and tuberculosis, there is insufficient reliable information about the clinical effects of holy basil for these conditions.
• Stress. It is unclear if oral holy basil is beneficial in patients with stress. Details: One small clinical trial in patients experiencing various symptoms of stress shows that taking a specific holy basil extract (OciBest, Natural Remedies Pvt. Ltd.) 400 mg in the morning and 800 mg at night for 6 weeks decreases self-reported symptoms of stress, including forgetfulness, sexual problems and sleep problems of recent origin, and frequency of exhaustion, when compared with placebo (18107). A moderate-sized clinical study in adults with stress and sleep problems shows that taking holy basil 125 mg twice daily for 8 weeks modestly improves stress scores but does not improve individual symptoms related to stress including anxiety, mood disturbance, physical function, depression, fatigue, or sleep disturbance when compared with placebo (112416). However, the interpretation of these findings is limited by self-reported outcome measures and unclear clinical significance.
• Tinea corporis. Although there has been interest in using topical holy basil for tinea corporis, there is insufficient reliable information about the clinical effects of holy basil for this purpose. More evidence is needed to rate holy basil for these uses.

(Read more about HOLY BASIL)

EFFECTIVE

• Pantothenic acid deficiency. Taking pantothenic acid 5-10 mg daily is effective for treating and preventing pantothenic acid deficiency (15).

POSSIBLY INEFFECTIVE

• Radiation dermatitis. Topical dexpanthenol does not seem to be beneficial for preventing or treating radiation dermatitis. Details: Applying dexpanthenol, an analog of pantothenic acid, twice daily to areas of irradiated skin does not seem to reduce erythema, desquamation, itching, or pain following radiation treatment (7192). Also, applying dexpanthenol 0.5% cream (Bepanthen, Hoffmann LaRoche ) daily during radiation therapy and for 2 weeks after completing radiation therapy is less effective than methylprednisolone aceponate 0.1% cream (Advantan) at reducing radiation-induced skin irritation (67779).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acne. Oral or topical pantothenic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In adults with mild to moderate acne, clinical research shows that taking a specific supplement (Pantothen, Avilan Marketing LLC) providing pantothenic acid 1.1 grams twice daily in addition to other B vitamins for 12 weeks modestly reduces total and non-inflammatory lesion counts when compared with placebo (105188). Also, in adolescents or young adults with mild to moderate acne, preliminary clinical research shows that topical application with a gel containing D-panthenol 4%, hydrogen peroxide 4%, and salicylic acid 0.5% once daily for 60 days modestly reduces acne lesions when compared with baseline (105189). The validity of this finding is limited by the lack of a comparator group.
• Alcoholism. Although there is interest in using oral pantothenic acid for improving recovery from alcoholism, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Allergic rhinitis (hay fever). Although there is interest in using oral pantothenic acid for allergic rhinitis, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Alopecia areata. Pantothenic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy adults with diffuse hair loss shows that intramuscular administration of dexpanthenol 250 mg and biotin 5 mg once weekly for 6 weeks reduces hair fall count at weeks 1 and 8, but only increases hair density at week 1, when compared to baseline (111366). The validity of these findings is limited by the study's small size, short duration, and lack of comparator group.
• Anxiety. Although there is interest in using oral pantothenic acid for anxiety, there is insufficient reliable information about the clinical effects of pantothenic acid for this purpose.
• Asthma. Although there is interest in using oral pantothenic acid for asthma, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Athletic performance. Although there is interest in using oral pantothenic acid to improve athletic performance, there is insufficient reliable information about the clinical effects of pantothenic acid for this purpose.
• Attention deficit-hyperactivity disorder (ADHD). Oral pantothenic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some small outdated clinical studies in children diagnosed with hyperkinesis suggest that taking calcium pantothenate 1.2 grams, alone or in combination with niacinamide, ascorbic acid, and pyridoxine, does not improve symptoms of hyperactivity when compared with placebo (3351,9957). It is unclear what effects pantothenic may have, if any, in children with a modern diagnosis of ADHD.
• Atopic dermatitis (eczema). It is unclear if topical pantothenic acid is beneficial in infants or children with atopic dermatitis. Details: One preliminary clinical trial in infants and children with stable mild atopic dermatitis shows that topical application of an emollient containing panthenol (Bepanthen, SensiDaily, Bayer Consumer Care AG) for 3 months is as effective as a reference emollient for reducing symptoms and preventing a flare. However, the efficacy of the reference emollient (Stelatopia Emollient Cream, Mustela; Laboratoires Expanscience) is unclear based on available preliminary clinical research (105190).
• Autism spectrum disorder. Although there is interest in using oral pantothenic acid for autism spectrum disorder, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Carpal tunnel syndrome. Although there is interest in using oral pantothenic acid for carpal tunnel syndrome, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Cheilitis. Topical pantothenic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small, open-label study in adults with mild-to-moderate cheilitis shows that applying a specific lip care product containing pantothenic acid and bisabolol (Eucerin Aquaphor SOS lip care) at least twice daily for 8 weeks reduces cheilitis severity scores by 5 points on a 12 point scale assessing erythema, scale, fissure, and inflammation when compared to baseline (114549). The validity of this finding is limited by the small study size and lack of a comparator group. Additionally, it is unclear if this effect is due to pantothenic acid, bisabolol, or the combination.
• Chronic fatigue syndrome (CFS). Although there is interest in using oral pantothenic acid for CFS, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Conjunctivitis. Although there is interest in using oral or ocular pantothenic acid for conjunctivitis, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Constipation. It is unclear if oral or intramuscular dexpanthenol is beneficial for constipation. Details: Preliminary clinical research shows that administering dexpanthenol (Bepanthene), an analog of pantothenic acid, 400 mg orally or 500 mg intramuscularly daily for 5 days decreases the time to a bowel movement in patients with chronic or occasional constipation when compared with an oral placebo (67822).
• Dandruff. Although there is interest in using oral or topical pantothenic acid for dandruff, is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Depression. Although there is interest in using oral pantothenic acid for depression, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Diaper rash. Although there is interest in using topical pantothenic acid for diaper rash, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Dry eye. Although there is interest in using ocular pantothenic acid for dry eye, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Dry skin. It is unclear if topical dexpanthenol is beneficial for patients with dry skin. Details: A small, open-label study in healthy adults with dry skin shows that cleansing the skin with a dexpanthenol-containing liquid cleanser (DCLC, Bepanthen SensiControl Daily Gentle Body Wash) daily for 4 weeks increases stratum corneum hydration by 17% without affecting skin barrier function, pH, or microbiome when compared to baseline (111262). The validity of these findings is limited by the lack of blinding and a comparator group.
• Epilepsy. Although there is interest in using oral pantothenic acid for epilepsy, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Eye trauma. It is unclear if ocular dexpanthenol is beneficial for eye trauma. Details: Some preliminary clinical research shows that using eyedrops containing dexpanthenol 5%, a derivative of pantothenic acid, two drops four times daily for 28 days following surgery for retinal detachment reduces eye pain and discomfort when compared with placebo drops (67783). However, using a specific dexpanthenol 5% ointment (Bepanthen) does not seem to improve corneal epithelial wound healing following phototherapeutic keratectomy when compared with placebo (67801).
• Heart failure. Although there is interest in using oral pantothenic acid for heart failure, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Herpes zoster (shingles). Although there is interest in using oral or topical pantothenic acid for shingles, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Insomnia. Although there is interest in using oral pantothenic acid for insomnia, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Laser skin resurfacing. It is unclear if topical dexpanthenol or pantothenic acid can reduce adverse effects after laser skin resurfacing procedures. Details: A preliminary clinical study shows that use of a dexpanthenol-containing ointment (Bepanthen Wound Healing Ointment, Bayer) once daily modestly reduces the diameter of lesions up to 3 days after fractional carbon dioxide laser resurfacing when compared with petroleum jelly (105743). Also, applying a specific cream (Cicaplast Baume B5 cream, L'Oreal) containing panthenol 5%, madecassoside, copper, zinc, and manganese to one side of the face for 28 days reduces decrustation time by approximately one day when compared with a control emollient. Redness and swelling were lower at 3 days, but there was no difference in pain and burning (105742). It is unclear if these effects are due to pantothenic acid, other ingredients, or the combination.
• Multiple sclerosis (MS). Although there is interest in using oral pantothenic acid for MS, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Muscular dystrophy. Although there is interest in using oral pantothenic acid for muscular dystrophy, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Nipple fissures. Although there is interest in using topical pantothenic acid for nipple fissures, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Obesity. Although there is interest in using oral pantothenic acid for obesity, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Pain (chronic). It is unclear if oral or topical pantothenic acid is beneficial for the management of various forms of chronic pain. Details: Although there is interest in using oral or topical pantothenic acid for various forms of chronic pain, including neuropathy and arthritis, there is limited information available about the clinical effects of pantothenic acid for this purpose. One review of preliminary clinical research found that calcium pantothenate does not reduce symptoms of arthritis in patients with rheumatoid arthritis or osteoarthritis (10433).
• Parkinson disease. Although there is interest in using oral pantothenic acid for Parkinson disease, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Poison oak and poison ivy dermatitis. Although there is interest in using topical pantothenic acid for poison ivy dermatitis, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Postoperative pain. It is unclear if oral pantothenic acid is beneficial for postoperative pain. Details: In post-tonsillectomy patients aged 5-12 years, preliminary clinical research shows that taking pastilles containing dexpanthenol (Bepanthene, Bayer) 100 mg three times daily reduces pain when compared with placebo. Postoperative pain was modestly reduced at 1, 3, 7, and 14 days after surgery (105191).
• Postoperative sore throat. It is unclear if pantothenic acid lozenges are beneficial for postoperative sore throat. Details: Preliminary clinical research shows that taking two lozenges containing dexpanthenol, an analog of pantothenic acid, 200 mg 30 minutes prior to general anesthesia reduces the incidence and severity of postoperative sore throat when compared with a benzydamine hydrochloride or placebo spray (67792).
• Pregnancy-related leg cramps. Although there is interest in using oral pantothenic acid for pregnancy-related leg cramps, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Premenstrual syndrome (PMS). Although there is interest in using oral pantothenic acid for PMS, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Respiratory tract infections. Although there is interest in using oral pantothenic acid for respiratory tract infections, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Rhinosinusitis. It is unclear if nasal dexpanthenol is beneficial for rhinosinusitis. Details: Preliminary clinical research shows that using a nasal spray (MarPlus) containing dexpanthenol, an analog of pantothenic acid, on the first, second, fourth, and sixth week after endoscopic sinus surgery reduces nasal discharge, but not other symptoms associated with chronic rhinosinusitis, when compared with saline nasal spray (67808).
• Skin irritation. It is unclear if topical dexpanthenol is beneficial for preventing or treating skin irritation due to sodium lauryl sulfate. Details: Preliminary clinical research shows that applying dexpanthenol (Bepanthol Handbalsam), an analog of pantothenic acid, twice daily for 26 days does not prevent sodium lauryl sulfate-induced skin irritation (67785). However, dexpanthenol may be effective for treating skin irritation caused by sodium lauryl sulfate. Use of an ointment containing dexpanthenol 1% to 5% twice daily for up to 30 days following skin exposure to sodium lauryl sulfate seems to reduce skin water loss, skin roughness, and skin inflammation when compared to control (67802,67806).
• Ulcerative colitis. Although there is interest in using oral or rectal pantothenic acid for ulcerative colitis, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Vertigo. Although there is interest in using oral pantothenic acid for vertigo, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
• Wound healing. Preliminary clinical research suggests that oral dexpanthenol might be beneficial for wound healing. Details: In post-tonsillectomy patients aged 5-12 years, preliminary clinical research shows that taking pastilles containing dexpanthenol (Bepanthene, Bayer) 100 mg three times daily improves wound healing when compared with placebo. Depending on the type of surgery, wound healing occurred in 2.3-2.9 times as many patients within 7 days of surgery, and in 13% to 35% more patients within 14 days, when compared with placebo (105191). More evidence is needed to rate pantothenic acid for these uses.

(Read more about PANTOTHENIC ACID)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Altitude sickness. It is unclear if oral rhodiola is beneficial for altitude sickness. Details: Preliminary clinical research shows that taking rhodiola 447 mg four times daily for 7 days does not improve blood oxygenation or markers of oxidative stress when compared with placebo in subjects exposed to simulated high-altitude conditions (25402).
• Anthracycline cardiotoxicity. It is unclear if oral rhodiola is beneficial for epirubicin-induced cardiotoxicity. Details: Preliminary clinical research in breast cancer patients shows that taking salidroside, a constituent of rhodiola, 600 mg daily, beginning one week prior to chemotherapy and continuing throughout chemotherapy administration, reduces epirubicin-induced early left ventricular regional systolic dysfunction when compared with placebo (90434).
• Anxiety. It is unclear if oral rhodiola is beneficial for anxiety. Details: Preliminary clinical research in college students with anxiety shows that taking a specific dried rhodiola extract (Vitango, Schwabe Pharma) 200 mg twice daily for 14 days modestly reduces reported levels of anxiety, anger, confusion, negative mood, and stress when compared with a control group. However, rhodiola extract does not seem to improve cognition (96462).
• Arrhythmia. Although there has been interest in using oral rhodiola for arrhythmia, there is insufficient reliable information about the clinical effects of rhodiola for this condition.
• Athletic performance. The evidence related to the use of rhodiola for athletic performance is mixed, although specific standardized extracts might be beneficial for certain performance endpoints. Details: The available evidence for rhodiola in athletic performance includes small clinical trials in recreationally active or trained athletes. Trials using rhodiola extracts standardized to 3% rosavins and 1% salidroside (eg. Finzelberg, GmbH) show that taking 3 mg/kg, 200 mg, or 500 mg prior to exercise testing, either as a single dose or with a 3-day lead-in dose, modestly improves performance endpoints on a cycle ergometer. Improved endpoints included time to exhaustion, peak oxygen use, time to completion, perceived exhaustion, anaerobic capacity, and power (13109,90432,100168). However, in trials in which rhodiola was not taken the morning of testing, or when performance endpoints included forearm endurance or marathon time and recovery, rhodiola 170 mg to 1500 mg daily did not affect perceived exertion, time to exhaustion, or peak oxygen use (15574,19284,90433). A small crossover trial shows that taking 500 mg of rhodiola extract, standardized to 3% rosavins and 1% salidroside, three times daily for 3 days followed by 500 mg 30-minutes before exercise testing increases bench press velocity but decreases bench press repetition volume when compared with placebo (110543). Furthermore, limited evidence suggests that rhodiola extract does not affect muscle strength, speed of limb movement, reaction times, or attention span (13109) but might reduce plasma creatine kinase levels (19284). Also, while some evidence suggests that rhodiola extract can reduce blood lactate levels (19284), other research shows that it increases blood lactate levels after resistance training to a greater degree than placebo (110543). In general, it appears that acute doses of rhodiola may improve specific physical performance parameters, but neither acute nor chronic doses appear to notably improve muscle function. Some research has also assessed rhodiola when used in combination with other ingredients. A small clinical study in trained male cyclists shows that taking a specific combination product (Optygen, First Endurance) containing rhodiola 600 mg (standardized to 3% rosavin and 2.5% salidroside) plus cordyceps 2000 mg (standardized to 7% cordycepic acid), daily for 6 days followed by a half-dose daily for 7 days does not improve time to exhaustion or muscle tissue oxygen saturation when compared with placebo (15573). Additionally, a small crossover study in healthy, recreationally active adult males shows that taking a 30:70 blend of rhodiola and maral root extracts at a dose of 350 mg or 175 mg, ninety minutes prior to isokinetic leg strength exercises, does not influence fatigability, performance variables, or affective responses when compared with placebo (105855).
• Bladder cancer. Although there has been interest in using oral rhodiola for bladder cancer, there is insufficient reliable information about the clinical effects of rhodiola for this condition.
• Chronic fatigue syndrome (CFS). Although there has been interest in using oral rhodiola for CFS, there is insufficient reliable information about the clinical effects of rhodiola for this condition.
• Coronavirus disease 2019 (COVID-19). Oral rhodiola extract has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults a with confirmed history of COVID-19 infection and at least 3 of 9 long COVID-19 symptoms for at least 30 days, but no longer than 3 months, after discharge shows that taking a specific combination product (ADAPT-232/Chisan, Swedish Herbal Institute), containing rhodiola extract 90 mg, schisandra extract 300 mg, and eleuthero extract 78 mg, twice daily for 14 days increases walking duration by around 13 minutes but does not reduce the duration of cough, fatigue, headache, pain, or other respiratory problems when compared with placebo (109635). It is unclear if these findings are due to rhodiola, other ingredients, or the combination.
• Depression. It is unclear if oral rhodiola is beneficial for depression. Details: Clinical practice guidelines from the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) state that rhodiola is not currently recommended for monotherapy or adjunctive use in major depressive disorder based on mixed evidence (110318). Clinical research shows that taking a specific rhodiola extract (SHR-5, Swedish Herbal Institute) 340 mg once or twice daily reduces symptoms of mild-to-moderate depression after 6 weeks of treatment when compared with placebo. Rhodiola decreased overall depressive symptoms, emotional instability, insomnia, and somatization; however, it did not improve feelings of self-esteem (17616). Another small clinical study in patients with major depressive disorder of moderate severity shows that adding a higher dose of rhodiola 600 mg to sertraline daily for 12 weeks improves depressive symptoms when compared with either sertraline alone or sertraline with a lower dose of rhodiola (300 mg) (102283).
• Diabetes. Although there has been interest in using oral rhodiola for diabetes, there is insufficient reliable information about the clinical effects of rhodiola for this condition.
• Fatigue. Preliminary clinical research suggests that oral rhodiola extract decreases fatigue in stressful situations. Details: Most preliminary clinical trials have evaluated a specific rhodiola root extract (SHR-5, Swedish Herbal Institute) in various doses and populations. Taking 50 mg of this product twice daily reduces mental fatigue and improves subjective well-being in students during an examination period (1927). Taking 144 mg twice daily for 7 days reduces fatigue, but not stress, in university students (19287). In night shift workers, 170 mg daily for 2 weeks reduces feelings of fatigue and improves mental performance (6877). In military cadets, a single dose of 370-555 mg after 24 hours without sleep improves tests of mental processing and short-term memory (16411). Finally, taking 576 mg daily for 28 days decreases symptoms of fatigue and increases attention, but does not improve quality of life or symptoms of depression, in patients with stress-related fatigue (19286). Other clinical research shows that taking a different rhodiola root extract (Rhodaxon, Teknofarm), 660 mg daily for 20 days, reduces mental fatigue by 30% in first-year university students (19288). Clinical research using another specific dried rhodiola extract (Vitango, Schwabe Pharma) also shows that taking 200 mg twice daily for 12 weeks modestly reduces perceived levels of stress, burnout, and fatigue when compared to baseline in adults experiencing symptoms of burnout. The validity of these findings is limited by the lack of a control group (96459). Rhodiola extract has also been studied in combination schisandra berry extract and Siberian ginseng root extract (ADAPT-232, Swedish Herbal Institute). However, evidence is mixed, with one study showing that 270 mg daily improves attention, accuracy, and speed in tired individuals performing stressful cognitive tasks (19289), and another study showing that 280 mg daily for 7 days does not reduce mental fatigue or stress in university students (19287).
• Generalized anxiety disorder (GAD). It is unclear if oral rhodiola is beneficial for GAD. Details: A small clinical study shows that taking a specific rhodiola extract (Rhodax, Bodyonics Ltd.) 170 mg twice daily for 10 weeks decreases anxiety and depression and improves symptom scores when compared to baseline in patients with GAD (16410). The validity of these findings is limited by the lack of a comparator group.
• Hearing loss. Although there has been interest in using oral rhodiola for hearing loss, there is insufficient reliable information about the clinical effects of rhodiola for this purpose.
• Hyperlipidemia. Although there has been interest in using oral rhodiola for hyperlipidemia, there is insufficient reliable information about the clinical effects of rhodiola for this condition.
• Menopausal symptoms. Oral rhodiola has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients experiencing menopausal symptoms shows that taking a combination product (Menopause Relief EP, EuroPharma USA) containing rhodiola extract 400 mg and black cohosh extract 13 mg daily for 12 weeks improves psychological symptoms of menopause when compared with placebo or black cohosh alone (103269). It is unclear if these findings are due to rhodiola, black cohosh, or the combination.
• Premature ejaculation. Oral rhodiola has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults with lifelong premature ejaculation shows that taking a specific combination product (EndEP) containing rhodiola 200 mg, folic acid 200 mcg, zinc 10 mg, and biotin 50 mcg once daily for 90 days increases time to ejaculation by about 29 seconds and improves control of ejaculation in about 60% of participants when compared to baseline. These improvements disappear within 90 days of discontinuing treatment. The validity of these findings is limited by the lack of a control group (96460).
• Sexual arousal. Although there has been interest in using oral rhodiola for improving sexual arousal, there is insufficient reliable information about the clinical effects of rhodiola for this condition.
• Stress. Preliminary clinical research suggests that oral rhodiola extract reduces feelings of stress. Details: Preliminary clinical research in adults with general stress shows that taking a specific dried rhodiola extract (Vitango, Schwabe Pharma) modestly reduces levels of stress in certain situations. Taking 200 mg twice daily before breakfast and lunch for 4 weeks improves stress, disability, and functional impairment when compared to baseline (90431). A small study in college students with anxiety shows that taking 200 mg twice daily for 14 days modestly reduces reported levels of stress, anxiety, anger, confusion, and negative mood when compared to a control group (96462). In adults experiencing symptoms of burnout, taking this specific extract 200 mg twice daily for 12 weeks modestly reduces perceived levels of stress, burnout, and fatigue and improves sexual satisfaction when compared to baseline. The validity of these findings is limited by the lack of a control group (96459). Rhodiola has also been evaluated in combination with other ingredients in individuals with stress. A small clinical study in healthy adults with chronic stress shows that taking a specific combination product (Mg-Teadiola, Sanofi-Aventis), containing rhodiola extract 222 mg, magnesium 150 mg, green tea extract 125 mg (providing theanine 50 mg), vitamin B6 0.7 mg, vitamin B9 0.1 mg, and vitamin B12 1.25 mcg, daily for 4 weeks reduces stress scores when compared with placebo (108672). It is unclear if these findings are due to rhodiola, other ingredients, or the combination.
• Tuberculosis. Although there has been interest in using oral rhodiola for tuberculosis, there is insufficient reliable information about the clinical effects of rhodiola for this condition.
• Upper respiratory tract infection (URTI). Although there has been interest in using oral rhodiola for URTI prevention, there is insufficient reliable information about the clinical effects of rhodiola for this purpose. More evidence is needed to rate rhodiola for these uses.

(Read more about RHODIOLA)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Aging. Although there is interest in using oral schisandra for aging, there is insufficient reliable information about the clinical effects of schisandra for this purpose.
• Asthma. Although there is interest in using oral schisandra for asthma, there is insufficient reliable information about the clinical effects of schisandra for this condition.
• Athletic performance. Although there is interest in using oral schisandra for athletic performance, there is insufficient reliable information about the clinical effects of schisandra for this purpose.
• Coronavirus disease 2019 (COVID-19). Oral schisandra has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults with a history of COVID-19 infection and current symptoms of long COVID-19 shows that taking 30 mL of a specific combination product (Chisan / ADAPT-232, Swedish Herbal Institute) containing schisandra extract 300 mg, rhodiola extract 90 mg, and eleuthero extract 78 mg twice daily for 2 weeks increases exercise capacity, but does not reduce the number of days with fatigue, headache, cough, respiratory problems, or other symptoms of long COVID-19, when compared with placebo (109635).
• Cough. Although there is interest in using oral schisandra for cough, there is insufficient reliable information about the clinical effects of schisandra for this purpose.
• Diarrhea. Although there is interest in using oral schisandra for diarrhea, there is insufficient reliable information about the clinical effects of schisandra for this purpose.
• Diabetes. Although there is interest in using oral schisandra for diabetes, there is insufficient reliable information about the clinical effects of schisandra for this condition.
• Familial Mediterranean fever. Oral schisandra has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical study in children ages 3-15 years with familial Mediterranean fever shows that taking a combination product (ImmunoGuard, Inspired Nutritionals) containing schisandra extract 100 mg, andrographis, Siberian ginseng, and licorice reduces symptom duration, frequency, and severity when compared with placebo (12382). It is unclear if these effects are due to schisandra, other ingredients, or the combination.
• Hepatitis. Although there is interest in using oral schisandra for hepatitis, there is insufficient reliable information about the clinical effects of schisandra for this condition.
• Hypercholesterolemia. Although there is interest in using oral schisandra for hypercholesterolemia, there is insufficient reliable information about the clinical effects of schisandra for this condition.
• Impaired glucose tolerance (prediabetes). Oral schisandra has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate sized clinical trial in adults with prediabetes shows that taking schisandra fruit extract with a soybean mixture 250 mg twice daily for 12 weeks decreases fasting plasma glucose by around 6 mg/dL and improves 30- and 60-minute post-prandial glucose levels but does not reduce glycated hemoglobin when compared with placebo (112887). The ratio of the schisandra extract to soybean mixture in the product was 5:1. It is unclear if these effects are due to schisandra, soybean, or the combination.
• Menopausal symptoms. It is unclear if oral schisandra is beneficial for improving menopausal symptoms. Details: A small clinical trial in healthy patients with moderate or severe menopausal symptoms shows that taking schisandra extract (BMO-30, Biomix Inc) 784 mg in two divided doses daily for 6 weeks improves hot flushes and other menopausal symptoms when compared with placebo (96632).
• Muscle strength. It is unclear if oral schisandra is beneficial for improving muscle strength. Details: A small clinical study in healthy middle-aged females shows that taking schisandra powdered extract (Bioport Korea Inc.) 500 mg twice daily for 12 weeks seems to modestly increase quadriceps muscle strength and grip strength, but does not affect overall muscle mass, when compared with placebo (105563).
• Myopia. Although there is interest in using topical schisandra for myopia in children, there is insufficient reliable information about the clinical effects of schisandra for this condition.
• Physical performance. It is unclear if oral schisandra is beneficial for improving physical function in older adults. Details: A small clinical study in healthy adults over 50 years of age shows that taking schisandra 500 mg twice daily, 30 minutes after breakfast and dinner, for 12 months improves knee extension peak torque, but does not improve hand grip strength or body composition, when compared with placebo (105562).
• Pneumonia. Oral schisandra has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults with acute, nonspecific pneumonia shows that taking 20 mL of a specific combination product (ADAPT-232 CHI San, Swedish Herbal Institute) containing schisandra berry extract 51%, rhodiola root extract 27.6%, and eleuthero root extract 24.4% twice daily for 10-15 days reduces the duration of antibiotic treatment and may improve quality of life when compared with standard treatment alone (71152). It is unclear if these effects are due to schisandra, other ingredients, or the combination.
• Stress. Oral schisandra has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy, fatigued females under experimental stress suggests that taking a single, 270 mg dose of a combination product (ADAPT-232, Swedish Herbal Institute) containing schisandra, rhodiola, and Siberian ginseng improves attention, as well as cognitive task speed and accuracy, when compared with placebo (19289). It is unclear if these effects are due to schisandra, other ingredients, or the combination. More evidence is needed to rate schisandra for these uses.

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EFFECTIVE

• Pyridoxine-dependent epilepsy. Intravenous vitamin B6 is effective for controlling pyridoxine-dependent seizures. Details: Pyridoxine-dependent seizures are a rare type of refractory seizures in neonates that do not respond to anticonvulsant drugs. These seizures are typically controlled within minutes of intravenous administration of pyridoxine, a form of vitamin B6. Pyridoxine-dependent seizures can be due to genetic (autosomal recessive) pyridoxine dependency, or more commonly, a result of the use of high-dose pyridoxine during pregnancy (8197,8198).
• Sideroblastic anemia. Oral vitamin B6 is effective for treating hereditary sideroblastic anemia. Details: Taking vitamin B6 (pyridoxine) orally is effective for treating hereditary sideroblastic anemia (15,9518). Taking the active form of vitamin B6 (pyridoxal-5'-phosphate) also seems to be effective in cases in which the patient does not respond to pyridoxine (93049).
• Vitamin B6 deficiency. Oral vitamin B6 is effective for preventing and treating vitamin B6 deficiency. Details: Taking oral vitamin B6 can prevent and treat vitamin B6 deficiency (15).

LIKELY EFFECTIVE

• Hyperhomocysteinemia. Taking vitamin B6 orally, alone or in combination with folic acid, is effective for reducing hyperhomocysteinemia. Details: Vitamin B6 (pyridoxine) seems to lower homocysteine concentrations when folic acid and vitamin B12 are at physiologic levels or when given with folic acid and vitamin B12 supplements (9451,83042,107136). A combination of vitamin B6 100 mg and folic acid 0.5 mg daily seems to lower homocysteine levels by about 35% and is recommended for people with postprandial hyperhomocysteinemia (1489,9406). Other research shows that taking pyridoxine 50-200 mg daily reduces postprandial homocysteine levels by 32% to 35% (9406,10350). Pyridoxine also seems to reduce homocysteine levels in patients with kidney failure, kidney transplant patients (1489,6884,9414,9415), or patients who receive general anesthesia with nitrous oxide (9481). However, some research in healthy adults suggests that adding pyridoxine to folic acid might not provide any additional benefit over folic acid alone (9400,9405,9409,50145). Hyperhomocysteinemia is considered by some to be an independent risk factor for atherosclerosis, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, and ischemic stroke (1899,3323,9402,9405,9408,9409). However, elevated homocysteine levels may be a marker, as opposed to a cause, of vascular disease (11387,11388). A 5 µmol/L increase in plasma homocysteine increases the risk of cerebrovascular disease by 50% and the odds of coronary heart disease by 60% and 80% in males and females, respectively (9407,9411). However, it is not clear if reducing homocysteine levels results in reduced cardiovascular morbidity and mortality (1489,6883,6884,9308,9400,9405,9409). Folic acid, vitamin B6, and vitamin B12 supplementation can reduce total homocysteine from 13.4 to 11 µmol/L. However, this reduction does not seem to help with secondary prevention of death or myocardial infarction, and some research even suggests an increase in cardiovascular disease (CVD) risk (11387,13482,50423,83050,97619). There is also debate about whether supplementation with homocysteine-lowering B vitamins can reduce the risk of stroke. A number of large clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with CVD or impaired renal function (11387,13482,50423,83050,96150). However, a more recent meta-analysis shows that B vitamin supplementation modestly reduces the relative risk of stroke by 10% when compared with placebo in patients at risk for or with a history of CVD (97619). Also, a meta-analysis in patients with a history of stroke shows that B vitamin supplementation modestly reduces the relative risk of stroke recurrence by 13% and the risk of vascular death by 11% when compared with placebo (107136).

POSSIBLY EFFECTIVE

• Antipsychotic-induced hyperprolactinemia. It is unclear if oral vitamin B6 is beneficial for patients with antipsychotic-induced hyperprolactinemia. Details: Clinical research in male patients with hyperprolactinemia who are on a consistent antipsychotic dose shows that taking vitamin B6 300 mg twice daily for 16 weeks reduces serum prolactin levels by 68%, compared with 37% in patients taking aripiprazole 5 mg twice daily. Also, 67% of patients taking vitamin B6 had prolactin levels less than 40 mcg/mL versus 2% of those taking aripiprazole (107128).
• Kidney stones (nephrolithiasis). Oral vitamin B6 seems to decrease urinary oxalate levels and decrease the risk of kidney stone formation in some patients. Details: There is some evidence that taking vitamin B6 (pyridoxine) orally, alone or in combination with magnesium, can decrease urinary oxalate levels in people with type I primary hyperoxaluria, a hereditary disorder (1201,6437,6438,6439,6440,8548,8549,8550). Additionally, a small clinical study in this population suggests that intravenous pyridoxine hydrochloride can reduce urinary oxalate by 25.5% when compared to baseline (90796). In patients with idiopathic hyperoxaluria, taking a combination of pyridoxine 25mg and magnesium oxide 400 mg for 3 months decreases urinary oxalate by approximately 16%, with 68% of patients experiencing a reduction. However, supplementation is less effective than following a low-oxalate diet, which reduces urinary oxalate in 91% of patients by an average of 31% (107127). There is also preliminary evidence that higher pyridoxine intake in females with no history of kidney stones is associated with decreased risk of kidney stone formation (6441), but this association has not been found in males (6442).
• Pregnancy-induced nausea and vomiting. Oral vitamin B6 may reduce nausea and vomiting in some pregnant patients and is sometimes used in combination with doxylamine. Details: While some conflicting evidence exists, most small clinical studies suggest that oral vitamin B6 is effective for improving nausea and vomiting associated with pregnancy when compared with baseline or placebo. However, vitamin B6 may not be as effective as ginger (110459). Two small clinical studies show that taking vitamin B6 (pyridoxine) 25 mg every 8 hours for 3-4 days decreases pregnancy-induced nausea severity and vomiting incidence when compared with placebo (6168,16306). A larger clinical trial shows that taking lower doses of vitamin B6, 10 mg every 8 hours over 5 days, improves pregnancy-induced nausea, but not vomiting, when compared with placebo (6167). A small clinical study in patients with mild to moderate nausea and vomiting shows that taking a higher dose of 40 mg twice daily for 4 days is more effective than placebo, but no better than ginger 500 mg twice daily (99404). The American College of Obstetrics and Gynecology (ACOG) considers vitamin B6 at a dose of 10-25 mg 3 to 4 times daily a first-line treatment for pregnancy-induced nausea and vomiting due to its benign safety profile (111601). However, it is not effective for all patients, such as those with hyperemesis gravidarum, a severe form of pregnancy-induced nausea and vomiting. Adding vitamin B6 20 mg three times daily for 2 weeks to intravenous rehydration, metoclopramide, and thiamine seems to be no more effective than placebo for reducing vomiting in hyperemesis gravidarum (99405). Vitamin B6 is also sometimes used in combination with doxylamine. In fact, a combination of vitamin B6 plus doxylamine (Diclegis or Bonjesta, Duchesnay Inc., and various generics) has been approved by the US Food and Drug Administration (FDA) as a prescription product111601). ACOG recommends vitamin B6 in combination with doxylamine as another first-line treatment option (111601). However, the clinical trial used to obtain FDA approval has some methodological problems, and the significance of the results has been questioned. The improvement in symptom scores seen with Diclegis was less than one point on a 13-point scale, which is unlikely to be clinically significant (97998). Also, some clinical research shows that taking pyridoxine 25 mg and doxylamine 12.5 mg is less effective than ondansetron 4 mg when taken every 8 hours for 5 days. Only 41% of the patients using pyridoxine and doxylamine had a clinically significant reduction in nausea, compared to 92% of patients using ondansetron (90797). The combination of vitamin B6 and doxylamine is also studied with acupuncture. A large clinical study in patients with moderate to severe pregnancy-induced nausea and vomiting conducted in China shows that taking vitamin B6-doxylamine (Diclegis, Duchesnay, Inc) 20 to 40 mg each at bedtime for 14 days in combination with daily acupuncture modestly improves patient-reported nausea and vomiting scores when compared with either intervention alone (111820). However, it is unclear whether this improvement is clinically significant.
• Premenstrual syndrome (PMS). Oral vitamin B6 seems to reduce PMS symptoms. Details: There is some evidence that taking vitamin B6 (pyridoxine) orally can improve symptoms of PMS such as breast pain or tenderness (mastalgia) and depression in some patients. Pyridoxine in doses of at least 50 mg daily, plus magnesium oxide 200 mg daily, seems to relieve PMS-related anxiety and other symptoms (8555,39007,82962). Although some clinicians advocate doses of pyridoxine 200-500 mg daily for PMS, doses of 50-100 mg daily seem to work just as well. There is no apparent dose-response curve for PMS, so the lowest effective dose should be used. Higher doses might increase the risk of side effects (3093).

POSSIBLY INEFFECTIVE

• Age-related cognitive decline. Oral vitamin B6 does not seem to slow age-related cognitive decline. Details: One clinical trial in elderly people with memory complaints shows that taking a combination of B vitamins, including folic acid 0.8 mg, vitamin B12 0.5 mg, and vitamin B6 (form not specified) 20 mg daily for 24 months reduces cerebral atrophy in the gray matter regions associated with Alzheimer disease by up to seven-fold when compared with placebo. However, this protection does not occur in patients with the lowest average blood levels of homocysteine (90374). Furthermore, other clinical research shows that taking vitamin B6 (pyridoxine) 3-75 mg daily in combination with folic acid and vitamin B12 does not improve cognitive function in elderly adults (14392,50225,50510).
• Alzheimer disease. Oral vitamin B6 does not seem to improve cognitive function in patients with Alzheimer disease when used in combination with other B vitamins. Also, oral vitamin B6 does not seem to reduce the risk of developing this condition. Details: Clinical research in patients with probable Alzheimer disease taking routine medications shows that taking vitamin B6 25 mg with folic acid 5 mg and vitamin B12 1 mg daily for 18 months does not have a beneficial effect on cognitive function or the severity of disease when compared with placebo. In this study, all patients were consuming a folate-fortified diet (50319). Also, population research in elderly adults has found that a high intake of vitamin B6 from dietary or supplemental sources is not associated with a decreased risk of Alzheimer disease when compared to lower vitamin B6 intake (13165,15270).
• Carpal tunnel syndrome. Oral vitamin B6 does not seem to reduce symptoms of carpal tunnel syndrome. Details: Most research shows that people with carpal tunnel syndrome are not generally deficient in vitamin B6 and do not benefit from taking vitamin B6 supplements (8203,8937,9448,9450,9478,9482). Although early studies by a single group of researchers, as well as anecdotal reports, suggest that taking vitamin B6 may relieve carpal tunnel symptoms, more reliable research has not supported these findings (8202,9445,9447,9449,9483,15955,83086).
• Cataracts. Oral vitamin B6 does not seem to slow cataract development. Details: Clinical research in females with existing cardiovascular disease (CVD) or at increased risk of CVD shows that taking a combination of folic acid 2.5 mg, vitamin B6 (form not specified) 50 mg, and vitamin B12 1 mg daily for an average of 7.3 years does not reduce the risk of cataracts when compared with placebo. Furthermore, the risk of cataract extraction was increased by 28% (96149).
• Chemotherapy-induced acral erythema. While some conflicting evidence exists, most research suggests that oral or topical vitamin B6 does not seem to prevent or reduce the severity of acral erythema induced by chemotherapy. Details: A meta-analysis of 10 clinical trials and 4 observational studies shows that taking vitamin B6 60-500 mg daily for up to 8 chemotherapy cycles does not prevent chemotherapy-induced acral erythema or reduce the incidence of severe cases when compared with control. Most studies used capecitabine chemotherapy alone or in combination, and one study used pegylated liposomal doxorubicin; however, no subgroup analysis was conducted to differentiate chemotherapy regimens. Results did not seem to vary based on study location, study design, or vitamin B6 dose (104930). However, a more recent preliminary clinical study in patients receiving doxorubicin for multiple myeloma shows that taking vitamin B6 100 mg on the first day of chemotherapy then twice daily for 7 days with each cycle reduces the risk of developing acral erythema by 72%, but does not improve the severity of acral erythema, when compared with no vitamin B6 supplementation (110458). Also, one small, low-quality clinical study suggests that taking vitamin B6 400 mg daily reduces the risk of moderate or severe chemotherapy-induced acral erythema when compared with vitamin B6 200 mg daily; however, the higher dose also seems to be associated with worsened tumor response and increased treatment failure (97620). Topical vitamin B6 has also failed to show benefit. A small clinical study in patients with acral erythema from capecitabine or pegylated liposomal doxorubicin shows that applying vitamin B6 1% cream to affected areas three times daily for 6 weeks does not improve symptoms when compared with placebo (104929).
• Colorectal adenoma. Oral vitamin B6 does not seem to reduce the risk of developing colorectal adenomas. Details: Clinical research shows that taking a combination of B vitamins, including folic acid 2.5 mg, vitamin B6 (pyridoxine) 50 mg, and vitamin B12 1 mg, daily for up to 9.2 years does not reduce the risk of colorectal adenoma in females at high risk of cardiovascular disease when compared with placebo (90389).
• Eclampsia. Oral or intramuscular vitamin B6 does not seem to reduce the risk of eclampsia. Details: Meta-analyses of limited clinical research in pregnant patients show that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of eclampsia when compared with control (83046,96166).
• Osteoporosis. Oral vitamin B6 does not seem to reduce the risk of osteoporotic fractures. Details: Clinical research in patients with cerebrovascular disease shows that taking a combination of B vitamins, including folic acid 2 mg, vitamin B6 (form not specified) 25 mg, and vitamin B12 500 mcg daily for up to 10.5 years does not prevent osteoporotic fractures when compared with placebo (90377). Furthermore, a secondary analysis of two large studies in patients with cardiovascular disease has found that taking vitamin B6 (pyridoxine) 40 mg daily in addition to folic acid and vitamin B12 for 1-3 years is associated with a 42% increased risk of hip fracture over an 11-year period when compared with only folic acid and vitamin B12 (96163). This finding is limited because these studies were not designed to assess the effects of vitamin B6 on fracture risk and the analyses were not adjusted for baseline bone health or fall risk.
• Pre-eclampsia. Oral or intramuscular vitamin B6 does not seem to reduce the risk of pre-eclampsia. Details: Meta-analyses of limited clinical research in pregnant patients show that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of pre-eclampsia when compared with placebo (83046,96166).
• Preterm labor. Oral or intramuscular vitamin B6 does not seem to reduce the risk of preterm labor. Details: Meta-analyses of limited clinical research in pregnant patients shows that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of preterm labor when compared with placebo (83046,96166).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acne. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults and children with inflammatory acne shows that taking 1-4 tablets of a specific product (NicAzel, Elorac Inc.) containing vitamin B6 (pyridoxine), nicotinamide, azelaic acid, zinc, copper, and folic acid for 8 weeks reduces inflammatory lesions and improves appearance in 88% and 81% of patients, respectively, when compared to baseline (90800). The validity of these findings is limited by the lack of a comparator group.
• Age-related macular degeneration (AMD). Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large-scale clinical study shows that taking vitamin B6 (pyridoxine) 50 mg, vitamin B12 1000 mcg, and folic acid 2.5 mg daily reduces the risk for AMD in females over 40 years of age with a history of cardiovascular disease (CVD) or with risk factors for CVD. Those who took this combination for an average of 7.3 years had a 34% reduced risk of developing AMD and a 41% reduced risk of visually significant AMD when compared with placebo (14620). It is unclear if this effect is due to vitamin B6, other ingredients, or the combination.
• Angioplasty. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some evidence suggests that vitamin B6 (pyridoxine) 10 mg, folic acid 1 mg, and vitamin B12 400 mcg daily can decrease the rate of restenosis in patients treated with balloon angioplasty (8009,9412). However, this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting (8009). An intravenous loading dose of folic acid, vitamin B6 (pyridoxine), and vitamin B12 followed by oral administration of folic acid 1.2 mcg, vitamin B6 (pyridoxine) 48 mg, and vitamin B12 60 mcg daily after bare metal coronary stenting also does not seem to reduce restenosis and might actually increase restenosis (12150,12151). Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents (12151). It is unclear if any effects are due to vitamin B6, other ingredients, or the combination.
• Antipsychotic-induced metabolic side effects. It is unclear if oral vitamin B6, as an adjunct to progesterone, is beneficial in patients with antipsychotic-induced amenorrhea. Details: A small clinical study in females with antipsychotic-induced amenorrhea shows that taking vitamin B6 80 mg three times daily for 1 month plus intramuscular progesterone daily for 5 days increases levels of estradiol and follicle stimulating hormone, reduces prolactin levels, and increases the rate of clinical efficacy, defined as the normalization of menstruation and improvement in endocrine indicators, by 14% when compared with progesterone alone (110457).
• Anxiety. It is unclear if oral vitamin B6 is beneficial in patients with anxiety. Details: Clinical research in college students shows that taking vitamin B6 100 mg daily for one month does not reduce anxiety scores when compared with placebo (110453). However, because a diagnosis of anxiety was not a requirement for study participation, it is unclear if these findings can be generalized to patients diagnosed with anxiety.
• Asthma. It is unclear if oral vitamin B6 is beneficial in patients with asthma. Details: Preliminary clinical studies show that taking vitamin B6 (pyridoxine) 200-300 mg daily may improve symptoms of asthma in some patients, but not others, when compared with placebo (7064,7065). Studies have yielded conflicting results, with some research suggesting that it may only be beneficial in children with severe asthma (7065). Additionally, some research suggests that theophylline may lower vitamin B6 levels, although it is unclear if vitamin B6 supplementation is beneficial (4522,7066,9503).
• Atherosclerosis. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in patients with intermediate risk for coronary heart disease shows that taking a specific supplement (Kyolic, Total Heart Health, Formula 108, Wakunga) containing vitamin B6 12.5 mg, aged garlic extract 250 mg, vitamin B12 100 mcg, folic acid 300 mcg, and L-arginine 100 mg daily for 12 months reduces coronary artery calcium progression when compared with placebo (88385). It is unclear if this effect is due to vitamin B6, other ingredients, or the combination.
• Atopic dermatitis (eczema). It is unclear if oral vitamin B6 is beneficial in patients with eczema. Details: A small clinical study in children with eczema shows that taking vitamin B6 (pyridoxine hydrochloride) 50 mg daily for 4 weeks does not reduce symptoms such as redness and itchiness when compared with placebo (83090).
• Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral vitamin B6 is beneficial for ADHD. Details: A small crossover study in children with ADHD shows that taking vitamin B6 600 mg, niacinamide and ascorbic acid 3 grams, and calcium pantothenate 1.2 grams daily for 6 weeks does not improve behavior scores when compared with placebo (9957).
• Autism spectrum disorder. Although there is interest in using oral vitamin B6 for autism, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
• Bipolar disorder. It is unclear if oral vitamin B6 is beneficial in patients with bipolar disorder. Details: A small clinical trial in patients with type 1 bipolar disorder who are taking lithium and experiencing an acute episode of mania shows that taking vitamin B6 80 mg daily for 8 weeks does not improve cognitive function or the severity of mania when compared with placebo. Cognitive function was reduced in patients taking vitamin B6; any effect on sleep was unclear (107132).
• Cancer. It is unclear if oral vitamin B6 reduces overall cancer risk. Details: Population research has found that higher dietary intake of vitamin B6 is associated with a 22% reduced risk of cancer, including esophageal, pancreatic, gastric, colorectal, and breast cancer. However, when dietary and supplemental vitamin B6 intake is considered, the inverse association between vitamin B6 and cancer risk is weaker and limited to fewer tumor sites. Furthermore, a meta-analysis of 9 clinical studies shows that taking vitamin B6 3-100 mg orally daily for 2-7.3 years, in combination with vitamin B12 and folate, does not reduce the risk of cancer in patients with cardiovascular disease or kidney failure (96164).
• Cardiovascular disease (CVD). Oral vitamin B6, taken along with other B vitamins, does not seem to improve secondary prevention of death or myocardial infarction in patients with CVD. However, it might slightly lower the risk of stroke. Details: Overall evidence from clinical research and meta-analyses shows that taking vitamin B6 in combination with folic acid and/or vitamin B12 does not seem to help with secondary prevention of death or myocardial infarction in patients with or at risk for CVD (11387,13482,34540,50423,83050,90379,97619). In fact, some research suggests that long-term supplementation with vitamin B6, folic acid, and vitamin B12 for secondary prevention increases the risk of CVD by 20% despite lowering homocysteine levels by 30% (13482). However, some research shows that taking vitamin B6 in combination with other B vitamins modestly reduces the risk of stroke, although results are conflicting (11387,13482,50423,83050,96150,96165,97619,107136). Additionally, it is unclear which specific combination of B vitamins is optimal for reducing stroke risk and which patients are most likely to benefit. In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) approved a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368).
• Cognitive function. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in healthy adults aged 40-65 years shows that taking a supplement containing vitamin B6, ginkgo leaf, bacopa, and other B vitamins twice daily for 12 weeks does not improve memory or attention when compared with placebo (111334).
• Colorectal cancer. It is unclear if oral vitamin B6 reduces the risk of colorectal cancer. Details: A meta-analysis of observational studies suggests that the highest dietary intake of vitamin B6 is associated with a 20% reduced risk of colorectal cancer when compared with the lowest dietary intake. However, this association was not shown in subgroup analyses of studies conducted in Australia, Europe, or North America (111600). The validity of this analysis is limited by the heterogeneity of the included studies.
• Dental caries. There is limited evidence on the oral use of vitamin B6 for dental decay during pregnancy. Details: Meta-analyses of limited clinical research show that taking vitamin B6 (pyridoxine), 25 mg daily or a single dose of 100 mg orally or intramuscularly, may reduce the risk of dental decay during pregnancy when compared with placebo (83046,96166).
• Depression. It is unclear if oral vitamin B6 reduces the risk of developing depression or improves symptoms of depression. Details: Clinical research in healthy college students shows that taking vitamin B6 100 mg daily for one month does not reduce depression scores when compared with placebo (1104453). However, because a diagnosis of depression was not a requirement for study participation, it is unclear if these findings can be generalized to patients diagnosed with depression. Whether vitamin B6 reduces the risk of developing depression is also unclear. A meta-analysis of population research has found that the highest dietary intake of vitamin B6 is associated with a 19% lower risk of depression when compared with the lowest intake. However, sub-analyses suggest that this association is only relevant in females and not males (107133). In one individual population study in community dwelling older adults included in the analysis, the consumption of at least 1.71 mg of vitamin B6 daily from food was associated with a 43% reduction in the likelihood of becoming depressed when compared with the consumption of 1.33 mg or less daily in females. However, there was no association between vitamin B6 levels and risk of depression in males, and the finding in females was no longer significant when adjusted for total energy intake, since foods rich in vitamin B6 are energy-dense (96168). Another observational longitudinal study in healthy adults starting oral contraceptives containing ethinyl estradiol and levonorgestrel has found that taking vitamin B6 25 mg daily for 6-12 months is associated with a 40% lower risk of depression when compared with no supplementation (90789). Most available studies are cross-sectional in nature, making any conclusions related to causation difficult.
• Diabetes. It is unclear if oral vitamin B6 is beneficial in patients with type 2 diabetes or gestational diabetes. Details: Observational research in Chinese adults with type 2 diabetes has found that dietary intake of vitamin B6 in the highest quartile is associated with 53% lower odds of developing cardiovascular disease, defined as a non-fatal myocardial infarction, non-fatal stroke, or hospitalization for unstable angina, when compared with vitamin B6 intake in the lowest quartile (110452). Small clinical studies in patients with gestational diabetes and vitamin B6 deficiency shows that taking vitamin B6 (pyridoxine) 100 mg daily for 2 weeks improves glucose tolerance and blood glucose levels when compared with baseline (82967,83088). However, there is concern that these findings were confounded by dietary alterations. This benefit was not observed in a subsequent small case series in patients with gestational diabetes (22380).
• Diabetic neuropathy. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research suggests that taking a combination of B vitamins, including folic acid (L-methylfolate), vitamin B12 (methylcobalamin), and vitamin B6 (pyridoxal-5'-phosphate) for 24 weeks does not improve neural dysfunction based on vibration perception when compared with placebo in patients with diabetic neuropathy. However, taking this combination appears to modestly improve neuropathy symptoms and quality of life related to mental functioning when compared with placebo (90375).
• Dysmenorrhea. It is unclear if oral vitamin B6 is beneficial in patients with dysmenorrhea. Details: Preliminary clinical research shows that taking vitamin B6 (form not specified) 200 mg daily reduces pain associated with dysmenorrhea when compared with placebo. However, taking vitamin B6 in combination with magnesium does not reduce pain when compared with placebo (77388).
• Fibromyalgia. It is unclear if oral vitamin B6 is beneficial in patients with fibromyalgia. Details: A small clinical study in patients with fibromyalgia shows that taking vitamin B6 80 mg daily for 8 weeks does not improve pain, disease severity, anxiety, depression, or quality of life when compared with placebo (110454).
• Gastroenteritis-associated nausea and vomiting. It is unclear if oral vitamin B6 is beneficial in children with gastroenteritis. Details: A small clinical study in children aged 6 months to 12 years with acute viral gastroenteritis shows that taking vitamin B6 (form not specified) does not improve symptoms of dehydration or the frequency of vomiting when compared with placebo (90793).
• Hypertension. It is unclear if oral vitamin B6 reduces blood pressure. Details: One small clinical study in patients with essential hypertension shows that taking vitamin B6 (pyridoxine hydrochloride) 5 mg/kg daily for 4 weeks can reduce systolic and diastolic blood pressure when compared with baseline (83091). The validity of this finding is limited by the lack of a control group.
• Hypertriglyceridemia. It is unclear if oral vitamin B6 reduces triglyceride levels. Details: Preliminary clinical research shows that vitamin B6 (form not specified) 50 mg daily for 12 weeks does not reduce triglyceride levels in people with hypertriglyceridemia when compared with placebo. However, vitamin B6 appears to decrease total cholesterol and high-density lipoprotein (HDL) cholesterol by approximately 9% in these patients (59028).
• Infertility. Although there is interest in using oral vitamin B6 for infertility, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
• Insomnia. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in healthy adults with self-reported sleep difficulty shows that taking a specific product (LZ Complex3, Sanofi Consumer Healthcare Pty Ltd.) containing vitamin B6, zizyphus extract, hops extract, hydrolyzed milk protein (Lactium), and magnesium oxide nightly, 30 minutes before bed, for 2 weeks does not improve sleep quality, daytime functioning, or physical fatigue when compared with placebo. However, due to the large improvement seen in both the treatment and placebo groups, the effectiveness of this product is unclear (95971).
• Isoniazid-induced neuropathy. It is unclear if oral vitamin B6 prevents the development of neuropathy in patients taking isoniazid. Details: Preliminary clinical research in patients taking isoniazid for tuberculosis shows that taking vitamin B6 (pyridoxine) 6 mg daily reduces the development of neuropathy when compared with control (83068).
• Lactation. It is unclear if oral vitamin B6 helps to suppress postpartum lactation. Details: A meta-analysis of two small clinical trials shows that taking vitamin B6 (pyridoxine) 400-600 mg daily for 6-7 days postpartum does not suppress lactation when compared with no treatment (83047).
• Levetiracetam-induced side effects. While some conflicting evidence exists, several small, low-quality studies suggest that oral vitamin B6 (pyridoxine) may reduce some neuropsychiatric adverse effects related to the use of levetiracetam. Details: In an analysis of case reports, retrospective studies, and a single low-quality prospective study, improvement in levetiracetam-associated neuropsychiatric symptoms occurred in approximately 73% of patients taking pyridoxine (107137). A more recent preliminary clinical trial in children ages 1-17 years shows that taking pyridoxine 10 or 15 mg/kg daily as needed based on symptoms improves behavioral side effects associated with levetiracetam by a small amount when compared with low-dose pyridoxine 0.5 mg/kg daily used as placebo (107124). Also, observational research in children ages 9 months to 14 years has found that taking vitamin B6 is associated with improved behavior and a 44% lower risk of levetiracetam discontinuation when compared with no vitamin B6 supplementation (110455). Some observational research in adults with levetiracetam-associated irritability has found that taking vitamin B6 is associated with an improvement in irritability in 45% of patients when compared to baseline (107129). However, a small clinical trial in adults with epilepsy shows that taking pyridoxine 40 mg daily for 3 weeks does not improve levetiracetam-related psychiatric adverse effects when compared with placebo (110456). This study may have been underpowered to detect differences between groups. Pyridoxine doses used in the studies above have ranged from 50-400 mg daily in children and 40-600 mg daily in adults (107124,107129,107137,110456).
• Lung cancer. It is unclear if dietary or oral vitamin B6 reduces lung cancer risk. Details: Epidemiological research has found that higher serum levels of vitamin B6 in male smokers is associated with a lower risk of lung cancer (9454). Also, people with blood levels of vitamin B6 in the top quartile have a modestly lower risk of lung cancer when compared with those whose levels are in the lowest quartile. The association is stronger for males and for people who have smoked (97999). However, other epidemiological research found that increased dietary intake of vitamin B6 is not associated with a reduced risk of lung cancer (96164).
• Menopausal symptoms. Although there is interest in using oral vitamin B6 for menopausal symptoms, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
• Motion sickness. Although there is interest in using oral vitamin B6 for motion sickness, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
• Nausea and vomiting. It is unclear if oral vitamin B6 is beneficial for nausea and vomiting in patients using oral contraceptives. Details: An observational longitudinal study in healthy females taking oral contraceptives containing ethinyl estradiol and levonorgestrel has found that taking vitamin B6 25 mg daily for 6-12 months is associated with a 43% reduced risk of nausea when compared with no supplementation (90789).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin B6 for patients with NAFLD. Details: A small clinical trial in patients with NAFLD shows that taking vitamin B6 (pyridoxine) 30 mg three times daily for 12 weeks does not reduce levels of liver transaminases or plasma lipids when compared with baseline. However, hepatic fat accumulation was modestly reduced (107130). The validity of this study is limited by the lack of a comparator group.
• Obesity. It is unclear if oral vitamin B6 in beneficial in overweight or obese individuals. Details: A small clinical trial in females with a body mass index (BMI) of at least 25 kg/m² shows that taking vitamin B6 as pyridoxine 80 mg daily for 8 weeks reduces fat mass and improves insulin resistance and triglyceride levels by a small amount when compared with placebo. Although some other anthropometric and metabolic indices were improved when compared with baseline, there was no effect of pyridoxine on body weight, visceral adiposity, or other endpoints when compared with placebo (107131).
• Overall mortality. It is unclear if oral vitamin B6 reduces the risk of overall mortality. Details: Observational research in US adults has found that dietary intake of vitamin B6 in the highest quintile is associated with a 12% to 21% lower risk of all-cause mortality and a 31% to 44% lower risk of cardiovascular mortality when compared with the lowest quintile of dietary vitamin B6 intake (110451).
• Pancreatic cancer. It is unclear if oral vitamin B6 reduces the risk of pancreatic cancer. Details: Observational research has found that higher dietary intake of vitamin B6 is associated with a 37% lower risk of developing pancreatic cancer when compared with lower intake (104927).
• Postpartum depression. It is unclear if oral vitamin B6 is beneficial in patients with postpartum depression. Details: Preliminary clinical research in individuals considered at increased risk for postpartum depression, but without clinical depression, shows that taking vitamin B6 80 mg daily from the 28th week of pregnancy until birth, and then 40 mg daily for one month, reduces symptoms of depression 1.5 months after birth when compared with baseline (measured during the third trimester) and when compared with placebo. However, it is unclear if any of the patients included in the study developed postpartum depression, as there were no changes in overall symptoms in patients taking placebo (107126).
• Restless legs syndrome (RLS). It is unclear if oral vitamin B6 is beneficial in patients with RLS. Details: A small clinical study in adults with RLS who are beginning treatment with pramipexole shows that also taking vitamin B6 40 mg daily for 2 months moderately improves RLS scores and sleep quality scores when compared with pramipexole and placebo (110052).
• Schizophrenia. It is unclear if oral vitamin B6 is beneficial for patients with treatment-resistant schizophrenia. Details: Clinical research in male patients with treatment-resistant schizophrenia who are on a consistent antipsychotic dose shows that adding vitamin B6 300 mg twice daily for 16 weeks modestly improves psychotic symptoms and some measures of cognitive performance when compared with adding aripiprazole 5 mg twice daily (107128). More research is needed to determine if these benefits are clinically relevant.
• Seizures. It is unclear if oral vitamin B6 is beneficial for preventing seizures in patients with glycosylphosphatidylinositol (GPI) deficiency. Details: Observational case series in a small number of children and young adults with GPI deficiency has found that taking vitamin B6 20-30 mg/kg daily for 3-12 months is associated with some reduction in seizure frequency in 9 of 13 patients. However, no patient reached seizure freedom (107125,107135). In one case series, treatment for 12 months was associated with modest developmental improvements in almost all patients (107135). The study patient populations were slightly different in terms of age and underlying genetic causes for GPI deficiency.
• Sickle cell disease. Oral vitamin B6 has only been evaluated in combination with other B vitamins; its effect when used alone is unclear. Details: Preliminary clinical research in adults with sickle cell disease shows that taking vitamin B6 4.2-6 mg, vitamin B12 4.2-6 mcg, and folic acid 700 mcg daily might lower homocysteine levels. However, it is unknown if this will reduce the risk of endothelial damage in these patients (9324).
• Stroke. It is unclear if oral vitamin B6, either alone or with other B vitamins, is beneficial for stroke prevention. Details: There is some debate about whether supplementation with homocysteine-lowering B vitamins, including vitamin B6, can reduce the risk of stroke. A number of clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with cardiovascular disease (CVD) or impaired kidney function (11387,13482,50423,83050,96150). However, a more recent meta-analysis of 10 clinical trials, including over 44,000 patients at risk for or with a history of CVD, shows that B vitamin supplementation reduces the relative risk of stroke by 10% when compared with placebo (97619). This meta-analysis differed from some of the earlier analyses due to the inclusion of several additional clinical trials. Also, another meta-analysis of three clinical trials including 9900 patients with a history of stroke shows that B vitamin supplementation reduces the relative risk of stroke recurrence by 13% when compared with placebo, although this finding was determined to have a low level of certainty. Based on two clinical trials, there was also a 17% reduced risk of vascular death and an 11% reduction in the combined risk of stroke, myocardial infarction, and vascular death (107136). In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Unfortunately, even after the publication of higher quality research, it is still unclear which specific combination of B vitamins is optimal and which patients are most likely to benefit. One network meta-analysis shows that a combination of folic acid and vitamin B6 lowers the risk of stroke more effectively than B vitamin mixtures that include vitamin B12 (96165). However, this analysis is limited because it didn't account for dosing. Exposure to low, but not high amounts, of vitamin B12 (cyanocobalamin) seems to reduce stroke risk (96150).
• Tardive dyskinesia. It is unclear if oral vitamin B6 prevents tardive dyskinesia in patients taking neuroleptic drugs. Details: A small clinical study in patients taking neuroleptic drugs for schizophrenia shows that taking vitamin B6 (form not specified) 400 mg daily seems to improve Parkinsonian, dystonic, and dyskinetic symptoms when compared with placebo (8558).
• Tourette syndrome. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small, nonblinded clinical study in children aged 4-17 years with untreated Tourette syndrome or with chronic tic disorder and associated symptoms of anxiety shows that taking a liquid nutritional supplement providing vitamin B6 2.8 mg and L-theanine 200 mg daily for 2 months improves scores on the Yale Global Tic Severity Scale, but does not reduce anxiety, when compared with patients receiving psychoeducation (108555). This study may have been inadequately powered to detect a difference between groups.
• Vincristine-induced neuropathy. Oral vitamin B6 has only been evaluated in combination with pyridostigmine; its effect when used alone is unclear. Details: A small clinical study in children ages 11 months to 13 years with neuropathy due to vincristine treatment for acute lymphoblastic leukemia, shows that taking vitamin B6 150 mg/m2 and pyridostigmine 3 mg/kg twice daily for 3 months is associated with reduced severity of sensory and motor neuropathy when compared with baseline (104928). The validity of this finding is limited by the lack of a control group. More evidence is needed to rate vitamin B6 for these uses.

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EFFECTIVE

• Vitamin C deficiency. Oral or intramuscular vitamin C is effective for preventing or treating vitamin C deficiency. Details: Administering vitamin C orally or intramuscularly prevents and treats vitamin C deficiency, including scurvy. Vitamin C administration can reverse complications of scurvy within 2 days to 3 weeks (4844). In newborns with transient tyrosinemia due to vitamin C deficiency, oral or intramuscular vitamin C can correct this condition (15).

POSSIBLY EFFECTIVE

• Anemia of chronic disease. Oral vitamin C seems to improve markers of anemia in patients on hemodialysis. Details: Meta-analyses of clinical research in hemodialysis patients with anemia shows that treatment with vitamin C 200-300 mg three times weekly for 3-6 months increases hemoglobin levels by approximately 0.9 grams/dL, increases transferrin saturation by about 8%, and decreases the required recombinant human erythropoietin dose by 17 U/kg weekly when compared with standard care (83447,83475).
• Atrial fibrillation. Oral and intravenous vitamin C seems to help prevent atrial fibrillation after cardiac surgeries. Details: Meta-analyses of clinical research show that taking vitamin C prior to and after cardiac surgery reduces the risk of postoperative atrial fibrillation by 27% to 53%. Most studies administered vitamin C at doses of 1-2 grams orally daily for 1-3 days prior to cardiac surgery, followed by 1-2 grams in two divided doses daily for 4-5 days after cardiac surgery. Some studies provided vitamin C intravenously at similar doses, but oral vitamin C seems to be more effective (91233,96703,96705). Despite these findings, a meta-analysis of clinical research conducted only in the U.S. does not support the benefit of vitamin C for reducing postoperative atrial fibrillation (96703). These differences may be related to lifestyle factors such as nutrition, as well as differences in hospital treatments. Vitamin C has also been studied in combination with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with evidence of benefit (90701).
• Bowel preparation. Powdered vitamin C is approved for use as part of a polyethylene glycol-based bowel preparation for colonoscopy. Details: Clinical research shows that treatment with 2 liters of oral solution containing polyethylene glycol (PEG) plus vitamin C achieves a similar quality of bowel cleansing as treatment with 4 liters of PEG when administered on the evening prior to colonoscopy or when administered in a split-dose regimen. Patients given 2 liters of PEG plus vitamin C solution also have better adherence and experience fewer adverse events, such as nausea, vomiting, or abdominal bloating, compared to patients treated with 4 liters of PEG solution without vitamin C (90413,90415,90420,90424,90428). This treatment also appears to be effective and tolerable in elderly patients aged 60-79 years, including those with poor bowel habits and a high number of comorbidities (108085). Other clinical research in older adults undergoing bowel preparation for colonoscopy also shows that taking 1 liter of PEG plus vitamin C (CleanViewAL, Taejoon Pharm) results in similar quality of bowel cleansing overall and per segment with similar tolerability and adverse effects as sodium picosulfate 170 mL plus magnesium citrate or oral sulfate solution alone (111297,112476). The most common PEG plus vitamin C preparation used in clinical research is MoviPrep (Norgine BV), which contains macrogol 3350 100 grams, sodium sulfate 7.5 grams, sodium chloride 2.7 grams, potassium chloride 1 gram, vitamin C 4.7 grams, and sodium ascorbate 5.9 grams per liter of solution (90413,90415,90424). In the U.S., MoviPrep is approved by the Food and Drug Administration (FDA) for bowel preparation prior to a colonoscopy.
• Cataracts. Dietary and supplemental intake of vitamin C may reduce the risk of developing cataracts. Details: Population research suggests that people with the highest total intake of vitamin C have about a 19% reduced risk of developing cataracts when compared with those with the lowest total intake, with the most benefit observed for nuclear cataracts (96711). Additionally, another observational study shows that higher supplemental intake of vitamin C over 10 years is associated with a 60% reduction in the incidence of nuclear and cortical cataracts (4208). Other population research suggests that individuals with the highest blood levels of vitamin C have a 33% lower odds of developing age-related cataract, but any benefit is limited to Asian populations (90944). An umbrella review of meta-analyses also shows that dietary intake of vitamin C is associated with a 27% lower odds of cataract development (112095). However, a prospective clinical study shows that a combination of vitamin C, vitamin E, and beta-carotene does not prevent age-related loss of vision from cataracts in well-nourished people with an average supplementation duration of 6.3 years (7304).
• Common cold. Oral high-dose vitamin C might modestly shorten and reduce cold symptoms; however, taking vitamin C prophylactically does not seem to prevent the development of a cold. Details: There is substantial controversy about the effectiveness of vitamin C for treating the common cold (1969,1989,7100,9835,9836). The majority of evidence shows that taking high doses of vitamin C orally might decrease the duration of cold symptoms by 1-1.5 days in some patients (1966,1967,1968,1987,6458,7102,9832,83487). However, other studies have found no effect with doses up to 3 grams daily (9833). A meta-analysis of clinical research in healthy children and adults shows that taking vitamin C 1-4 grams daily for one week to 5 months reduces cold severity by 13%, limits absences from daily activities, and improves the duration of severe symptoms, but does not reduce the duration of mild symptoms, when compared with placebo (113665). Vitamin C has also been investigated for preventing the common cold. A meta-analysis of clinical research suggests that vitamin C supplementation decreases the incidence of cold in individuals exposed to physical stress, but not in the general population (83487). Other research suggests vitamin C may be more effective for treating cold symptoms in children than in adults. Also, there may be a dose-dependent response; doses of at least 2 grams daily seem to work better than 1 gram doses (9834). Taking vitamin C supplements prophylactically does not decrease the risk of catching a cold (1966,1967,1968,1987,3042,6458,7101,9832). Dietary intake of vitamin C also does not seem to affect the risk of getting a cold (10780).
• Complex regional pain syndrome. Most research shows that taking oral vitamin C after a wrist or distal radius fracture or after orthopedic surgery seems to reduce the risk of developing complex regional pain. Details: Although some research has found no benefit in patients with distal radius (i.e. wrist) fractures (90411,96702), most clinical research shows that taking vitamin C 500 mg daily, and possibly doses of up to 1500 mg daily, for 45-50 days beginning immediately after fracture can reduce the risk of developing complex regional pain syndrome (2045,16302,96700,96706). Reasons for discrepancies are unclear but might relate to differences in diagnostic criteria for complex regional pain syndrome (96702). Research in patients undergoing orthopedic surgery has also shown benefit with the use of vitamin C for the prevention of complex regional pain syndrome (90422,108076,108087). One meta-analysis of clinical research in patients undergoing wrist, foot, or ankle surgery shows that taking vitamin C 500-1000 mg for 42-50 days following surgery reduces the rate of complex regional pain syndrome, and may improve pain following ankle or foot surgery, when compared with placebo (108076). The validity of these findings is limited by the high heterogeneity of included trials. Another meta-analysis of clinical research in patients undergoing orthopedic surgery (i.e. wrist, knee, ankle, foot, lumbar, rotator cuff) suggests that oral and intravenous vitamin C may have similar effectiveness; however, this evidence is low quality (108087).
• Exercise-induced respiratory infections. High-dose oral vitamin C seems to reduce the risk of respiratory infections associated with strenuous exercise. Details: Some preliminary clinical research suggests that prophylactic use of vitamin C in doses of 600 mg to 1 gram daily for 3-8 weeks before heavy physical exercise, such as a marathon, might prevent upper respiratory infections that sometimes follow heavy exercise (9831,83370). More recently, high doses of vitamin C have been studied. A large clinical study in army recruits undergoing basic military training shows that taking vitamin C 6 grams daily for one month reduces the odds of getting a cold by 20% when compared with placebo (102975).
• Hypercholesterolemia. Oral vitamin C seems to reduce lipid levels in patients with hypercholesterolemia. Details: A meta-analysis of clinical research in patients with hypercholesterolemia shows that taking vitamin C 500 mg daily for at least 4 weeks reduces low-density lipoprotein (LDL) cholesterol by about 8 mg/dL and reduces triglycerides by about 20 mg/dL when compared with control (83445).
• Hypertension. Oral vitamin C seems to modestly reduce blood pressure in patients with hypertension, but some evidence is conflicting. Details: Vitamin C seems to modestly reduce systolic blood pressure (SBP), without meaningful effects on diastolic blood pressure (DBP) (2044,9822,13162,83483,102974). A meta-analysis of 13 clinical trials in patients with hypertension, with or without other comorbidities, shows that taking a median dose of vitamin C 500 mg daily for 8 weeks reduces SBP but not DBP by about 5 mmHg. Some of the studies used vitamin C in combination with other supplements, such as vitamin E and magnesium. When studies assessing vitamin C alone were analyzed, the magnitude of reduction in SBP decreased (83483). A newer meta-analysis of small clinical studies in patients with essential hypertension shows that taking vitamin C 200 mg or more daily reduces SBP by about 4 mmHg and DBP by about 2 mmHg (102974). However, this newer analysis omitted numerous relevant studies and included studies with normotensive patients and those without an adequate control, limiting the validity of its findings. In contrast, a network meta-analysis of small, low-quality clinical studies comparing five different vitamins in adults with essential hypertension shows that vitamin C does not reduce SBP, DBP, mean 24-hour SBP, mean 24-hour DBP, or heart rate when compared with placebo and when indirectly compared with vitamin B2, vitamin D, vitamin E, and folic acid. However, the included studies were of low quality and high heterogeneity, particularly in dosing, limiting the validity of the results (113668).
• Laser skin resurfacing. Topical vitamin C seems to reduce erythema occurring after cosmetic laser skin resurfacing procedures intended to reduce scars and wrinkles. Details: There is some evidence that an aqueous formulation of topical vitamin C can decrease the degree and duration of erythema following cutaneous carbon dioxide laser resurfacing for scar and wrinkle removal (1959).
• Lead toxicity. Dietary vitamin C seems to lower concentrations of lead in the blood. Details: Observational research has found that consuming more vitamin C from dietary sources is associated with lower blood concentrations of lead. People who consumed at least 340 mg of vitamin C daily as part of the diet had lower blood lead levels than those who consumed less than 100 mg vitamin C daily (3097,3098,3099).
• Nitrate tolerance. Oral vitamin C might prevent nitrate tolerance in some patients. Details: Small clinical studies show that taking vitamin C orally seems to prevent the development of nitrate tolerance in patients taking sublingual nitroglycerin. There is some evidence that short-term vitamin C supplementation can prevent tolerance to the vasodilatory effects of nitrates (1441,1961).
• Postoperative pain. Oral or intravenous vitamin C might prevent acute postoperative pain following certain surgeries. It is unclear if vitamin C reduces chronic postoperative pain. Details: A meta-analysis of 7 small clinical studies in adults undergoing elective surgery shows that receiving perioperative vitamin C, either as 1 gram orally, 2-3 grams intravenously, or 50 mg/kg intravenously, modestly reduces acute pain and opioid requirements for up to 24 hours when compared with control (105457). Most surgeries were laparoscopic and included cholecystectomy, colectomy, hysterectomy; two non-laparoscopic surgeries included uvulopalatopharyngoplasty with tonsillectomy and major abdominal surgery (90418,99840,105457). A meta-analysis of clinical trials in adults undergoing noncardiac surgery (i.e., orthopedic, abdominal, gynecologic, kidney transplantation) shows that administering perioperative vitamin C, either orally or intravenously, reduces postoperative intravenous morphine requirements at 2, 24, and 48 hours after surgery and improves pain scores at 2, 6, and 24 hours after surgery when compared with placebo. The dose of vitamin C did not appear to impact outcomes. However, when only laparoscopic surgeries are included, perioperative vitamin C does not improve pain or morphine use when compared with placebo (108087). A moderate-sized clinical study in adults undergoing transurethral resection of a bladder tumor under general anesthesia shows that administering intravenous vitamin C 1 gram after induction of anesthesia reduces the incidence and severity of catheter-related bladder discomfort immediately after surgery and at 1 and 2 hours postoperatively, but not 6 hours, when compared with placebo. However, vitamin C does not reduce postoperative pain scores or analgesic requirements when compared with placebo (111645). For dental surgery, a small observational study in adults undergoing surgery for wisdom tooth extraction shows that taking vitamin C 500 mg three times daily for 7 days in addition to standard treatment reduces pain 24, 48, and 72 hours after surgery when compared with control (113664). Further research is needed to determine the effects of vitamin C for acute postoperative pain. Vitamin C has also been evaluated for reducing chronic pain after surgery. Clinical research in patients undergoing surgery for foot or ankle trauma shows that taking vitamin C 500 mg orally twice daily postoperatively for 6 weeks reduces pain scores when compared with placebo at 2 weeks and 6 weeks. The mean total amount of diclofenac used for pain relief over the 6-week period is also reduced, from 5.7 grams with placebo to 3.4 grams with vitamin C (102131).
• Wrinkled skin. Topical vitamin C might reduce the appearance of existing wrinkles. Details: Topical preparations containing vitamin C seem to improve the appearance of wrinkled skin. Some evidence shows that vitamin C 3% applied for 12 weeks might reduce facial wrinkles (14008). A small clinical study shows that applying a dissolving microneedle patch containing vitamin C 5.6% every 4 days for 12 weeks to crow's feet on one side of the face reduces wrinkles when compared to control treatment applied on the other side of the face (98780). Other clinical research in females aged 30-60 years shows that applying an oil-soluble cream containing the vitamin C derivative tetra-isopalmitoyl ascorbic acid 1%, 2%, or 3% to the periorbital area twice daily for 8 weeks reduces visual wrinkle grading when compared with placebo. A dose analysis shows greater improvements in wrinkle parameters, average wrinkle depth, and mean depth with the lower concentration, while greater improvements in maximum roughness and maximum depth are observed with the higher concentration (108072). This study only included individuals defined as having Fitzpatrick skin type III or IV; it effects on other skin types is unclear. Preparations containing vitamin C in combination with other ingredients have also been investigated. A small low-quality trial in females with moderately photodamaged and hyperpigmented facial skin shows that applying a moisturizer with vitamin C 30%, vitamin E, and coenzyme Q10 once daily in the morning, along with applying retinol 0.5% once daily or once every other day for 12 weeks, seems to improve skin tone, photodamage, and wrinkles when compared to baseline (99085). In another small trial, a topical preparation containing vitamin C 10% as L-ascorbic acid along with acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (Cellex-C High Potency Serum) applied to photo-aged facial skin for 3 months improves fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone when compared with placebo (6155). It is unclear if the beneficial effects of these products are due to vitamin C, other ingredients, or the combination.

POSSIBLY INEFFECTIVE

• Acute bronchitis. Oral vitamin C doesn't seem to improve symptoms of acute bronchitis. Details: A clinical study in adults with acute bronchitis shows that taking vitamin C orally 500 mg on day 1, then 250 mg on days 2 through 5 (similar to an azithromycin regimen) doesn't seem to have any effect on quality of life or bronchitis duration when compared with azithromycin (9827).
• Asthma. Oral vitamin C doesn't seem to prevent asthma or improve lung function. Details: Although some observational research has found that some patients with asthma might have lower serum vitamin C levels (5873), other observational research found that increased dietary vitamin C intake is not associated with a reduced risk of asthma or improved lung function (15006,34567). In addition, clinical research shows that supplemental intake of vitamin C does not reduce asthma symptoms, improve lung function, or reduce the use of inhaled steroids in asthma patients (90409).
• Atherosclerosis. Oral vitamin C does not seem to reduce the progression of atherosclerosis. Details: A clinical study shows that taking a specific combination product containing slow-release vitamin C 250 mg and vitamin E 136 IU (CellaVie, Ferrosan A/S) twice daily modestly slows the 3-year progression of atherosclerosis of the carotid artery in males, but not females. This result persisted at a 6-year follow-up of this study (1918,10473). However, when this form of vitamin C is used alone, it does not slow the 3-year progression of atherosclerosis of the carotid artery (1918).
• Bladder cancer. Oral vitamin C does not reduce the risk of bladder cancer or mortality from bladder cancer. Details: Epidemiological research has found that supplemental vitamin C intake is not associated with mortality rate in patients with bladder cancer (9839). A secondary analysis of a large clinical trial, the Physicians' Health Study II, in healthy men aged at least 50 years also shows that taking vitamin C 500 mg daily alone or with vitamin E 400 IU daily for up to 10 years does not reduce the risk of developing bladder cancer or bladder cancer-related deaths when compared with placebo (90097).
• Cardiovascular disease (CVD). Oral vitamin C does not seem to be beneficial for either primary or secondary CVD prevention. Details: Vitamin C does not seem to be beneficial for primary prevention of CVD. Some population research has found that higher supplemental vitamin C or dietary vitamin C has been associated with a reduced risk of developing CVD (10358,14108,109779), while other observational research has found no benefit (34566,10358,14108). However, meta-analyses of clinical research in healthy patients show that vitamin C supplementation does not prevent CVD or coronary heart disease when compared with control (97308,104025). In 2004, the American Heart Association stated that current evidence does not justify use of antioxidants such as vitamin C for reducing the risk of CVD (12142). Evidence is also negative for secondary prevention in people with coronary heart disease. Population studies have found that higher serum vitamin C was associated with no effect or decreased CVD mortality from CVD (3910,5878). A meta-analysis of two large clinical trials shows that vitamin C supplementation does not reduce CVD events or CVD mortality when compared with control (97308).
• Colorectal cancer. Oral vitamin C does not seem to prevent colorectal cancer. Details: Population research has found that dietary vitamin C intake is not associated with a reduced risk of developing colon cancer. When total vitamin C intake from food and supplements is considered, there is a modest association (34600). However, most clinical trials show that supplemental vitamin C, alone or along with other antioxidants, does not reduce the risk of colorectal cancer development, colorectal cancer or adenoma recurrence, or colorectal cancer-related mortality (34580,34581,34594,90097,90089,92903).
• Fetal and premature infant mortality. Oral vitamin C does not seem to prevent neonatal death. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of neonatal death (83472,96707).
• Fractures. Oral vitamin C does not seem to improve fracture healing. Details: Clinical research shows that taking vitamin C 500 mg daily for 50 days following an acute distal radial fracture does not improve physical function, symptoms, or healing rates when compared with placebo (90411).
• Helicobacter pylori. Oral vitamin C does not seem to improve eradication of H. pylori. Details: Most clinical research shows that treatment with vitamin C, alone or in combination with vitamin E, does not improve the eradication rate of H. pylori when taken with a standard eradication regimen when compared with the eradication regimen alone (83476,90094).
• Hereditary motor and sensory neuropathy. Oral vitamin C does not seem to improve neuropathy in these patients. Details: In a meta-analysis of five studies in patients with Charcot-Marie-Tooth disease type 1A, taking vitamin C 1-4 grams orally daily for 1 year did not improve neuropathy when compared with placebo (99084). Continuing vitamin C 4 grams daily for 2 years also does not improve neuropathy in these patients (90419).
• Interferon-related retinopathy. Oral vitamin C does not seem to improve retinopathy associated with interferon therapy. Details: A small clinical study in patients with chronic hepatitis C receiving interferon therapy shows that taking vitamin C 600 daily orally does not seem to reduce the risk of retinopathy from interferon therapy when compared with control (10355).
• Leukemia. Oral vitamin C does not seem to reduce the risk of leukemia or mortality from leukemia. Details: A large clinical trial in men aged at least 50 years shows that taking vitamin C 500 mg daily, alone or along with vitamin E 400 IU daily, for up to 10 years does not reduce the risk of developing leukemia or leukemia-related deaths when compared with placebo (90097).
• Low birth weight. Oral vitamin C does not seem to reduce the risk of infants being born with a low birth weight. Details: Meta-analyses of clinical research show that maternal use of oral vitamin C alone or with other supplements does not reduce the risk of giving birth to infants with low birth weight when compared with control (83450,83472).
• Lung cancer. Oral vitamin C does not seem to reduce the risk of lung cancer. Details: Two meta-analyses of clinical research suggest that taking vitamin C, alone or in combination with vitamin E, does not reduce the incidence of lung cancer or lung cancer-related mortality (34528,34632). Also, a clinical study in females shows that taking supplemental vitamin C 500 mg daily, with or without vitamin E and beta carotene, is associated with an INCREASED risk of lung cancer when compared with placebo (34580). However, another large epidemiological cancer screening trial with a mean follow-up of over 12 years suggests that moderate dietary intake of vitamin C around 500 mg daily is protective against lung cancer, but higher doses of vitamin C might increase the risk of lung cancer (112096).
• Melanoma. Oral vitamin C does not seem to reduce the risk of melanoma. Details: Clinical research shows that taking vitamin C 500 mg daily, alone or along with vitamin E 400 IU daily, for up to 10 years does not reduce the risk of developing melanoma or melanoma-related deaths when compared with placebo in men aged at least 50 years (90097).
• Miscarriage. Oral vitamin C does not seem to reduce the risk of miscarriage. Details: A meta-analysis of clinical research shows that taking vitamin C alone or with other supplements does not reduce the risk of miscarriage when compared with control (94820).
• Overall mortality. Oral vitamin C does not reduce overall mortality. Details: Although population research suggests that higher dietary intake and higher plasma vitamin C levels are associated with a reduced risk of mortality from all causes (3910,109779), vitamin C supplementation does not seem to affect overall mortality. Meta-analyses of clinical research show that taking vitamin C supplements does not reduce overall mortality when compared with control (34622,111641). Clinical studies of vitamin C used in combination with vitamin E, beta carotene, and/or selenium and zinc, also show no benefit for overall mortality (9817,14109).
• Pancreatic cancer. Oral vitamin C does not seem to prevent pancreatic cancer. Details: Observational research has found that increased dietary vitamin C intake is associated with up to a 30% reduced risk of pancreatic cancer (99083,99086). However, clinical research shows that supplemental vitamin C 500 mg daily does not reduce the risk of pancreatic cancer in females (34580). Also, taking vitamin C in combination with beta-carotene plus vitamin E does not reduce the risk of pancreatic cancer (12185,34581).
• Pre-eclampsia. Oral vitamin C does not seem to prevent pre-eclampsia. Details: Despite some early positive research in high-risk pregnancies, the majority of meta-analyses and clinical studies show that taking vitamin C alone or with vitamin E or other supplements does not reduce the risk of pre-eclampsia when compared with control. There is even some concern that vitamin C supplementation may increase the risk of gestational hypertension (3236,83450,83472,83474,96707).
• Preterm labor. Oral vitamin C does not seem to prevent preterm labor. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of preterm labor when compared with control (83450,83472,96707).
• Prostate cancer. Oral vitamin C does not seem to prevent prostate cancer. Details: A large-scale clinical study (The SU.VI.MAX study) shows that a combination of vitamin C 120 mg, vitamin E (alpha-tocopherol) 30 mg, beta-carotene 6 mg, selenium 100 mcg, and zinc 20 mg, taken daily for an average of 8 years, does not reduce the risk of prostate cancer overall. However, it might reduce the risk of prostate cancer in those who have normal PSA levels. It does not seem to be beneficial for reducing the risk of prostate cancer in patients with PSA levels above 3 mcg/L (14135). Another large scale study (Physician's Health Study II) shows that taking vitamin C 500 mg daily for an average of 8 years does not significantly reduce the risk of prostate cancer when compared with placebo (16708). Similarly, results from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial seem to show that supplemental or dietary intake of vitamin C does not reduce the risk of prostate cancer when compared to individuals not taking vitamin C (14124).
• Radiation dermatitis. Topical vitamin C does not seem to prevent radiation dermatitis in cancer patients. Details: A small clinical study shows that applying a 10% vitamin C solution does not appear to protect from radiation dermatitis when applied to the scalps of patients treated with radiation for intracranial tumors (789).
• Small for gestational age (SGA). Oral vitamin C does not seem to reduce SGA. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of small for gestational age birth when compared with control (83450,83472).
• Stillbirth. Oral vitamin C does not seem to prevent stillbirth. Details: Meta-analyses of clinical research show that maternal use of vitamin C alone or with other supplements does not reduce the risk of stillbirth when compared with control (83472,96707).

LIKELY INEFFECTIVE

• Coronavirus disease 2019 (COVID-19). Oral vitamin C, even at high doses, does not seem to speed recovery from COVID-19 in non-hospitalized patients. Most studies show that oral or intravenous vitamin C given to patients hospitalized with COVID-19 does not improve organ function or survival, but the evidence is conflicting. It is unclear whether vitamin C is beneficial for long COVID. Details: A clinical study in adult outpatients with confirmed COVID-19 shows that taking oral vitamin C (ascorbic acid) 8000 mg in 2-3 divided doses daily, alone or with zinc gluconate 50 mg daily, for 10 days does not reduce symptom severity when compared with standard care (104450). The study was terminated prior to complete enrollment due to futility and apparent lack of effect from vitamin C and/or zinc supplementation. Limitations of this study include a lack of placebo control and blinding. Additionally, this study has been criticized for methodologic concerns (106624). Another small clinical trial in adult outpatients with confirmed COVID-19 shows that taking vitamin C 1000 mg daily for 14 days does not improve symptoms or quality of life when compared with placebo (109462). Vitamin C has also been evaluated in patients hospitalized with COVID-19. A very large analysis of two multinational clinical studies in critical and non-critical adults hospitalized with COVID-19 shows that administering intravenous vitamin C 50 mg/kg every 6 hours for 96 hours does not improve organ support-free days or survival and has a high probability of futility and worsened outcomes when compared with placebo (113666). Individual prospective and retrospective studies in critically ill patients hospitalized with COVID-19 in various countries have found that administering vitamin C, either enterally as 500-1000 mg daily or intravenously as 8-24 grams daily or 50 mg/kg daily, does not significantly reduce in-hospital or short-term mortality, hospital length of stay, or end-organ failure when compared with control groups receiving standard care alone. Additionally, all but one study found no change in the need for mechanical ventilation (105458,105465,106937,106938,108075,108079,108081). However, a meta-analysis and some small individual studies have found that vitamin C is modestly beneficial for patients hospitalized with COVID-19. A meta-analysis of 10 clinical trials and 9 observational studies in patients hospitalized with COVID-19 shows that receiving oral or intravenous vitamin C daily reduces the odds of in-hospital mortality by 41% when compared with control. When only clinical trials were considered, the odds of in-hospital mortality were decreased by 56%; however, this reduction was only identified in studies using vitamin C 10 grams daily or less. Conversely, supplementation with vitamin C increased the length of intensive care unit (ICU) stay by nearly 2 days and did not impact length of hospital stay or reduce the need for mechanical ventilation, liver injury, or cardiac injury (109955). Additionally, a small study found a small improvement in survival when compared with standard care; however, the overall survival rate in this study was low (108075). Another clinical study in patients hospitalized in Turkey with COVID-19 shows that adding high-dose intravenous sodium ascorbate 50 mg/kg to a treatment regimen of hydroxychloroquine, azithromycin, and zinc may improve recovery time, with 57% and 39% of patients achieving total recovery at day 15 in the vitamin C and control groups, respectively (108071). However, the validity of this trial is limited due to unclear reporting. Additionally, these small studies were likely underpowered to detect differences between the vitamin C and control groups. Vitamin C has also been evaluated in combination with other ingredients in patients with long COVID. Preliminary clinical research in adults with long COVID and persistent fatigue shows that taking a specific combination product containing vitamin C 500 mg and L-arginine 1.66 grams (Bioarginina C, Farmacetici Damor) for 28 days increases 6-minute walk test distance by 10% and reduces self-reported fatigue when compared with placebo (110390). However, it is unclear whether these effects are due to vitamin C, L-arginine, or the combination.
• Sepsis. Intravenous vitamin C, alone or in combination with thiamine and/or hydrocortisone, does not prevent organ failure, reduce intensive care or hospital length of stay, or reduce mortality in sepsis or septic shock. Details: Observational research suggests that patients with septic shock are more likely to have low plasma levels of vitamin C (100317). However, two randomized clinical trials in patients with sepsis show no benefit with intravenous vitamin C, with or without thiamine, for improving organ function and preventing organ failure when compared with control treatment (102130,104027). A clinical study in patients with septic shock shows that administering an intravenous bolus of vitamin C 1000 mg followed by a continuous infusion of 250 mg/hour for 96 hours, starting within 24 hours of vasopressor initiation, does not improve 28-day or intensive care unit (ICU) mortality when compared with placebo. A subgroup analysis shows that the addition of corticosteroids does not affect outcomes in either group (108078). This study may have been inadequately powered to detect a difference between groups. Also, a larger clinical trial in adults with sepsis receiving vasopressor therapy in the ICU shows that intravenous administration of vitamin C 50 mg/kg every 6 hours for up to 4 days increases the risk of death or persistent organ dysfunction at day 28 by 14% to 21% when compared with placebo. There were no differences in mortality at 6 months (109459,111643). Vitamin C has also been frequently studied in patients with sepsis and septic shock in a specific combination regimen (HAT therapy) which includes intravenous vitamin C 1.5-2 grams with hydrocortisone 50 mg every 6 hours and thiamine 200 mg every 12 hours. While some retrospective research has found HAT therapy to be beneficial in sepsis (100315,102980), high quality, prospective clinical research has not confirmed these findings (105447,106620,109956). Several meta-analyses of randomized controlled trials and small clinical studies in patients with sepsis or septic shock show that intravenous vitamin C, either alone, as a component of HAT therapy, or in combination with thiamine, does not reduce short- or long-term mortality, ICU or hospital length of stay, kidney injury, or duration of mechanical ventilation, but modestly improves duration of vasopressor use and procalcitonin clearance, when compared with placebo or standard care. These analyses also show mixed results with respect to improvement in sequential organ failure assessment (SOFA) scores within 72 hours (105447,106620,106935,108073,109460,111298,111300,111301,111642,112479). Most studies included in the analyses administered HAT therapy for 2-10 days and compared it with normal saline control or with hydrocortisone alone (102129,102998,104027,104028,104032,105446). Although some subgroup analyses suggests that intravenous vitamin C alone in patients with sepsis may improve short-term mortality (106620,111298), other meta-analyses have not shown this benefit in subgroup analyses (111300). In addition, meta-analyses have identified significant publication bias (111298,111300). Long-term follow up from a study in patients with sepsis-induced respiratory and/or cardiovascular dysfunction shows that receiving HAT therapy does not improve cognitive, psychological, or functional status after 6 months and, for some domains, HAT therapy was worse when compared with placebo (111299). Studies evaluating intravenous vitamin C, either alone, as a component of HAT therapy, or in combination with thiamine, in mixed critically ill populations have also shown mixed findings. Four meta-analyses of randomized controlled trials and observational studies show that intravenous vitamin C does not have a significant effect on the length of hospital stay, mortality at 1 month, ICU mortality, use of invasive ventilation, use of renal replacement therapy, organ function, or incidence of kidney injury when compared with placebo or standard care. The meta-analyses reach conflicting conclusions on whether intravenous vitamin C reduces the risk of in-hospital mortality, 30-day mortality, and the duration of ICU stay. When only data from low risk-of-bias clinical trials are considered, the effects of intravenous vitamin C on mortality at any point are no longer significant (106933,106934,109957,113663). However, a subgroup analysis in one of these analyses suggests that intravenous vitamin C as monotherapy, or in doses of at least 10 grams daily, may improve overall mortality (106934). Vitamin C also does not appear to benefit complications from sepsis, such as vasoplegic shock. A small clinical study in adults in the ICU with vasoplegic shock mostly secondary to sepsis and requiring moderate vasopressor support shows that administering intravenous vitamin C as sodium ascorbate 1.5 grams every 6 hours for 5 days or until cessation of vasoactive therapy does not reduce the duration of vasopressors, vasopressor dose, hospital or ICU length of stay, or mortality outcomes when compared with placebo (112475).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Atrophic acne scars. It is unclear if applying topical vitamin C after microblading improves atrophic acne scars. Details: A clinical study in adults with mild to severe atrophic acne scarring shows that applying a serum containing vitamin C 17% to the face after a once-monthly home microblade treatment for 4 months improves the appearance of acne scars at month 5 when compared with baseline (108086). Although this study enrolled a control group that used topical insulin in place of vitamin C, no between-group statistical comparisons were conducted, limiting the validity of this study.
• Age-related macular degeneration (AMD). It is unclear if dietary vitamin C or oral vitamin C taken in combination with other ingredients prevents AMD. Details: An umbrella review of meta-analyses shows that increased dietary intake of vitamin C is associated with 21% higher odds of developing AMD (112095). A population study suggests that vitamin C intake is associated with increased odds of developing age-related maculopathy (9823). However, other population studies have found no association between dietary or supplemental vitamin C intake and the risk of developing AMD (14007,14257). When taken in combination with other ingredients, most clinical and population research shows that taking vitamin C 500 mg along with other antioxidants such as vitamin E 400 IU, beta-carotene 15 mg, and/or elemental zinc 80 mg reduces the risk of visual acuity loss by 23% to 27%, progression to advanced AMD at 5 years by 25% to 32%, and AMD overall (7303,7304,11326,14257,90069). The antioxidant plus zinc combination seems to reduce the risk of progression to advanced AMD in these patients more than taking the antioxidants without zinc (7303,90069). More evidence is needed to determine what role, if any, vitamin C intake has on the risk of developing AMD.
• Aging skin. Topical vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in females aged 30-65 years shows that applying a specific liquid (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% to the face nightly for 8 weeks, in addition to regular facial skin products, improves skin color, elasticity, radiance, smoothness, and appearance of wrinkles when compared with regular facial skin products alone (102355).
• Albuminuria. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that taking vitamin C 1250 mg plus vitamin E 680 IU daily for 4 weeks can reduce the excretion of albumin by about 19% when compared with placebo in patients with type 2 diabetes (10434).
• Allergic rhinitis (hay fever). It is unclear if oral vitamin C is beneficial in patients with hay fever. Details: Epidemiological research has found that higher vitamin C plasma levels are not associated with a decreased risk of allergic rhinitis (15200). However, clinical research shows that some forms of vitamin C might help. In one small clinical study, intranasal vitamin C administered three times daily for 2 weeks reduces nasal secretions, nasal blockage, and edema in up to 74% of patients with perennial allergic rhinitis (15201). Another small clinical study in patients with seasonal allergic rhinitis shows that taking a single oral dose of vitamin C 2 grams reduces bronchial responsiveness to histamine at one hour after ingestion (15202). However, in another small study in patients with seasonal allergic rhinitis taking vitamin C orally in doses up to 4 grams daily for 3 days does not appear to suppress cutaneous or nasal response to histamine when compared to placebo (15203).
• Alzheimer disease. It is unclear if dietary vitamin C helps to prevent this condition. Details: Most epidemiological research has found that dietary intake of vitamin C is associated with a 17% reduced risk of developing Alzheimer disease (4636,9824,10131,13165,90082).
• Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if oral vitamin C helps to prevent ALS. Details: Observational research has found that increased dietary or supplemental intake of vitamin C is not associated with risk of developing ALS (90412).
• Anthracycline cardiotoxicity. Although there is interest in using oral vitamin C for anthracycline-induced cardiac toxicity, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Aspirin-associated gastric damage. It is unclear if oral vitamin C helps to prevent gastric damage caused by aspirin. Details: Some clinical research shows that vitamin C 480 mg might prevent gastric damage associated with taking aspirin 400 mg by decreasing blood loss and preventing decreased gastric blood flow (10357). However, a small clinical study in healthy patients shows that taking vitamin C 500 mg as ascorbic acid with aspirin 600 mg actually increases gastrointestinal permeability to a greater extent than either ingredient taken alone (98781).
• Athletic performance. It is unclear if oral vitamin C improves athletic performance. Details: Although some small preliminary clinical studies suggest that vitamin C might improve certain biomarkers during exercise (82922), a meta-analysis of small clinical trials in older and younger adults shows that taking vitamin C 500-1000 mg daily, with or without vitamin E, does not improve endurance, lean mass, or muscle strength when compared with placebo (102973). A more recent, small clinical study in recreationally trained males shows that taking vitamin C 1000 mg and vitamin E (as alpha-tocopherol) 235 mg daily for 10 weeks while participating in a resistance training program does not improve measures of muscle strength when compared with placebo (109959).
• Atopic disease. It is unclear if dietary vitamin C helps to prevent atopic disease. Details: Population research has found that higher intake of vitamin C is not associated with a reduced risk of eczema, wheeze, IgE-mediated food allergy, or allergic sensitization (90098).
• Attention deficit-hyperactivity disorder (ADHD). Small clinical studies suggest that high-dose oral vitamin C may not improve symptoms in patients with ADHD. Details: Some research suggests that taking megadose vitamins, including vitamin C, does not improve ADHD symptoms (9957,9958,9959). However, other preliminary clinical research shows that taking 25 mg of vitamin C in combination with flaxseed oil providing alpha-linolenic acid 200 mg twice daily might improve measures of attention, impulsivity, restlessness, and self-control in children with ADHD when compared with baseline (14443). It is not clear if these effects are due to vitamin C, flaxseed oil, or the combination.
• Autism spectrum disorder. It is unclear if oral vitamin C is beneficial in patients with autism spectrum disorder. Details: One small clinical study shows that taking vitamin C 8 grams per 70 kg daily for 10 weeks modestly reduces autism symptom severity in school children when compared with placebo (83604).
• Bleeding. It is unclear if intravenous vitamin C can reduce bleeding after total abdominal hysterectomy. Details: A small clinical study in patients undergoing total abdominal hysterectomy shows that administration of intravenous vitamin C 1 gram the night before surgery and 1 gram during surgery reduces postoperative hemorrhage volume by around 40 mL when compared with placebo (109465).
• Brain tumor. It is unclear if oral vitamin C helps to prevent brain tumors. Details: Population research has found that vitamin C intake is associated with a 14% reduced risk of glioma. This risk reduction was more prevalent in America compared to other geographic locations (98782).
• Breast cancer. It is unclear if oral vitamin C helps to prevent breast cancer, its recurrence, or breast cancer-related mortality. Details: Some epidemiological research has found that dietary vitamin C is associated with a reduced risk of breast cancer (1444,10823,10824). However, other epidemiological research has found no association with dietary or supplemental vitamin C (10825,10826,108080). One cohort study found no association between breast cancer risk and total, dietary, or supplemental vitamin C, regardless of dose, treatment duration, or formulation (single ingredient or combination product). Additionally, hormone and menopausal status did not appear to impact risk. Vitamin C intake might be associated with a reduced risk in individuals with a family history of breast cancer in first-degree relatives (108080). In patients with breast cancer, supplemental or dietary intake of vitamin C might be associated with a reduced risk of mortality. A meta-analysis of results from population research shows that vitamin C supplementation following breast cancer diagnosis is associated with a 15% lower risk of breast cancer-related mortality when compared with no supplementation (90416). A large, observational study in patients with breast cancer undergoing radiation therapy has found that vitamin C supplementation does not reduce the risk of breast cancer recurrence over a period of 5 years when compared with no supplementation. Although the vitamin C group had notably less aggressive tumor types, recurrence-free survival was similar in both vitamin C and control groups (108082). The validity of these findings is limited due to unknown doses of vitamin C and the inclusion of various breast cancer subtypes.
• Burns. Small studies suggest that intravenous vitamin C may modestly improve symptoms in patients with severe burns. Details: A small clinical study in patients with severe burns shows that administering vitamin C intravenously (IV) 66 mg/kg hourly over 24 hours, as part of fluid resuscitation using lactated ringer solution, reduces wound edema and the volume of fluid needed when compared with fluid resuscitation alone (83145). A retrospective review of adults hospitalized with severe burns has found that those who receive a continuous IV infusion of at least 10 grams of vitamin C within 2 days of admission have an in-hospital mortality rate of 46%, compared with 58% for those who do not receive vitamin C (102128).
• Cancer. It is unclear if oral or intravenous vitamin C helps to prevent cancer or cancer-related mortality. Details: Some population research has found that DIETARY intake of vitamin C is linked with a lower risk of cancer and cancer-related mortality (3910,5878,10819,109779). However, clinical research shows that taking vitamin C SUPPLEMENTS does not reduce the risk for cancer (10819,14109,34580,90097). In people with cancer, although some clinical research has shown that taking high-dose vitamin C supplements can improve survival rates (9809,96704), other clinical research has not shown this benefit (4842,4843). In 2003, the US Food and Drug Administration (FDA) determined that it would allow a qualified health claim stating that some scientific evidence suggests that antioxidant vitamins, such as vitamin C, may reduce the risk of certain forms of cancer. However, the FDA has determined that there is little scientific evidence supporting this claim (102334). Preliminary clinical research has also evaluated vitamin C supplements in patients with cancer. High-dose oral vitamin C, 10 grams daily, in patients with advanced cancer does not seem to improve survival or decrease disease progression (4842,4843,106617). However, preliminary clinical research suggests high doses of vitamin C, given intravenously, might have a beneficial effect on some outcomes, including survival rate in some patients with cancer (9809,96704,106617). However, there is no benefit to other patients studied in the case reports and this has not been tested in well-designed clinical trials (9809,96704).
• Cardiac arrest. It is unclear if intravenous vitamin C is beneficial for patients after cardiac arrest. Details: A small clinical study conducted in Slovenia in adult survivors of out-of-hospital cardiac arrest shows that administering intravenous vitamin C 1.5 grams every 12 hours for 8 consecutive doses, with the first dose administered within 6 hours of resuscitation, in addition to standard care protects against arrhythmias and reduces the length of intensive care unit (ICU) stay when compared with placebo and standard care. However, intravenous vitamin C does not appear to protect against neurological or myocardial injury, reduce the need for mechanical ventilation, reduce the duration of hospital stay, or increase survival when compared with placebo (113667).
• Carpal tunnel syndrome. Vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in adults with mild to moderate carpal tunnel syndrome shows that taking a combination product containing vitamins C, E, B1, B2, B6, and B12, alpha-lipoic acid, acetyl-L-carnitine, phosphatidylserine, and turmeric twice daily for 60 days reduces symptom severity and pain but does not improve measures of hand and wrist function when compared with control (111702). The validity of these effects is limited by a lack of blinding. The study may also be inadequately powered to detect a difference between groups. Additionally, it is unclear if the effects are due to vitamin C, other ingredients, or the combination.
• Cervical cancer. It is unclear if oral vitamin C helps to prevent cervical cancer. Details: Observational research has found that higher vitamin C intake is associated with a 33% to 42% reduced odds of cervical neoplasm. Increasing vitamin C intake by 50 mg daily is associated with an 8% reduced odds of cervical neoplasm (34609,98771).
• Chronic fatigue syndrome (CFS). Although there is interest in using oral vitamin C for CFS, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Colistin-induced nephrotoxicity. It is unclear if intravenous vitamin C helps to prevent nephrotoxicity from colistin. Details: A small clinical study shows that intravenous administration of vitamin C 2 grams every 12 hours along with colistin for around 9-10 days does not prevent nephrotoxicity when compared with colistin therapy alone (99839). However, this study was limited by a lack of statistical power to detect differences between the study groups.
• Contrast induced nephropathy. It is unclear if oral vitamin C helps to prevent contrast-induced nephropathy (CIN). Details: Some clinical research shows that taking vitamin C before and after coronary angiography reduces the risk of developing CIN by 33% to 55% when compared with placebo in patients with renal dysfunction (12234,90421). However, other clinical evidence published since 2012 suggests that vitamin C given orally and/or intravenously before and after angiography does not reduce the risk of CIN compared with control in high-risk patients with chronic renal insufficiency or diabetes (91232,91236,90410,90425). Reasons for the discrepancies are not entirely clear. However, it is possible that the lack of significant benefit from vitamin C in the latter studies results from the fact that incidences of CIN have become less common than in the past due to avoidance of dehydration, use of smaller catheters, and use of contrast agents with reduced nephrotoxicity (90429).
• Coronary artery bypass graft (CABG) surgery. It is unclear if intravenous vitamin C helps to improve patient outcomes after CABG surgery. Details: A small clinical study shows that giving vitamin C 5 grams intravenously (IV) before anesthesia induction and 5 grams in the cardioplegia solution used during surgery shortens the length of stay in the intensive care unit (ICU) by about 8 hours (102127). However, some limited research suggests that IV vitamin C does not resolve cardiac surgery complications. A small clinical study in patients with vasoplegia after receiving CABG and other cardiac surgeries shows that receiving IV vitamin C 1.5 grams every 6 hours after being admitted to the ICU does not improve vasoplegia when compared with control (102981).
• Delirium. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Observational research in adults with septic shock has found that receiving intravenous thiamine 400 mg daily with vitamin C 6 grams daily, both in divided doses, is not associated with reduced delirium when compared with control (103001).
• Dental plaque. It is unclear if vitamin C in a chewing gum helps to reduce dental plaque formation. Details: A small clinical study in patients with calculus shows that chewing 10 pieces of gum, each containing 60 mg of vitamin C, daily for 3 months reduces the formation of dental calculus, visible plaque, and the number of bleeding sites when compared not chewing gum (83303). The validity of this finding is limited by a lack of placebo group.
• Depression. It is unclear if oral vitamin C is beneficial for the treatment or prevention of depression. Details: A small clinical study in children and adolescents shows that taking vitamin C 500 mg orally twice daily in combination with fluoxetine 10-20 mg daily for 6 months reduces most symptoms of major depressive disorder when compared with taking fluoxetine alone (90404). However, a small clinical study in adults shows that taking vitamin C up to 1000 mg daily for 2 months does not improve the response rate or decrease symptoms of depression in adults also taking citalopram when compared with citalopram alone (96708). Reasons for these conflicting results may relate to the age of the patients, study duration, or differences in antidepressant medication being taken. One clinical guideline also provisionally recommends against the use of oral vitamin C to treat patients with depression based on low-quality evidence (110318). Some research has also evaluated vitamin C intake for the prevention of depression. A secondary analysis of pre- and peri-menopausal adults enrolled in the Study of Women's Health Across the Nation (SWAN) program suggests that vitamin C intake is inversely associated with depressive symptoms. This association persisted regardless of age, race, physical activity, body mass index, antidepressant use or menopausal status (108083). The validity of these findings is limited due to the secondary nature of this study; additionally, follow-up time is unclear.
• Diabetes. It is unclear if oral vitamin C prevents diabetes. Some low-quality research suggests that vitamin C might improve glycemic control in patients with diabetes. Details: Population research has not found a link between dietary vitamin C and the risk of developing type 2 diabetes (14004). However, low certainty clinical research has found some benefit of taking vitamin C supplements for glycemic control. Two meta-analyses of several small, heterogeneous clinical studies in patients with type 2 diabetes show that taking vitamin C 200-3000 mg daily for 2-48 weeks reduces fasting blood glucose by approximately 11 mg/dL (112478) and glycated hemoglobin (HbA1c) by an average of 0.5% when compared with placebo, standard treatment, or no treatment (105461,112478). Subgroup analyses suggest that durations of supplementation longer than 12 weeks show greater glycemic benefit, and although one meta-analysis suggests there is no dose-response relationship (105461), another meta-analysis suggests that doses of vitamin C 1000 mg and higher are most beneficial for improving glycemic indices (112478). Some research has evaluated the effects of vitamin C supplementation on the lipid profile in patients with diabetes, with mixed findings. One meta-analysis of 17 small clinical studies shows that taking vitamin C 200-3000 mg daily for 2 to 48 weeks improves levels of triglycerides and total cholesterol, but not low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol. Subgroup analysis suggests that study durations of at least 12 weeks show greater benefit (106621). However, two other meta-analyses in patients with diabetes, one of 16 small heterogenous clinical studies and one of 11 small clinical studies, show no clinically important improvement in lipid levels after vitamin C supplementation (105461,105464).
• Dry mouth. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical trial in patients receiving radiotherapy for head and neck cancer shows that taking vitamin E 100 IU and vitamin C 500 mg twice daily for an average of 3 months improves dry mouth when compared to baseline (99080). The validity of these results is limited by the lack of comparison with a control group.
• Endometrial cancer. Increased dietary vitamin C has been linked to reduced risk of endometrial cancer. Details: Population research has found that intake of vitamin C from dietary sources is associated with a slightly decreased risk of endometrial cancer when compared with control. However, this benefit is not observed when results from a prospective cohort study are assessed (34578).
• Endometriosis. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical study in patients with endometriosis and pelvic pain shows that taking vitamin C 1000 mg and vitamin E 800 IU daily for 8 weeks improves dysmenorrhea, dyspareunia, and chronic pelvic pain scores when compared with placebo. Vitamin C and vitamin E supplementation also reduces some biochemical markers of oxidative stress when compared with placebo (106622).
• Endoscopy-associated adverse effects. It is unclear if a topical vitamin C spray reduces mucosal irritation in patients undergoing Lugol chromoendoscopy. Details: A small clinical trial in patients receiving a Lugol chromoendoscopy shows that spraying a vitamin C 2% solution after the application of the Lugol iodine 2% solution reduces the severity of mucosal irritation, heartburn, and pain when compared with using a normal saline spray after the Lugol iodine 2% solution (104030).
• Esophageal cancer. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Population research has found that higher dietary intake of vitamin C is associated with reduced odds of esophageal adenocarcinoma. A 50 gram increase in dietary vitamin C intake is associated with a 13% reduced odds of esophageal cancer (34551,98770). However, a meta-analysis of clinical research shows that taking a vitamin C supplement in combination with beta-carotene and vitamin E does not reduce the risk of esophageal cancer (34581).
• Exercise-induced asthma. Small clinical studies suggest that oral vitamin C may modestly improve symptoms in patients with exercise-induced asthma. Details: A meta-analysis of the available clinical research shows that vitamin C supplementation might reduce exercise-induced breathlessness when compared with placebo or control. However, the available research is of poor quality, and no clear conclusions can be drawn regarding its benefits for exercise-induced asthma (90409).
• Exercise-induced muscle damage. It is unclear if oral vitamin C is beneficial in exercise-induced muscle damage. Details: A small clinical study in healthy females shows that taking vitamin C 1000 mg before moderate intensity cycling does not prevent muscle damage when compared with placebo (99837). Another small clinical study in endurance-trained runners shows that taking vitamin C 1000 mg and vitamin E (as alpha-tocopherol) 235 mg 2 hours prior to an exercise protocol does not reduce delayed onset muscle soreness or improve other markers of exercise-induced muscle damage when compared with placebo (109961).
• Gallbladder disease. It is unclear if oral vitamin C reduces the risk of gallbladder disease. Details: Cross-sectional epidemiological evidence has found that vitamin C supplementation and increased vitamin C serum levels are associated with a decreased risk of developing gallbladder disease in females, but not males (5877).
• Gastric cancer. It is unclear if dietary or supplemental vitamin C reduces the risk of gastric cancer. Details: Most population research has not found an association between DIETARY intake of vitamin C and gastric cancer risk (9194,10822,10819,90083). Also, clinical research shows that taking vitamin C supplements in combination with other antioxidants does not reduce the risk of gastric cancer or precancerous gastric lesions (14447,34581,90085). However, some research suggests that it might be associated with a reduced risk for specific forms of gastric cancer (9838,90083). One clinical study shows that taking vitamin C orally 500 mg daily for 6 months after eradication of Helicobacter pylori infection decreases the incidence of precancerous changes in stomach tissue when compared with no treatment (10359). Also, other clinical research shows that taking vitamin C orally 1 gram daily helps promote the regression of precancerous gastric lesions in people at high risk for gastric cancer (2579). In 2009, the US Food and Drug Administration (FDA) determined that it would allow a qualified health claim stating that vitamin C supplements may reduce the risk of gastric cancer. However, the FDA has concluded that it is highly uncertain that vitamin C supplements actually reduce the risk of gastric cancer (102332).
• Gastritis. There is limited evidence on the oral use of vitamin C in omeprazole-induced corpus gastritis. Details: A small clinical study shows that taking vitamin C orally 1200 mg daily along with omeprazole decreases corpus gastritis associated with omeprazole therapy in patients with H. pylori infection (10360).
• Gout. It is unclear if oral vitamin C helps to prevent or manage gout. Details: Population research in men has found that taking vitamin C 500-1500 mg daily from the diet and/or supplements is associated with up to a 34% reduced risk of gout when compared with less than 250 mg daily (16755). Also, men who ingest over 500 mg of vitamin C daily from the diet and supplements have serum uric acid levels that are slightly lower than men who consume less than 90 mg daily (16820). However, taking supplemental vitamin C 500 mg daily for 8 weeks does not seem to lower serum uric acid levels in patients who already have gout (90423).
• Hearing loss. There is limited evidence on the intravenous use of vitamin C in idiopathic sudden sensorineural hearing loss. It is unclear if dietary vitamin C intake can affect the risk of hearing loss. Details: A small clinical study in patients with idiopathic sudden sensorineural hearing loss shows that receiving intravenous high-dose vitamin C 200 mg/kg daily in combination with steroid therapy for 10 days, followed by oral vitamin C 2000 mg daily for 30 days, increases recovery rate two-fold and modestly improves hearing threshold levels when compared with receiving steroid therapy only (90417). In addition, population research in females has found that high dietary intake of vitamin C is associated with a 22% increased risk of developing self-reported hearing loss over a 22-year period when compared with low intake (109807).
• Heart transplant complications. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial shows that a combination of vitamin C 500 mg and vitamin E 400 IU, taken twice daily for 1 year starting within the first 2 years after cardiac transplant, reduced the progression of vasculopathy as measured by intravascular ultrasonography (IVUS) when compared with placebo. This suggests that the combination may help slow the progression of CAV (82826).
• Hepatitis C. It is unclear if oral vitamin C is beneficial in patients with hepatitis C. Details: A small clinical study in patients with confirmed hepatitis C shows that taking vitamin C 1000 mg daily with conventional therapy (sofosbuvir plus daclatasvir) for 4 weeks improves serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, and albumin when compared with conventional therapy alone (109463).
• HIV/AIDS. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small, low-quality study in men with HIV shows that taking vitamin C 250 mg daily in combination with vitamin A, beta-carotene, vitamin E, selenium, and coenzyme Q10 does not improve viral load, although it seems to improve markers of oxidative stress when compared to baseline. However, a 1000 mg dose of vitamin C, as well as higher doses of the other antioxidants, do not seem to provide any additional effect (9830).
• HIV transmission. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in HIV-positive mothers shows that taking vitamin B, vitamin C, and vitamin E daily during pregnancy and while breast-feeding for 20 weeks seems to reduce child mortality and HIV transmission through breast milk when compared with taking vitamin A (9801).
• Hyperphosphatemia. Intravenous vitamin C might be beneficial for reducing phosphate levels in patients with end-stage renal disease. Details: A small clinical study in hemodialysis patients with elevated phosphorus levels suggests that administering vitamin C 500 mg intravenously three times weekly for 8 weeks reduces phosphorus levels about seven-fold when compared with placebo (90414).
• Idiopathic interstitial pneumonia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with idiopathic pulmonary fibrosis, a form of idiopathic interstitial pneumonia, shows that taking a combination of vitamin C 250 mg every other day, vitamin D 50,000 IU daily, and vitamin E 200 IU daily for 12 weeks improves some, but not all, measures of lung function and reduces markers of inflammation and oxidative stress when compared to baseline (109464). The validity of these findings is limited by a lack of placebo control group.
• Infertility. It is unclear if oral vitamin C is beneficial in anovulatory females. Details: A very small clinical study suggests that taking vitamin C 400-1000 mg daily might improve fertility, resulting in ovulation and pregnancy in some anovulatory females, when compared to baseline (14018). The validity of these findings is limited by the small study size and lack of a comparator group. However, a very large observational study suggests that there is no association between dietary vitamin C intake and in-vitro fertilization (IVF) outcomes including good oocyte quality, embryo transfer success rates, clinical pregnancy rates, and successful term pregnancy rates in subfertile couples who are candidates for IVF (112097).
• Male infertility. It is unclear if oral or intravenous vitamin C is beneficial in males with infertility. Details: A meta-analysis of three small, low-quality clinical trials in males with infertility shows that taking vitamin C up to 1000 mg daily for up to 12 weeks can improve sperm count, motility, and vitality, but does not seem to increase semen volume or sperm concentration, when compared with control (109461). It is unclear if vitamin C can increase pregnancy rates, as these studies did not assess this outcome. A retrospective study in males with or without varicocele-related infertility has found that taking a specific combination product containing vitamin C 90 mg, zinc 10 mg, L-carnitine fumarate 1725 mg, acetyl-L-carnitine 500 mg, coenzyme Q10 20 mg, folic acid 0.2 mg, selenium 0.05 mg, and vitamin B12 0.015 mg (Proxeed Plus, Sigma-Tau) orally twice daily for 6 months improves sperm count, sperm concentration, and sperm motility when compared with baseline. Improvement in semen parameters were greatest in subjects with more severe varicoceles. The validity of this study is limited by the lack of a comparator group (111296).
• Mastalgia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in patients with mastalgia shows that taking a combination of vitamin C 100 mg, vitamin B12, and gamma-linolenic acid daily for 12 weeks does not improve the proportion of patients with minimal or no pain when compared with placebo (111059).
• Melasma. It is unclear if topical vitamin C is beneficial in patients with melasma. Details: A small clinical study in patients with bilateral symmetrically distributed facial melasma shows that topical application of 0.5 mL of vitamin C (Cosmotech, Alpha Medical Cosmotech) following dermapen microneedling every 2 weeks for 6 weeks is similarly effective to tranexamic acid for improving melasma severity and pigmented, but not vascular, findings on dermoscopic examination (106939).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin C is beneficial in patients with NAFLD. Details: A clinical study in patients with NAFLD shows that taking vitamin C 250 mg, 1000 mg, or 2000 mg daily for 12 weeks improves some biochemical markers of liver health and glucose metabolism when compared with baseline. However, the improvement from baseline was similar between groups (106942).
• Nonalcoholic steatohepatitis (NASH). Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research suggests vitamin C in combination with vitamin E might improve hepatic fibrosis in patients with NASH. However, it does not seem to decrease liver inflammation (14005).
• Non-Hodgkin lymphoma. It is unclear if oral vitamin C reduces the risk of developing diffuse large B-cell lymphoma. Details: In one population study, higher dietary or supplemental intake of vitamin C was associated with a reduced risk of diffuse large B-cell lymphoma, a type of non-Hodgkin lymphoma, when compared with lower intake in postmenopausal adults (90945).
• Oral cancer. It is unclear if oral vitamin C reduces the risk of developing oral cancer. Details: Population research has found that higher dietary intake of vitamin C is associated with a reduced risk of oral cancer (10821). However, clinical research has not shown benefit with oral vitamin C supplements. A small clinical trial in Japanese adults with oral leukoplakia shows that taking vitamin C 500 mg and beta-carotene 10 mg daily for 12 months does not reduce the development of oral cancer over 5 years when compared with vitamin C 50 mg daily (91384).
• Oral leukoplakia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in Japanese adults with oral leukoplakia shows that taking vitamin C 500 mg and beta-carotene 10 mg daily for 12 months does not improve leukoplakia symptoms or reduce the development of oral cancer over 5 years when compared with vitamin C 50 mg daily (91384).
• Osteoarthritis. It is unclear if dietary vitamin C reduces the risk of developing osteoarthritis. Details: Observational research has found that increased vitamin C from dietary sources is associated with a reduced risk of cartilage loss and disease progression in people with osteoarthritis (5881).
• Osteoporosis. It is unclear if dietary vitamin C improves bone density or reduces fracture risk in patients at risk for osteoporosis. Details: Some cross-sectional observational research in postmenopausal patients without a history of smoking or estrogen use has found that higher serum vitamin C levels are associated with lower bone mineral density (9828). However, other observational research in a larger population of adults at risk for osteoporosis has found that higher dietary vitamin C intake is not associated with fracture risk (104415).
• Ovarian cancer. Dietary vitamin C might not affect the risk of ovarian cancer. Details: Epidemiological research has found that dietary vitamin C intake is not linked with ovarian cancer risk (9193,102977).
• Pancreatitis. It is unclear if intravenous vitamin C is beneficial in patients with acute pancreatitis. Details: A small meta-analysis of clinical studies in patients with acute pancreatitis shows that intravenous vitamin C does not improve the odds of developing organ failure when compared with placebo or no intervention. Intravenous vitamin C seems to reduce hospital stay, but not in-hospital mortality (106941).
• Parkinson disease. Dietary vitamin C might not affect the risk of developing this condition. Details: Observational research has found that moderate or high dietary intake of vitamin C is not associated with a reduced risk of Parkinson disease (83316).
• Periodontitis. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. It is also unclear if dietary vitamin C reduces the risk of periodontitis. Details: A small clinical study in patients with moderate or advanced periodontitis shows that taking a supplement containing vitamin C 100 mg, alpha-lipoic acid, coenzyme Q10, cranberry extract, grapeseed extract, selenium, vitamin E, and zinc twice daily for 8 weeks in addition to standard nonsurgical therapy does not improve periodontal indices including bleeding on probing, gingival recession, plaque index, or inflammation, among others, when compared with placebo (111708). It is unclear if these effects are due to vitamin C, other ingredients, or the combination. There is also interest in whether dietary vitamin C intake impacts the risk of periodontitis. Observational research in US adults has found that individuals with dietary intake of vitamin C in the third quartile, but not the second or fourth quartiles, have lower odds of periodontitis when compared with vitamin C intake in the lowest quartile. Furthermore, the investigators identified a non-linear relationship between vitamin C intake and periodontitis risk, suggesting that individuals with intakes either much lower or much higher than 158 mg daily are at increased risk of developing periodontitis (109958).
• Peripheral arterial disease (PAD). It is unclear if dietary vitamin C helps to reduce the risk of developing PAD. Details: In females, epidemiological evidence has found that dietary intake of vitamin C of 142 mg daily or greater is associated with a 36% reduced risk of PAD when compared with lower intake levels of less than 80 mg daily (10130).
• Physical performance. It is unclear if oral vitamin C helps to improve physical performance and muscle strength in older people. Details: Population research has found that higher intake of dietary vitamin C is associated with improved physical performance and muscle strength in elderly people (14006). In contrast, a small clinical study in elderly men undergoing strength training shows that taking vitamin C 1000 mg and vitamin E 258IU daily for 12 weeks does not increase strength, and might even attenuate increases in muscle mass, when compared with strength training alone (96701).
• Pneumonia. It is unclear if oral vitamin C helps to prevent pneumonia. Details: A meta-analysis of two small, low-quality clinical studies in children shows that vitamin C does not seem to reduce the occurrence of pneumonia when compared to control (104033).
• Postoperative recovery. It is unclear if oral or intravenous vitamin C improves postoperative recovery. Details: Meta-analyses of clinical research show that oral or intravenous vitamin C can shorten the duration of hospitalization after cardiac surgery when compared with control (91233,96703). However, other research shows no decrease in intensive care or hospital stay with vitamin C supplementation (96705). A meta-analysis of 37 clinical trials in adults undergoing low- to high-risk noncardiac surgery (i.e., orthopedic, abdominal, gynecologic, or kidney transplantation), shows that receiving perioperative vitamin C, either orally or intravenously, does not improve duration of hospitalization or overall mortality when compared with control (108087). There's also some limited evidence that vitamin C might reduce postoperative pulmonary complications such as lung infection, pleural effusion, and pneumothorax. A small clinical trial in low-risk cardiac surgery patients shows that receiving intravenous vitamin C 1 gram 10 minutes after anesthesia might slightly reduce the rate of postoperative pulmonary complications when compared with receiving a saline injection (104034).
• Postoperative swelling. It is unclear if vitamin C reduces postoperative swelling after dental surgery. Details: A small observational study in adults undergoing surgery for wisdom tooth extraction shows that taking vitamin C 500 mg three times daily for 7 days in addition to standard treatment reduces swelling 7 days after surgery when compared with control. However, vitamin C does not seem to reduce swelling 3 days after surgery when compared with control, suggesting that longer durations are needed for anti-inflammatory effects (113664).
• Premature rupture of membranes (PROM). Oral vitamin C seems to reduce the risk of PROM in some patients; however, the addition of oral vitamin E seems to negate any benefit. Details: A meta-analysis of clinical research shows that taking vitamin C alone decreases the risk of both term and preterm PROM by 45% and 34%, respectively, when compared with placebo or control (96707). Also, a more recent clinical study in patients with a history of PROM shows that taking vitamin C 100 mg daily, starting at 14 weeks' gestation, increases the gestational age at recurrent PROM by around 1 week and increases the gestational age at birth by around 1.3 weeks when compared with placebo (109960). Taking vitamin C in combination with vitamin E, however, does not seem to reduce the risk of term or preterm PROM; some research suggests that it might even increase the risk of non-preterm PROM (83472,96707). However, other research shows that taking vitamin C 1000 mg plus vitamin E 400 IU daily, beginning at 24 to 34 weeks gestation and continuing until delivery, may help increase the latency period until delivery by 5 days and increase gestational age at delivery by almost 1 week when compared with placebo in patients with preterm PROM (90078).
• Pressure ulcers. It is unclear if oral vitamin C, when used alone or in combination with other ingredients, can improve the healing of pressure ulcers. Details: A small clinical study in institutionalized patients with pressure ulcers shows that taking vitamin C 500 mg twice daily for 12 weeks does not improve wound closure or increase healing rates when compared with vitamin C 10 mg twice daily (83617). Oral vitamin C has also been evaluated in combination with other ingredients for the treatment of grade II-IV pressure ulcers. Two small clinical studies in hospitalized patients with pressure ulcers shows that administering an oral nutritional supplement enriched with vitamin C, L-arginine, and zinc improves ulcer healing when compared with a standard diet (31953,87173). Also, clinical research in patients living in long-term care facilities shows that taking an oral nutritional supplement enriched in protein, vitamin C, L-arginine, and zinc daily for 9 weeks reduces ulcer area and decreases oozing when compared to baseline (32045). The validity of this finding is limited by the lack of a comparator group.
• Radiation proctopathy. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical study in patients with chronic radiation proctitis shows that vitamin C 500 mg plus vitamin E 400 IU three times daily might improve symptoms when compared with baseline (9825). The validity of these findings is limited by the lack of a comparator group.
• Renal cell carcinoma. It is unclear if increased dietary intake of vitamin C helps to reduce the risk of renal cell carcinoma. Details: Population research has found that increased dietary intake of vitamin C is associated with a 12% reduced risk of renal cell carcinoma (98779).
• Respiratory tract infections. It is unclear if oral vitamin C is beneficial for preventing respiratory tract infections or reducing the duration of these infections. Details: A meta-analysis of clinical research in children and adults shows that, when compared with placebo, oral vitamin C supplementation reduces the average number of symptomatic days per individual, but does not reduce the average symptom days per respiratory episode. Also, vitamin C intake does not reduce the incidence or severity of respiratory disease or improve recovery in hospitalized patients with respiratory tract infections (108077). The validity of this trial is limited by the high heterogeneity of included studies, which evaluated various vitamin C regimens, ranging from 100 mg to 8 grams daily, as preventive therapy or as an adjuvant to active treatment. A clinical study in children aged 3-10 years shows that taking vitamin C 50 mg in combination with a specific product (Lab4) containing Lactobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium animalis subsp. lactis daily for 6 months reduces the incidence of cough and sore throat by 16% and 20%, respectively, when compared with placebo. However, it did not improve total symptoms, nasal congestion, nasal discharge, or sneezing. Also, aside from a 33% reduction in the average number of days with a sore throat, daily supplementation does not reduce the duration of individual symptoms or total symptoms (106943). It is unclear if these effects are due to vitamin C, the probiotics, or the combination.
• Restless legs syndrome (RLS). It is unclear if oral vitamin C helps to reduce symptoms of stress. Details: A small clinical study in hemodialysis patients with RLS shows that taking vitamin C 200 mg daily, alone or in combination with vitamin E 400 mg, for 8 weeks reduces the severity of RLS when compared with placebo (90093). More research is needed to determine if vitamin C is beneficial in treating RLS that is not associated with hemodialysis.
• Smoking cessation. It is unclear whether supplemental vitamin C improves lung function in the offspring of pregnant adults with tobacco use disorder. Details: A meta-analysis of large clinical studies in pregnant adults who smoke at least one cigarette daily shows that taking supplemental vitamin C 500 mg daily during pregnancy reduces lower airway resistance and improves lung capacity of the offspring but does not improve airway obstruction when compared with control (113670).
• Sunburn. Topical and oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking vitamin C orally in combination with vitamin E seems to prevent ultraviolet (UV) radiation-induced erythema (sunburn) (4715,4716). Vitamin C in combination with high dose oral RRR-alpha-tocopherol (natural vitamin E) seems to protect against skin inflammation after exposure to UV radiation (4715). Also, applying topical vitamin C in combination with topical vitamin E and melatonin seems to provide modest photoprotective effects when used prior to UV exposure. However, it has no effect when used during or after UV exposure (4713,4714).
• Stress. It is unclear if oral vitamin C helps to reduce symptoms of stress. Details: A small clinical study in healthy adults shows that taking vitamin C 3000 mg daily for 14 days modestly reduces blood pressure and subjective stress response to psychological stress when compared with placebo (10353).
• Stroke. Observational research has found that although taking vitamin C supplements does not seem to be beneficial, eating more vitamin C-rich food is linked with reduced risk of stroke. Details: Lower plasma levels of vitamin C have been associated with increased stroke risk (90408). Additionally, population research has found that higher dietary intake of vitamin C is associated with a 8% to 19% reduction in stroke risk when compared to lower intake (90408,109779). This reduction appears to be dose-dependent, with each 100 mg/day increase in dietary vitamin C intake associated with about a 17% reduction (90408). However, taking vitamin C supplements has not been found to be associated with reduced stroke risk (1449,90408).
• Tetanus. It is unclear if intravenous vitamin C helps to reduce symptoms of tetanus. Details: A low quality clinical trial in children and young adults with tetanus shows that intravenous vitamin C 1 gram daily along with conventional treatment reduces fatality when compared to control (21539).
• Tooth extraction. It is unclear if oral vitamin C is beneficial for reducing pain or improving healing after tooth extraction. Details: A small clinical study in healthy patients aged 14-41 years who are undergoing bilateral premolar extraction shows that taking vitamin C 200 mg three times daily, beginning immediately after extraction and continued for 10 days, improves pain on days 1-3, and may reduce mesio-distal wound size between days 1 and 7, when compared with placebo, but not when compared with vitamin C 500 mg three times daily. A dose of 500 mg three times daily did not improve pain scores or extraction wound healing when compared with placebo (108084). The validity of this trial is limited by the short duration of treatment; additionally, this study did not report baseline vitamin C levels.
• Urinary tract infections (UTIs). Although there is interest in using oral vitamin C for UTIs, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Vascular dementia. It is unclear if oral vitamin C reduces the risk of vascular dementia. Details: Population research has found that supplemental intake of vitamin C and vitamin E is associated with a reduced risk of vascular dementia in Japanese-American men (4636). However, when cases in which dementia was diagnosed prior to the study are excluded from data analysis, intake of vitamin C and vitamin E is not associated with a reduced risk of vascular dementia in these patients (9824).
• Wound healing. It is unclear if oral vitamin C improves the healing of chronic foot ulcers. It is also unclear if intravenous vitamin C improves healing of surgical wounds after total abdominal hysterectomy. Details: A very small clinical study in adults with chronic foot ulcers shows that taking slow-release vitamin C 500 mg daily for 8 weeks seems to result in a median of 100% ulcer healing, compared with a median of 14% ulcer healing in patients taking glucosamine 1000 mg daily (105456). This finding is limited due to the small and heterogeneous patient population, which included patients with diabetes, vascular disease, and/or vitamin C deficiency. Another small clinical study in patients undergoing total abdominal hysterectomy shows that administration of intravenous vitamin C 1 gram the night before surgery and 1 gram during surgery does not reduce the rate of surgical site infection or wound dehiscence when compared with placebo (109465). However, this study may not have been adequately powered to detect differences between groups. More evidence is needed to rate vitamin C for these uses.

(Read more about VITAMIN C)

POSSIBLY SAFE ...when used orally and appropriately, short-term. Ashwagandha has been used with apparent safety in doses of up to 1250 mg daily for up to 6 months (3710,11301,19271,90649,90652,90653,97292,101816,102682,102683) (102684,102685,102687,103476,105824,109586,109588,109589,109590). ...when used topically. Ashwagandha lotion has been used with apparent safety in concentrations up to 8% for up to 2 months (111538).

PREGNANCY: LIKELY UNSAFE
when used orally. Ashwagandha has abortifacient effects (12).

LACTATION:
Insufficient reliable information available; avoid using.

(Read more about ASHWAGANDHA)

POSSIBLY SAFE ...when used orally and appropriately. Cordyceps has been used with apparent safety in doses of 3-6 grams daily for up to 1 year (12,12095,92828,95905,105076,111903).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about CORDYCEPS)

POSSIBLY SAFE ...when used orally, short-term. Holy basil leaf extract has been used with apparent safety at a dose of 500 mg daily for 60-90 days (12242,18107,19575,91571,96944). ...when used topically in the mouth, short-term. Holy basil has been used with apparent safety as a 4% mouthwash solution for up to 30 days (91570,103621).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used in high doses during pregnancy or when trying to conceive. Animal research suggests that relatively high doses of holy basil extract (200 mg/kg) may reduce implantation rate when used for one week, while long-term use of higher doses (2-4 grams/kg) may decrease the number of full-term pregnancies (55040,91569). There is insufficient reliable information available regarding the safety of holy basil during lactation; avoid using.

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LIKELY SAFE ...when used orally and appropriately. The pantothenic acid derivative calcium pantothenate has a generally recognized as safe (GRAS) status for use in food products (111258). While a tolerable upper intake level (UL) has not been established, pantothenic has been used in doses of 10-20 grams daily with apparent safety (15,6243,111258) ...when applied topically and appropriately, short-term. The Cosmetic Ingredient Review Expert Panel has concluded that pantothenic acid and its derivatives are safe for use in cosmetic products in concentrations up to 5.3% (111258). Gels or ointments containing a derivative of pantothenic acid, dexpanthenol, at concentrations of up to 5%, have been used safely for up to 30 days (67802,67806,67817).

POSSIBLY SAFE ...when applied intranasally and appropriately, short-term. A dexpanthenol nasal spray has been used with apparent safety up to four times daily for 4 weeks (67826). ...when applied in the eyes appropriately, short-term. Dexpanthenol 5% eyedrops have been used with apparent safety for up to 28 days (67783). ...when injected intramuscularly and appropriately, short-term. Intramuscular injections of dexpanthenol 500 mg daily for up to 5 days or 250 mg weekly for up to 6 weeks have been used with apparent safety (67822,111366).

CHILDREN: LIKELY SAFE
when used orally and appropriately (15,6243). Calcium pantothenate is generally recognized as safe (GRAS) when used as a food additive and in infant formula (111258). However, a tolerable upper intake level (UL) has not been established (15,6243). ...when applied topically and appropriately (67795,105190,111262). Infant products containing pantothenic acid and its derivatives have been used safely in concentrations of up to 5% for infant shampoos and 2.5% for infant lotions and oils. The Cosmetic Ingredient Review Expert Panel has concluded that pantothenic acid and derivatives are safe for use in topical infant products. (111258).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. The daily adequate intake (AI) during pregnancy is 6 mg (3094).

LACTATION: LIKELY SAFE
when used orally and appropriately. The daily adequate intake (AI) during lactation is 7 mg (3094).

(Read more about PANTOTHENIC ACID)

POSSIBLY SAFE ...when used orally and appropriately, short-term. There is some clinical research showing that taking rhodiola extract up to 300 mg twice daily has been used without adverse effects for up to 12 weeks (13109,16410,17616,71172,96459,102283,103269).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about RHODIOLA)

POSSIBLY SAFE ...when used orally and appropriately. Schisandra extract up to 1 gram daily has been used for up to 12 weeks with apparent safety (12,96632,105562,105563,112887).

PREGNANCY: POSSIBLY UNSAFE
when used orally. Some evidence suggests schisandra fruit is a uterine stimulant (11).

LACTATION:
Insufficient reliable information available; avoid using.

(Read more about SCHISANDRA)

LIKELY SAFE ...when used orally and appropriately in doses that do not exceed the tolerable upper intake level (UL) of 100 mg daily for adults (15). ...when used parenterally and appropriately. Injectable vitamin B6 (pyridoxine) is an FDA-approved prescription product (15).

POSSIBLY SAFE ...when used orally and appropriately in doses of 101-200 mg daily (6243,8558).

POSSIBLY UNSAFE ...when used orally in doses at or above 500 mg daily. High doses, especially those exceeding 1000 mg daily or total doses of 1000 grams or more, pose the most risk. However, neuropathy can occur with lower daily or total doses (6243,8195). ...when used intramuscularly in high doses and frequency due to potential for rhabdomyolysis (90795).

CHILDREN: LIKELY SAFE
when used orally and appropriately (3094).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately in amounts exceeding the recommended dietary allowance (5049,8579,107124,107125,107135).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses, long-term (3094).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. A special sustained-release product providing vitamin B6 (pyridoxine) 75 mg daily is FDA-approved for use in pregnancy. Vitamin B6 (pyridoxine) is also considered a first-line treatment for nausea and vomiting in pregnancy by the American College of Obstetrics and Gynecology (111601). However, it should not be used long-term or without medical supervision and close monitoring.

PREGNANCY: POSSIBLY UNSAFE
when used orally in excessive doses. There is some concern that high-dose maternal vitamin B6 (pyridoxine) can cause neonatal seizures (4609,6397,8197).

LACTATION: LIKELY SAFE
when used orally in doses not exceeding the recommended dietary allowance (RDA) (3094). The RDA in lactating women is 2 mg daily. There is insufficient reliable information available about the safety of vitamin B6 when used in higher doses in breast-feeding women.

(Read more about VITAMIN B6)

LIKELY SAFE ...when used orally, topically, intramuscularly, or intravenously and appropriately. Vitamin C is safe when taken orally in doses below the tolerable upper intake level (UL). Tell patients not to exceed the UL of 2000 mg daily (1959,4713,4714,4844). ...when used intravenously or intramuscularly and appropriately. Injectable vitamin C is an FDA-approved prescription product (15).

POSSIBLY UNSAFE ...when used orally in excessive doses. Doses greater than the tolerable upper intake level (UL) of 2000 mg daily can significantly increase the risk of adverse effects such as osmotic diarrhea and gastrointestinal upset (4844).

CHILDREN: LIKELY SAFE
when used orally and appropriately (4844,10352,14443).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive amounts. Tell patients not to use doses above the tolerable upper intake level (UL) of 400 mg daily for children ages 1 to 3 years, 650 mg daily for children 4 to 8 years, 1200 mg daily for children 9 to 13 years, and 1800 mg daily for adolescents 14 to 18 years. Higher doses can cause osmotic diarrhea and gastrointestinal upset (4844).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately (4844).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. Tell patients over age 19 not to use doses exceeding the UL of 2000 mg daily when pregnant or breast-feeding and for those 14-18 years of age not to use doses exceeding 1800 mg daily when pregnant or breast-feeding. Higher doses can cause osmotic diarrhea and gastrointestinal upset. Large doses of vitamin C during pregnancy can also cause newborn scurvy (4844); avoid using.

(Read more about VITAMIN C)

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking ashwagandha with antidiabetes drugs might increase the risk of hypoglycemia.  Details There is preliminary clinical evidence suggesting that ashwagandha might lower blood glucose levels. Theoretically, ashwagandha might have additive effects when used with antidiabetes drugs and increase the risk of hypoglycemia (19274,90649,102685).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha with antihypertensive drugs might increase the risk of hypotension.  Details Animal research suggests that ashwagandha might lower systolic and diastolic blood pressure (19279). Theoretically, ashwagandha might have additive effects when used with antihypertensive drugs and increase the risk of hypotension.

BENZODIAZEPINES Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha might increase the sedative effects of benzodiazepines.  Details There is preliminary evidence that ashwagandha might have an additive effect with diazepam (Valium) and clonazepam (Klonopin) (3710). This may also occur with other benzodiazepines.

CNS DEPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha might increase the sedative effects of CNS depressants.  Details Ashwagandha seems to have sedative effects. Theoretically, this may potentiate the effects of barbiturates, other sedatives, and anxiolytics (3710).

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, ashwagandha might decrease the levels and clinical effects of CYP1A2 substrates.  Details In vitro research shows that ashwagandha extract induces CYP1A2 enzymes (111404).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, ashwagandha might decrease the levels and clinical effects of CYP3A4 substrates.  Details In vitro research shows that ashwagandha extract induces CYP3A4 enzymes (111404).

HEPATOTOXIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha with hepatotoxic drugs might increase the risk of liver damage.  Details Ashwagandha has been linked to cases of acute hepatitis, liver failure, hepatic encephalopathy, autoimmune hepatitis, the need for liver transplantation, and death due to liver failure (102686,107372,110490,110491,111533,111535,112111,113610).

IMMUNOSUPPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha might decrease the effects of immunosuppressants.  Details Ashwagandha has demonstrated immunostimulant effects in humans (3710,3711,4114,11301,106786). Animal research has shown that ashwagandha can attenuate the immunosuppression caused by cyclophosphamide (3711,4114).

THYROID HORMONE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Ashwagandha might increase the effects and adverse effects of thyroid hormone.  Details Concomitant use of ashwagandha with thyroid hormones may cause additive therapeutic and adverse effects. Preliminary clinical research and animal studies suggest that ashwagandha boosts thyroid hormone synthesis and secretion (19281,19282,97292). In one clinical study, ashwagandha increased triiodothyronine (T3) and thyroxine (T4) levels by 41.5% and 19.6%, respectively, and reduced serum TSH levels by 17.4% from baseline in adults with subclinical hypothyroidism (97292).

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ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, cordyceps may increase the risk of bleeding when used with antiplatelet or anticoagulant drugs.  Details In vitro and animal research suggests that cordyceps extract inhibits platelet aggregation and function (3429,46112). However, this interaction has not been reported in humans.

IMMUNOSUPPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, concurrent use of cordyceps might interfere with immunosuppressive therapy.  Details Animal and in vitro research suggests that cordyceps stimulates the immune system (3403,3404,3414,3431,3432). However, limited clinical research suggests that taking cordyceps may lower the necessary therapeutic dose of the immunosuppressant cyclosporine (92828), which suggests that cordyceps may have an immunosuppressive effect.

TESTOSTERONE Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, concurrent use of cordyceps and testosterone might have additive effects.  Details Animal research suggests that cordyceps can increase testosterone levels (46087). The clinical significance of this finding is unclear.

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ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, holy basil seed oil might increase the risk of bleeding when used with anticoagulant or antiplatelet drugs.  Details Animal research shows that holy basil seed oil can prolong bleeding time, possibly due to inhibition of platelet aggregation (13251). However, it is not known if this occurs in humans.

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, holy basil might increase the risk of hypoglycemia when taken with antidiabetes drugs.  Details Small clinical studies show that taking holy basil can decrease fasting blood glucose and other measures of glycemic control in patients with type 2 diabetes (12242,91571).

PENTOBARBITAL (Nembutal) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, holy basil seed oil might increase the sedative effects of pentobarbital.  Details Animal research shows that holy basil seed oil increases pentobarbitone-induced sleeping time (13056,13251). However, it is not known if this occurs in humans or if this applies to other barbiturates or sedatives.

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ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking rhodiola with antidiabetes drugs might increase the risk of hypoglycemia.  Details In vitro and animal research shows that rhodiola extract can decrease blood glucose due to alpha-glucosidase activity (15717,15719).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking rhodiola with antihypertensive drugs might increase the risk of hypotension.  Details In vitro and animal research shows that rhodiola extract inhibits angiotensin-converting enzyme (ACE) and might lower blood pressure (15719,19495).

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, rhodiola might increase levels of drugs metabolized by CYP1A2.  Details In vitro research shows that rhodiola inhibits CYP1A2. This effect is highly variable and appears to be dependent on the rhodiola product studied (96461). However, a clinical study in healthy young males found that taking rhodiola extract 290 mg daily for 14 days does not inhibit the metabolism of caffeine, a CYP1A2 substrate (96463).

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, rhodiola might increase levels of drugs metabolized by CYP2C9.  Details In vitro research shows that rhodiola inhibits CYP2C9. This effect is highly variable and appears to be dependent on the rhodiola product studied (96461). Also, a clinical study in healthy young males found that taking rhodiola extract 290 mg daily for 14 days reduces the metabolism of losartan, a CYP2C9 substrate, by 21% after 4 hours (96463).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, rhodiola might increase levels of drugs metabolized by CYP3A4.  Details In vitro research shows that rhodiola inhibits CYP3A4 (19497,96461). This effect is highly variable and appears to be dependent on the rhodiola product studied (96461). However, a clinical study in healthy young males found that taking rhodiola extract 290 mg daily for 14 days does not inhibit the metabolism of midazolam, a CYP3A4 substrate (96463).

IMMUNOSUPPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, rhodiola use might interfere with immunosuppressive therapy.  Details In vitro and animal research show that rhodiola has immunostimulatory effects (19498,19499,19500,19501).

LOSARTAN (Cozaar) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Rhodiola might increase the levels and adverse effects of losartan.  Details A clinical study in healthy young males found that taking rhodiola extract 290 mg daily for 14 days reduces the metabolism of losartan, a CYP2C9 substrate, by 21% after 4 hours (96463).

P-GLYCOPROTEIN SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, rhodiola might increase levels of P-glycoprotein substrates.  Details In vitro research shows that rhodiola inhibits P-glycoprotein (19497). Theoretically, using rhodiola with P-glycoprotein substrates might increase drug levels and potentially increase the risk of adverse effects.

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CYCLOPHOSPHAMIDE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, schisandra might increase the levels and clinical effects of cyclophosphamide.  Details In vitro research shows that schisandra increases the concentration of cyclophosphamide, likely through inhibition of cytochrome P450 3A4. After multiple doses of the schisandra constituents schisandrin A and schisantherin A, the maximum concentration of cyclophosphamide was increased by 7% and 75%, respectively, while the overall exposure to cyclophosphamide was increased by 29% and 301%, respectively (109636).

CYCLOSPORINE (Neoral, Sandimmune) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Schisandra can increase the levels and clinical effects of cyclosporine.  Details A small observational study in children with aplastic anemia found that taking schisandra with cyclosporine increased cyclosporine trough levels by 93% without increasing the risk of adverse events. However, the dose of cyclosporine was reduced in 9% of children to maintain appropriate cyclosporine blood concentrations (109637).

CYTOCHROME P450 2C19 (CYP2C19) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, schisandra might increase the levels and clinical effects of CYP2C19 substrates.  Details In vitro research shows that schisandra inhibits CYP2C19, and animal research shows that schisandra increases the concentration of voriconazole, a CYP2C19 substrate (105566). Theoretically, schisandra may also inhibit the metabolism of other CYP2C19 substrates. This effect has not been reported in humans.

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, schisandra might decrease the levels and clinical effects of CYP2C9 substrates.  Details In vitro and animal research suggests that schisandra induces CYP2C9 enzymes (14441). This effect has not been reported in humans.

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Schisandra can increase the levels and clinical effects of drugs metabolized by CYP3A4.  Details Most clinical and laboratory research shows that schisandra, administered either as a single dose or up to twice daily for 14 days, inhibits CYP3A4 and increases the concentration of CYP3A4 substrates such as cyclophosphamide, midazolam, tacrolimus, and talinolol (13220,17414,23717,91386,91388,91387,96631,105564,109636,109638,109639,109640,109641). Although one in vitro and animal study shows that schisandra may induce CYP3A4 metabolism (14441), this effect appears to be overpowered by schisandra's CYP3A4 inhibitory activity and has not been reported in humans.

MIDAZOLAM (Versed) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Schisandra can increase the levels and clinical effects of midazolam.  Details A small pharmacokinetic study in healthy adults shows that taking schisandra extract (Hezheng Pharmaceutical Co.) containing deoxyschizandrin 33.75 mg twice daily for 8 days and a single dose of midazolam 15 mg on day 8 increases the overall exposure to midazolam by about 119%, increases the peak plasma level of midazolam by 86%, and decreases midazolam clearance by about 52%. This effect has been attributed to inhibition of CYP3A4 by schisandra (91388).

P-GLYCOPROTEIN SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Schisandra might increase the levels and clinical effects of P-glycoprotein substrates.  Details In vitro research shows that schisandra extracts and constituents such as schisandrin B inhibit P-glycoprotein mediated efflux in intestinal cells and in P-glycoprotein over-expressing cell lines (17414,105643,105644). Additionally, a small clinical study shows that schisandra increases the peak concentration and overall exposure to talinolol, a P-glycoprotein probe substrate (91386). Theoretically, schisandra might inhibit the efflux of other P-glycoprotein substrates.

SIROLIMUS (Rapamune) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Schisandra can increase the levels and clinical effects of sirolimus.  Details A small pharmacokinetic study in healthy volunteers shows that taking 3 capsules of schisandra (Hezheng Pharmaceutical Company) containing a total of 33.75 mg deoxyschizandrin twice daily for 13 days and then taking a single dose of sirolimus 2 mg increases the overall exposure and peak level of sirolimus by two-fold. This effect is thought to be due to inhibition of cytochrome P450 3A4 by schisandra, as well as possible inhibition of the P-glycoprotein drug transporter (105643).

TACROLIMUS (Prograf) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Schisandra can increase the levels and clinical effects of tacrolimus.  Details Clinical research in healthy children and adults, transplant patients, and patients with nephrotic syndrome and various rheumatic immunologic disorders shows that taking schisandra with tacrolimus increases tacrolimus peak levels by 183% to 268%, prolongs or delays time to peak tacrolimus concentrations, increases overall exposure to tacrolimus by 126% to 343%, and decreases tacrolimus clearance by 19% to 73% (17414,91387,15570,96631,105623,109638,109639,109640,109641,112889)(112890,112972,112973,112974). This effect is thought to be due to inhibition of P-glycoprotein drug transporter and CYP3A4 and CYP3A5 by schisandra (17414,96631,105623,105643,105644,112974). Some clinical and observational studies suggest that schisandra increases tacrolimus levels similarly in both expressors and non-expressors of CYP3A5, while other studies suggest it does so to a greater degree in CYP3A5 expressors than non-expressors (105623,109638,109639,109640,112889,112890,112973,112974). Animal research suggests that the greatest increase in tacrolimus levels occurs when schisandra is taken either concomitantly or up to 2 hours before tacrolimus (105564), and clinical and observational research in humans suggests that schisandra may increase whole blood levels of tacrolimus and decrease clearance of tacrolimus in a dose-dependent manner (109639,109640,112972).

TALINOLOL Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Schisandra can increase the levels and clinical effects of talinolol.  Details A small pharmacokinetic study in healthy volunteers shows that taking schisandra extract 300 mg twice daily for 14 days with a single dose of talinolol 100 mg on day 14 increases the peak talinolol level by 51% and the overall exposure to talinolol by 47%. This effect is thought to be due to the possible inhibition of cytochrome P450 3A4 and P-glycoprotein by schisandra (91386). tly.

VORICONAZOLE (Vfend) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, schisandra might increase the levels and clinical effects of voriconazole.  Details Animal research shows that oral schisandra given daily for 1 or 14 days increases levels of intravenously administered voriconazole, a cytochrome P450 (CYP) 2C19 substrate. This effect is thought to be due to inhibition of CYP2C19 by schisandra (105566). However, this interaction has not been reported in humans.

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, schisandra might decrease the levels and clinical effects of warfarin.  Details Animal research suggests that oral schisandra extract, given daily for 6 days, reduces levels of intravenously administered warfarin. This effect might be due to the induction of cytochrome P450 (CYP) 2C9 metabolism by schisandra (14441). However, this interaction has not been reported in humans.

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AMIODARONE (Cordarone) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, vitamin B6 might increase the photosensitivity caused by amiodarone.  Details Despite initial case reports suggesting that pyridoxine may have a protective effect against amiodarone-induced photosensitivity, preliminary clinical research suggests that pyridoxine may actually exacerbate this adverse effect (8892,8893).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, vitamin B6 may have additive effects when used with antihypertensive drugs.  Details Research in hypertensive rats shows that vitamin B6 can decrease systolic blood pressure (30859,82959,83093). Similarly, clinical research in patients with hypertension shows that taking high doses of vitamin B6 may reduce systolic and diastolic blood pressure, possibly by reducing plasma levels of epinephrine and norepinephrine (83091).

LEVODOPA Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Vitamin B6 may increase the metabolism of levodopa when taken alone, but not when taken in conjunction with carbidopa.  Details Vitamin B6 (pyridoxine) enhances the metabolism of levodopa, reducing its clinical effects. However, this interaction does not occur when carbidopa is used concurrently with levodopa (Sinemet). Therefore, it is not likely to be a problem in most people (3046).

PHENOBARBITAL (Luminal) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D High doses of vitamin B6 may reduce the levels and clinical effects of phenobarbital.  Details Preliminary clinical evidence suggests that vitamin B6 200 mg daily can reduce plasma levels of phenobarbital, possibly by increasing metabolism. It is not known whether lower doses have any effect. Advise people taking phenobarbital to avoid high doses of vitamin B6 (3046,10801).

PHENYTOIN (Dilantin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D High doses of vitamin B6 may reduce the levels and clinical effects of phenytoin.  Details Preliminary clinical evidence suggests that vitamin B6 200 mg daily can reduce plasma levels of phenytoin, possibly by increasing metabolism. It is not known whether lower doses have any effect. Advise people taking phenytoin to avoid high doses of vitamin B6 (3046,10801).

(Read more about VITAMIN B6)

ACETAMINOPHEN (Tylenol, others) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Probable •  Level of Evidence = B High-dose vitamin C might slightly prolong the clearance of acetaminophen.  Details A small pharmacokinetic study in healthy volunteers shows that taking high-dose vitamin C (3 grams) 1.5 hours after taking acetaminophen 1 gram slightly increases the apparent half-life of acetaminophen from around 2.3 hours to 3.1 hours. Ascorbic acid competitively inhibits sulfate conjugation of acetaminophen. However, to compensate, elimination of acetaminophen glucuronide and unconjugated acetaminophen increases (6451). This effect is not likely to be clinically significant.

ALKYLATING AGENTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, antioxidant effects of vitamin C might reduce the effectiveness of alkylating agents.  Details The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs that generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effect, if any, antioxidants such as vitamin C have on chemotherapy.

ALUMINUM Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Vitamin C can increase the amount of aluminum absorbed from aluminum compounds.  Details Research in animals and humans shows that vitamin C increases aluminum absorption, theoretically by chelating aluminum and keeping it in solution where it is available for absorption (10549,10550,10551,21556). In people with normal renal function, urinary excretion of aluminum will likely increase, making aluminum retention and toxicity unlikely (10549). Patients with renal failure who take aluminum-containing compounds such as phosphate binders should avoid vitamin C supplements in doses above the recommended dietary allowances.

ANTITUMOR ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.  Details The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.

ASPIRIN Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase aspirin levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction is not clinically significant.

CHOLINE MAGNESIUM TRISALICYLATE (Trilisate) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase choline magnesium trisalicylate levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046,4531). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.

ESTROGENS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Vitamin C might increase blood levels of estrogens.  Details Increases in plasma estrogen levels of up to 55% occur under some circumstances when vitamin C is taken concurrently with oral contraceptives or hormone replacement therapy, including topical products (129,130,11161). It is suggested that vitamin C prevents oxidation of estrogen in the tissues, regenerates oxidized estrogen, and reduces sulfate conjugation of estrogen in the gut wall (129,11161). When tissue levels of vitamin C are high, these processes are already maximized and supplemental vitamin C does not have any effect on estrogen levels. Increases in plasma estrogen levels may occur when patients who are deficient in vitamin C take supplements (11161). Monitor these patients for estrogen-related side effects.

FLUPHENAZINE (Prolixin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, vitamin C might decrease levels of fluphenazine.  Details In one patient there was a clinically significant decrease in fluphenazine levels when vitamin C (500 mg twice daily) was started (11017). The mechanism is not known, and there is no further data to confirm this interaction.

INDINAVIR (Crixivan) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Vitamin C can modestly reduce indinavir levels.  Details One pharmacokinetic study shows that taking vitamin C 1 gram orally once daily along with indinavir 800 mg orally three times daily reduces the area under the concentration-time curve of indinavir by 14%. The mechanism of this interaction is unknown, but it is unlikely to be clinically significant in most patients. The effect of higher doses of vitamin C on indinavir levels is unknown (11300,93578).

LEVOTHYROXINE (Synthroid, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Vitamin C can increase levothyroxine absorption.  Details Two clinical studies in adults with poorly controlled hypothyroidism show that swallowing levothyroxine with a glass of water containing vitamin C 500-1000 mg in solution reduces thyroid stimulating hormone (TSH) levels and increases thyroxine (T4) levels when compared with taking levothyroxine alone. This suggests that vitamin C increases the oral absorption of levothyroxine, possibly due to a reduction in pH (102978).

NIACIN Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = A Vitamin C might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.  Details A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease (7388,11537). It is not known whether this adverse effect is due to a single antioxidant such as vitamin C, or to the combination. It also is not known whether it will occur in other patient populations.

SALSALATE (Disalcid) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase salsalate levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams/day vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D High-dose vitamin C might reduce the levels and effectiveness of warfarin.  Details Vitamin C in high doses may cause diarrhea and possibly reduce warfarin absorption (11566). There are reports of two people who took up to 16 grams daily of vitamin C and had a reduction in prothrombin time (9804,9806). Lower doses of 5-10 grams daily can also reduce warfarin absorption. In many cases, this does not seem to be clinically significant (9805,9806,11566,11567). However, a case of warfarin resistance has been reported for a patient who took vitamin C 500 mg twice daily. Cessation of vitamin C supplementation resulted in a rapid increase in international normalized ratio (INR) (90942). Tell patients taking warfarin to avoid taking vitamin C in excessively high doses (greater than 10 grams daily). Lower doses may be safe, but the anticoagulation activity of warfarin should be monitored. Patients who are stabilized on warfarin while taking vitamin C should avoid adjusting vitamin C dosage to prevent the possibility of warfarin resistance.

(Read more about VITAMIN C)

General ...Orally, ashwagandha seems to be well-tolerated. Topically, no adverse effects have been reported. However, a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Diarrhea, gastrointestinal upset, nausea, and vomiting. However, these adverse effects do not commonly occur with typical doses.
Serious Adverse Effects (Rare):
Orally: Some case reports raise concerns about acute hepatitis, acute liver failure, hepatic encephalopathy, the need for liver transplantation, and death due to liver failure with ashwagandha treatment.

Dermatologic ...Orally, dermatitis has been reported in three of 42 patients in a clinical trial (19276).

Endocrine ...A case report describes a 73-year-old female who had taken an ashwagandha root extract (unspecified dose) for 2 years to treat hypothyroidism which had been previously managed with levothyroxine. The patient was diagnosed with hyperthyroidism after presenting with supraventricular tachycardia, chest pain, tremor, dizziness, fatigue, irritability, hair thinning, and low thyroid stimulating hormone (TSH) levels. Hyperthyroidism resolved after discontinuing ashwagandha (108745). Additionally, an otherwise healthy adult who was taking ashwagandha extract orally for 2 months experienced clinical and laboratory-confirmed thyrotoxicosis. Thyrotoxicosis resolved 50 days after discontinuing ashwagandha, without other treatment (114111).

Gastrointestinal ...Orally, large doses may cause gastrointestinal upset, diarrhea, and vomiting secondary to irritation of the mucous and serous membranes (3710). When taken orally, nausea and abdominal pain (19276,110490,113609) and gastritis and flatulence (90651) have been reported.

Genitourinary ...In one case report, a 28-year-old male with a decrease in libido who was taking ashwagandha 5 grams daily over 10 days subsequently experienced burning, itching, and skin and mucous membrane discoloration of the penis, as well as an oval, dusky, eroded plaque (3 cm) with erythema on the glans penis and prepuce (32537).

Hepatic ...Orally, ashwagandha in doses of 154 mg to 20 grams daily has played a role in several case reports of cholestatic, hepatocellular, and mixed liver injuries. In most of these cases, other causes of liver injury were excluded, and liver failure did not occur. Symptoms included jaundice, pruritus, malaise, fatigue, lethargy, weight loss, nausea, diarrhea, abdominal pain and distension, stool discoloration, and dark urine. Symptom onset was typically 5-180 days from first intake, although in some cases onset occurred after more than 12 months of use (102686,107372,110490,110491,111533,111535,112111,113610,114113). Laboratory findings include elevated aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase, serum bilirubin, and international normalized ratio (INR) (112111,113610,114113). In most cases, liver enzymes normalized within 1-5 months after discontinuation of ashwagandha (102686,107372,110491,111535,112111,114113). However, treatment with corticosteroids, lactulose, ornithine, ursodeoxycholic acid, and plasmapheresis, among other interventions, was required in one case (111533). Rarely, use of oral ashwagandha has been reported to cause hepatic encephalopathy, liver failure requiring liver transplantation, and acute-on-chronic liver failure resulting in death (110490,113610).

Neurologic/CNS ...Orally, ashwagandha has been reported to cause drowsiness (110492,113609). Headache, neck pain, and blurry vision have been reported in a 47-year-old female taking ashwagandha, cannabis, and venlafaxine. Imaging over the course of multiple years and hospital admissions indicated numerous instances of intracranial hemorrhage and multifocal stenosis of intracranial arteries, likely secondary to reversible cerebral vasoconstriction syndrome (RCVS) (112113). It is unclear whether the RCVS and subsequent intracranial hemorrhages were precipitated by ashwagandha, cannabis, or venlafaxine.

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General ...Orally, cordyceps seems to be generally well tolerated when used for up to 1 year.
Most Common Adverse Effects:
Orally: Abdominal discomfort, constipation, diarrhea.

Gastrointestinal ...Orally, cordyceps has been associated with diarrhea, constipation, abdominal discomfort, dry mouth, and throat discomfort in clinical research. However, these events were uncommon, and in some cases symptoms could be reduced by taking cordyceps after eating (92829,105076,109705).

Hematologic ...Two cases of lead poisoning, characterized by loss of appetite and other symptoms, have been reported for patients taking cordyceps powder. After discontinuing cordyceps supplementation, both patients were treated with chelating agents (46135).

Hepatic ...There is a case report of acute cholestatic hepatitis probably associated with the use of a product containing cordyceps. The 64-year-old male was asymptomatic except for jaundice and laboratory markers and recovered once the supplement was stopped. However, it is unclear whether the hepatitis is associated with the cordyceps or with an unknown contaminant (109704).

Renal ...One case of a mild increase in serum creatinine level (< 30%) has been reported (95905).

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General ...Orally and topically, holy basil extract seems to be well tolerated.
Most Common Adverse Effects:
Orally: Loose stools and nausea.
Topically: Bitter taste with oral application.

Gastrointestinal ...Orally, two out of 24 participants taking capsules containing holy basil extract in one clinical study experienced nausea or loose stools (55037).
Topically, holy basil mouthwash has been reported to cause a bitter taste in clinical trials (55038).

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General ...Orally, pantothenic acid is generally well tolerated. Topically and intramuscularly, dexpanthenol, a synthetic form of pantothenic acid, seems to be well tolerated.
Most Common Adverse Effects:
Topically: Burning, contact dermatitis, eczema, irritation, and itching related to dexpanthenol.

Cardiovascular ...There is one case of eosinophilic pleuropericardial effusion in a patient taking pantothenic acid 300 mg per day in combination with biotin 10 mg per day for 2 months (3914).

Dermatologic ...Topically, dexpanthenol has been associated with itching, burning, skin irritation, contact dermatitis, and eczema (67779,67781,67788,111258,111262). Three cases of allergic contact dermatitis have been reported (111260,111261).

Gastrointestinal ...Orally, pantothenic acid has been associated with diarrhea (67822,111258).

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General ...Orally, rhodiola seems to be well tolerated.
Most Common Adverse Effects:
Orally: Dizziness, increased or decreased production of saliva.

Gastrointestinal ...Orally, rhodiola extract may cause dry mouth or excessive saliva production (16410,16411).

Neurologic/CNS ...Orally, rhodiola extract can cause dizziness (16410).

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General ...Orally, schisandra seems to be generally well tolerated.
Most Common Adverse Effects:
Orally: Decreased appetite, heartburn, stomach upset, and urticaria.

Dermatologic ...Orally, schisandra can cause urticaria in some patients (11).

Gastrointestinal ...Orally, schisandra can cause heartburn, decreased appetite, and stomach upset (11).

(Read more about SCHISANDRA)

General ...Orally or by injection, vitamin B6 is well tolerated in doses less than 100 mg daily.
Most Common Adverse Effects:
Orally or by injection: Abdominal pain, allergic reactions, headache, heartburn, loss of appetite, nausea, somnolence, vomiting.
Serious Adverse Effects (Rare):
Orally or by injection: Sensory neuropathy (high doses).

Dermatologic ...Orally, vitamin B6 (pyridoxine) has been linked to reports of skin and other allergic reactions and photosensitivity (8195,9479,90375). High-dose vitamin B6 (80 mg daily as pyridoxine) and vitamin B12 (20 mcg daily) have been associated with cases of rosacea fulminans characterized by intense erythema with nodules, papules, and pustules. Symptoms may persist for up to 4 months after the supplement is stopped, and may require treatment with systemic corticosteroids and topical therapy (10998).

Gastrointestinal ...Orally or by injection, vitamin B6 (pyridoxine) can cause nausea, vomiting, heartburn, abdominal pain, mild diarrhea, and loss of appetite (8195,9479,16306,83064,83103,107124,107127,107135). In a clinical trial, one patient experienced infectious gastroenteritis that was deemed possibly related to taking vitamin B6 (pyridoxine) orally up to 20 mg/kg daily (90796). One small case-control study has raised concern that long-term dietary vitamin B6 intake in amounts ranging from 3.56-6.59 mg daily can increase the risk of ulcerative colitis (3350).

Hematologic ...Orally or by injection, vitamin B6 (pyridoxine) can cause decreased serum folic acid concentrations (8195,9479). One case of persistent bleeding of unknown origin has been reported in a clinical trial for a patient who used vitamin B6 (pyridoxine) 100 mg twice daily on days 16 to 35 of the menstrual cycle (83103). It is unclear if this effect was due to vitamin B6 intake.

Musculoskeletal ...Orally or by injection, vitamin B6 (pyridoxine) can cause breast soreness or enlargement (8195).

Neurologic/CNS ...Orally or by injection, vitamin B6 (pyridoxine) can cause headache, paresthesia, and somnolence (8195,9479,16306). Vitamin B6 (pyridoxine) can also cause sensory neuropathy, which is related to daily dose and duration of intake. Doses exceeding 1000 mg daily or total doses of 1000 grams or more pose the most risk, although neuropathy can occur with lower daily or total doses as well (8195). The mechanism of the neurotoxicity is unknown, but is thought to occur when the liver's capacity to phosphorylate pyridoxine via the active coenzyme pyridoxal phosphate is exceeded (8204). Some researchers recommend taking vitamin B6 as pyridoxal phosphate to avoid pyridoxine neuropathy, but its safety is unknown (8204). Vitamin B6 (pyridoxine) neuropathy is characterized by numbness and impairment of the sense of position and vibration of the distal limbs, and a gradual progressive sensory ataxia (8196,10439). The syndrome is usually reversible with discontinuation of pyridoxine at the first appearance of neurologic symptoms. Residual symptoms have been reported in patients taking more than 2 grams daily for extended periods (8195,8196). Tell patients daily doses of 100 mg or less are unlikely to cause problems (3094).

Oncologic ...In females, population research has found that a median intake of vitamin B6 1. 63 mg daily is associated with a 3.6-fold increased risk of rectal cancer when compared with a median intake of 1.05 mg daily (83024). A post-hoc subgroup analysis of results from clinical research in adults with a history of recent stroke or ischemic attack suggests that taking folic acid, vitamin B12, and vitamin B6 does not increase cancer risk overall, although it was associated with an increased risk of cancer in patients who also had diabetes (90378). Also, in patients with nasopharyngeal carcinoma, population research has found that consuming at least 8.6 mg daily of supplemental vitamin B6 during treatment was associated with a lower overall survival rate over 5 years, as well as a reduced progression-free survival, when compared with non-users and those with intakes of up to 8.6 mg daily (107134).

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General ...Orally, intravenously, and topically, vitamin C is well-tolerated.
Most Common Adverse Effects:
Orally: Abdominal cramps, esophagitis, heartburn, headache, osmotic diarrhea, nausea, vomiting. Kidney stones have been reported in those prone to kidney stones. Adverse effects are more likely to occur at doses above the tolerable upper intake level of 2 grams daily.
Topically: Irritation and tingling.
Serious Adverse Effects (Rare):
Orally: There have been rare case reports of carotid inner wall thickening after large doses of vitamin C.
Intravenously: There have been case reports of hyperoxalosis and oxalate nephropathy following high-dose infusions of vitamin C.

Cardiovascular ...Evidence from population research has found that high doses of supplemental vitamin C might not be safe for some people. In postmenopausal adults with diabetes, supplemental vitamin C intake in doses greater than 300 mg per day is associated with increased risk of cardiovascular mortality. However, dietary intake of vitamin C is not associated with this risk. Also, vitamin C intake is not associated with an increased risk of cardiovascular mortality in patients without diabetes (12498).
Oral supplementation with vitamin C has also been associated with an increased rate of carotid inner wall thickening in men. There is preliminary evidence that supplemental intake of vitamin C 500 mg daily for 18 months can cause a 2.5-fold increased rate of carotid inner wall thickening in non-smoking men and a 5-fold increased rate in men who smoked. The men in this study were 40-60 years old (1355). This effect was not associated with vitamin C from dietary sources (1355).
There is also some concern that vitamin C may increase the risk of hypertension in some patients. A meta-analysis of clinical research suggests that, in pregnant patients at risk of pre-eclampsia, oral intake of vitamin C along with vitamin E increases the risk of gestational hypertension (83450). Other clinical research shows that oral intake of vitamin C along with grape seed polyphenols can increase both systolic and diastolic blood pressure in hypertensive patients (13162).

Dental ...Orally, vitamin C, particularly chewable tablets, has been associated with dental erosion (83484).

Dermatologic ...Topically, vitamin C might cause tingling or irritation at the site of application (6166). A liquid containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) has been reported to cause mild tingling and skin tightness (102355). It is unclear if these effects are due to vitamin C, the other ingredients, or the combination.

Gastrointestinal ...Orally, the adverse effects of vitamin C are dose-related and include nausea, vomiting, esophagitis, heartburn, abdominal cramps, gastrointestinal obstruction, and diarrhea. Doses greater than the tolerable upper intake level (UL) of 2000 mg per day can increase the risk of adverse effects such as osmotic diarrhea and severe gastrointestinal upset (3042,4844,96707,104450). Mineral forms of vitamin C, such as calcium ascorbate (Ester-C), seem to cause fewer gastrointestinal adverse effects than regular vitamin C (83358). In a case report, high dose intravenous vitamin C was associated with increased thirst (96709).

Genitourinary ...Orally, vitamin C may cause precipitation of urate, oxalate, or cysteine stones or drugs in the urinary tract (10356). Hyperoxaluria, hyperuricosuria, hematuria, and crystalluria have occurred in people taking 1 gram or more per day (3042,90943). Supplemental vitamin C over 250 mg daily has been associated with higher risk for kidney stones in males. There was no clear association found in females, but the analysis might not have been adequately powered to evaluate this outcome (104029). In people with a history of oxalate kidney stones, supplemental vitamin C 1 gram per day appears to increase kidney stone risk by 40% (12653). A case of hematuria, high urine oxalate excretion, and the presence of a ureteral stone has been reported for a 9-year-old male who had taken about 3 grams of vitamin C daily since 3 years of age. The condition resolved with cessation of vitamin C intake (90936).

Hematologic ...Prolonged use of large amounts of vitamin C can result in increased metabolism of vitamin C; subsequent reduction in vitamin C intake may precipitate the development of scurvy (15). In one case, a patient with septic shock and a large intraperitoneal hematoma developed moderate hemolysis and increased methemoglobin 12 hours after a high-dose vitamin C infusion. The patient received a blood transfusion and the hemolysis resolved spontaneously over 48 hours (112479).

Neurologic/CNS ...Orally, the adverse effects of vitamin C are dose-related and include fatigue, headache, insomnia, and sleepiness (3042,4844,83475,83476).

Renal ...Hyperoxalosis and oxalate nephropathy have been reported following high-dose infusions of vitamin C. Hyperoxalosis and acute kidney failure contributed to the death of a 76-year-old patient with metastatic adenocarcinoma of the lung who received 10 courses of intravenous infusions containing vitamins, including vitamin C and other supplements over a period of 1 month. Dosages of vitamin C were not specified but were presumed to be high-dose (106618). In another case, a 34-year-old patient with a history of kidney transplant and cerebral palsy was found unresponsive during outpatient treatment for a respiratory tract infection. The patient was intubated for acute hypoxemic respiratory failure, initiated on vasopressors, hydrocortisone, and antibacterial therapy, and received 16 doses of vitamin C 1.5 grams. Serum creatinine level peaked at greater than 3 times baseline and the patient required hemodialysis for oliguria and uncontrolled acidosis. Kidney biopsy revealed oxalate nephropathy with concomitant drug-induced interstitial nephritis (106625). In another case, a 41-year-old patient with a history of kidney transplant presented with fever, nausea, and decreased urine output 4 days after receiving intravenous vitamin C 7 grams for urothelial carcinoma. Serum creatinine levels increased from 1.7 mg/dL to 7.3 mg/dL over those 4 days, and hemodialysis was initiated 3 days after admission due to anuria. Renal biopsy confirmed the diagnosis of acute oxalate nephropathy (109962).

Other ...Intravenously, hypernatremia and falsely elevated ketone levels is reported in a patient with septic shock and chronic kidney disease after a high-dose vitamin C infusion. The hypernatremia resolved over 24 hours after cessation of the infusion (112479).

(Read more about VITAMIN C)