Royal Power by North American Herb & Spice

There is insufficient reliable information available about the effectiveness of camu camu.

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POSSIBLY EFFECTIVE

• Memory. Oral rosemary seems to improve memory in young adults. It is unclear if rosemary aromatherapy improves memory. Details: Clinical research in healthy adults shows that taking rosemary 500 mg orally twice daily for one month improves memory by approximately 14% when compared with placebo (98536). Other preliminary clinical research shows that applying four drops of pure rosemary essential oil (Tisserand Aromatherapy) to an aromatherapy diffuser pad 5 minutes before a single test period can improve the quality, but not the speed, of memory recall, and increase alertness and contentment more than lavender aromatherapy or no aroma (18323). Rosemary aromatherapy has also been evaluated for improving memory in adults with kidney failure. A small clinical study in patients (mean age 53 years) undergoing hemodialysis shows that aromatherapy with rosemary essential oil three times weekly for 1 month does not improve medication adherence or measures of prospective and retrospective memory when compared with a control group. In this study, five drops of rosemary essential oil were applied to gauze, which was then placed 10 cm from the patient's nose for 30 minutes starting 1 hour after hemodialysis (109559).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Abortion. Although there has been interest in the use of oral rosemary as an abortifacient, there is insufficient reliable information about the clinical effects of rosemary for this purpose.
• Age-related cognitive decline. It is unclear if oral rosemary is beneficial for age-related cognitive decline. Details: A small clinical study in healthy individuals aged 65-90 years shows that a single 750 mg dose of powdered rosemary leaf in tomato juice may improve memory speed. However, higher single doses of 1500-6000 mg seem to have a deleterious effect on memory speed. For other measures of attention and memory, there were no clear benefits across the range of doses from 750-6000 mg (18246). Oral rosemary has also been evaluated in combination with other ingredients. A small clinical study in healthy adults aged 62 years or younger shows that taking a combination product containing equal parts rosemary, lemon balm, and sage twice daily for 2 weeks modestly improves word recall when compared with placebo. However, it does not appear to have benefit in adults aged 63 years and older (97277). It is unclear if any benefit is due to rosemary, other ingredients, or the combination.
• Alopecia areata. Topical rosemary oil has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that rosemary oil 114 mg, in combination with lavender oil 108 mg, thyme oil 88 mg, and cedarwood oil 94 mg, mixed with jojoba oil 3 mL and grapeseed oil 20 mL and applied topically to the scalp, improves hair growth in 44% of patients, compared with 15% of those receiving placebo. This combination was massaged into the scalp for a minimum of 2 minutes, followed by wrapping the head in a warm towel, every night for 7 months (5177).
• Androgenic alopecia. It is unclear if topical rosemary is beneficial for androgenic alopecia. Details: Preliminary clinical research shows that applying rosemary oil (Barij Essence Pharmaceutical Company) 1 mL to the scalp twice daily for 6 months is as effective as minoxidil 2% for increasing hair count in patients with androgenic alopecia (91729).
• Depression. It is unclear if oral rosemary is beneficial for major depressive disorder. Details: A small clinical trial among adults newly diagnosed with major depressive disorder and recent initiation of antidepressant medication shows that taking rosemary dried leaf extract 650 mg twice daily for 8 weeks might reduce some symptoms of depression and anxiety when compared with placebo (112141). However, the validity of these findings is limited by differences in baseline depression symptom scores between groups.
• Diabetes. It is unclear if oral rosemary is beneficial for improving glycemic control in patients with type 2 diabetes. Details: In patients with type 2 diabetes, preliminary clinical research shows that taking rosemary tea daily for 90 days decreases glycated hemoglobin levels by 15% and waist and hip circumference by 6% and improves insulin resistance. However, there was no effect on fasting blood glucose, lipid profile, body weight, or body mass index (BMI). The tea was made by adding rosemary 2 grams to a liter of boiling water for 3 minutes and then passing through a sieve (105323). Other preliminary clinical research in adults with type 2 diabetes shows that taking rosemary powder 3 grams daily for 4 weeks does not reduce fasting blood glucose levels or improve lipid profile when compared with baseline. These endpoints were improved in a group of healthy adults (105327). The validity of the findings from these studies is limited by the lack a comparator group.
• Diabetic nephropathy. Oral rosemary has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a specific combination product (Canephron N, Bionorica) containing 18 mg each of rosemary leaf, centaury herb, and lovage root per tablet, as two tablets three times daily for 6 months along with standard antidiabetes treatment and enalapril (Vasotec), decreases microalbuminuria by 73%, decreases albumin:creatinine ratio by 46%, increases high-density lipoprotein (HDL) cholesterol by 25%, and lowers triglyceride levels by 43%, but does not improve glomerular filtration rate, when compared to baseline. Improvements were greater in those taking the combination product than in those treated only with standard antidiabetes therapy and enalapril. However, the combination product does not appear to improve reductions in total cholesterol or low-density lipoprotein (LDL) cholesterol (91726).
• Dysmenorrhea. It is unclear if oral rosemary is beneficial for dysmenorrhea. Details: In patients with moderate primary dysmenorrhea, clinical research shows that taking rosemary extract 220 mg every 8 hours for the first three days of the menstrual cycle, repeated for two menstrual cycles, is as effective as mefenamic acid for reducing average pain and bleeding when compared with two baseline cycles (105328).
• Fatigue. Oral rosemary has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in healthy young adults with below-average energy levels shows that taking a single dose of a mixture of rosemary from Albania (Rosmarinus officinalis) and Morocco (Rosmarinus eriocalyx) 1.7 grams does not consistently improve sustained attention, motivation to perform cognitive tasks, mental energy, or mental fatigue when compared with placebo (91731).
• Fibromyalgia. Oral rosemary has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with fibromyalgia shows that taking an oral product containing rosemary leaf extract, oleanolic acid from olive leaf, and rho iso-alpha acids from hops (Meta050, Metagenics), at a dose of 440 mg three times daily for 4 weeks, then 880 mg twice daily for 4 weeks, does not improve symptoms when compared to baseline (18327).
• Gingivitis. A mouth rinse containing rosemary has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults with mild to moderate gingivitis and mild plaque shows that rinsing the mouth with 10 mL of mouthwash containing 5% v/v of a combined alcoholic extract of rosemary, calendula, and ginger for 30 seconds twice daily after meals for 2 weeks decreases plaque formation, gingival inflammation, and gingival bleeding similarly to chlorhexidine gluconate 0.2% mouthwash and better than a placebo mouthwash (93555).
• Hypertension. Although there is interest in using oral rosemary for hypertension, there is insufficient reliable information about the clinical effects of rosemary for this condition.
• Hypotension. It is unclear if oral rosemary is beneficial for hypotension. Details: Preliminary clinical research in patients with primary hypotension shows that taking rosemary essential oil (Metapharmaceutical) 1 mL every 8 hours for 44 weeks increases systolic blood pressure by 13 mmHg and diastolic blood pressure by 7 mmHg when compared to baseline. However, blood pressure returned to near baseline values after treatment discontinuation (91730).
• Mental alertness. It is unclear if rosemary aromatherapy is beneficial for improving mental alertness. Details: Preliminary clinical research in nurses working on a night shift shows that placing one drop of rosemary oil on a surgical mask that is worn for 2 hours with a 10-minute on/15-minute off cycle modestly increases alertness and reduces sleepiness when compared with a water drop control (105324).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral rosemary leaf is beneficial in patients with NAFLD. Details: A small clinical study in patients with NAFLD shows that taking rosemary leaf powder 2 grams twice daily for 8 weeks, in conjunction with diet and exercise recommendations, does not improve measures of liver function, glycemic control, cholesterol, or body weight when compared with placebo (109561).
• Opioid withdrawal. It is unclear if oral rosemary is beneficial for opioid withdrawal when used in combination with methadone. Details: Preliminary clinical research shows that taking rosemary leaf along with methadone for 2 weeks improves symptoms of opioid withdrawal and the ability to sleep when compared with methadone alone after 3 and 7 days of treatment, but not after 2 weeks. Rosemary leaf was provided in capsules containing 300 mg each (Barij Essence Pharmaceutical Company) at a dose of 16 capsules daily for the first 3 days, 12 capsules daily for the next 4 days, and eight capsules daily for the next 7 days, in divided doses (91727).
• Osteoarthritis. Oral rosemary has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows subjective reductions in pain associated with osteoarthritis when oral formulations containing rosemary leaf extract, oleanolic acid from olive leaf, and rho iso-alpha acids from hops (NG440-2, Metagenics; Meta050, Metagenics) are used (18326,18327). The formulation used in one of these studies (Meta050, Metagenics) was taken in a dose of 440 mg three times daily for 4 weeks, then 880 mg twice daily for 4 weeks (18327). The formulation used in the other study, which was taken daily for 4 weeks, contained rosemary leaf extract 112.5 mg, oleanolic acid from olive leaf 1 mg, and rho iso-alpha acids from hops 225 mg per tablet (18326).
• Raynaud syndrome. It is unclear if topical rosemary essential oil is beneficial in patients with Raynaud syndrome. Details: A very small, open-label study in patients with Raynaud syndrome caused by systemic scleroderma shows that applying 10 drops of rosemary 10% essential oil to the hands does not increase skin temperature or improve warmth perception when compared with olive oil (109560). However, this study may have been inadequately powered to detect a difference between groups.
• Rheumatoid arthritis (RA). Oral rosemary has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows subjective decreases in pain associated with RA when oral formulations containing rosemary leaf extract, oleanolic acid from olive leaf, and rho iso-alpha acids from hops (NG440-2, Metagenics; Meta050, Metagenics) are used (18326,18327). The formulation used in one of these studies (Meta050, Metagenics) was taken in a dose of 440 mg three times daily for 4 weeks, then 880 mg twice daily for 4 weeks (18327). The formulation used in the other study, which was taken daily for 4 weeks, contained rosemary leaf extract 112.5 mg, oleanolic acid from olive leaf 1 mg, and rho iso-alpha acids from hops 225 mg per tablet (18326).
• Stress. It is unclear if rosemary aromatherapy is beneficial for stress. Details: Preliminary clinical research on the use of rosemary aromatherapy for anxiety and stress is conflicting. In a group of graduate nursing students, perceived stress associated with taking a test was lower when inhalers containing rosemary or lavender oil were used. Three drops of rosemary essential oil were added to an inhaler and inhaled before and during the test. Pulse rates, but not blood pressure, were also reduced (18324). In contrast, a small clinical study in adults aged 18-30 years shows that the aroma from diluted rosemary essential oil applied to the wrist during timed crossword puzzle completion actually increases subjective feelings of anxiety and tension when compared with placebo (18325).
• Sunburn. Oral rosemary has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a combination of rosemary and grapefruit extracts in a 1:1 ratio (NutroxSun, Monteloeder, Inc.), 250 mg orally once daily for 12 weeks, increases the amount of UV radiation needed to cause sunburn by 34% after 8 weeks and 56% after 12 weeks when compared to baseline (91728). The validity of these findings is limited by the lack of a comparator group.
• Upper respiratory tract infection (URTI). Oral rosemary has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial among healthy adults shows that taking a combination product containing rosemary leaf extract, aloe gel powder, and poria mushroom extract daily for 8 weeks does not reduce the frequency, duration, or severity of URTI-related symptoms when compared with placebo. However, in patients receiving an influenza vaccine midway through the study, this product does seem to improve some immune response biomarkers when compared with placebo (111921). The amount of rosemary leaf extract in the supplement was not disclosed.
• Wound healing. It is unclear if topical rosemary cream is beneficial for wound healing. Details: A moderate-sized clinical trial among primiparous adults with medio-lateral episiotomy shows that applying a cream containing rosemary extract to the wound twice daily for 10 days improves episiotomy wound healing and reduces redness and discharge when compared with placebo cream (112143). More evidence is needed to rate rosemary for these uses.

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POSSIBLY EFFECTIVE

• Menopausal symptoms. Several clinical studies suggest that oral royal jelly, taken alone or in combination with other ingredients, modestly improves menopausal symptoms. It is unclear if topical royal jelly is beneficial for this use. Details: One clinical study in postmenopausal patients shows that taking royal jelly 1000 mg daily for 8 weeks reduces menopausal symptom scores by around 30% when compared with placebo (102527). Other small clinical studies show that taking one to two capsules of a specific combination product containing royal jelly and flower pollen (Melbrosia) daily for 12 weeks reduces menopausal symptoms and improves feelings of well-being when compared with baseline or placebo (18064,71956,72005). Another clinical trial in postmenopausal patients shows that taking two capsules of a specific combination product containing royal jelly, evening primrose oil, damiana, and ginseng (Lady 4) daily for 4 weeks decreases self-rated menopausal symptoms when compared with placebo (21003). Topical royal jelly has also been evaluated. A small clinical study in postmenopausal adults shows that applying vaginal cream containing royal jelly 15% daily for 12 weeks improves quality of life, sexual problems, and urinary problems similarly to vaginal estrogen cream 0.625 mg. However, estrogen cream improves vaginal atrophy better than royal jelly (92884).

POSSIBLY INEFFECTIVE

• Allergic rhinitis (hay fever). Oral royal jelly does not appear to prevent or treat symptoms of allergic rhinitis in children. Details: A clinical trial in children 5-16 years of age with allergic rhinitis shows that taking a specific royal jelly product (Bidro) 150 mg twice daily for 3-6 months before and during pollen season does not prevent or treat nasal congestion, sneezing, or eye discomfort when compared with placebo (71968).
• Diabetes. Oral royal jelly does not appear to improve glycemic control in patients with type 2 diabetes. Details: Most clinical research in patients with type 2 diabetes, along with a meta-analysis of five small clinical trials including patients with or without type 2 diabetes, shows that taking royal jelly 0.5-6 grams daily for 4-8 weeks does not improve markers of glycemic control such as fasting plasma glucose and glycated hemoglobin (HbA1c) (92879,92880,92881,102529).
• Physical performance. Oral royal jelly does not appear to improve physical performance in elderly nursing home residents. Details: A clinical trial in elderly nursing home residents shows that taking royal jelly 1.2 grams or 4.8 grams daily for one year does not improve hand grip strength, walking, or ability to stand on one leg when compared with placebo (95870).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Androgenic alopecia. Although there has been interest in using topical royal jelly for androgenic alopecia, there is insufficient reliable information about the clinical effects of royal jelly for this purpose.
• Atherosclerosis. Although there has been interest in using oral royal jelly for atherosclerosis, there is insufficient reliable information about the clinical effects of royal jelly for this purpose.
• Athletic performance. Oral royal jelly has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Two small clinical trials in elite male swimmers and runners show that taking royal jelly 400 mg and coenzyme Q10 60 mg daily for 10 days does not improve high-intensity interval training performance when compared with placebo (109992,109993). These studies were small and may not have been adequately powered to detect a difference between groups.
• Cancer-related fatigue. It is unclear if oral royal jelly is beneficial for improving cancer-related fatigue. Details: A small clinical study in patients with solid (nonhematologic) malignancies shows that taking 5 mL of processed honey and royal jelly twice daily for 4 weeks reduces fatigue when compared with 5 mL of honey alone (92877).
• Chemotherapy-induced acral erythema. It is unclear if oral royal jelly is beneficial for preventing acral erythema from tyrosine kinase inhibitors (TKIs). Details: One small clinical trial in patients receiving TKI therapy for renal cell carcinoma shows that taking royal jelly 900 mg four times daily for 3 months does not reduce the risk of acral erythema when compared with placebo (105773). However, this study may have been inadequately powered to detect a difference between groups.
• Chemotherapy-induced hepatotoxicity. It is unclear if oral royal jelly is beneficial for preventing hepatotoxicity from tyrosine kinase inhibitors (TKIs). Details: One small clinical trial in patients receiving TKI therapy for renal cell carcinoma shows that taking royal jelly 900 mg four times daily for 3 months does not reduce the risk of hepatotoxicity when compared with placebo (105773). However, this study may have been inadequately powered to detect a difference between groups.
• Chemotherapy-induced nephrotoxicity. It is unclear if oral royal jelly is beneficial for preventing chemotherapy-induced nephrotoxicity. Details: A small clinical study in patients receiving two cycles of cisplatin therapy shows that taking royal jelly capsules daily may attenuate increases in serum creatinine and urea levels when compared with placebo. However, it is unclear if this effect is clinically significant; the increased levels that occurred in the placebo group were still within normal limits (95871). The validity of these results is also limited by the short study duration and lack of statistical comparison between groups. Another small clinical trial in patients receiving tyrosine kinase inhibitor therapy for renal cell carcinoma shows that taking royal jelly 900 mg four times daily for 3 months does not reduce the risk of kidney dysfunction when compared with placebo (105773). However, this study may have been inadequately powered to detect a difference between groups.
• Chemotherapy-related fatigue. It is unclear if oral royal jelly is beneficial for preventing fatigue from tyrosine kinase inhibitors (TKIs). Details: One small clinical trial in patients receiving TKI therapy for renal cell carcinoma shows that taking royal jelly 900 mg four times daily for 3 months reduces the frequency of chemotherapy-related fatigue when compared with placebo (105773,105774).
• Cognitive impairment. Oral royal jelly has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in elderly patients with mild cognitive impairment shows that taking a specific combination product (Memo, Pharco Pharmaceuticals), which contains natural lyophilized royal jelly 750 mg, ginkgo leaf extract 120 mg, and Panax ginseng root extract 150 mg, daily for 4 weeks improves cognitive ability when compared with placebo (89712).
• Coronavirus disease 2019 (COVID-19). Oral royal jelly has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in adults without diabetes in Iran hospitalized with moderately severe COVID-19 receiving corticosteroids shows that taking a specific combination supplement (Tang Forte, HealthAid) containing royal jelly extract 350 mg and vitamin E 2 mg daily for 7 days does not improve markers of the clinical course of COVID-19, such as oxygen saturation or length of hospital stay, when compared with placebo (114535). However, this study may not have been adequately powered to detect a difference between groups. It is unclear if this effect is due to royal jelly, other ingredients, or the combination.
• Diabetic foot ulcers. Small clinical studies suggest that topical application of royal jelly plus panthenol may improve healing of diabetic foot ulcers. It is unclear if topical royal jelly alone is beneficial for this use. Details: One small clinical study shows that applying royal jelly 5% to a wound after conventional cleansing and debriding three times weekly for 3 months does not improve the healing of diabetic foot ulcers when compared with placebo (92882). However, other small clinical studies show that applying 1-3 grams of a specific combination ointment (Pedyphar) containing royal jelly and panthenol after conventional cleansing and debriding procedures twice weekly for up to 6 months may improve the healing of diabetic foot ulcers (71980,102526). In one of these studies, the rate of complete healing of life-threatening ulcers was 2.7-fold greater with this combination ointment when compared with panthenol alone (102526). Possible reasons for these discrepancies include the use of combination versus single ingredient ointments and the duration of treatment.
• Dry eye. It is unclear if oral royal jelly is beneficial in patients with dry eye. Details: A small clinical trial in Japanese patients with dry eye shows that taking enzyme-treated royal jelly 2.4 grams daily for 8 weeks does not improve tear stability or dry eye symptoms when compared with placebo (95869).
• Fractures. Although there has been interest in using oral royal jelly for healing of fractures, there is insufficient reliable information about the clinical effects of royal jelly for this purpose.
• Hepatitis. Although there has been interest in using oral royal jelly for hepatitis, there is insufficient reliable information about the clinical effects of royal jelly for this purpose.
• Male infertility. Intravaginal application of royal jelly has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in couples experiencing infertility due to asthenozoospermia shows that applying a saline solution containing royal jelly 3 grams, Egyptian bee honey 100 grams, and bee bread 1 teaspoon intravaginally before or after intercourse, starting one day after menstruation and continuing for 2 weeks, can increase the rate of pregnancy when compared with intrauterine insemination (55131). It is unclear if this effect is due to royal jelly, other ingredients, or the combination.
• Obesity. It is unclear if oral royal jelly is beneficial for reducing body weight in patients who are overweight or obese. Details: One small clinical study in overweight patients with type 2 diabetes shows that taking fresh royal jelly 1 gram daily for 8 weeks reduces body weight by around 2 kg and body mass index (BMI) by around 0.7 kg/m², as well as carbohydrate and total energy intake, when compared with placebo. However, the improvement is modest and may not be clinically significant (92878). Another small clinical study in overweight adults shows that taking royal jelly 1000 mg daily for 8 weeks does not reduce body weight, BMI, or appetite when compared with placebo (102528). However, this study may have been inadequately powered to detect a difference in these outcomes.
• Oral mucositis. It is unclear if oral royal jelly is beneficial for preventing or treating oral mucositis in patients receiving radiotherapy and/or chemotherapy. Details: One small clinical trial in patients receiving chemotherapy and radiotherapy shows that swishing and swallowing royal jelly 1 gram in two divided doses daily, in addition to standard rinses with benzydamine and nystatin, improves healing time of mild or moderate oral mucositis when compared with standard rinses alone (95867).
• Osteoporosis. It is unclear if oral royal jelly is beneficial in patients with osteoporosis. Details: A small clinical trial in postmenopausal adults shows that taking royal jelly powder 1000 mg, equivalent to 3000 mg of fresh royal jelly, daily for 6 months maintains bone mineral density (BMD) in the proximal femur and lumbar spine, while patients taking placebo saw significant reductions in lumbar spine BMD. Also, markers of bone turnover were significantly reduced with placebo, while significant changes in these markers were lacking in patients taking royal jelly (105775). It is unclear whether these findings can be generalized to patients with documented osteoporosis.
• Peptic ulcers. Although there has been interest in using oral royal jelly for peptic ulcers, there is insufficient reliable information about the clinical effects of royal jelly for this purpose.
• Premenstrual syndrome (PMS). It is unclear if oral royal jelly, taken alone or in combination with other ingredients, is beneficial in patients with PMS. Details: A small clinical study in healthy college students shows that taking royal jelly 1 gram daily starting on the first day of menstruation and continuing for two consecutive menstrual cycles improves PMS symptoms when compared with placebo (95873). However, methodological flaws associated with the study limit the validity of these results. A small clinical study shows that taking a specific combination product (Femal, Natumin Pharma), providing royal jelly 12 mg, bee pollen extract 72 mg, and bee pollen plus pistil extract 240 mg, twice daily over 2 menstrual cycles seems to decrease some symptoms of PMS including irritability, weight increases, and edema (12008). It is unclear if these effects are due to royal jelly, other ingredients, or the combination.
• Renal cell carcinoma. It is unclear if oral royal jelly is beneficial in patients with renal cell carcinoma. Details: One small clinical trial in patients receiving tyrosine kinase inhibitor (TKI) therapy for renal cell carcinoma shows that taking royal jelly 900 mg four times daily for 3 months reduces tumor size, improves chemotherapy-related fatigue and anorexia, and reduces the need for dose reduction or the discontinuation of therapy when compared with placebo (105773,105774). Royal jelly does not seem to reduce other TKI-related adverse effects, including gastrointestinal symptoms, oral mucositis, acral erythema, anemia, hepatotoxicity, or nephrotoxicity, when compared with placebo (105773). However, this study may have been inadequately powered to detect a difference in these outcomes. More evidence is needed to rate royal jelly for these uses.

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POSSIBLY EFFECTIVE

• Cognitive function. Oral sage seems to be beneficial for improving cognitive function in healthy adults. The benefits of sage aromatherapy are unclear. Details: Clinical research shows that taking a specific product providing common sage polyphenols and Spanish sage terpenoids (Cognivia), either as a single dose or daily for 29 days, modestly improves working memory and accuracy when compared with placebo. A single dose of this product contains common sage leaf extract 400 mg and Spanish sage essential oil 200 mg (105337). In addition, preliminary clinical research shows that Spanish sage essential oil 25-50 mcL orally as a single dose seems to dose-dependently enhance some measures of cognitive performance in young adults by a small amount (10811,72609,72616,72660). When used as aromatherapy, essential oils of common sage, but not Spanish sage, seem to improve quality of memory and secondary memory. Neither species improves speed of memory or working memory when used as aromatherapy. In this study, five drops of common sage essential oil and 5 mL water were placed on a warmed stone and allowed to diffuse for 5 minutes prior to exposure (72658).
• Hyperlipidemia. Oral sage seems to be beneficial for reducing low-density lipoprotein (LDL) cholesterol and triglyceride levels. Details: Clinical research in adults with mixed hyperlipidemia types shows that taking common sage leaf extract 500 mg, standardized to quercetin 2.16%, three times daily for 2 months reduces LDL cholesterol and triglyceride levels by about 20% and 23%, respectively, and increases high-density lipoprotein (HDL) cholesterol levels by 20%, when compared with placebo (72662). Also, preliminary clinical research in adults with type 2 diabetes and hypercholesterolemia shows that taking common sage leaf extract 500 mg three times daily for 3 months lowers total cholesterol by 17%, LDL cholesterol by 36%, and triglycerides by 56%, and increases HDL cholesterol by 28%, when compared with placebo (91971).
• Menopausal symptoms. Oral sage seems to be beneficial for reducing menopausal symptoms. Details: Clinical research shows that taking a thujone-free common sage extract (Menosan, A.Vogel AG) 280 mg daily for 4 weeks reduces overall symptoms of menopause by 39% when compared with placebo. About 41% of patients taking common sage had at least a 50% reduction in symptoms, compared with 8% of those taking placebo. Hot flushes, sleep problems, joint and muscle discomfort, irritability, and physical and mental exhaustion were improved, whereas urogenital symptoms such as sexual desire and vaginal dryness were not (105338). Other clinical research shows that taking common sage extract 300 mg daily for 3 months moderately reduces overall symptoms of menopause after about 10 weeks when compared with placebo. However, there was no effect on vaginal dryness, physical and mental exhaustion, or urinary incontinence (103379). Another small clinical study shows that taking a specific thujone-free common sage extract (Sage Menopause, Bioforce AG) 280 mg daily for 56 days reduces daily hot flash frequency by 40% and reduces hot flash intensity when compared with baseline (17177). The validity of these findings is limited by the lack of a comparator group.

POSSIBLY INEFFECTIVE

• Postoperative pain. Using an oral rinse containing common sage does not seem to be beneficial for reducing postoperative pain. Details: A large open-label clinical trial in children and adults shows that using a common sage oral rinse 6 times daily in combination with ibuprofen or diclofenac is less effective than benzydamine hydrochloride, a local anesthetic, for reducing pain following tonsillectomy and/or adenoidectomy. Furthermore, treatment with common sage oral rinse is associated with an increased risk of postoperative infection in adults when compared with benzydamine hydrochloride (72700).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if a single oral dose of common sage is beneficial for age-related cognitive decline. Details: Clinical research in healthy, older adults shows that taking a single dose of common sage extract 333 mg improves accuracy of attention and some measures of memory when compared with placebo. However, not all doses were effective and some measures of cognitive function were not affected (72642).
• Alzheimer disease. It is unclear if oral sage is beneficial for Alzheimer disease. Details: Preliminary clinical research shows that taking extracts of common sage and Spanish sage orally seems to improve cognitive function in patients with mild to moderate Alzheimer disease when used for up to 4 months (10334,10810). In one study, a fixed dose of common sage hydroalcoholic extract, equivalent to 1 gram of sage per day, was used for 4 months (10810). In the other, an extract of Spanish sage titrated up to 2.5 mg three times daily for 6 weeks was used (10334). These studies are limited by their short duration and small numbers of participants.
• Androgen deprivation therapy (ADT)-associated hot flashes. It is unclear if oral sage is beneficial for ADT-associated hot flashes. Details: Preliminary clinical research in patients with prostate cancer receiving ADT shows that taking common sage extract 150 mg three times daily with meals for 4 weeks reduces hot flash severity by 48% and hot flash frequency by 42% when compared with baseline. These improvements were maintained with an additional 8 weeks of treatment (91970). The validity of these findings is limited by the lack of a comparator group.
• Athletic performance. It is unclear if oral sage is beneficial for improving athletic performance. Details: In young, healthy, physically active adults, taking a specific supplement (Cognivia, Nexira) containing 400 mg common sage leaf extract and 200 mg Spanish sage oil, orally 2 hours prior to a 40-minute stationary cycling session at 80% of maximum aerobic power, lowers perceived exertion scores and improves working memory and reaction times when compared with placebo (108961).
• Chemotherapy-induced nausea and vomiting (CINV). It is unclear if topical sage is beneficial for the treatment or prevention of CINV. Details: A small clinical study in patients undergoing chemotherapy shows that using common sage oil 2 mL topically during 15-minute sessions of Swedish abdominal massage twice daily for 3 days modestly reduces nausea severity scores, but does not affect vomiting frequency, when compared with massage alone (107023).
• Dental plaque. It is unclear if rinsing the mouth with sage is beneficial for reducing plaque. Details: Preliminary clinical research shows that rinsing the mouth with 10-15 mL of a solution containing common sage, twice for 30 seconds four times daily for 4 days, in addition to standard oral care with brushing and use of an oral gel (Biotene), is as effective as normal saline for reducing dental plaque. However, there was no effect on tongue plaque. The rinse was made by steeping 2.5 grams of dried sage leaf in 100 mL boiled water for two minutes (105339).
• Diabetes. It is unclear if oral sage is beneficial for diabetes. Details: A small clinical study in adults with type 2 diabetes shows that taking common sage leaf extract 500 mg three times daily for 3 months lowers fasting blood glucose by 32% and glycated hemoglobin (HbA1c) by 23% when compared with placebo (91971). However, another small clinical study in patients with type 2 diabetes shows that taking common sage extract 150 mg three times daily for 3 months does not lower fasting blood glucose or HbA1c when compared with placebo, although there is a modest reduction in 2-hour postprandial blood glucose levels (105340). A meta-analysis of 3 small studies, including the 2 described above, shows that taking common sage, 150-500 mg three times daily for 2-3 months, modestly reduces fasting blood glucose and 2-hour postprandial blood glucose levels, as well as HbA1c, when compared with placebo (108962). These studies were all conducted in Iran; it is unclear if these findings are generalizable to other geographic locations.
• Dry mouth. It is unclear if rinsing the mouth with common sage is beneficial for dry mouth. Details: Preliminary clinical research in patients receiving palliative cancer care shows that rinsing the mouth with 10-15 mL of a solution containing common sage, twice for 30 seconds four times daily for 4 days, in conjunction with standard care involving brushing and an oral gel (Biotene), is as effective as normal saline for improving overall oral health and modestly more effective than normal saline for improving dry mouth. The rinse was made by steeping 2.5 grams dried sage leaf in 100 mL boiled water for two minutes (105339).
• Gingivitis. Sage has only been evaluated as a mouthwash in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in elderly individuals shows that rinsing the mouth with a mouthwash containing sage, marshmallow, calendula, tormentil, horse chestnut, neem, and myrrh, once daily for 30 seconds for 6 weeks, is no more effective than placebo for improving plaque and gingival bleeding (105341).
• Herpes labialis (cold sores). It is unclear if topical sage is beneficial for herpes labialis. Details: Clinical research shows that topical application of a cream containing either sage alone or sage with rhubarb, starting within 1 day of the first symptoms and continuing for 10-14 days, heals herpes labialis legions in 7.6 days or 6.7 days, respectively, compared to a healing time of 6.3 days with acyclovir cream. The combination of sage and rhubarb also improves the time to healing and reduces pain when compared with sage alone. The cream provided 23 mg sage extract, with or without 23 mg rhubarb extract, per gram and was applied every 2-4 hours while awake (10437).
• Lung cancer. It is unclear if dietary sage is beneficial for lung cancer prevention. Details: Epidemiological research has found that regularly consuming sage is associated with a 54% lower risk of developing lung cancer when compared with those who do not use sage as a spice (72593).
• Oral mucositis. It is unclear if rinsing the mouth with sage is beneficial for oral mucositis. Details: Preliminary clinical research in patients receiving palliative cancer care shows that rinsing the mouth with 10-15 mL of a rinse containing common sage, twice for 30 seconds four times daily for 4 days, in addition to standard oral care with brushing and use of an oral gel (Biotene), does not improve oral mucositis when compared with baseline or normal saline rinse. The rinse was made by steeping 2.5 grams of dried sage leaf in 100 mL boiled water for two minutes (105339).
• Pharyngitis. It is unclear if inhaling a spray containing sage, with or without other ingredients, is beneficial for pharyngitis. Details: Clinical research in patients with acute viral pharyngitis shows that inhaling three puffs (140 mcL) of a specific spray (Valverde Salvia Rachenspray) containing common sage extract 15%, six to nine times daily for 3 days, reduces throat pain intensity over 2 hours when compared with placebo. However, sprays containing common sage extract 5% or 30% do not seem to be more effective than placebo for reducing throat pain (72619). Other preliminary clinical research in patients with sore throat due to acute pharyngitis or tonsillitis shows that applying a combination spray product containing common sage leaf tincture 430 mg/mL, Echinacea flowering aerial parts tincture 863.3 mg/mL, and Echinacea root tincture 45.5 mg/mL, every 2 hours up to 10 times daily for up to 5 consecutive days improves symptoms as effectively as a chlorhexidine-lidocaine spray (20077).
• Polycystic ovary syndrome (PCOS). It is unclear if oral sage is beneficial for PCOS. Details: Clinical research shows that taking common sage extract 330 mg daily for 8 weeks modestly reduces body mass index (BMI), diastolic blood pressure, and fasting blood glucose, and modestly improves measures of insulin resistance, when compared with placebo in individuals with PCOS. However, there was no effect on waist to hip ratio or systolic blood pressure (103380).
• Sunburn. It is unclear if topical sage is beneficial for sunburn prevention. Details: Clinical research shows that a single application of a hydrophilic ointment containing common sage extract 2% to the skin immediately after exposure to ultraviolet light reduces the development of skin redness when compared with placebo (72638).
• Swallowing dysfunction. It is unclear if rinsing the mouth with sage is beneficial for swallowing dysfunction. Details: Preliminary clinical research in patients receiving palliative cancer care shows that rinsing the mouth with 10-15 mL of a solution containing common sage, twice for 30 seconds four times daily for 4 days, in addition to standard oral care with brushing and use of an oral gel (Biotene), does not improve swallowing when compared with baseline or normal saline rinse. The rinse was made by steeping 2.5 grams of dried sage leaf in 100 mL boiled water for two minutes (105339).
• Tonsillitis. Sage has only been evaluated in a spray in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with sore throat due to acute pharyngitis or tonsillitis shows that applying a combination spray product containing common sage leaf tincture 430 mg/mL, Echinacea flowering aerial parts tincture 863.3 mg/mL, and Echinacea root tincture 45.5 mg/mL, every 2 hours up to 10 times daily for up to 5 consecutive days improves symptoms as effectively as a chlorhexidine-lidocaine spray (20077).
• Tonsillopharyngitis. It is unclear if oral sage is beneficial for treating tonsillopharyngitis. Details: A moderate-sized observational study in patients aged 12-75 years old with acute tonsillopharyngitis suggests that taking lozenges containing sage extract 378.5 mg and echinacea extract 5 times daily for 4 days reduces throat pain and tonsillopharyngitis symptoms when compared to baseline, both acutely within 90 minutes and after 4 days of treatment (111530). The validity of these findings is limited by the lack of a comparator group. Also, it is unclear if these effects are due to sage, echinacea, the combination, or natural resolution of the condition. More evidence is needed to rate sage 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). Similarly, a meta-analysis of 8 clinical studies in primarily hospitalized patients with moderate to severe COVID-19 shows that vitamin C administered orally or intravenously decreases the risk of all-cause mortality by 16% when compared with control (114488). 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. 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, three randomized clinical trials in patients with sepsis or septic shock show no benefit with intravenous vitamin C, with or without thiamine, for improving organ function and preventing organ failure when compared with control treatment (102130,104027,114489). A small clinical study in patients with septic shock shows that intravenous vitamin C 50 or 150 mg/kg daily for 4 days does not improve organ dysfunction or failure rates, duration of hospital or intensive care unit (ICU) length of stay, duration of mechanical ventilation, or mortality rate when compared with placebo (114489). Another 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 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).
• Child growth. Some clinical research in pregnant smokers suggests that taking vitamin C during pregnancy may improve pulmonary function in the offspring from birth to 6 years of age. Details: A meta-analysis of 4 data sets from one large clinical study 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 at 0, 3, 12, and 60 months of age, but does not improve airway obstruction, when compared with control (113670). Additionally, one of the clinical studies included the meta-analysis shows that taking vitamin C during pregnancy lowers the occurrence of wheezing in offspring at 4-6 years of age (114496,114497).
• 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). Additionally, a meta-analysis of 4 other, mostly small clinical studies in patients with endometriosis shows that taking vitamin C 1000 mg and vitamin E 800-1200 IU daily for 6-8 weeks reduces chronic pelvic pain and improves dysmenorrhea and dyspareunia when compared with placebo (114491).
• 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 or intravenous vitamin C helps to prevent or treat pneumonia. Details: A meta-analysis of 6 clinical studies in adults with community-acquired pneumonia shows that oral or intravenous vitamin C does not reduce overall mortality, hospital or intensive care unit length of stay, or the risk of mechanical ventilation when compared with control (114490). The interpretation of these results is limited by significant heterogeneity of the included studies. An earlier meta-analysis of two small, low-quality clinical studies in children shows that vitamin C does not seem to reduce the risk of pneumonia when compared with a 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 unit (ICU) or hospital stay with vitamin C supplementation (96705), while another clinical study in patients undergoing cardiac surgery with extracorporeal circulation shows that intravenous vitamin C administered during surgery and 48 hours after surgery reduces ICU stay and re-admission rates, wound infection, and hospital mortality, but not length of hospital stay, when compared with control (114492). 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).
• Postoperative pulmonary complications. It is unclear if intravenous vitamin C improves postoperative pulmonary complications. Details: A large, single-blind clinical study in patients with recent cardiac surgery with extracorporeal circulation shows that parenteral administration of vitamin C 50 mg/kg intraoperatively and 50 mg/kg every 6 hours for the next 48 hours, followed by oral vitamin C 2000 mg daily until 1-week post-discharge, reduces the incidence of postoperative pulmonary complications (PPC) by 22% and improves PPC severity scores when compared with control. Specifically, vitamin C reduces the incidence of pneumothorax, pleural effusion, pneumonia, and re-intubation and may ameliorate lung damage as suggested by higher Horowitz index when compared with control (114492). A small clinical trial in patients undergoing low-risk cardiac surgery 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). Another meta-analysis of clinical research shows that taking vitamin C during pregnancy decreases the risk of PROM by 43% and preterm PROM by 33%, but does not decrease the risk of term PROM, when compared with a control. While vitamin C was studied in doses of 100, 500, and 1000 mg daily, the decreased risk of PROM was only observed in studies of 100 mg daily (114493). A moderate-sized 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). Additionally, a meta-analysis of observational studies suggests that vitamin C levels in the blood tend to be lower in patients with PROM, particularly preterm PROM (114493). 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.
• 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)

There is insufficient reliable information available about the safety of camu camu.

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

(Read more about CAMU CAMU)

LIKELY SAFE ...when used orally in amounts typically found in foods. Rosemary has Generally Recognized as Safe (GRAS) status in the US (4912).

POSSIBLY SAFE ...when the leaf is used orally and appropriately in medicinal amounts (18). Powdered rosemary leaf has been used with apparent safety as a single dose of up to 1.5 grams (18246,91731) or at a dose of 1-4 grams daily for up to 8 weeks (91727,98536,105327,109561). ...when the essential oil is used topically and appropriately for up to 7 months (5177,91729,109560). ...when the essential oil is used by inhalation as aromatherapy, short-term (7107,18323,105324,109559).

LIKELY UNSAFE ...when the essential oil or very large quantities of rosemary leaf are used orally. Ingestion of undiluted rosemary oil or very large quantities of rosemary leaf can cause serious adverse effects (18,515).

PREGNANCY: POSSIBLY UNSAFE
when used orally in medicinal amounts. Rosemary might have uterine and menstrual flow stimulant effects (4,12,18), and might increase metabolism of estradiol and estrone (18331); avoid using. There is insufficient reliable information available about the safety of rosemary when used topically during pregnancy.

LACTATION:
There is insufficient reliable information available about the safety of using rosemary in medicinal amounts during lactation; avoid using.

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POSSIBLY SAFE ...when used orally and appropriately, short-term. Royal jelly 1-4.8 grams daily for up to 1 year has been used in clinical research without reported adverse effects (95869,95870,102527,102528,105773,105774)....when used topically and appropriately for up to 6 months (71980,102526).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately for up to 6 months. A specific royal jelly product (Bidro) 150 mg twice daily has been used with apparent safety for 3-6 months in children 5-16 years of age (71968).

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

(Read more about ROYAL JELLY)

LIKELY SAFE ...when used orally in amounts commonly found in foods. Sage is approved for use as a food in the United States (4912).

POSSIBLY SAFE ...when used orally in medicinal doses, short-term. Common sage (Salvia officinalis) and Spanish sage (Salvia lavandulaefolia) have been used with apparent safety when taken orally in doses of 280 mg daily for up to 8 weeks (10334,10810,17177,105338). ...when used topically. Common sage (Salvia officinalis) has been used with apparent safety as a single agent or in combination products for up to one week (10437,72619,107023). ...when the essential oil is inhaled as aromatherapy, short-term (72658).

POSSIBLY UNSAFE ...when used orally in high doses or long-term (12,1304). Some species of sage, including common sage (Salvia officinalis), contain a thujone constituent that can be toxic if consumed in large enough quantities (12,1304).

PREGNANCY: LIKELY UNSAFE
when used orally. The constituent thujone can have menstrual stimulant and abortifacient effects (19).

LACTATION: POSSIBLY UNSAFE
when used orally; sage is thought to reduce the supply of mother's milk (19).

(Read more about SAGE)

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) and has been used with apparent safety in clinical trials up to 150 mg/kg daily for up to 4 days (114489) and up to 200 mg/kg daily for up to 2 days (114492).

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)

(Read more about CAMU CAMU)

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, rosemary may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.  Details In vitro and animal research suggests that rosemary inhibits platelet aggregation (18334,18335,18336,18337).

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking rosemary with antidiabetes drugs might increase the risk of hypoglycemia.  Details Animal research shows that rosemary extract can decrease blood glucose levels in diabetic models (71821,71923). However, research in humans is conflicting. Although rosemary powder decreased blood glucose levels in healthy adults (105327), no change in blood glucose levels was seen in adults with type 2 diabetes, most of whom were taking antidiabetes drugs (105323,105327).

ASPIRIN Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, rosemary might have additive effects with salicylate-containing drugs such as aspirin.  Details Rosemary is reported to contain salicylates (18330).

CHOLINE MAGNESIUM TRISALICYLATE (Trilisate) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, rosemary might have additive effects with salicylate-containing drugs such as choline magnesium trisalicylate.  Details Rosemary is reported to contain salicylate (18330).

CYTOCHROME P450 1A1 (CYP1A1) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, rosemary might decrease the levels and clinical effects of CYP1A1 substrates.  Details In vitro research shows that rosemary induces CYP1A1 enzymes (18332,18333). This effect has not been reported in humans.

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, rosemary might decrease the levels and clinical effects of CYP1A2 substrates.  Details In vitro research shows that rosemary induces CYP1A2 enzymes (18332,18333). This effect has not been reported in humans.

SALSALATE (Disalcid) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, rosemary might have additive effects with salicylate-containing drugs such as salsalate.  Details Rosemary is reported to contain salicylate (18330).

(Read more about ROSEMARY)

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, royal jelly might increase the risk of hypotension when taken with antihypertensive drugs.  Details Animal research suggests that royal jelly might lower blood pressure (71982,71963).

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Royal jelly might increase the risk of bleeding when taken with warfarin.  Details In one case, an 87-year-old male who was previously stabilized on warfarin developed hematuria and was found to have an INR of 7.29 after taking a royal jelly supplement for one week (14303).

(Read more about ROYAL JELLY)

ANTICHOLINERGIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might decrease the clinical effects of anticholinergic drugs.  Details In vitro evidence suggests that common sage (Salvia officinalis) and Spanish sage (Salvia lavandulaefolia) can inhibit acetylcholinesterase and might increase acetylcholine levels (31438,39566,72603,72616).

ANTICONVULSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might interfere with the clinical effects of anticonvulsant drugs.  Details Some species of sage can cause convulsions when consumed in large quantities (10812).

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking sage with antidiabetes drugs might increase the risk of hypoglycemia.  Details In patients with polycystic ovary syndrome (PCOS) or inadequately controlled type 2 diabetes, common sage (Salvia officinalis) has demonstrated hypoglycemic activity (91971,103380). However, other clinical research in patients with inadequately controlled type 2 diabetes shows that common sage extract does not lower fasting blood glucose levels (105340).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might increase or decrease the effects of antihypertensive drugs.  Details Animal research suggests that common sage (Salvia officinalis) can cause prolonged blood pressure reduction (4152). However, clinical research suggests that Spanish sage (Salvia lavandulaefolia) can increase blood pressure in some people with hypertension (10334). Until more is known, use with caution.

BENZODIAZEPINES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking sage might increase the sedative and adverse effects of benzodiazepines.  Details In vitro evidence suggests that certain components of common sage (Salvia officinalis) can bind to benzodiazepine receptors (72588). This effect has not been reported in humans.

CHOLINERGIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might have additive effects when used with cholinergic drugs.  Details In vitro evidence suggests that common sage (Salvia officinalis) and Spanish sage (Salvia lavandulaefolia) can inhibit acetylcholinesterase and might increase acetylcholine levels (31438,39566,72603,72616).

CNS DEPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking sage might increase the sedative and adverse effects of CNS depressants.  Details Some constituents of sage have CNS depressant activity (10334).

CYTOCHROME P450 2C19 (CYP2C19) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might increase the levels and clinical effects of drugs metabolized by CYP2C19.  Details In vitro evidence suggests that aqueous extracts of sage can inhibit CYP2C19 (10848). So far, this interaction 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, sage might increase the levels and clinical effects of drugs metabolized by CYP2C9.  Details In vitro evidence suggests that aqueous extracts of sage can inhibit CYP2C9 (10848). So far, this interaction has not been reported in humans.

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might increase the levels and clinical effects of drugs metabolized by CYP2D6.  Details In vitro evidence suggests that aqueous extracts of sage can inhibit CYP2D6 (10848,19430). So far, this interaction has not been reported in humans.

CYTOCHROME P450 2E1 (CYP2E1) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might decrease the levels and clinical effects of drugs metabolized by CYP2E1.  Details Animal research suggests that drinking common sage (Salvia officinalis) tea increases the expression of CYP2E1 (72627). So far, this interaction has not been reported in humans.

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might increase the levels and clinical effects of drugs metabolized by CYP3A4.  Details In vitro evidence suggests that aqueous extracts of sage can inhibit CYP3A4 (10848,72641). So far, this interaction has not been reported in humans.

ESTROGENS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might interfere with hormone therapy.  Details In vitro evidence suggests that geraniol, a constituent of Spanish sage (Salvia lavandulaefolia), exerts estrogenic activity (39572). The clinical significance of this effect is unclear.

P-GLYCOPROTEIN SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, sage might increase levels of drugs transported by P-glycoprotein.  Details In vitro research suggests that common sage (Salvia officinalis) can inhibit the multi-drug transporter protein, P-glycoprotein (72641). This effect has not been reported in humans.

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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.

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General ...There is currently a limited amount of information on the adverse effects of camu camu. A thorough evaluation of safety outcomes has not been conducted.

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General ...Orally, rosemary seems to be well tolerated when used in appropriate medicinal amounts. Undiluted rosemary oil or very large quantities of rosemary leaf should not be consumed. Topically and as aromatherapy, rosemary seems to be well tolerated.

Dermatologic ...Topically, rosemary use can lead to photosensitivity, erythema, dermatitis, and cheilitis in hypersensitive individuals (4,6).

Immunologic ...Topically, allergic reactions can occur. When used in the mouth, lip and gum edema have occurred (101173). When used on the skin, allergic contact dermatitis has occurred, likely due to the constituent carnosol (71715,71924,71926).
Rosemary might also cause occupational asthma. A case of occupational asthma caused by several aromatic herbs including thyme, rosemary, bay leaf, and garlic has been reported. The diagnosis was confirmed by inhalation challenges. Although all of the herbs caused immediate skin reactivity, a radioallergosorbent test (RAST) showed that garlic was the most potent allergen by weight, with rosemary and the other herbs showing less reactivity (783).

Neurologic/CNS ...Orally, the undiluted oil, as well as the camphor constituent of rosemary, might cause seizures (4,5,6,12868).

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General ...Orally and topically, royal jelly seems to be well tolerated.
Most Common Adverse Effects:
Orally: Dyspnea, eczema, oral allergy syndrome, pruritus, and urticaria in people with a history of asthma or atopy.
Topically: Contact dermatitis and skin irritation.
Serious Adverse Effects (Rare):
Orally: Anaphylaxis, status asthmaticus, and death in people with a history of asthma or atopy.

Gastrointestinal ...There is one case report of hemorrhagic colitis with abdominal pain, bloody diarrhea with concomitant hemorrhagic and edematous mucosa of the sigmoid colon after ingestion of royal jelly. Symptoms resolved within 2 weeks following discontinuation of royal jelly and conservative treatment (3516).

Immunologic ...In people with a history of atopy or asthma, royal jelly taken orally appears to cause a high rate of allergic symptoms including pruritus, urticaria, eczema, eyelid and facial edema, conjunctivitis, rhinorrhea, dyspnea, oral allergy syndrome, and asthma (7314,7315,7316,10623,95872). In severe cases, royal jelly can cause status asthmaticus, anaphylaxis, and death (792,7315,7316,10623,10624,108511). Allergic symptoms are associated with IgE-mediated hypersensitivity reactions (3513,10623).
Topically, skin irritation, exacerbation of dermatitis, or contact dermatitis may occur (791).
From occupational exposure, royal jelly can cause allergic rhinoconjunctivitis and asthma (95868).

Neurologic/CNS ...There is one report of dizziness in a patient who took a combination product containing royal jelly, bee pollen extract, and a bee pollen plus pistil extract (12008).

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General ...Orally, topically, and when inhaled, sage seems to be well tolerated.
Most Common Adverse Effects:
Orally: Abdominal pain, agitation, diarrhea, dizziness, nausea, and vomiting.
Topically: Burning, dermatitis, pain.
Serious Adverse Effects (Rare):
Orally: Generalized tonic-clonic seizures associated with the thujone, camphor, and/or cineol constituents.

Cardiovascular ...By inhalation, sage essential oil has been reported to increase the blood pressure of hypertensive patients (10334).

Dermatologic ...Orally, sage extract has been reported to cause acneiform skin eruptions in one patient in a clinical trial (91970).
Topically, sage leaves can cause contact dermatitis (46902,72661,72710). Sage extract can cause burning and pain (10437).

Gastrointestinal ...Orally, sage can cause nausea, vomiting, abdominal pain, and diarrhea (10810,17177).
Topically, sage extract sprayed into the mouth and throat can cause dryness or mild burning of the throat (72619).

Neurologic/CNS ...Orally, sage can cause dizziness or agitation (10810,17177). Thujone, a constituent of common sage (Salvia officinalis), is a neurotoxin and can cause seizures (10812,12868). Camphor and cineol, constituents of common sage and Spanish sage, can also cause neurotoxicity and seizures in high doses (10334,12868). Generalized tonic-clonic seizures have been reported in adults, children, and infants after ingestion of sage oil (12868,72666).

Pulmonary/Respiratory ...Orally, sage can cause wheezing (10810,17177).
Occupational exposure to sage dust can cause reduction in ventilatory capacity and chronic respiratory impairment (72672,72682,72686).

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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). Three cases of transient hypotension and tachycardia during intravenous administration of vitamin C have also been reported (114490).

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 (3042,4844,96707,104450,114493,114490). 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).

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