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POSSIBLY EFFECTIVE

• Alzheimer disease. Oral alpha-GPC, taken alone or in combination with donepezil, may be beneficial for improving cognitive function in patients with Alzheimer disease. Details: A meta-analysis of 3 moderate-sized clinical studies in patients with Alzheimer disease shows that taking alpha-GPC 1200 mg daily for up to 6 months improves cognitive function as measured using the Mini-Mental State Examination (MMSE) when compared with placebo. Additionally, an analysis of 4 different clinical trials in patients with Alzheimer disease shows that taking alpha-GPC 1200 mg with donepezil 10 mg daily for up to 2 years improves cognitive function as measured using the MMSE and Alzheimer's Disease Assessment Scale - cognition subscale (ADAS-Cog) and may decrease behavioral symptoms and improve functional abilities when compared with donepezil alone (111731).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Brain tumor. It is unclear if oral alpha-GPC is beneficial in patients with brain tumors. Details: Observational research in patients being treated for glioblastoma suggests that taking alpha-GPC, around 400 mg 2-3 times daily, for 12 months or longer is associated with a 14-month-increase in overall survival but no improvement in progression-free survival when compared with patients not taking alpha-GPC (111732). The validity of these findings is limited by the retrospective nature of the study.
• Cognitive function. Although there has been interest in using oral alpha-GPC to improve cognitive function in healthy adults, there is insufficient reliable information about the clinical effects of alpha-GPC for this purpose.
• Stroke. It is unclear if intramuscular or oral alpha-GPC is beneficial for preventing stroke or improving post-stroke outcomes. Details: A large, open-label, uncontrolled clinical trial in patients who experienced a stroke or transient ischemic attack within the past 10 days shows that intramuscular administration of alpha-GPC 1200 mg daily for 28 days, followed by 400 mg three times daily by mouth for 6 months, modestly improves cognitive and behavioral function when compared to baseline (12102). The validity of this finding is limited by the lack of a comparator group. While this evidence suggests that alpha-GPC may offer some benefit in patients recovering from stroke, observational research in healthy individuals aged 50 years and older has found that alpha-GPC use is associated with a 43% greater risk of stroke, including a 34% greater risk of ischemic stroke and a 37% greater risk of hemorrhagic stroke, when compared with non-users at 10-years' follow-up. Additionally, alpha-GPC use for 2-6 months, 6-12 months, or greater than 12 months is associated with a greater risk of stroke when compared with alpha-GPC use for less than 2 months, suggesting that the increase in stroke risk may be dependent on the total dose received or duration of exposure (108883).
• Vascular dementia. It is unclear if intramuscular alpha-GPC is beneficial in patients with vascular dementia. Details: A small, open-label study in adults with mild to moderate vascular dementia shows that intramuscular administration of a prescription-only formulation of alpha-GPC (Delecit; not available in the US) 1000 mg daily for 90 days improves cognitive function, behavior, mood, and functionality similarly to cytosine diphosphocholine (CDP) 1 gram daily (12101). It is not clear how these improvements compare with standard care. More evidence is needed to rate alpha-GPC for these uses.

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INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. Oral astaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small study in healthy adults over 40 years of age with mild forgetfulness shows that taking a specific combination supplement (BGG Japan Co.) containing astaxanthin 9 mg and tocotrienols 50 mg daily for 12 weeks might improve composite and verbal memory when compared with placebo (105099). This study was funded by the supplement manufacturer.
• Age-related macular degeneration (AMD). Oral astaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with non-advanced AMD shows that a specific combination product (Azyr, Sifi S.p.A.) containing astaxanthin 4 mg, lutein, zeaxanthin, vitamin E, vitamin C, zinc, and copper, taken daily for 12 months, improves selective dysfunction in the central retina, but does not improve dysfunction in the peripheral retinal areas, when compared with baseline (19196). The validity of this finding is limited by the lack of a comparator group.
• Aging skin. Small studies suggest that oral and topical astaxanthin may be beneficial in aging skin; however, there is conflicting evidence regarding its effects on wrinkles. Details: Small studies in middle-aged adults show that taking astaxanthin (Astavita Astaxanthin, Astavita; AstaReal Oil 50F, Fuji Chemical Industry Co., Ltd.) 2-3 mg orally twice daily for 6-8 weeks improves elasticity, fine lines, wrinkles, and skin moisture when compared with placebo (19561,91734). However, a meta-analysis of small clinical studies in healthy adults shows that taking oral astaxanthin 2-12 mg daily for 4-16 weeks modestly improves moisture content and skin elasticity, but has no effect on wrinkle depth, when compared with placebo (107961). The validity of this meta-analysis is limited due to the population heterogeneity and variety of astaxanthin formulations utilized. In addition to oral astaxanthin, one study also used topical astaxanthin 0.094% (AstaTROL-Hp, Fuij Chemical Industry Co., Ltd.) 1 mL applied twice daily (91734). A systematic review of two very small, nonblinded studies in healthy adults suggests that topical application, either in combination with oral astaxanthin or alone, might have anti-aging skin effects when used for 2-3 weeks (107961).
• Alzheimer disease. Although there is interest in using oral astaxanthin for Alzheimer disease, there is insufficient reliable information about the clinical effects of astaxanthin for this condition.
• Athletic performance. Small studies suggest that oral astaxanthin may improve some aspects of athletic performance. Details: Two small studies in trained cyclists show that taking astaxanthin (Fuji Health Science, Inc. or AstaReal) 4-12 mg daily for 1 or 4 weeks decreases the time to complete a 20-40 km cycling trial by about 50-100 seconds when compared with placebo (91735,105096). However, a larger study in trained cyclists shows that taking astaxanthin (BioReal) 20 mg, vitamin C 300 mg, and vitamin E 50 mg daily for 4 weeks does not decrease time needed to complete a predetermined amount of cycling work (a timed trial) when compared with placebo (91738). Reasons for the discrepancies are not clear but may relate to the fitness level of the athletes in the studies or the differences in timed trial protocols used in the studies.
• Carpal tunnel syndrome. Oral astaxanthin 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 astaxanthin 4 mg, lutein, beta-carotene, and vitamin E (BioAstin, Cyanotech) orally 3 times daily for 8 weeks does not reduce the rate or duration of pain due to carpal tunnel syndrome when compared with placebo (19164).
• Diabetes. It is unclear if oral astaxanthin is beneficial for diabetes. Details: A small clinical trial in adults with diabetes shows that taking astaxanthin (Nature Vision) 8 mg daily for 8 weeks does not reduce levels of cholesterol or fasting blood glucose or reduce diastolic blood pressure when compared with placebo. However, there were some modest beneficial effects on visceral fat, triglyceride level, and systolic blood pressure (109778).
• Dry eye. It is unclear if oral astaxanthin is beneficial for dry eye syndrome. Details: A clinical study in adults and elderly patients with mild to moderate dry eye syndrome shows that taking oral astaxanthin 6 mg twice daily for 30 days improves symptom severity, tear break-up time, fluorescein break-up time, and meibomian gland dysfunction, but not visual acuity or intraocular pressure, when compared with baseline (107962). The validity of these findings is limited by the lack of a comparator group.
• Dyspepsia. It is unclear if oral astaxanthin improves symptoms of dyspepsia. Details: One clinical study in adults with functional dyspepsia with or without Helicobacter pylori infection shows that taking astaxanthin (AstaCarox, AstaReal AB) 16 mg or 40 mg daily for 4 weeks does not reduce indigestion, pain, or H. pylori counts when compared with placebo. However, astaxanthin 40 mg daily may reduce reflux in H. pylori-positive patients (19165).
• Exercise-induced muscle damage. Small clinical studies in trained athletes suggest that oral astaxanthin may not improve markers of muscle damage from exercise. Details: A small study in professional male soccer players shows that taking astaxanthin 4 mg daily for 90 days does not seem to reduce exercised-induced biomarkers of muscle damage, such as creatinine kinase, when compared with placebo (91739). Taking a combination of astaxanthin 4 mg and lutein 480 mg (BioAstin, Cyanotech) daily for 3 weeks also did not reduce creatinine kinase levels after exercise in trained athletes when compared with placebo (safflower oil) (19199).
• Exercise-induced muscle soreness. Oral astaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small study in resistance trained athletes shows that taking a combination of astaxanthin 4 mg and lutein 480 mg (BioAstin, Cyanotech) daily for 3 weeks does not reduce muscle soreness or improve muscle performance 96 hours after exercise when compared with placebo (safflower oil) (19199).
• Fatigue. Oral astaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy patients shows that taking a specific combination product (ASTOTS, Fujifilm Co.) containing astaxanthin 6 mg and sesamin 10 mg after breakfast daily for 4 weeks does not improve overall fatigue after completion of mental and physical tasks when compared with placebo (98769).
• Heart failure. Oral astaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with heart failure with reduced left ventricular ejection fraction (LVEF) shows that taking a specific supplement containing astaxanthin 12 mg, tocotrienol 40 mg, and L-ascorbic acid 2-glucoside 30 mg (AstaReal ACT, AstaReal Co., Ltd.) daily for 3 months may increase LVEF from 34% to 38% and modestly increase exercise tolerance as measured by the six-minute walk test when compared with baseline (105097). The validity of these findings is limited by the lack of a comparator group. Furthermore, this study was funded by the supplement manufacturer.
• Hyperlipidemia. Small clinical studies suggest that oral astaxanthin is not beneficial for reducing cholesterol levels. Details: One small clinical study in adults with mild hyperlipidemia shows that taking astaxanthin (AstaReal Astaxanthin, Fuji Chemical Industry) 12 mg or 18 mg daily for 12 weeks reduces triglyceride levels, while taking 6 mg or 12 mg daily increases high-density lipoprotein (HDL) cholesterol levels, when compared with placebo. However, total cholesterol and low-density lipoprotein (LDL) cholesterol levels were not affected (19167). Meta-analyses of small clinical studies mostly in adults without hyperlipidemia have also been conducted. One shows that taking astaxanthin 4-18 mg daily for up to 12 weeks does not reduce total or LDL cholesterol levels, but may increase HDL cholesterol levels, when compared with control (105100). A more recent analysis shows that taking astaxanthin 4-20 mg daily for up to 6 months has no beneficial effects on blood lipid levels and might actually increase levels of LDL cholesterol (109776).
• Hypertension. It is unclear if oral astaxanthin reduces blood pressure. Details:A meta-analysis of four small clinical trials shows that taking astaxanthin does not have a clinically beneficial effect on systolic or diastolic blood pressure (109776). However, none of the trials were conducted in patients with hypertension.
• Impaired glucose tolerance (prediabetes). It is unclear if oral astaxanthin is beneficial in patients with prediabetes. Details: A small clinical study in healthy adults and adults with prediabetes shows that taking oral astaxanthin 12 mg daily for 12 weeks improves glycated hemoglobin (HbA1c) when compared with baseline, but not when compared with placebo. Insulin sensitivity and postprandial glucose levels were also improved when compared with baseline, but no statistical comparison to the placebo group was conducted (107965). The validity of this study is limited due to unclear reporting.
• Infertility. It is unclear if oral astaxanthin improves reproductive outcomes in patients with infertility due to endometriosis or polycystic ovary syndrome (PCOS). Details: A small clinical study in adults with infertility secondary to moderate or severe endometriosis undergoing assisted reproductive therapy in Iran shows that taking astaxanthin (AstaReal, AstaReal Co.) 6 mg daily for 12 weeks improves the numbers of oocytes retrieved, mature oocytes, and high-quality embryos but not the quantity of immature oocytes, fertilization rate, number of transferred embryos, or clinical pregnancy rate when compared with placebo (112434). Similarly, a small clinical study also conducted in Iran in patients with infertility due to PCOS undergoing assisted reproductive therapy shows that taking astaxanthin (Algalife Pure astaxanthin) 8 mg daily for 40 days prior to egg retrieval modestly improves the high-quality embryo rate, but not the total number of embryos or the clinical pregnancy rate, when compared with placebo (109775).
• Male infertility. It is unclear if oral astaxanthin improves male infertility. Details: A small low-quality clinical study in males with infertility who are participating in intra-uterine insemination shows that taking astaxanthin (AstaCarox, AstaReal AB) 16 mg daily for 3 months does not seem to increase sperm count and quality, but might result in a higher total pregnancy rate of 23% compared with a 3.6% rate in the placebo group (19197). The validity of this finding is limited by poor study methodology and differences between treatment groups. Another small clinical study in males with infertility and oligospermia shows that taking astaxanthin (Astasan, Sensilab) 16 mg daily does not increase sperm concentration or sperm motility when compared with placebo (105098).
• Menopausal symptoms. Although there is interest in using oral astaxanthin for menopausal symptoms, there is insufficient reliable information about the clinical effects of astaxanthin for this purpose.
• Metabolic syndrome. Although there is interest in using oral astaxanthin for metabolic syndrome, there is insufficient reliable information about the clinical effects of astaxanthin for this condition.
• Nonalcoholic fatty liver disease (NAFLD). Although there is interest in using oral astaxanthin for NAFLD, there is insufficient reliable information about the clinical effects of astaxanthin for this condition.
• Osteoarthritis. Oral astaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults with mild knee or hip osteoarthritis shows that taking a combination product containing astaxanthin 2 mg, krill oil, and hyaluronic acid daily for 12 weeks (FlexPro MD, Valensa) reduces joint pain and stiffness and improves objective and subjective measures of joint function but does not improve overall physical function when compared with placebo (112432). It is unclear if these effects are due to astaxanthin, other ingredients, or the combination.
• Obesity. Although there is interest in using oral astaxanthin for weight loss, there is insufficient reliable information about the clinical effects of astaxanthin for this purpose.
• Parkinson disease. Although there is interest in using oral astaxanthin for Parkinson disease, there is insufficient reliable information about the clinical effects of astaxanthin for this condition.
• Physical performance. It is unclear if oral astaxanthin improves physical performance in older adults. Details: A small clinical trial in healthy nursing home residents shows that taking astaxanthin (AstaReal) 12 mg twice daily for 16 weeks, in combination with vitamin E 40 mg and vitamin C 30 mg daily, increases the 6-minute walking distance by about 38 meters, a significant increase when compared with placebo containing vitamin E and vitamin C. However, there was no effect on muscle strength (109777). Another small clinical trial in healthy, older adults (aged 65-85 years) undergoing exercise endurance testing shows that a specific combination product (AstaReal; Fuji Health Science, Inc) containing astaxanthin 12 mg, tocotrienol 10 mg, and zinc 6 mg, taken as 2 capsules daily for 12 weeks, reduces the respiratory exchange ratio, but does not improve leg muscle endurance or perceived exertion, when compared with placebo. In a subgroup analysis of males, but not females, those taking astaxanthin had a greater total exercise efficiency when compared with placebo (107963).
• Rheumatoid arthritis (RA). Oral astaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with RA shows that taking a supplement containing astaxanthin 4 mg, lutein 40 mcg, vitamin A 65 IU, vitamin E 50 IU, and safflower oil 460 mg (BioAstin, Cyanotech) three times daily for 8 weeks reduces pain and improves satisfaction by approximately 40% when compared with placebo (94125).
• Stroke. Although there is interest in using oral astaxanthin for recovery from stroke, there is insufficient reliable information about the clinical effects of astaxanthin for this purpose.
• Sunburn. It is unclear if oral astaxanthin might help to prevent sunburn. Details: A very small clinical study in Japanese adults shows that taking astaxanthin (Astots, Fujifilm Corporation) 4 mg daily for 9 weeks might increase skin tolerance to ultraviolet (UV) light when compared with placebo (96884). It is unclear if this translates to a lower risk of sunburn. More evidence is needed to rate astaxanthin for these uses.

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POSSIBLY EFFECTIVE

• Dry eye. Applying eye drops containing hyaluronic acid alone or in combination with other ingredients, seems to improve symptoms of dry eye. Details: A large meta-analysis of clinical studies in patients with dry eye disease shows that using eye drops containing hyaluronic acid 0.1% to 0.4% for at least 14 days modestly improves tear production when compared with artificial tears or saline control, with a more significant improvement when compared with saline control. Tear stability is also modestly improved when compared with saline control (108622). Several individual clinical studies using specific hyaluronic acid eye drops have also demonstrated improvement. One clinical study in patients with dry eye disease shows that applying eye drops containing hyaluronic acid 0.1% to 0.3% 5-6 times daily for 12 weeks might improve symptoms to a similar degree as cyclosporine 0.05% eye drops. The products used in this study included Hyalein ophthalmic solution 0.1%, New Hyaluni ophthalmic solution 0.15%, and Hyaluni ophthalmic solution 0.3% (97885). Another clinical study shows similar efficacy between hyaluronic acid 0.15% eye drops (New Hyaluni), applied 6 times daily for 12 weeks, and eye drops containing cyclosporine 0.05% and carboxymethylcellulose 0.5%, applied twice daily (110555). A smaller clinical study in patients with dry eye disease shows that applying specific eye drops containing hyaluronic acid 0.2% (Hyalistil) seems to have similar efficacy as using tamarind seed polysaccharide eye drops (16301). Furthermore, adding hyaluronic acid to conventional treatment seems to offer additional benefit. A large multicenter clinical trial in patients with dry eye disease shows that applying 1-2 drops of artificial tears containing carboxymethylcellulose 0.5% and hyaluronic acid 0.1% (Optive Fusion, Allergan) at least 2 times daily for 3 months seems to further improve pain and discomfort when compared with using artificial tears containing carboxymethylcellulose alone (104384). One small clinical study also shows that hyaluronic acid 0.3% ocular gel and hyaluronic acid 0.18% eye drops, applied 4-6 times daily for 12 weeks, are equally effective for improving dry eye symptoms (110556). Hyaluronic acid has also been studied in combination with other ingredients. Several small clinical studies in patients with dry eye syndrome ranging from mild to severe shows that applying eye drops containing hyaluronic acid 0.2% or 0.3%, polyvinylpyrrolidone, and glycerin (Visaid 0.2% or 0.3%, Avizor S.A.), administered as one drop 3-8 times daily for one month, improves some signs and symptoms of dry eye when compared with sodium chloride 0.9% (97894,97895). Conversely, a large clinical study in patients with mild to moderate dry eye disease shows that applying preservative-free eye drops containing sodium hyaluronate with chondroitin sulfate (Humylub Ofteno PF, Laboratorios Sophia), one drop into each eye four times daily for 90 days, seems to be no different for improving dry eye severity when compared with using polyethylene/propylene glycol eye drops (104443).
• Venous leg ulcers. Topical application of hyaluronic acid-impregnated gauze reduces wound size and promotes wound healing. Details: Clinical studies in patients with at least one leg ulcer of venous or mixed arterial/venous origin show that once daily application of a specific hyaluronic acid-impregnated gauze (Ialuset, Laboratoires Genévrier) reduces wound size at 45 days by 73% and produces complete wound healing at or before 20 weeks in 40% of patients. In those receiving a neutral vehicle gauze, these improvements occurred in 46% and 19% of patients, respectively (108627,108640).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Aging skin. Oral hyaluronic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. It is also unclear if topical hyaluronic acid is beneficial for aging skin. Details: A very small study shows that taking a specific combination product (GliSODin Skin Nutrients Advanced Anti-Aging Formula, Isocell North America Inc.) containing hyaluronic acid, krill oil, sea buckthorn berry oil, and cacao bean extract orally three times daily for 90 days, along with applying tazarotene 0.1% cream, moderately decreases wrinkling and photodamage and improves skin moisture and elasticity when compared with tazarotene cream alone (91778). Another small clinical study in females with aging skin shows that taking a specific combination product (BioCell Collagen, BioCell Technology, LLC) containing hyaluronic acid 100 mg, chondroitin sulfate 200 mg, and collagen peptides 600 mg daily for 12 weeks reduces lines and wrinkles by about 13% when compared with baseline (28681). The validity of this finding is limited by the lack of a comparator group. Furthermore, it should be noted that both studies were funded by the product manufacturer. A small open-label clinical study in females with mild to moderate lip dryness and mild to severe lip condition shows that three daily applications of a two-step lip treatment containing hyaluronic acid for 4 weeks improves the overall condition of lips, as well as texture/visual roughness, plumpness, color/rosiness, definition/contour, and lines/wrinkles when compared with baseline (108634). The validity of these findings is limited by the lack of a comparator group.
• Allergic rhinitis (hay fever). It is unclear if nasal irrigation with sodium hyaluronate is beneficial in patients with mild, persistent seasonal allergic rhinitis. Details: A small clinical study in patients with mild, persistent seasonal allergic rhinitis receiving an oral antihistamine and an intranasal corticosteroid shows that nasal irrigation with sodium hyaluronate twice daily for 1 month improves mucociliary clearance time by 3 minutes, compared with 1 minute with the use of isotonic saline and 5 minutes with the use of surfactant (108630). It is unclear if this change is associated with clinically relevant symptom improvement.
• Burns. It is unclear if topical hyaluronic acid is beneficial in patients with burns. Details: A meta-analysis of small clinical trials suggests that topical hyaluronic acid and hyaluronic acid derivatives might improve the healing of wounds, including burns, when compared with control (104389). A small nonrandomized clinical study in patients with partial- to full-thickness burns shows that hyaluronic acid 0.2% gel daily for 12 weeks during the re-epithelialization phase reduces erythema, tension, pruritus, burning, and neoangiogenesis when compared with baseline (108636). The lack of statistical comparison to the ozonated oil group and the single-blinded nature of the study limit the validity of these findings.
• Canker sores. It is unclear if topical hyaluronic acid is beneficial for canker sores. Details: A clinical study in adults with recurrent canker sores shows that applying a gel containing hyaluronic acid 0.2% two to three times daily for 7 days reduces soreness immediately and for up to 30 minutes after application when compared with baseline. However, these improvements are numerically similar to those seen with placebo (108637). The lack of statistical comparison to placebo limits the validity of this finding. A small observational study in children with recurrent canker sores has found that applying a gel containing hyaluronic acid 0.2% twice daily for 7 days is similarly effective to dexamethasone topical ointment applied three times daily for 5 days for reducing pain and ulcer size (104388).
• Corneal abrasion. It is unclear if eye drops containing hyaluronic acid are beneficial in preventing recurrence in patients with a history of traumatic corneal abrasion. Details: A small clinical study in patients with fully healed traumatic corneal abrasion at risk for recurrence shows that administration of eye drops containing hyaluronic acid 0.3% five times daily for 3 months does not reduce the incidence rate of major symptomatic episodes at 12 months when compared with observation alone (108623).
• Diabetic foot ulcers. Oral hyaluronic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A meta-analysis of results from 4 clinical studies shows that applying hyaluronic acid combination gels or hyaluronic acid-based biomaterials to diabetic foot ulcers increases the odds of complete healing at 12 weeks by about 1.7-fold when compared to control treatment. Forms of hyaluronic acid assessed in the evaluated studies included zinc hyaluronate, hyaluronic acid-based biomaterial (Hyalograft 3D autograft), and a gel containing hyaluronic acid and amino acids (Vulnamin Gel, Errekappa) (91776). It is not clear if the beneficial effects were due to hyaluronic acid or other components of the treatments.
• Exercise-induced muscle soreness. Oral hyaluronic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in healthy, recreationally active adults shows that a specific product (BioCell Collagen, BioCell Technology, LLC) containing hyaluronic acid 150 mg, chondroitin sulfate 300 mg, and collagen peptides 900 mg, taken twice daily for 6 weeks prior to two bouts of resistance exercise, attenuates muscle damage and decreases delayed-onset muscle soreness when compared with placebo (96301). It is unclear if these effects are due to hyaluronic acid, the other ingredients, or the combination. Furthermore, it should be noted that both studies were funded by the product manufacturer.
• Gastroesophageal reflux disease (GERD). Oral hyaluronic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Patients with non-erosive GERD are thought to be less responsive to conventional acid suppression with proton pump inhibiters (PPIs) and H-2 blockers. A small preliminary clinical study shows that taking a syrup containing hyaluronic acid and chondroitin sulfate along with PPIs, H2-receptor antagonists, and/or antacids, reduces the intensity of symptoms associated with non-erosive GERD by about 3.5-fold when compared with placebo (89592). A larger clinical study in patients with non-erosive GERD shows that taking a different formulation of the same combination of chondroitin sulfate and hyaluronic acid (Esoxx, Alfa Wassermann) 4 times daily for 14 days, in conjunction with a PPI, improves GERD symptom severity by 21%, heartburn by 15%, and regurgitation by 10% when compared with using a PPI and placebo (101271). Hyaluronic acid has also been evaluated in combination with chondroitin sulfate in patients with extraesophageal symptoms of GERD. A small, open-label study shows that taking a specific combination product (Gerdoff, SOFAR S.p.A.) containing hyaluronic acid and chondroitin sulfate three times daily with omeprazole 40 mg daily for 6 weeks increases the rate of treatment response, defined as a 50% or greater improvement in reflux symptoms index scores, by around 40% when compared with omeprazole alone. While average symptom scores were not significantly improved with the combination product over omeprazole, the need for omeprazole as rescue therapy for breakthrough symptoms was reduced in the treatment group (109648). It is unclear if the findings described above are due to hyaluronic acid, chondroitin sulfate, or the combination.
• Gingivitis. It is unclear if hyaluronic acid used in a mouthwash reduces gingivitis severity. Details: A small clinical study in patients with biofilm-induced gingivitis shows that rinsing with 10 mL of hyaluronic acid 0.025% mouth wash (Gengigel, RICERFARMA SRL) for 1 minute twice daily reduces probing index and bleeding when compared with rinsing with a placebo solution, but is less effective when compared with chlorhexidine 0.12% solution (104383). Another small clinical study in patients with plaque-induced gingivitis shows that rinsing with 10 mL of a mouthwash containing hyaluronic acid 0.1% and hydrogen peroxide 1.8% for 30 seconds twice daily for 21 days reduces gingival index scores but not plaque index scores when compared with placebo (110554). It is unclear if these findings are due to hyaluronic acid, hydrogen peroxide, or the combination.
• Intranasal surgery. It is unclear if topical hyaluronic acid irrigation improves recovery in patients after nasal surgery. Details: A small clinical study in patients that underwent nasal surgery for chronic rhinosinusitis shows that performing nasal irrigation with high molecular weight sodium hyaluronate 9 mg twice daily for 6 weeks improves sinus scarring, crusting, and headache when compared with nasal irrigation with saline. However, the sodium hyaluronate irrigation did not improve sinus inflammation or secretions, nasal obstruction, or facial pain (101288).
• Intrauterine adhesions. Several small studies suggest that intrauterine administration of hyaluronic acid gel seems to prevent intrauterine adhesions after uterine surgery. Details: Meta-analyses of 11-12 small clinical studies in patients undergoing uterine surgery shows that intrauterine application of 1-10 mL of hyaluronic acid gel after surgery reduces the risk of intrauterine adhesions by around 50% and increases pregnancy rates when compared with no treatment (110551,110552). One analysis suggests that hyaluronic acid is most effective for prevention of intrauterine adhesions when at least 5 mL of gel is applied (110551).
• Lichen planus. It is unclear if topical hyaluronic acid is beneficial in patients with oral lichen planus. Details: A clinical study in patients with oral lichen planus shows that application of a gel containing hyaluronic acid 0.2% four to five times daily for 28 days reduces soreness in as little as 5 minutes for up to 4 hours when compared with baseline. These findings are numerically similar to those seen with placebo; however, the lack of statistical comparison to placebo limits the validity of this finding (108635). A small clinical study in patients with symptomatic oral lichen planus (including mixed forms) shows that application of a gel containing hyaluronic acid 0.2% three times daily for 4 weeks is similarly effective to triamcinolone for improving pain, erythema, and lesion size (108633). It is unclear if the improvement from baseline differed between groups.
• Melasma. It is unclear if topical hyaluronic acid is beneficial in patients with moderate to severe facial melasma. Details: A small clinical study in patients with mostly mixed-type, moderate to severe facial melasma shows that twice daily application of hyaluronic acid along with isobutylamido thiazolyl resorcinol reduces melasma severity similarly to isobutylamido thiazolyl resorcinol alone (108628). The single-blinded nature of the study limits the validity of these findings.
• Oral mucositis. Topical hyaluronic acid has only been evaluated in combination with other ingredients; its effects when used alone is unclear. Details: A small clinical study in children aged 5 years or older with chemotherapy-induced oral mucositis shows that using a solution containing sodium hyaluronate, verbascoside, and polyvinylpyrrolidone (Mucosyte; Biopharm) three times daily is more effective than placebo for improving pain and other symptoms (97890). Another small clinical study in adults in recovery from hematopoietic stem cell transplantation shows that using a spray product containing sodium hyaluronate with synthetic amino acid precursors of collagen (Mucosamin) attenuates the development of severe oral mucositis when compared with chlorhexidine 0.2% (97889).
• Osteoarthritis. It is unclear if oral hyaluronic acid is beneficial in patients with osteoarthritis of the knee. Details: A small study in patients with knee osteoarthritis shows that taking chicken comb extract (Hyal-Joint, Bioibérica) 80 mg, standardized to contain hyaluronic acid 60% to 70%, once daily for 8 weeks does not reduce pain when compared with placebo (55742). This study was limited by small size and a significant placebo effect. Another small study in patients with knee osteoarthritis shows that taking a different supplement (Oralvisc, Bioibérica) 80 mg standardized to contain hyaluronic acid 70% and glycosaminoglycans once daily for 3 months modestly reduces pain when compared with placebo (91779). Reasons for these differing findings may relate to hyaluronic acid formulation, study funding sources, or the magnitude of placebo effect. Hyaluronic acid has also been studied in combination with chondroitin and collagen peptides (BioCell Collagen, BioCell Technology, LLC) with some evidence of benefit (28680).
• Otitis media. It is unclear if using intranasal hyaluronic acid solution is beneficial for otitis media in children. Details: Preliminary clinical research in children 3-12 years of age who have recurrent or chronic middle ear inflammation and adenoiditis shows that using a compound (Yabro, IBSA Farmaceutici Italia S.r.l.) containing hyaluronic acid in saline intranasally 15 days per month for 3 months modestly reduces the number of patients with impaired otoscopy or middle ear function when compared to baseline (97888). It is unclear if this effect is due to the hyaluronic acid product or to the natural resolution of inflammation over time.
• Radiation dermatitis. It is unclear if topical hyaluronic acid is beneficial for the prevention of radiation dermatitis. Details: A small clinical study in patients with breast cancer undergoing adjuvant radiation therapy following lumpectomy shows that three daily applications of a specific hyaluronic acid gel (RadiaPlex, MPM Medical) to one side of the breast results in a grade 2 or greater dermatitis occurrence rate of 62%, compared with a rate of 48% on the side receiving petrolatum-based gel. A review of a planned interim analysis led to early trial discontinuation (108638).
• Rhinosinusitis. It is unclear if hyaluronic acid solution is beneficial for acute or chronic rhinosinusitis when used in an intranasal saline rinse. Details: A small clinical study in adults with acute rhinosinusitis who are being treated with levofloxacin and prednisone shows that using a 3% hyaluronic acid in saline nasal douche twice daily improves smell, obstruction, and discharge within 14 days when compared with saline alone (97886). A very small clinical study in patients with chronic rhinosinusitis without nasal polyps shows that receiving micronized nasal hyaluronic acid douches twice daily for 30 days improves nasal symptoms, nasal obstruction, and ability to smell to a similar degree as normal saline (104387).
• Sexual dysfunction. It is unclear if vaginal hyaluronic acid is beneficial for improving sexual function in adults with dyspareunia. Details: A small nonrandomized clinical study in females with dyspareunia while taking oral hormonal contraceptives shows that once daily vaginal application of a hyaluronic acid gel for 12 weeks reduces pain and improves sexual function at 12 weeks when compared baseline. Though patients treated with twice weekly vaginal estrogen therapy had better 12-week scores than patients treated with hyaluronic acid, it is unclear if the improvements from baseline differed between groups (108639).
• Tooth extraction. It is unclear if topical hyaluronic acid is beneficial for wound healing after tooth extraction. Details: A small clinical study in patients undergoing tooth extraction shows that application of hyaluronic acid 0.2% gel or hyaluronic acid 0.1% spray to the extraction socket twice daily for 7 days increases the rate of wound closure when compared with no treatment (110553). The validity of these findings is limited by a lack of placebo control group.
• Urinary tract infections (UTIs). Oral and intravesical hyaluronic acid have been evaluated for the prevention of UTI in combination with other ingredients; its effect when used alone is unclear. Details: A meta-analysis of prospective and retrospective studies shows that intravesical administration of 50 mL of specific solutions containing chondroitin sulfate 2% and hyaluronic acid 1.6% (iAluRil, IBSA Farmaceutici; Cystistat, Bioniche), once weekly to once monthly for up to 6 months, reduces the rate of UTI recurrence by about 2-3 incidents per year and delays the time to the first UTI recurrence when compared with placebo or prophylaxis with sulfamethoxazole-trimethoprim (99688). However, the validity of these findings is limited by the low quality and high heterogeneity of the included studies, as well as concerns for publication bias. Also, the effect of hyaluronic acid alone is unclear. Oral hyaluronic acid has also been evaluated in combination with other ingredients for the prevention of recurrent UTI. A small prospective observational study shows that taking 1-2 capsules of a combination of hyaluronic acid, chondroitin sulfate, curcumin, and quercetin daily for 15 days each month, in conjunction with the use of local topical estrogen therapy for up to 12 months, reduces the number of women with recurrent UTIs when compared with taking the oral combination product or the vaginal estrogen product alone (96781). It is unclear if this effect is due to hyaluronic acid, other ingredients, or the combination.
• Vaginal atrophy. It is unclear if topical hyaluronic acid is beneficial for improving symptoms of vaginal atrophy. Details: A small, open-label clinical trial in patients going through menopause with symptoms of vaginal atrophy shows that applying 3 grams of a topical vaginal preparation of hyaluronic acid (Hyalo Gyn, Fidia Farmaceutici) every 3 days for 30 days improves vaginal health scores and reduces vaginal itching, vaginal burning, and pain during intercourse when compared to baseline. However, it does not appear to be any more effective than a polycarbophil vaginal gel (110549). Also, a small observational study in postmenopausal patients with vulvovaginal atrophy has found that applying a topical vaginal preparation containing hyaluronic acid (Justgin, JustPharma) three times weekly for 8 weeks is associated with improved symptoms of vaginal dryness, burning, and itching, as well as pain during intercourse, when compared to baseline (97887). The validity of these findings is limited by the lack of a comparator group and retrospective nature of the study. Some research has evaluated combination products containing hyaluronic acid for vaginal atrophy. A clinical trial in patients with cervical cancer shows that intravaginal administration of a specific suppository (Santes, Lo.Li. Pharma) containing hyaluronic acid, vitamin E, and vitamin A, once daily for the 5 week duration of radiotherapy reduces vaginal dryness, inflammation, and dyspareunia when compared with no additional treatment (101283). Also, a small, open-label clinical study in patients with vaginal atrophy after treatment for breast cancer shows that intravaginal application of a suppository containing hyaluronic acid and extract of aloe, marigold, tiger grass, and tea tree daily for 10 days then every 3 days for 80 days improves vaginal health scores and reduces vaginal dryness and pain during intercourse when compared to baseline, with no difference between the hyaluronic acid-containing suppository and vaginal laser therapy (110550). It is unclear if these findings are due to hyaluronic acid, other ingredients, or the combination.
• Wound healing. Small clinical studies show that topical hyaluronic acid and hyaluronic acid derivatives may improve the healing of various types of wounds. Details: A meta-analysis of small clinical trials suggest that topical hyaluronic acid and hyaluronic acid derivatives might improve the healing of burns, wounds, and skin ulcers when compared with control (104389). More evidence is needed to rate hyaluronic acid for these uses.

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INSUFFICIENT RELIABLE EVIDENCE to RATE

• Cancer. It is unclear if oral limonene is beneficial in patients with cancer. Details: D-limonene taken orally in 21-day cycles seems to concentrate in tumor tissue in patients with advanced cancer and may slow disease progression, but its effect on survival is uncertain (12709).
• Irritable bowel syndrome (IBS). Oral limonene has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with IBS (constipation- or diarrhea-dependent) shows that taking a combination of peppermint oil 240 mg (1.5% limonene, 40% menthol), ginger oil 50 mg, and olive oil 440 mg (Standart Zdorovya Gastro) once daily for 30 days, in combination with regular IBS therapy, decreases symptoms and reduces patients' disease categories from moderately ill to mildly ill or borderline, when compared with placebo. Treatment with limonene does not significantly alter bowel flora (110420). More evidence is needed to rate Limonene for these uses.

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POSSIBLY SAFE ...when used orally and appropriately. Alpha-GPC has been used with apparent safety at doses of 400 mg three times daily (1200 mg/day) for up to 6 months (12102,12176). ...when used intramuscularly and appropriately. Alpha-GPC has been administered intramuscularly with apparent safety at doses of 1000-1200 mg/day for 28 to 90 days (12100,12102).

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

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

POSSIBLY SAFE ...when taken orally and appropriately. Astaxanthin 4-18 mg daily has been used with apparent safety for up to 12 weeks. Doses of 40 mg daily have been used with apparent safety for up to 4 weeks (19165,19167,19197,32621,96884,105100).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using in amounts greater than those typically found in foods.

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LIKELY SAFE ...when used orally and appropriately. Supplements standardized to contain hyaluronic acid 70%, in an 80 mg daily dose, have been used daily for up to 3 months with no reports of adverse effects (55742,91779). ...when used topically and appropriately. Hyaluronic acid, in a gel or impregnated gauze, has been safely applied to the skin in clinical trials (7889,7892,104389,108627,108640). ...when eye drop preparations containing up to 0.3% hyaluronic acid are used multiple times per day for up to 3 months (97885,97894,97895,110555).

PREGNANCY:
There is insufficient reliable information available about the safety of hyaluronic acid; avoid using.

LACTATION:
There is insufficient reliable information available about the safety of hyaluronic acid. It is not known if hyaluronic acid is excreted in breast milk (7890); avoid using.

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LIKELY SAFE ...when consumed in amounts commonly found in foods. Limonene has Generally Recognized As Safe (GRAS) status in the US (4912).

POSSIBLY SAFE ...when used orally and appropriately in medicinal amounts. Limonene has been safely used in doses of up to 8 mg/m2 in one trial for up to a year (12709). ...when used topically in amounts found in fragrances and personal hygiene products. Limonene is a common ingredient in fragrances and personal hygiene products (99871,99873). It can cause allergic contact dermatitis in some people (99871,99872,99873).

PREGNANCY AND LACTATION: LIKELY SAFE
when consumed in amounts commonly found in foods. Limonene has Generally Recognized As Safe (GRAS) status in the US (4912). There is insufficient reliable information available about using limonene in medicinal amounts during pregnancy or breast-feeding; avoid using.

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SCOPOLAMINE (Transderm Scop) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, alpha-GPC might decrease the effects of scopolamine.  Details A small clinical study shows that alpha-GPC can partially counteract the attention and memory impairment effects caused by scopolamine given intramuscularly (12103). Whether alpha-GPC can decrease the beneficial anti-motion sickness effects of the scopolamine patch (Transderm Scop) is unclear.

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CYTOCHROME P450 2B6 (CYP2B6) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, astaxanthin may decrease levels of drugs metabolized by CYP2B6.  Details In vitro research shows that astaxanthin induces cytochrome CYP2B6 enzyme activity in human hepatocytes (32613). This effect 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, astaxanthin may decrease levels of drugs metabolized by CYP3A4.  Details In vitro research shows that astaxanthin induces CYP3A4 enzyme activity in human hepatocytes (32613). This effect has not been reported in humans.

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General ...Orally, alpha-GPC seems to be well tolerated.
Serious Adverse Effects (Rare):
Orally: Stroke.

Dermatologic ...Orally, some patients can experience skin rash (12102). Intramuscularly, alpha-GPC can cause erythema at the injection site (12101).

Gastrointestinal ...Orally, alpha-GPC has been rarely associated with diarrhea, heartburn, nausea, and vomiting (12102).
Intramuscularly, alpha-GPC has been rarely associated with diarrhea, heartburn, nausea, and vomiting (12102).

Neurologic/CNS ...Orally, alpha-GPC has been rarely associated with dizziness, excitation, headache, and insomnia (12102). Alpha-GPC use for at least 2 months has also been associated with an elevated risk of stroke when compared with non-users or those who used alpha-GPC for less than 2 months (108883).
Intramuscularly, alpha-GPC has been rarely associated with confusion, excitation, fainting, headache, and insomnia (12102).

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General ...Orally, astaxanthin seems to be well tolerated.
Most Common Adverse Effects:
Orally: Abdominal pain, diarrhea, red fecal color.

Gastrointestinal ...Orally, astaxanthin 6 mg daily has caused two cases of increased bowel movements and two cases of red fecal color (91736). A higher dose of astaxanthin (AstaCarox, AstaReal AB) 40 mg daily has caused severe stomach/abdominal pain in two patients (19165).

Ocular/Otic ...Canthaxanthin, another carotenoid substance that is chemically related to astaxanthin, has caused crystals in the retina and loss of visual acuity in one patient (8455). This effect has not been observed with astaxanthin, but patients who have visual changes while taking astaxanthin should stop taking it immediately.

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General ...Orally and topically, hyaluronic acid appears to be well tolerated.
Most Common Adverse Effects:
Topically: Eczema, erythema, itching, wound hemorrhage, wound infection (e.g., erysipelas).

Dermatologic ...The use of needle-free devices to inject hyaluronic acid for cosmetic purposes has been reported to cause serious injury, and in some cases permanent harm, to the skin, lips, and eyes (108613).
Topically, hyaluronic acid application has been reported to cause eczema, erythema, itching, wound hemorrhage, and wound infection (e.g., erysipelas) (108628,108640).

Ocular/Otic ...Ocular pain has been reported rarely in patients using eye drops containing up to 0. 3% hyaluronic acid (97885).

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General ...Orally, limonene is generally well tolerated. It can cause nausea, vomiting, and diarrhea (12709). Topically, limonene can cause contact dermatitis (12715,12716,99871,99872,99873). Observational research has found that increased exposure to ambient air limonene from household cleaning products is associated with wheezing and asthma, particularly in children (99870).

Dermatologic ...Topically, limonene can cause contact dermatitis (12715,12716,99871,99872,99873). Observational studies have found that 8% to 9.4% of patients with a suspected fragrance allergy have allergic skin reactions to limonene hydroperoxides (99871,99873). In one case, a 35-year-old female presented with lymphomatoid contact dermatitis, characterized by a pruritic skin eruption that covered her abdomen and lower limbs, after exposure to limonene in various personal hygiene and household cleaning products. Patch testing showed a positive reaction to limonene hydroperoxides. The patient's skin lesions cleared with topical corticosteroids, sun exposure, and avoidance of limonene-containing products (99872).

Gastrointestinal ...Orally, limonene can cause nausea, vomiting, and diarrhea (12709).

Pulmonary/Respiratory ...When inhaled, limonene has been linked to wheezing and asthma. Observational research has found that a 100% increase in exposure to ambient air limonene from fragrances and household cleaning products is associated with 17% and 18% greater odds of wheezing and asthma, respectively. This link appears to be even stronger in children (99870).

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