Children's Eye Health Formula by CATALO

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Diabetic nephropathy. Preliminary clinical research shows that taking a specific combination tablet containing centaury herb, lovage root, and rosemary leaf (Canephron N, Bionorica) as two tablets three times daily for 6 months in conjunction with antidiabetes medications and enalapril 20 mg daily, reduces microalbuminuria by 73% and the albumin creatinine ratio by 46%, increases high-density lipoprotein (HDL) cholesterol by 25%, and lowers triglyceride levels by 43% when compared to baseline. These improvements are also greater than those observed for patients treated with the antidiabetes medications and enalapril alone (91726). More evidence is needed to rate centaury for this use.

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INSUFFICIENT RELIABLE EVIDENCE to RATE

• Allergic rhinitis (hay fever). Although there has been interest in using oral eyebright for allergic rhinitis, there is insufficient reliable information about the clinical effects of eyebright for this purpose.
• Asthenopia (eye strain). Although there has been interest in using topical eyebright for asthenopia, there is insufficient reliable information about the clinical effects of eyebright for this purpose.
• Blepharitis. Although there has been interest in using topical eyebright for blepharitis, there is insufficient reliable information about the clinical effects of eyebright for this purpose.
• Cancer. Although there has been interest in using oral eyebright for cancer, there is insufficient reliable information about the clinical effects of eyebright for this purpose.
• Common cold. Although there has been interest in using oral eyebright for the common cold, there is insufficient reliable information about the clinical effects of eyebright for this purpose.
• Conjunctivitis. It is unclear if topical eyebright eye drops are beneficial in patients with conjunctivitis. Details: A small observational study shows that applying one drop of eyebright eye drops (WALA Heilmittel GmbH, Eck-walden/Bad Boll) up to five times daily results in complete recovery in about 82% of patients with conjunctivitis after two weeks of treatment (49391). However, due to the lack of a comparator group, it is not clear if this improvement is due to eyebright or to the natural resolution of conjunctivitis symptoms.
• Cough. Although there has been interest in using oral eyebright for cough, there is insufficient reliable information about the clinical effects of eyebright for this purpose.
• Pharyngitis. Although there has been interest in using oral eyebright for pharyngitis, there is insufficient reliable information about the clinical effects of eyebright for this purpose.
• Rhinosinusitis. Although there has been interest in using oral eyebright for rhinosinusitis, there is insufficient reliable information about the clinical effects of eyebright for this purpose. More evidence is needed to rate eyebright for these uses.

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POSSIBLY EFFECTIVE

• Age-related macular degeneration (AMD). When used alone or in combination with other ingredients, oral lutein seems to improve some aspects of vision in patient with AMD. However, it does not seem to slow the progression of AMD. Details: Epidemiological research has found that people who consume higher amounts of lutein plus zeaxanthin in the diet have a reduced risk of developing AMD (219,2394,60238,106353). The association between intake of lutein specifically and the development of AMD is not clear; however, dietary lutein levels are much higher than dietary zeaxanthin levels. Although one study found no association between increased dietary lutein consumption and a reduced risk for age-related maculopathy, people in this study already had high lutein intake at baseline (14007). Some research has assessed whether lutein supplements can reduce symptoms and progression of existing AMD. Clinical research, including pooled analyses, in adults with AMD shows that taking supplemental lutein 10-20 mg daily for up to 36 months modestly improves some aspects of vision, such as macular pigment optical density, the ability of the eyes to adapt to varying light conditions (glare recovery), the ability to see details of near objects (near vision acuity), and the ability to see under low-contrast conditions (contrast sensitivity) (11798,48213,60185,60242,60245,60268,60270,60280,90678,91160)(91165,97225,102887,106366). Meta-analyses of these and other studies shows that taking lutein or a related xanthophyll carotenoid (zeaxanthin or meso-zeaxanthin) improves macular optical density when compared with placebo in patients with or without AMD. Treatment duration of at least 3 months, doses greater than 5 mg, and/or combination treatment with all three carotenoids are associated with a greater improvement in macular optical density (97225,106366). However, lutein supplements do not appear to affect the progression of AMD (60281). A meta-analysis of 6 studies in patients with AMD shows that taking supplemental lutein 10 or 20 mg daily, with or without zeaxanthin, for 0.5-5 years does not reduce the risk of progression to visual loss or late-stage AMD, neovascular AMD, or geographic atrophy, nor does it improve visual acuity when compared with placebo (113088). Lutein has also been evaluated in combination with other ingredients, with conflicting findings. Although not all research agrees, lutein-containing combination supplements might improve some symptoms of AMD (19196,60134,60180,60207,60237,60244,97226). A specific supplement (AZYR SIFI) containing lutein 10 mg, vitamin C 180 mg, vitamin E 30 mg, zinc 22.5 mg, copper 1 mg, zeaxanthin 1 mg, and astaxanthin 4 mg has been used daily for 1-2 years in some research with moderate evidence of benefit (19196,60244). Taking lutein 10 mg plus zeaxanthin 2 mg in addition to the original Age-Related Eye Disease Study (AREDS) formulation (vitamins C and E, beta carotene, and zinc) does not seem to prevent the progression to advanced AMD more than the AREDS formulation alone. However, this progression was modestly inhibited in individuals with low dietary intakes of lutein and zeaxanthin. While progression to late AMD was only modestly inhibited at 5 years when these doses of lutein and zeaxanthin were included in a revised formulation devoid of beta-carotene (AREDS2) (60281), results of an additional 5 years of follow up showed that this revised formulation reduces the risk of progression to late AMD by 15% when compared with the formulation containing beta-carotene (108615). This suggests that lutein with or without zeaxanthin may be a suitable replacement for beta-carotene, which is associated with an increased risk of lung cancer in people who have smoked or have a history of exposure to asbestos (113088). Reasons for these discrepancies are not clear but may relate to lutein dose, dietary lutein intake, treatment duration, or the other ingredients included in the combination products. The effect of lutein on children of parents with AMD is unclear. In first-generation offspring of parents with neovascular AMD, taking lutein 10 mg, zeaxanthin 2 mg, vitamin C 180 mg, vitamin E 30 mg, zinc 15 mg, and copper 1 mg daily for 6 months does not improve the macular pigment optical density (106347).
• Cataracts. Increased dietary lutein seems to reduce the odds of developing cataracts. It is unclear if oral lutein supplementation is beneficial in those who already have cataracts. Details: Observational research and a meta-analysis of this evidence suggests that higher blood levels and/or higher dietary intake of lutein are associated with a 25% lower odds of developing age-related cataracts, and more specifically, a 25% to 27% decreased risk of developing nuclear cataracts (90944,91161,91162,112095). Population research has also found that people who consume higher amounts of lutein (6.9-11.7 mg daily) as part of their diet have a reduced risk of developing severe cataracts that require surgical removal (2395,3219,3220). Clinical research shows that taking lutein 10 mg and zeaxanthin 2 mg per day orally for an average of 4.7 years decreases the risk of needing cataract surgery by 32% in patients with low dietary intake of lutein and zeaxanthin; however, it doesn't benefit patients with higher dietary intake of lutein and zeaxanthin (94703). Some evidence shows that supplemental lutein might benefit patients who already have cataracts. Preliminary clinical research in adults with grade 2 or 3 senile cataracts shows that taking lutein 15 mg orally three times weekly for up to 2 years can improve the ability to see clearly when compared to baseline (60133).

POSSIBLY INEFFECTIVE

• Bronchopulmonary dysplasia. Oral lutein does not seem to prevent bronchopulmonary dysplasia in preterm and low birth weight infants. Details: Clinical research shows that giving preterm and low birth weight infants a specific product (LUTEINofta, SOOFT Italia SpA) containing lutein 0.14 mg and zeaxanthin 0.0006 mg orally once daily, starting at birth and continuing until 36 weeks corrected gestational age, does not decrease the incidence of bronchopulmonary dysplasia when compared with placebo (91163).
• Necrotizing enterocolitis (NEC). Oral lutein does not seem to prevent NEC in preterm and low birth weight infants. Details: Clinical research shows that giving preterm and low birth weight infants a specific product (LUTEINofta, SOOFT Italia SpA) containing lutein 0.14 mg and zeaxanthin 0.0006 mg orally once daily, starting at birth and continuing until 36 weeks corrected gestational age, does not decrease the incidence of NEC when compared with placebo (91163).
• Retinitis pigmentosa. Oral lutein does not seem to improve vision or slow down retinal degeneration in patients with this condition. Details: While some preliminary clinical evidence suggests that oral lutein might be helpful in the treatment of retinitis pigmentosa (10279), most clinical research shows that taking lutein does not improve vision or other markers of retinal degeneration in patients with retinitis pigmentosa (60117,60165,60225).
• Retinopathy of prematurity. Oral lutein does not seem to prevent retinopathy of prematurity in preterm and low birth weight infants. Details: Clinical research in preterm and low birth weight infants shows that giving 0.5 mL or 1.8 mL/kg of a specific product (LUTEINofta, SOOFT Italia SpA) providing lutein 0.14 mg, or giving 0.5 mg/kg plus zeaxanthin 0.0006 mg or 0.02 mg/kg orally once daily, starting at birth and continuing until 36-40 weeks corrected gestational age, does not decrease the incidence or severity of retinopathy of prematurity when compared with placebo (60240,60243,91163,102889).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral lutein is beneficial for attenuating cognitive decline in older adults. Details: Clinical research in adults 40-75 years old shows that taking lutein 10 mg with zeaxanthin 2 mg daily for 6 months improves some, but not all, measures of visual memory when compared with placebo. However, other measures of memory and cognitive function were not improved (109763). Preliminary clinical research in older adults shows that taking the same dose of lutein and zeaxanthin for one year modestly improves some measures of cognitive function, such as complex attention and cognitive flexibility, when compared with placebo (106367). Other preliminary clinical research in older females shows that taking lutein 12 mg alone or with docosahexaenoic acid (DHA) 800 mg daily for 4 months can improve verbal fluency and memory scores when compared to baseline (48216). Also, some observational research in patients 50 years and older has found that higher dietary lutein and zeaxanthin intake is associated with greater word recall when compared with lower intake (102891). However, clinical research in patients over 60 years old shows that taking lutein 10 mg with zeaxanthin 2 mg daily for 5 years in addition to vitamins C and E, beta-carotene, and zinc (AREDS) does not improve markers of cognitive function, such as memory and verbal fluency, when compared with AREDS alone (94702). More research is needed to determine whether lutein is beneficial for specific measures of cognitive function in older adults.
• Alzheimer disease. Oral lutein has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with mild to moderate Alzheimer disease shows that taking lutein 10 mg, zeaxanthin 2 mg, meso-zeaxanthin 10 mg, fish oil 1 gram (providing docosahexaenoic acid 500 mg and eicosapentaenoic acid 150 mg), and vitamin E 15 mg (Memory Health) daily for 12 months does not affect disease severity when compared with placebo. However, there were modest increases the number of patients experiencing either an improvement or an attenuated decline in memory and mood (109764). The effect of lutein alone is unclear.
• Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if oral lutein is beneficial for ALS prevention. Details: Population research has found that higher dietary intake of lutein is associated with a 21% lower risk of developing ALS when compared with lower dietary intake (90412). It is unknown if supplemental lutein has any effect on the risk of developing ALS.
• Asthenopia (eye strain). It is unclear if oral lutein is beneficial for eye strain. Details: Preliminary clinical research shows that some combination lutein supplements might reduce symptoms of eye strain. Results from one clinical trial show that taking a combination product containing lutein, zeaxanthin, and black currant extract daily for 2 weeks improves visual fatigue and eye stress when compared with placebo in patients completing a two-hour visual proof reading task (60214). Other clinical research shows that taking lutein 17.5 mg plus omega-3 fatty acids (standardized to contain docosahexaenoic acid 783 mg and eicosapentaenoic acid 162 mg) and bilberry extract (standardized to contain anthocyanidin 59 mg) daily for 4 weeks reduces symptoms of eye strain when compared with placebo (35470). The effect of lutein alone on eye strain is unclear.
• Asthma. It is unclear if oral lutein is beneficial for asthma prevention. Details: Population research has found that a higher dietary intake of lutein plus zeaxanthin is associated with up to 30% lower odds of having asthma when compared with a lower dietary intake (109765). The effects of lutein intake alone or lutein supplementation are unclear.
• Cardiovascular disease (CVD). Eating more lutein in the diet seems to reduce the risk of CVD. However, taking oral lutein supplements does not seem to prevent CVD events or mortality. Details: One observational study has found that increased intake of dietary lutein is marginally associated with a reduced risk of developing coronary heart disease (14108). A meta-analysis including this and other studies shows that high dietary lutein intake or high lutein serum concentrations are associated with a 12% reduction in the incidence of coronary heart disease, an 18% reduction in stroke, and a 25% reduction in the incidence of metabolic syndrome when compared with low lutein intake or serum concentrations (97227). However, clinical research shows that taking lutein 10 mg plus zeaxanthin 2 mg daily for an average of 4.8 years does not decrease the risk of CVD-related mortality or cardiovascular events such as stroke, myocardial infarction, or angina when compared with no supplementation in patients 50-85 years old (94701). Unlike the analysis above, individual cardiovascular outcomes were not separately evaluated in this study. The effect of lutein on CVD in younger patients or in doses greater than 10 mg is unknown.
• Central serous retinopathy. Oral lutein has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a supplement containing lutein 15 mg, vitamin C 288 mg, vitamin E 150 IU, zinc 9 mg, and copper 1.2 mg (Sante Lutax 15, Santen Pharmaceutical Co. Ltd) three times daily after meals for 6 months has no effect on mean best-corrected visual acuity, serous retinal detachment, or subfoveal fluid remission when compared with placebo in patients with central serous retinopathy (97224).
• Cervical cancer. It is unclear if oral lutein is beneficial for cervical cancer prevention. Details: Epidemiological research has found that low dietary intake of lutein is not associated with an increased risk for developing cervical cancer (60297).
• Child development. It is unclear if oral lutein is beneficial for child development. Details: Epidemiological research has found that a higher dietary intake of lutein in the first and second trimesters of pregnancy is associated with increased verbal intelligence and improved behavior in the child at 6-10 years of age. However, the ability to discriminate between a novel or familiar visual stimulus was reduced at about 6 months of age, and there were no effects on most cognitive outcomes in children aged 3-6 years (107106). Other epidemiological research has found that a higher dietary intake of lutein plus zeaxanthin in children aged 3-6 years may be associated with modestly improved executive function at 6-10 years. However, there were no effects on most cognitive outcomes in children aged 3-6 years or 6-10 years (109761). Additionally, a small clinical study conducted in India in children aged 5-12 years shows that taking lutein 10 mg with zeaxanthin 2 mg (Lutemax Kids, Omniactive) daily for 180 days improves some measures of cognitive performance, such as attention and focus, when compared with placebo (114698).
• Choroideremia. It is unclear if oral lutein is beneficial for improving vision. Details: Preliminary clinical research shows that taking lutein 20 mg daily for 6 months does not improve vision in patients with choroideremia (60124).
• Cognitive function. It is unclear if oral lutein is beneficial for improving cognitive function. Details: A meta-analysis of clinical research shows that increased dietary lutein does not improve cognitive function measures, such as attention, executive function, or memory, when compared with placebo or an isocaloric meal (107082). However, the dietary source of lutein used in the included studies was heterogeneous and any conclusions remain unclear. Doses of lutein ranged from 8-12 mg daily, alone or in combination with daily zeaxanthin 2-26 mg and/or meso-zeaxanthin 10 mg and docosahexaenoic acid (DHA) 800 mg (107082). However, some preliminary clinical research in younger adults shows that taking lutein 10 mg and zeaxanthin 2 mg for one year modestly improves some measures of cognitive function, such as spatial memory, when compared with placebo (106348). Also, observational research has found that intake of choline and lutein plus zeaxanthin is positively associated with cognitive flexibility task performance speed. However, this association is not present with the intake of lutein plus zeaxanthin in the absence of choline (106354). Reasons for these discrepancies are not clear but may relate to lutein dose, treatment duration, or the addition of other nutrients to the diet or supplements.
• Colorectal cancer. It is unclear if oral lutein is beneficial for colorectal cancer prevention. Details: Some epidemiological research has found that higher dietary intake of lutein is associated with a reduced risk of developing colon cancer (3962). However, most epidemiological research has found that higher dietary intake of lutein is not associated with a reduced risk of colorectal cancer (34481,106372). It is not known if supplemental lutein has any effect on colorectal cancer risk.
• Depression. It is unclear if oral lutein is beneficial for depression. Details: A cross-sectional study in 8655 adults with cardiometabolic disease including diabetes, hypertension, coronary heart disease, heart failure, and stroke suggests that higher dietary lutein and zeaxanthin intake is associated with a 31% reduced risk of depression when compared with lower dietary intake. The study also found that adults with depression had lower dietary lutein and zeaxanthin intake than those without depression. Additionally, the study found a nonlinear U-shaped relationship between total dietary carotenoid intake and the risk of depression among patients with cardiometabolic disease, where the risk of depression decreased with increasing total dietary carotenoid intake up until an inflection point where the risk of depression increased with increasing total dietary carotenoid intake (112098). Further research is needed to establish causality.
• Diabetes. Observational research suggests that oral lutein may not be beneficial for the prevention of diabetes or diabetic complications. Details: Some epidemiological research has found that low serum levels of carotenoids, including lutein, are associated with impaired glucose tolerance. This may indicate that taking carotenoids such as lutein might reduce the risk of diabetes development (60161). However, population research has found that increasing intake of dietary lutein plus zeaxanthin does not decrease the risk of developing type 2 diabetes (14004,97227). Other epidemiological research in patients with type 2 diabetes has found that an increased serum concentration of lutein is not associated with reduced cardiovascular mortality over 14 years (109768).
• Diabetic retinopathy. It is unclear if oral lutein is beneficial in diabetic retinopathy. Details: Preliminary clinical research shows that taking lutein 10 mg daily for 36 weeks has no effect on visual acuity or glare sensitivity in patients with non-proliferative diabetic retinopathy (97223). Observational research in a small group of patients with non-proliferative diabetic retinopathy has also found that taking lutein 4 mg with zeaxanthin 0.5 mg daily for 4 months does not improve visual acuity, contrast sensitivity, or glare sensitivity when compared with zeaxanthin alone (100986).
• Esophageal cancer. It is unclear if oral lutein is beneficial for esophageal cancer prevention. Details: Population research has found that people who consume higher amounts of lutein and zeaxanthin in their diet have a 29% lower risk of developing esophageal squamous cell cancer when compared with those with lower intake (91159). It is unknown if supplemental lutein has any effect on esophageal cancer risk.
• Exercise-induced muscle soreness. It is unclear if oral lutein is beneficial in relieving muscle soreness due to exercise. Details: Some clinical research shows that taking a specific lutein-containing combination product (BioAstin, Cyanotech Corp.) containing haematococcus algae extract with astaxanthin 4 mg and lutein 480 mg daily for 3 weeks prior to exercise does not significantly reduce post-exercise muscle soreness when compared with placebo (19199). The effect of lutein alone is unclear.
• Fractures. It is unclear if oral lutein is beneficial for fracture prevention. Details: A meta-analysis of observational research has found that increased dietary intake of lutein and/or zeaxanthin is not associated with a reduced risk of hip fractures (97228).
• Gastric cancer. It is unclear if oral lutein is beneficial for gastric cancer prevention. Details: Two meta-analyses of observational research have found that increased dietary intake of lutein and/or zeaxanthin is not associated with a reduced risk of developing gastric cancer (97231,114694). The validity of these findings is limited by the heterogeneity of the included studies, including populations and outcomes.
• Glaucoma. Oral lutein has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with open-angle glaucoma shows that taking oral lutein 10 mg, zeaxanthin 2 mg, and meso-zeaxanthin 10 mg daily for 18 months increases macular pigment density, but does not affect visual function, when compared with placebo (109756).
• Hyperlipidemia. It is unclear if oral lutein is beneficial for hyperlipidemia. Details: A meta-analysis of clinical research shows that supplementation with lutein does not reduce the levels of total, low-density lipoprotein (LDL), or high-density lipoprotein (HDL) cholesterol when compared with placebo (109757). Most publications included in this analysis evaluated lutein alone in healthy adults or in patients with age-related macular degeneration, two studies combined lutein with another ingredient, and one study evaluated zeaxanthin alone. The effect of lutein in patients with existing hyperlipidemia is unclear.
• Infertility. It is unclear if oral lutein is beneficial for infertility. Details: An observational study suggests that there is no association between dietary lutein 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).
• Lung cancer. Research is conflicting whether oral lutein is beneficial for lung cancer prevention. Details: Epidemiological research has found that low serum levels of carotenoids, including lutein, are associated with an increased risk of lung cancer (12874). However, other epidemiological research has found that higher serum levels or higher dietary intake of lutein are not associated with a reduced risk of developing or dying from lung cancer (39690,60090,60160). Another large epidemiological cancer screening trial with a mean follow-up of over 12 years suggests that dietary intake of lutein and zeaxanthin is protective against lung cancer as shown by a non-linear dose response curve, where lower doses of lutein and zeaxanthin are associated with a sharp decrease in the incidence of lung cancer, followed by a more gradual decrease in incidence at higher doses (112096).
• Macular telangiectasia type 2. It is unclear if oral lutein is beneficial for macular telangiectasia type 2. Details: In patients with macular telangiectasia type 2, observational research has found that taking a specific combination of lutein 10 mg, meso-zeaxanthin 10 mg, and zeaxanthin 2 mg (MacuShield; Alliance Pharmaceuticals) for at least 6 months, with an average duration of 15.7 months, was associated with a stabilization of visual acuity. Also, the number and size of cavitations in the macula were reduced (106355).
• Metabolic syndrome. Oral lutein has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A meta-analysis of observational research shows that high dietary lutein intake or high lutein serum concentrations are associated with a 25% reduction in the incidence of metabolic syndrome when compared with low lutein intake or serum concentrations (97227). Additional population research in females shows that the highest dietary intake of lutein plus zeaxanthin is associated with 54% reduced odds of developing metabolic syndrome when compared with the lowest intake. However, when supplements containing lutein plus zeaxanthin were included in the total intake, there was no association with metabolic syndrome (109760).
• Myopia. It is unclear if oral lutein is beneficial for myopia. Details: A very small clinical study in adults aged 20-50 years with high myopia shows that taking lutein 20 mg daily for 6 months does not improve macular pigment optical density, visual acuity, contrast sensitivity, or electroretinogram measurements when compared with placebo (112099). The validity of these findings is limited by the very small sample size and short study duration.
• Non-Hodgkin lymphoma. It is unclear if oral lutein is beneficial for Non-Hodgkin lymphoma prevention. Details: A meta-analysis of observational population research has found that increased intake of lutein/zeaxanthin in the diet is associated with an 18% lower risk of developing non-Hodgkin lymphoma when compared with low dietary intake. However, no dose-response relationship was reported (97229). It is unknown if supplemental lutein has any effect on non-Hodgkin lymphoma risk.
• Obesity. It is unclear if oral lutein is beneficial for obesity. Details: A small clinical trial in obese middle-aged individuals shows that taking lutein 20 mg daily in addition to following a low-calorie diet for 10 weeks does not affect most anthropometric or cardiometabolic indices when compared with a low-calorie diet alone. However, there was a small beneficial effect on body fat and total cholesterol levels (107107).
• Pancreatic cancer. It is unclear if oral lutein is beneficial for pancreatic cancer prevention. Details: A meta-analysis of population research has found that increased dietary intake of lutein and/or zeaxanthin is not associated with a reduced risk of pancreatic cancer (97230). The effects of supplemental lutein are unclear.
• Parkinson disease. It is unclear if oral lutein is beneficial for Parkinson disease prevention. Details: Population research has found that higher dietary intake of lutein is not associated with the risk of developing Parkinson disease (91164). The effects of supplemental lutein are unclear.
• Pre-eclampsia. It is unclear if oral lutein is beneficial for pre-eclampsia prevention. Details: Some epidemiological research has found that high plasma concentrations of lutein are associated with a decreased risk of pre-eclampsia (60142). Other epidemiological research has found that the highest dietary intake of lutein plus zeaxanthin during pregnancy is associated with 68% reduced odds of having pre-eclampsia when compared with the lowest intake (109762). The effects of lutein supplements are unclear.
• Respiratory tract infections. It is unclear if oral lutein is beneficial in respiratory tract infection prevention or treatment. Details: Epidemiological research has found that high serum levels of lutein are not associated with a decreased incidence or severity of respiratory tract infections in the elderly (60152). The effects of supplemental lutein are unclear.
• Ulcerative colitis. It is unclear if oral lutein is beneficial for ulcerative colitis. Details: In patients in the remission phase of ulcerative colitis, observational research has found that a higher dietary intake of lutein plus zeaxanthin is associated with a reduced incidence of constipation, but not flatulence or feelings of urgency (tenesmus) (106362). The effects of supplemental lutein are unclear.
• Visual development. It is unclear if taking oral lutein during pregnancy can improve the visual acuity or vision health of children. Details: Some observational research has found that higher maternal lutein levels are associated with a 22% to 40% lower risk of poor visual acuity in children at 3 years of age when compared with lower maternal lutein levels (102888). However, other epidemiological research has found that dietary intake of lutein plus zeaxanthin during the first or third trimesters of pregnancy is not associated with contrast vision or visual acuity in the child at 11-12 years of age (109759). The effects of lutein supplements taken in pregnancy are unclear. A small clinical study conducted in India in children aged 5-12 years shows that taking lutein 10 mg with zeaxanthin 2 mg (Lutemax Kids. Omniactive) daily for 180 days improves a key biomarker of vision health (macular pigment optical density, MPOD)when compared with placebo (114698). More evidence is needed to rate lutein for these uses.

(Read more about LUTEIN)

POSSIBLY EFFECTIVE

• Congestive heart failure (CHF). Oral taurine may improve left ventricular function, heart failure-related symptoms, and exercise capacity in patients with CHF. Details: Taking taurine 2-6 grams in two or three divided doses daily for 6-8 weeks seems to improve left ventricular function (5248,5271,8221) and symptoms of heart failure (5271,5306,8221) when compared with placebo or coenzyme Q10 in patients with New York Heart Association (NYHA) functional class II to IV. Also, taking taurine 500 mg three times daily for 2 weeks seems to improve exercise capacity when compared with placebo in patients with heart failure (77176). Some patients with severe heart failure rapidly improve from NYHA class IV to II after 4-8 weeks of treatment. Improvement seems to continue for as long as taurine treatment is continued, up to one year (5306,8217,8218,8221).
• Hepatitis. Oral taurine may improve liver function in patients with acute or chronic hepatitis. Details: Several small clinical trials show that taking taurine 1.5-4 grams daily for up to 3 months improves liver function in patients with acute and chronic hepatitis when compared with placebo (10454,77114,77147).

POSSIBLY INEFFECTIVE

• Obesity. Oral taurine does not appear to improve body weight in adults who are obese or overweight. Details: A meta-analysis of 12 small clinical trials shows that taurine supplementation does not reduce body weight or body mass index (BMI) when compared with placebo. The studies included in this analysis evaluated taurine doses of 0.5-6 grams daily for 15 days to 6 months. Most of the patient populations evaluated in the included studies had liver or metabolic disorders; three studies specifically evaluated overweight or obese adults (104166). Additionally, a more recent clinical trial in a small group of females with obesity shows that taking taurine 1 gram three times daily along with a calorie-restricted diet for 8 weeks does not reduce body weight, BMI, or waist circumference when compared with calorie restriction alone (104167). In contrast, a very small study in adults with type 2 diabetes on antidiabetes medication shows that taking taurine 500 mg twice daily for 8 weeks reduces body mass, BMI, and body fat percentage when compared with control (112271). The validity of these effects is limited by the small sample size.

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Academic performance. It is unclear if oral taurine is beneficial to improve academic performance. Details: A very small clinical study in college entrance examinees over age 19 shows that taking a jelly containing taurine 3 grams daily for 14 days does not improve academic achievement when compared with baseline or placebo (110579). Due to its small size, this study may have been inadequately powered to detect a difference between groups.
• Age-related macular degeneration (AMD). Although there has been interest in using oral taurine for AMD, there is insufficient reliable information about the clinical effects of taurine for this purpose.
• Androgenic alopecia. Oral taurine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in adults with androgenic alopecia or telogen effluvium shows that taking a combination product containing taurine, cysteine, methionine, iron, selenium, and hydrolyzed collagen (GFM Oral, Cantabria Labs) along with conventional therapy, consisting primarily of finasteride or minoxidil, daily for 12 weeks improves hair loss when compared with conventional therapy alone (111636). It is unclear if this effect is due to taurine, other ingredients, or the combination.
• Athletic performance. Research on the use of taurine for improving endurance or power output is limited and conflicting; however, it may improve performance by a small amount in some athletes. Details: Research is conflicting on the effects of taurine on athletic performance. Several clinical studies in trained and untrained athletes show that taking taurine 1-6 grams as a single dose before endurance exercise, or 3 grams daily for 8 weeks after endurance exercise, does not improve endurance or aerobic capacity when compared with placebo (77159,77203,95613,98334). However, a meta-analysis of 7 small clinical trials shows that taking taurine 1-6 grams daily for up to 2 weeks slightly improves endurance when compared with control. Also, preliminary studies in male cyclists, recreationally active males, Olympic-level athletes, and female athletes habituated to caffeine show that taking taurine 50 mg/kg or 1-6 grams one time 1.5-2 hours prior to a cycling test increases the time to exhaustion and peak, mean, and minimum power output but does not improve perceived exertion, fatigue index, heart rate, or anaerobic capacity when compared with placebo (101475,103211,112265,112269). The reasons for these discrepancies are unclear; the meta-analysis did not identify a dose or duration-related benefit. One small clinical trial shows that taking taurine 40 mg/kg improves muscle power in caffeine-deprived athletes who regularly use caffeine, but actually seems to worsen muscle power in athletes who do not regularly use caffeine (98335). Overall, it is not clear which population is most likely to benefit from taurine use (98337,98338). Study results are mixed when taurine has been evaluated in combination with other ingredients. One small study shows that taking a specific product containing taurine and caffeine (AdvoCare Spark) does not improve sprint performance in college athletes when compared with placebo (77195). However, other small studies of cyclists and boxers suggest that taking taurine in combination with a variety of other ingredients including B vitamins, caffeine, and glucuronolactone (Red Bull Energy Drink) or ginseng, kudzu, and soybean, may improve measures such as endurance, power, balance, or agility (37815,57945,110577,112269). It is unclear if the benefits seen in these studies are due to taurine, other ingredients, or the combinations.
• Attention deficit-hyperactivity disorder (ADHD). Although there has been interest in using oral taurine for ADHD, there is insufficient reliable information about the clinical effects of taurine for this purpose.
• Autism spectrum disorder. Although there has been interest in using oral taurine for autism spectrum disorder, there is insufficient reliable information about the clinical effects of taurine for this purpose.
• Chemotherapy-induced nausea and vomiting (CINV). It is unclear if oral taurine is beneficial in patients with CINV. Details: One small clinical trial in patients with acute lymphoblastic leukemia receiving 6 months of chemotherapy shows that taking taurine (pure powder, Aviforme) 1000 mg twice daily, starting 6 hours after receiving chemotherapeutic agents, significantly improves CINV in 87.5% of patients. Other symptoms, such as reduced appetite and smell and taste impairment, are also improved in some patients (91512).
• Chemotherapy-induced nephrotoxicity. It is unclear if oral taurine is beneficial for preventing or treating chemotherapy-induced nephrotoxicity. Details: One small clinical trial in patients with acute lymphoblastic leukemia receiving 6 months of chemotherapy shows that taking taurine (pure powder, Aviforme) 1000 mg twice daily reduces plasma creatinine, urea, bilirubin, and liver enzymes after 4 months when compared with placebo. This suggests a protective effect against chemotherapy-induced nephrotoxicity and hepatotoxicity. A reduction in overall fatigue is also observed (95616).
• Cirrhosis. It is unclear if oral taurine is beneficial in patients with cirrhosis. Details: One small, uncontrolled clinical study in patients with cirrhosis shows that taking taurine 1 gram three times daily for 4 weeks reduces the severity and frequency of muscle cramps when compared to baseline (104165). Another small clinical trial in patients with cirrhosis shows that taking taurine 6 grams daily for 4 weeks reduces portal hypertension by 12%, compared with a 2% increase in the placebo group (98336). However, it is unclear if this is associated with a reduced risk for complications such as variceal bleeding and ascites.
• Cognitive function. It is unclear if oral taurine is beneficial for improving cognitive function; however, taking an energy drink (Red Bull Energy Drink) containing taurine and other ingredients may modestly improve some measures of cognitive function. Details: Levels of taurine decrease with age, but supplementation does not seem to have neuroprotective effects or cognitive benefits in the elderly (101471,110574,110578). In one small crossover study, taurine alone did not reduce errors in sleep-deprived individuals when compared with placebo (38154). However, taurine taken as part of an energy drink formulation containing taurine, caffeine, glucuronolactone, and B vitamins (Red Bull Energy Drink) improves focused and sustained attention, wakefulness, verbal reasoning, driving ability and quality, and reaction speed when compared with placebo (9899,38117,77088,77202). Preliminary clinical research in young adults also shows that consuming the Red Bull Energy Drink might improve attention and verbal reasoning, but does not seem to improve memory, when compared with placebo (9899,77088).
• Cystic fibrosis. Oral taurine may reduce steatorrhea in children with cystic fibrosis, but it does not seem to improve other measures of nutritional status. Details: Some small clinical studies in children with cystic fibrosis show that taking taurine 30-40 mg/kg daily for 7 days to 6 months might be useful as adjunctive therapy to reduce steatorrhea when compared with baseline or placebo (10455,77227,77231). However, it does not seem to improve growth, lung function, muscle protein breakdown, or other symptoms of cystic fibrosis (77224,77228). Also, adding taurine 500-1500 mg daily to treatment with ursodeoxycholic acid for up to one year does not improve liver function tests, fat absorption, or nutritional status in patients with cystic fibrosis and associated liver disease when compared with ursodeoxycholic acid alone (77246,77256).
• Delirium. It is unclear if oral taurine prevents delirium in patients in the intensive care unit. Details: A large clinical study of hospitalized adults in Iran who underwent liver transplantation shows that taking a specific taurine powder product (100% Taurine Amino Acid, MyProtein) 2 grams daily for 30 days post-transplant reduces the risk of delirium by 73% when compared with placebo. These results also suggest that for every four patients treated with taurine over placebo, one additional case of delirium is prevented. Patients who took taurine also had less time on the ventilator and shorter intensive care and hospital stays (110575). However, it is unclear if these effects are due to taurine or other factors since ventilator time and intensive care length of stay are risk factors for delirium.
• Diabetes. It is unclear if oral taurine is beneficial in patients with diabetes. Details: Plasma levels of taurine are reported to be lower in patients with diabetes than in healthy controls (101473). However, clinical research evaluating taurine for glycemic control is mixed (77074,103212). One small clinical trial in patients with type 2 diabetes shows that taking taurine 1 gram three times daily for 8 weeks reduces blood glucose, insulin resistance, total cholesterol, and low-density lipoprotein (LDL) cholesterol when compared with placebo (103212). Although there was no improvement in glycated hemoglobin (HbA1c), the study was not long enough to detect a meaningful reduction in HbA1c. Other preliminary clinical research shows that taking taurine 1-1.5 grams twice daily for 2-4 months does not affect fasting blood glucose, HbA1c, or insulin but may improve measures of insulin resistance in patients with type 2 diabetes when compared with placebo (77074,112271). However, taking taurine while following an exercise program 3 times weekly does appear to reduce fasting blood sugar and HbA1c when compared with exercise plus placebo (112271). The reasons for these discrepant findings are unclear; however, all the included studies were small and potentially inadequately powered to detect a difference in outcomes.
• Epilepsy. Although there has been interest in using oral taurine for epilepsy, there is insufficient reliable information about the clinical effects of taurine for this condition.
• Exercise-induced muscle soreness. Small clinical studies suggest that oral taurine may modestly improve exercise-induced muscle soreness. Details: One small clinical trial in healthy, untrained adults shows that taking taurine 2 grams in combination with branched chain amino acids (BCAAs) three times daily for 2 weeks reduces subjective muscle soreness by 37% when compared with placebo (77212). Another small clinical trial in young, untrained males shows that taking taurine (Taisho Pharmaceutical Co., LTD.) 2 grams three times daily after meals before exercise, and continuing for three days after exercise, reduces delayed onset muscle soreness (DOMS), but not creatine kinase levels, when compared with placebo (91513).
• Fatigue. It is unclear if oral taurine is beneficial for improving fatigue. Details: One small clinical trial shows that taurine seems to reduce fatigue when taken alone, but increases fatigue when taken in combination with caffeine (77202). However, an observational study in young adults has found that subjective scores for physical and mental fatigue do not seem to correlate with dietary taurine intake (101472). One small clinical trial shows that drinking 500 mL of an energy drink providing taurine 1 gram plus other ingredients including caffeine and B vitamins decreases measures of driving-related fatigue in a driving simulation when compared with placebo (91075).
• Helicobacter pylori. It is unclear if oral taurine can aid in the eradication of helicobacter pylori (H. pylori). Details: One clinical trial shows that taking taurine 500 mg twice daily in combination with conventional treatment for 6 weeks increases H. pylori eradication and shortens duodenal ulcer scarring time in patients with confirmed H. pylori infection when compared with conventional treatment alone (77145).
• Hyperlipidemia. It is unclear if oral taurine is beneficial for lowering lipid levels. Details: A meta-analysis of 12 small clinical trials in adults with various liver or metabolic disorders, but without a specific diagnosis of hyperlipidemia, shows that taurine supplementation reduces total cholesterol by 11 mg/dL and triglycerides by 13 mg/dL, but does not seem to improve low-density lipoprotein (LDL) cholesterol or high-density lipoprotein (HDL) cholesterol levels, when compared with placebo. The studies included in this analysis evaluated doses of 0.5-6 grams daily for 15 days to 6 months (104166). The benefits of taurine in adults with hyperlipidemia are unclear. The effect of taurine has also been investigated in combination with exercise. A very small study in adults with type 2 diabetes on antidiabetes medication shows that taking taurine 500 mg twice daily while participating in an exercise program 3 times weekly for 8 weeks reduces triglycerides, total cholesterol, and LDL cholesterol and increases HDL cholesterol when compared with exercise plus placebo (112271).
• Hypertension. Oral taurine may modestly reduce blood pressure in patients with hypertension; however, the long-term antihypertensive effects of taurine are unclear. Details: One clinical study in patients with elevated blood pressure or stage 1 hypertension shows that taking taurine 1.6 grams daily for 12 weeks reduces systolic blood pressure (SBP) by 5 mmHg and diastolic blood pressure (DBP) by 3 mmHg when compared with placebo. The benefit is seen after 8 weeks of continued supplementation (95614). A small clinical trial in patients with stage 2 hypertension (previously classified as borderline hypertension) shows that taking taurine 6 grams daily for 7 days reduces both SBP and DBP when compared to baseline (77229). The long-term effects of taurine on blood pressure are unclear. A meta-analysis of 12 small clinical trials in adults with various liver or metabolic disorders, but without a specific hypertension diagnosis, shows that taurine supplementation reduces SBP by 5 mmHg and DBP by 3 mmHg when compared with placebo. The studies included in this analysis evaluated doses of 0.5-6 grams daily for 15 days to 6 months (104166). Taurine is commonly found in energy drinks, and its effect on blood pressure when used in combination with other ingredients in the form of an energy drink has been evaluated. A small observational study in young adults suggests that drinking a specific combination product containing taurine 100 mg, caffeine, and group B vitamins (Redbull Energy Drink) reduces heart rate but does not change SBP or DBP when compared to baseline (112266). However, another small observational study in young healthy adults suggests that drinking a specific combination product containing taurine 2000 mg, caffeine, ginseng, glucuronolactone, inositol, guarana, L-carnitine, and B vitamins (Monster Energy Drink) increases both SBP and DBP by about 16 mmHg and raises heart rate by 17 beats per minute 15 minutes after consumption when compared to baseline. However, 90 minutes after consumption only DBP and heart rate remain elevated (112268). In both studies, the validity of the effects is limited by a lack of a comparator group. Additionally, it is unclear if the effects are due to taurine, other ingredients, or the combination.
• Infant development. Higher maternal intake of taurine from the diet may be linked to increased newborn length and weight; however, feeding taurine-containing formula to newborns does not appear to improve infant development. Details: One observational study has found a positive correlation between maternal dietary taurine intake and newborn length. In pregnant patients with high taurine intake (>120 mg/day), neonatal birth weight and length were significantly higher when compared with groups with lower taurine intake (101474). However, clinical research shows that administering infant formula containing taurine 45 mg/L for up to 12 weeks does not affect weight, length, head circumference, or behavior in preterm and full-term infants when compared with formula without taurine (77119,77216,77218,77239,77260).
• Iron deficiency anemia. It is unclear if oral taurine is beneficial in patients with iron deficiency anemia. Details: One small clinical trial in females with iron deficiency anemia shows that taking taurine 1000 mg plus ferrous sulfate 325 mg daily for 20 weeks improves hemoglobin concentrations, red blood cell counts, and serum ferritin levels when compared with ferrous sulfate plus placebo (77070).
• Muscular dystrophy. It is unclear if oral taurine is beneficial in patients with muscular dystrophy. Details: One very small crossover trial in patients with muscular dystrophy shows that taking taurine 100-150 mg/kg for 6 months improves the ability to relax muscles after voluntary use when compared with placebo (77235).
• Physical performance. It is unclear if oral taurine improves physical performance in older adults. Details: A small study in elderly females living in a care facility shows that taking taurine powder 1.5 grams daily for 14 weeks in addition to standardized exercise training may modestly improve some measures of physical fitness (i.e. agility, endurance) when compared to baseline. These measures were not improved in patients who took taurine but did not participate in exercise training or who participated in exercise training but did not take taurine (110574). The validity of these findings is limited by lack of randomization, blinding, and statistical comparison between groups.
• Postoperative recovery. It is unclear if oral taurine is beneficial for improving postoperative recovery. Details: One small clinical trial in patients recovering from surgery after a hip fracture shows that taking taurine 6 grams daily for 7 days after surgery does not improve morbidity and mortality outcomes after 1 year when compared with placebo (95615).
• Psychosis. It is unclear if oral taurine is beneficial in patients with psychosis. Details: One small clinical trial in adults up to 25 years of age with first-episode psychosis shows that taking taurine 4 grams daily for 12 weeks in combination with prescribed antipsychotics reduces positive psychotic symptoms, but not negative or cognitive symptoms, when compared with placebo (95612).
• Sleep deprivation. Oral taurine 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 product containing taurine, caffeine, glucuronolactone, and B vitamins (Red Bull Energy Drink) reduces lane drifting and sleepiness and improves driving quality and reaction time during a car-driving simulator exercise in sleep-deprived individuals when compared with placebo (38117,77066). Other preliminary clinical research in sleep-deprived surgical trainees shows that taking taurine 2 grams in addition to caffeine 150 mg improves reaction time during performance of simulated laparoscopic surgery when compared with placebo, although error-making is not reduced (38154).
• Tourette syndrome. Oral taurine may improve tic severity in children with Tourette syndrome who are taking tiapride at a dose of 300 mg or less. Taurine may not be effective in children taking higher doses of tiapride. Details: One clinical trial in children 6-16 years of age with Tourette syndrome or other tic disorders shows that taking taurine along with tiapride reduces the severity of tics when compared with tiapride alone. For every 6 children taking taurine, one additional child saw a 60% or greater reduction in tic severity as measured on the Yale Global Tic Severity Scale when compared with placebo. However, taurine did not improve tic severity in children taking tiapride at a dose greater than 300 mg daily (103210). Taurine was taken in age-dependent doses of 2.4 grams daily in those 6-8 years, 3.6 grams daily in those 9-13 years, and 4.8 grams daily in those 14-16 years.
• Traumatic brain injury (TBI). It is unclear if oral taurine is beneficial in patients with a TBI. Details: A small clinical study of adults in Iran receiving treatment in the intensive care unit (ICU) following TBI shows that adding a specific taurine powder product (Nutricost) 30 mg/kg/day up to 3 grams daily to enteral nutrition for 14 days may modestly improve disease severity scores, but does not reduce days on the ventilator, ICU length of stay, or mortality at 30 days when compared with usual enteral nutrition (110573). Due to its small size, this study may have been underpowered to detect differences between groups. More evidence is needed to rate taurine for these uses.

(Read more about TAURINE)

POSSIBLY EFFECTIVE

• Age-related macular degeneration (AMD). Oral zeaxanthin, when used in low levels as part of multi-ingredient products containing lutein, seems to improve some aspects of vision in patient with AMD. It is unclear if oral zeaxanthin alone or in amounts similar to lutein is beneficial for slowing AMD progression. Details: Epidemiological research has found that people who consume higher amounts of zeaxanthin plus lutein in the diet have a reduced risk of developing late AMD, but not early or intermediate AMD (60238,106353,106359). However, any association between intake of zeaxanthin itself and the development of AMD is not clear. Some clinical research has assessed whether zeaxanthin alone can reduce symptoms and progression of AMD. A small clinical trial shows that taking supplemental zeaxanthin 8 mg daily for 12 months modestly improves some aspects of vision, such as macular pigment optical density, the ability to see details of near objects (near vision acuity), and resolution of scotoma (blind spot), when compared with placebo in patients with AMD (60245). Other clinical research in a healthy population shows that taking zeaxanthin alone (Optisharp) as 10 mg daily for 6-12 months increases macular pigment optical density (60175). Most clinical research in patients with AMD has assessed zeaxanthin in combination with lutein. In general, this combination has been shown to increase macular pigment optical density, as well as the ability to see under low-contrast conditions (contrast sensitivity) and visual acuity. However, most research has used much higher doses of lutein compared with zeaxanthin (60281,91160,97225,106366,108615). Use of near equal amounts, such as zeaxanthin 8-10 mg daily plus lutein 9-10 mg daily for up to 2 years, seems to improve macular density in adults with or without AMD (60175,60268,60270,106358); however, effects on vision when used for up to 2 years in patients with AMD are conflicting (60245,60268,60270,106358). Zeaxanthin has also been evaluated in combination with other ingredients, with conflicting findings. A specific supplement (AZYR SIFI) containing zeaxanthin 1 mg, lutein 10 mg, vitamin C 180 mg, vitamin E 30 mg, zinc 22.5 mg, copper 1 mg, and astaxanthin 4 mg has been used daily for 1-2 years with moderate evidence of benefit (19196,60244). Taking zeaxanthin 2 mg plus lutein 10 mg in addition to the original Age-Related Eye Disease Study (AREDS) formulation (vitamins C and E, beta-carotene, and zinc) does not seem to prevent the progression to advanced AMD more than the AREDS formulation alone. However, this progression was modestly inhibited in individuals with low dietary intakes of lutein and zeaxanthin. While progression to late AMD was only modestly inhibited at 5 years when these doses of lutein and zeaxanthin were included in a revised formulation devoid of beta-carotene (60281), results of an additional 5 years of follow up showed that this revised formulation reduces the risk of progression to late AMD by 15% when compared with the formulation containing beta-carotene (108615). Clinical research shows that adding meso-zeaxanthin 10 mg to this revised AREDS formulation (AREDS2) does not further improve contrast sensitivity in patients with non-advanced AMD (106369). In first-generation offspring of parents with neovascular AMD, taking zeaxanthin 2 mg, lutein 10 mg, vitamin C 180 mg, vitamin E 30 mg, zinc 15 mg, and copper 1 mg daily for 6 months does not improve the macular pigment optical density (106347). Reasons for these discrepancies are not clear but may relate to the patient population, zeaxanthin dose, treatment duration, or other ingredients included in combination products.

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral zeaxanthin is beneficial for attenuating cognitive decline in older adults. Details: Clinical research in adults 40-75 years old shows that taking zeaxanthin 2 mg with lutein 10 mg daily for 6 months improves some, but not all, measures of visual memory when compared with placebo. However, other measures of memory and cognitive function were not improved (109763). Also, preliminary clinical research in older adults shows that taking the same dose of zeaxanthin and lutein for one year modestly improves some measures of cognitive function, such as complex attention and cognitive flexibility, when compared with placebo (106367). Some observational research in patients 50 years and older has found that higher dietary lutein and zeaxanthin intake is associated with greater word recall when compared with lower intake (102891). However, clinical research in patients over 60 years old shows that taking zeaxanthin 2 mg with lutein 10 mg daily for 5 years in addition to vitamins C and E, beta-carotene, and zinc (AREDS) does not improve markers of cognitive function, such as memory and verbal fluency, when compared with AREDS alone (94702).
• Alzheimer disease. Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with mild to moderate Alzheimer disease shows that taking zeaxanthin 2 mg, lutein 10 mg, meso-zeaxanthin 10 mg, fish oil 1 gram (providing docosahexaenoic acid 500 mg and eicosapentaenoic acid 150 mg), and vitamin E 15 mg (Memory Health) daily for 12 months does not affect disease severity when compared with placebo. However, there were modest increases in the number of patients experiencing either an improvement or attenuated decline in memory and mood (109764). The effect of zeaxanthin alone is unclear.
• Asthenopia (eye strain). Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Results from one clinical trial show that taking a combination product (Cerebos Pacific Limited) containing zeaxanthin 1 mg, lutein 5 mg, and black currant extract 200 mg daily for 2 weeks modestly improves visual fatigue and eye stress when compared with placebo in patients completing a two-hour visual proof reading task (60214). The effect of zeaxanthin alone on eye strain is unclear.
• Asthma. It is unclear if oral zeaxanthin is beneficial for asthma prevention. Details: Population research has found that a higher dietary intake of zeaxanthin plus lutein is associated with up to 30% lower odds of having asthma when compared with a lower dietary intake (109765). The effects of zeaxanthin intake alone or zeaxanthin supplementation are unclear.
• Breast cancer. It is unclear if oral zeaxanthin is beneficial for breast cancer prevention. Details: Epidemiological research has found that higher serum levels of lutein plus zeaxanthin are associated with a reduced risk of developing breast cancer (10132). The effects of supplemental zeaxanthin are unclear.
• Bronchopulmonary dysplasia. Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that giving preterm and low birth weight infants a specific product (LUTEINofta, SOOFT Italia SpA) containing zeaxanthin 0.0006 mg and lutein 0.14 mg orally once daily, starting at birth and continuing until 36 weeks' corrected gestational age, does not decrease the incidence of bronchopulmonary dysplasia when compared with placebo (91163). The effect of zeaxanthin alone is unclear.
• Cardiovascular disease (CVD). Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in adults 50-85 years old shows that taking lutein 10 mg plus zeaxanthin 2 mg daily for an average of 4.8 years does not decrease the risk of CVD-related mortality or cardiovascular events such as stroke, myocardial infarction, or angina when compared with no supplementation (94701). Individual cardiovascular outcomes were not separately evaluated in this study. The effect of zeaxanthin alone on CVD prevention is unknown.
• Cataracts. Increased levels of zeaxanthin in the blood seems to reduce the odds of developing cataracts. It is unclear if dietary or supplemental zeaxanthin is beneficial for cataract treatment or prevention. Details: Some population research has found that higher blood levels of zeaxanthin are associated with a 30% lower odds of developing age-related cataracts, and more specifically, a 37% decreased risk of developing nuclear cataracts (90944,91161). Population research has also found that higher dietary combined intake of lutein plus zeaxanthin is associated with lower odds of developing cataracts. However, any association between intake of zeaxanthin itself and the development of cataracts is unclear (91162). Clinical research shows that taking zeaxanthin 2 mg and lutein 10 mg daily orally, in addition to the Age-Related Eye Disease Study (AREDS) formulation containing vitamin C 500 mg, vitamin E 400 IU, beta-carotene 15 mg, zinc 80 mg, and copper 2 mg, for an average of 4.7 years decreases the risk of needing cataract surgery by 32% when compared with the AREDS formulation alone in patients with low dietary intake of lutein and zeaxanthin, but not in those with higher dietary intake of lutein and zeaxanthin (94703).
• Child development. It is unclear if oral zeaxanthin is beneficial for child development. Details: Epidemiological research has found that a higher dietary intake of zeaxanthin in the first and second trimesters of pregnancy is associated with increased verbal intelligence and improved behavior in the child at 6-10 years of age. However, the ability to discriminate between a novel or familiar visual stimulus was reduced at about 6 months of age, and there were no effects on most cognitive outcomes in children aged 3-6 years (107106). Other epidemiological research has found that a higher dietary intake of zeaxanthin plus lutein in children aged 3-6 years may be associated with modestly improved executive function at 6-11 years. However, there were no effects on most cognitive outcomes in children aged 3-6 years or 6-11 years (109761).
• Cognitive function. Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in younger adults shows that taking zeaxanthin 2 mg and lutein 10 mg for one year modestly improves some measures of cognitive function, such as spatial memory, when compared with placebo (106348). Observational research has found that intake of choline and lutein plus zeaxanthin is positively associated with cognitive flexibility task performance speed. However, this association is not present with the intake of lutein plus zeaxanthin in the absence of choline (106354). The effect of zeaxanthin alone is unclear.
• Colorectal cancer. It is unclear if oral zeaxanthin is beneficial for colorectal cancer prevention. Details: Although some individual epidemiological research disagrees (3962), most research has found that dietary intake of lutein plus zeaxanthin is not associated with a reduced risk of developing colorectal cancer (34481,106372). However, any association with intake of zeaxanthin alone, as supplements or in the diet, is unclear.
• Diabetes. Observational research suggests that oral zeaxanthin may not be beneficial for the prevention of diabetes or diabetic complications. Details: Some epidemiological research has found that low serum levels of carotenoids, including zeaxanthin and lutein, are associated with impaired glucose tolerance (60161). Other population research has found that increased dietary intake of zeaxanthin plus lutein does not decrease the risk of developing type 2 diabetes (14004,97227). Other epidemiological research in patients with type 2 diabetes has found that an increased serum concentration of zeaxanthin is not associated with reduced cardiovascular mortality over 14 years (109768).
• Esophageal cancer. It is unclear if oral zeaxanthin is beneficial for esophageal cancer prevention. Details: Population research has found that people who consume higher combined amounts of zeaxanthin and lutein in the diet have a 29% lower risk of developing esophageal squamous cell cancer when compared with lower intake (91159). The effects of supplemental zeaxanthin are unclear.
• Fractures. It is unclear if oral zeaxanthin is beneficial for fracture prevention. Details: A meta-analysis of observational research has found that increased dietary intake of zeaxanthin and/or lutein is not associated with a reduced risk of hip fractures (97228). The effects of supplemental zeaxanthin are unclear.
• Gastric cancer. It is unclear if oral zeaxanthin is beneficial for gastric cancer prevention. Details: A meta-analysis of observational research has found that increased dietary intake of lutein and/or zeaxanthin is not associated with a reduced risk of developing gastric cancer (97231). The effects of supplemental zeaxanthin are unclear.
• Glaucoma. Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with open-angle glaucoma shows that taking oral zeaxanthin 2 mg, lutein 10 mg, and meso-zeaxanthin 10 mg daily for 18 months increases macular pigment density, but does not affect visual function, when compared with placebo (109756).
• Hyperlipidemia. Although there has been interest in using oral zeaxanthin for hyperlipidemia, there is insufficient reliable information about the clinical effects of zeaxanthin for this condition.
• Lung cancer. It is unclear if oral zeaxanthin is beneficial for lung cancer prevention. Details: Epidemiological research has found that low serum levels of carotenoids, including zeaxanthin, are associated with an increased risk of lung cancer (12874). However, other epidemiological research has found that higher serum levels of zeaxanthin are not associated with a reduced risk of dying from lung cancer (39690,60160).
• Macular telangiectasia type 2. It is unclear if oral zeaxanthin is beneficial for macular telangiectasia type 2. Details: In patients with macular telangiectasia type 2, observational research has found that taking a specific combination of lutein 10 mg, meso-zeaxanthin 10 mg, and zeaxanthin 2 mg (MacuShield; Alliance Pharmaceuticals) for at least 6 months, with an average duration of 15.7 months, was associated with a stabilization of visual acuity. Also, the number and size of cavitations in the macula were reduced (106355).
• Metabolic syndrome. Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Population research in females shows that the highest dietary intake of zeaxanthin plus lutein is associated with 54% reduced odds of developing metabolic syndrome when compared with the lowest intake. However, when supplements containing zeaxanthin plus lutein were included in the total intake, there was no association with metabolic syndrome (109760).
• Necrotizing enterocolitis (NEC). Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that giving preterm and low birth weight infants a specific product (LUTEINofta, SOOFT Italia SpA) containing zeaxanthin 0.0006 mg and lutein 0.14 mg orally once daily, starting at birth and continuing until 36 weeks' corrected gestational age, does not decrease the incidence of NEC when compared with placebo (91163).
• Non-Hodgkin lymphoma. It is unclear if oral zeaxanthin is beneficial for non-Hodgkin lymphoma prevention. Details: A meta-analysis of observational research has found that increased intake of zeaxanthin/lutein in the diet is associated with an 18% lower risk of developing non-Hodgkin lymphoma when compared with low dietary intake. However, no dose-response relationship was reported (97229). It is unknown if supplemental zeaxanthin has any effect on non-Hodgkin lymphoma risk.
• Pancreatic cancer. It is unclear if oral zeaxanthin is beneficial for pancreatic cancer prevention. Details: A meta-analysis of population research has found that increased dietary intake of zeaxanthin and/or lutein is not associated with a reduced risk of pancreatic cancer (97230). The effects of supplemental zeaxanthin are unclear.
• Parkinson disease. It is unclear if oral zeaxanthin is beneficial for Parkinson disease prevention. Details: Population research has found that people who consume higher amounts of zeaxanthin in the diet do not have a lower risk of developing Parkinson disease (91164). The effects of supplemental zeaxanthin are unclear.
• Pre-eclampsia. It is unclear if oral zeaxanthin is beneficial for the prevention of pre-eclampsia. Details: Some epidemiological research has found that the highest intake of lutein plus zeaxanthin during pregnancy is associated with 68% reduced odds of having pre-eclampsia when compared with the lowest intake (109762). The effects of zeaxanthin supplements are unclear.
• Prostate cancer. It is unclear if oral zeaxanthin is beneficial for prostate cancer prevention. Details: Epidemiological research has found that low serum levels of carotenoids, including zeaxanthin, are not associated with an increased risk of prostate cancer (12874). The effects of supplemental zeaxanthin are unclear.
• Respiratory tract infections. It is unclear if oral zeaxanthin is beneficial for the treatment or prevention of respiratory tract infections. Details: Epidemiological research has found that high serum levels of zeaxanthin are not associated with decreased incidence or severity of respiratory tract infections in the elderly (60152). The effects of supplemental zeaxanthin are unclear.
• Retinopathy of prematurity. Oral zeaxanthin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in preterm and low birth weight infants shows that giving a specific product (LUTEINofta, SOOFT Italia SpA) providing lutein 0.14 mg or 0.5 mg/kg plus zeaxanthin 0.0006 mg or 0.02 mg/kg orally once daily, starting at birth and continuing until 36-40 weeks' corrected gestational age, does not decrease the incidence or severity of retinopathy of prematurity when compared with placebo (60240,60243,91163,102889).
• Ulcerative colitis. It is unclear if oral zeaxanthin is beneficial for ulcerative colitis. Details: In patients in the remission phase of ulcerative colitis, observational research has found that a higher dietary intake of lutein plus zeaxanthin is associated with a reduced incidence of constipation, but not flatulence or feelings of urgency (tenesmus) (106362). The effects of supplemental zeaxanthin are unclear.
• Visual development. It is unclear if taking oral zeaxanthin during pregnancy can improve the visual acuity of the child. Details: Some observational research has found that the highest maternal plasma zeaxanthin levels at delivery are associated with a 38% lower risk of poor visual acuity in children at 3 years of age when compared with the lowest maternal zeaxanthin levels (102888). However, other epidemiological research has found that dietary intake of zeaxanthin plus lutein during the first or third trimesters of pregnancy is not associated with contrast vision or visual acuity in the child at 11-12 years of age (109759). The effects of zeaxanthin supplements are unclear. More evidence is needed to rate zeaxanthin for these uses.

(Read more about ZEAXANTHIN)

EFFECTIVE

• Zinc deficiency. Orally or intravenously, zinc is effective for treating and preventing zinc deficiency. Details: Taking zinc orally or intravenously prevents and treats zinc deficiency (2619). However, routine zinc supplementation is not recommended (403). Zinc deficiency requiring supplementation may occur in patients with severe diarrhea, malabsorption syndromes, liver cirrhosis, and alcoholism; after major surgery, renal failure, and dialysis; or during long-term administration of total parenteral nutrition (3900,24321). Zinc supplementation (136 mg of elemental zinc per day) in patients with cirrhosis and zinc deficiency seems to improve liver function and glucose tolerance, possibly by increasing insulin-like growth factor (8624,87520).

LIKELY EFFECTIVE

• Diarrhea. Oral zinc reduces duration and severity of acute diarrhea in malnourished children. Doses of 5-20 mg seem to be effective, while 5-10 mg daily is less likely to cause vomiting. Details: Most research, including meta-analyses and over 30 clinical trials, show that taking zinc orally reduces the duration and severity of acute and persistent diarrhea in malnourished or zinc-deficient children, but not in well-nourished children (87236,96074). Most studies have been conducted in Bangladesh and India, so it is unclear if these findings are generalizable to other geographic locations. The most comprehensive meta-analysis of clinical studies in children older than 6 months shows that zinc supplementation reduces the duration of acute diarrhea by about 11 hours and the duration of persistent diarrhea by about 16 hours when compared with placebo. However, zinc does not seem to reduce the duration of acute diarrhea in children younger than 6 months. Zinc supplementation seems to have the greatest benefit in children with clear malnutrition and diarrhea. In these children, zinc reduces diarrhea duration by about 26 hours and reduces the risk of diarrhea persisting through days 3, 5, and 7 by 18% to 24% when compared with placebo. There was no clear benefit of using zinc in a specific dose or salt form. The most common dose of zinc was 20 mg daily and salt forms included zinc sulfate, gluconate, and acetate (96074). Also, a large clinical trial in children with acute diarrhea shows that taking zinc 5 or 10 mg daily for 14 days is non-inferior to taking 20 mg. Furthermore, zinc 5 or 10 mg results in a respective 29% and 19% lower risk of vomiting within the first 30 minutes when compared with zinc 20 mg (104045). It's unclear whether zinc supplementation reduces mortality in children with diarrhea. A meta-analysis of clinical research in children under the age of five years shows that supplementation with zinc reduces the risk of mortality from diarrhea by 15% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation (106239). However, many studies were conducted in hospitals where rates of mortality are low and were not adequately powered to determine whether zinc has an effect on mortality in children with acute diarrhea (87210,96074,106239).
• Wilson disease. Taking zinc orally improves symptoms of this condition. Details: Zinc acetate (Galzin) is an FDA-approved orphan drug for treating this condition. Zinc blocks copper absorption and increases copper elimination in the stool of people with Wilson disease (2692,2693,87327). Small clinical studies suggest that taking zinc after 8 weeks of treatment with tetrathiomolybdate alone can improve Kayser-Fleischer rings, urine copper levels, and neurological symptoms for up to 6 years post-treatment (63588,87491).

POSSIBLY EFFECTIVE

• Acne. Orally, zinc might help to reduce symptoms of acne. However, it's unclear how oral zinc compares to conventional acne treatments. Topical zinc doesn't seem to be beneficial if used alone. Details: Observational research has found that people with acne seem to have lower zinc levels in the serum and skin (104056). A meta-analysis of small, low quality clinical trials suggests that taking zinc sulfate or zinc gluconate 137-300 mg 2-3 times daily by mouth can modestly improve acne when compared with placebo (104056). However, not all individual trials show benefit (87002,104056). So far, it is not clear how oral zinc compares to other treatments. Trials comparing zinc sulfate with various tetracyclines have yielded conflicting results (6505,6506,86946,106233). One large open-label clinical trial shows that taking zinc sulfate 200 mg twice daily for 12 weeks is at least as effective as lymecycline 300 mg daily for reducing acne severity. Quality of life related to acne was modestly improved in the patients using zinc sulfate (106233). However, in another clinical trial, a 3-month treatment of oral zinc gluconate 30 mg daily reduced the number of acne lesions from baseline, but was not as effective as minocycline (86946). When applied topically, clinical research shows that zinc does not help treat acne when compared with placebo (87297,104056). However, when used in combination with erythromycin, topical zinc seems to result in improvement (819,820,2687,2688).
• Acrodermatitis enteropathica. Oral zinc seems to improve symptoms of this rare genetic disorder. Details: Multiple case reports have found that taking oral zinc seems to help improve symptoms of acrodermatitis enteropathica, a rare disorder (821,2689,2690,2691). One case report in a female with necrolytic acral erythema and hepatitis C suggests that adding oral zinc sulfate 225 mg twice daily to interferon alfa-2b for 6 months contributed to resolving all lesions. Necrolytic acral erythema is categorized in the family of necrolytic erythemas that includes acrodermatitis enteropathica (6192).
• Age-related macular degeneration (AMD). Oral zinc, especially in combination with antioxidant vitamins, seems to slow the progression of AMD. Details: Clinical research shows that taking elemental zinc 80 mg plus vitamin C 500 mg, vitamin E 400 IU, and beta-carotene 15 mg daily reduces the odds of progression to advanced AMD by 28%. In patients with more severe AMD, this combination reduced the odds of progression to advanced AMD by 34%. This combination also reduced the odds of visual acuity loss by 27% in patients with severe AMD (7303,11326). However, there is contradictory evidence about the effects of zinc plus antioxidants on visual acuity loss or the progression to advanced AMD in low-risk patients with AMD (6583,6584,7303). Some clinical evidence shows that, when taken without antioxidant vitamins, zinc supplementation does not slow the progression of existing AMD (6580,90069). However, a subgroup analysis of results from a large clinical trial that included patients with intermediate or advanced AMD suggests that the effect of zinc on AMD progression might vary depending on a patient's genetic predisposition. Complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) are two genes for which specific variations (i.e., risk alleles) have been associated with an increased risk of AMD. Results from the retrospective subgroup analysis suggest that zinc supplementation may DECREASE the progression of AMD in patients with ARMS2 risk alleles and INCREASE the progression of AMD in patients with CFH risk alleles (90193). However, some experts question the results from this analysis due to the retrospective nature of the study (93045). Another retrospective analysis of similar data found that only zinc plus antioxidants, but not zinc alone, was beneficial for slowing the progression of AMD, regardless of the patient's genotype (93046). Consequently, the American Academy of Ophthalmology does not currently recommend routine genetic screening to determine which patients would benefit from zinc, antioxidants, or the combination. Instead, patients with intermediate or advanced AMD are recommended to take an antioxidant and zinc supplement similar to those used in the Age-Related Eye Disease Study (AREDS) and the Age-Related Eye Disease Study 2 (AREDS2) (93047). Large scale population studies suggest that increasing dietary intake of zinc might reduce the risk of developing AMD (6579,14257).
• Child growth. Oral zinc seems to increase growth when taken by children and improve infant growth in the first year of life when taken by pregnant adults. Details: A meta-analysis of 8 clinical studies in healthy children over 2 years old shows that taking supplemental zinc 5-15 mg daily for 6-56 weeks modestly increases height and weight when compared with placebo. This analysis also shows that taking zinc may improve height for age, but not weight for age when compared with placebo (112474). Most of these studies were conducted in developing countries; results may not apply elsewhere. Another clinical study in pregnant adults in Peru shows that taking zinc 15 mg daily in addition to iron and folic acid, starting during the first or second trimester and continuing up to one month after delivery, modestly improves growth measures of infants at one year when compared with taking iron and folic acid alone. Improved growth measures include body weight, calf and chest circumference, and calf muscle area (87130).
• Common cold. Oral zinc seems to help treat cold symptoms in adults. However, it is unclear if zinc is beneficial for common cold prevention. Details: Using zinc oral lozenges seems to be beneficial in helping TREAT the common cold in adults. The majority of clinical trials and analyses of clinical research show a significant decrease in the duration of symptoms of the common cold when adults take zinc gluconate or zinc acetate lozenges providing 9-24 mg of elemental zinc per dose. It is recommended that lozenges be taken every 2 hours while awake, starting within 48 hours of symptom onset for a total daily dose of at least 75 mg in order to attain a mean cold duration reduction of 3 days (333,334,335,337,6703,6705,87501,92212,106902). However, not all studies have been positive (333,338,339,6522,6700,87512). The reasons for these different findings are not clear, but might be due to differences in zinc formulations and doses and study methodologies. In some cases, flavoring agents such as citric acid, mannitol, and sorbitol might chelate zinc and decrease zinc ionization. Since ionization is thought to be necessary for zinc activity, a decrease in zinc ionization could decrease effectiveness (300,340,6522). Some of the positive studies have also been criticized for inadequately blinding the unpleasant, distinctive taste of zinc (6522,6706). Allergy and smoking status do not appear to impact the efficacy of zinc acetate lozenges (92212). Overall, zinc products may be beneficial for modestly reducing the duration of symptoms of the common cold in adults, but adverse effects such as bad taste and nausea may limit their usefulness (18216). There is conflicting evidence for the use of oral zinc products to PREVENT colds. Some clinical research suggests that taking zinc prophylactically does not prevent the common cold in adults (10780,10784) or children (341). However, other clinical research suggests that administering zinc gluconate lozenges can reduce the incidence of colds in children and adolescents (10803,86972). In a meta-analysis of 28 randomized controlled trials with a total of 5446 participants, oral zinc prevented 5 viral upper respiratory tract infections per 100 person months of zinc use when compared with placebo, with a number needed to treat (NNT) of 20 (106902). Intranasal zinc is not recommended for the prevention or treatment of the common cold due to the risk for anosmia. See the Adverse Effects section for more information. Some research shows that zinc nasal spray (as a sulfate, gluconate emulsion, or gluconium gel) reduces the severity and duration of cold symptoms; however, other research has found no effect (6471,8628,8629,10247,87035). Zinc nasal spray does not seem to prevent experimentally-induced colds (8628).
• Coronavirus disease 2019 (COVID-19). While oral zinc does not seem to speed recovery from COVID-19 in non-hospitalized patients, an analysis of a small number of studies suggests that oral or intravenous zinc might reduce the risk of death in hospitalized patients with COVID-19. Details: A small observational study in patients with COVID-19 has found that lower serum zinc levels are associated with worse clinical outcomes, such as admission to the intensive care unit (ICU) and death, when compared with higher zinc levels (105681). Another small observational study has found that 96% of patients with confirmed COVID-19 were zinc-deficient based on plasma levels of zinc, and that these patients had lower plasma zinc levels than a group of individuals without COVID-19. However, plasma zinc concentrations were only weakly correlated with length of hospital stay and there was no correlation with morbidity or mortality (106236). One clinical study in adult outpatients with COVID-19 shows that taking zinc gluconate 50 mg daily at bedtime, alone or with vitamin C (ascorbic acid) 8000 mg daily, for 10 days does not reduce symptom severity when compared with standard care (104450). This study was terminated prior to complete enrollment due to a lack of effect with zinc and/or vitamin C supplementation. Limitations of this study include a lack of placebo control and blinding. Zinc supplementation also does not appear to enhance the clinical efficacy of hydroxychloroquine in patients with confirmed COVID-19 infection. Taking zinc sulfate 220 mg twice daily during a 6-day course of hydroxychloroquine does not improve the clinical recovery rate, reduce the mortality rate, or reduce the need for mechanical ventilation when compared with hydroxychloroquine alone (104818). Other research has evaluated zinc in hospitalized patients. Multiple meta-analyses of small and low-quality clinical studies, including randomized controlled trials and retrospective studies, involving hospitalized patients with COVID-19 shows that supplementation with oral or intravenous zinc is associated with a 29% to 43% reduction in the odds of in-hospital mortality when compared with control (109451,110631). However, in one meta-analysis, the odds of 30-day mortality were not different between groups (110631). These meta-analyses did not elevate the most effective form, dose, frequency, or duration of zinc supplementation (109451,110631). Additionally, a retrospective study in adults admitted to the ICU with COVID-19 has found that those who received oral zinc sulfate, 220 mg daily for a median of 11 days, had a lower 30-day mortality rate when compared with those who did not receive zinc. However, there was no difference in hospital length of stay or in-hospital mortality (106903).
• Depression. Oral zinc seems to be beneficial when used in combination with antidepressant treatments. Details: Population research has found that higher zinc levels and higher dietary intake of zinc are associated with a 28% lower incidence of depression (90227,97139,104057). Oral zinc seems to be beneficial as an adjunct therapy in depression. A meta-analysis of small, low-quality studies in patients with major depression shows that taking zinc in addition to antidepressant therapy is associated with modestly improved depression symptoms when compared with antidepressant therapy alone (104044). Clinical studies used zinc doses of 7-25 mg daily for up to 12 weeks (86985,90221,104044). One small clinical study also shows that adding zinc to imipramine therapy might improve depression that was previously resistant to antidepressant treatment (87158). One clinical guideline also provisionally recommends use of zinc 25 mg elemental orally daily to treat patients with depression based on low-quality evidence. This guideline recommends use of chelated or picolinate zinc products over other forms of zinc (110318).
• Diabetes. Oral zinc might modestly improve glycemic control in some patients. Details: A meta-analysis of 12 clinical studies in patients with diabetes shows that taking zinc supplements reduces fasting blood glucose by up to 20 mg/dL and glycated hemoglobin (HbA1c) by 0.35% when compared with control. However, when only high quality studies were included, the reduction in fasting blood glucose dropped to 12 mg/dL. Zinc seems to only have glycemic benefit in patients living in the Eastern hemisphere, and not the Western hemisphere. Also, glucose reduction seems to be higher with inorganic zinc formulations at doses of at least 30 mg daily taken for at least one month (104080). Zinc has also been evaluated for improving lipid parameters in patients with diabetes. A meta-analysis of nine studies in patients with diabetes shows that taking zinc reduces triglycerides by 17 mg/dL, but does not seem to affect low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol levels, when compared with placebo (104041). The findings from these meta-analyses are limited by the high heterogeneity and small size of the included studies. Zinc has also been studied for gestational diabetes. Some clinical research in patients with gestational diabetes shows that taking zinc gluconate for 6 weeks, starting at 24-28 weeks' gestation, reduces fasting plasma glucose levels by about 10% and improves insulin resistance by 14% when compared to baseline (96072). However, taking zinc gluconate does not reduce the need for caesarean section or insulin therapy, or improve infant outcomes, such as size or health at birth, in these patients (96073).
• Diaper rash. Topical and oral zinc seem to reduce the incidence and severity of diaper rash in infants. Details: Clinical research shows that administering oral zinc gluconate 10 mg daily for 4 months can reduce the incidence of diaper rash in infants when compared with placebo (87281). Other clinical research shows that applying 47% zinc oxide paste to affected areas for 5 days can improve the healing of diaper rash. However, the effect of zinc oxide paste is inferior to eosin 2% solution (86918).
• Gingivitis. Topical zinc seems to reduce the development of gingivitis. Details: While some clinical research shows that zinc, in combination with triclosan, does not prevent plaque and gingivitis (24093,87020), most clinical research shows that using zinc toothpaste or mouthwash, alone or in combination with triclosan, can prevent plaque accumulation, gingivitis, or the formation of calculus (6523,6524,6525,6526,6527,6528,6529,87418,87507). However, most studies used zinc citrate in combination with triclosan, which is not available in the US (6523). For treating existing plaque, calculus, and gingivitis, some clinical research suggests that using zinc citrate 0.5% toothpaste three times daily for 3 months reduces calculus scores by 14% when compared with placebo (87205). However, other evidence suggests that stannous fluoride 0.454% toothpaste is more effective than zinc citrate 0.75% toothpaste for reducing plaque levels (87136).
• Halitosis. Oral zinc seems to reduce halitosis when taken as a gum, mouth rinse, or candy. Details: Clinical research shows that chewing zinc-containing gum reduces volatile sulfur compounds and related odor levels when compared with placebo gum in patients with moderate to severe halitosis (87538). Clinical research also shows that using one of two mouth rinses (Halita, which contains 0.05% chlorhexidine and 0.14% zinc lactate, or Meridol, which contains 0.025% fluoride plus 0.2% zinc lactate) improves breath odor and volatile sulfur compounds by approximately two-fold when compared with mouth rinse containing only 0.05% fluoride or chlorhexidine 0.12% (90206). Additional clinical research shows that sucking a candy containing abrasive substances and zinc gluconate 0.5% or candy containing abrasive substances plus zinc 0.25% and propolis 1% improves breath malodor two- to three-fold when compared with sucking placebo candy (90196).
• Herpes labialis (cold sores). Topical zinc seems to reduce the severity and duration of cold sores. Details: Applying zinc topically seems to help treat herpes simplex infection (6538,6539,8623,11051). Zinc sulfate seems to reduce the severity and duration of symptoms in both orolabial and genital herpes (6538,6539). Zinc oxide (0.3%) in combination with glycine cream applied topically every 2 hours to facial and circumoral herpes seems to reduce symptoms such as blistering, soreness, itching, and tingling. It can also reduce the duration of lesions from 6.5 days to 5 days when treatment is begun within 24 hours of onset of symptoms (8623). A specific combination product containing zinc oxide and L-lysine plus 14 other ingredients (Super Lysine Plus +) also seems to help decrease symptoms and duration of herpes lesions when applied topically every 2 hours (11051). However, zinc may not be effective for recurrent herpes simplex infections. In one clinical study, applying zinc sulfate 0.0025% or 0.05% solution to affected areas did not reduce the frequency, severity, or duration of herpes episodes when compared with a placebo solution in patients experiencing more than five episodes per year (87330).
• Hypogeusia. Oral zinc might improve taste disturbance and taste acuity in people with hypogeusia of various etiologies. Details: A meta-analysis of low-quality studies in patients with taste disorders that are idiopathic or due to zinc deficiency shows that taking oral zinc modestly improves taste acuity when compared with placebo (104055). Studies tested zinc gluconate, zinc sulfate, zinc acetate, and zinc-carnosine as Polaprezinc (Promac, Zeria Pharmaceutical Co., Ltd.), containing 17-68 mg elemental zinc, daily for up to 12 weeks (104055). Zinc also might improve hypogeusia conditions unrelated to zinc deficiency, such as gustin/carbonic anhydrase VI deficiency, captopril-induced taste disturbances, hypogeusia due to chronic renal failure, and post-traumatic olfactory disorder (6543,6544,104055). It also seems be beneficial in radiation-induced dysgeusia. A meta-analysis of three small clinical trials shows that oral zinc reduces the risk of radiation-induced dysgeusia by 28%, but does not improve taste acuity when compared with placebo (104043). However, patients with hypogeusia from other causes may not benefit. Zinc supplementation does not seem to improve taste perception when compared with placebo in patients with acetazolamide-induced taste dysfunction or chemotherapy-induced taste dysfunction (87388,90214).
• Leishmania lesions. Oral zinc and intralesional injections of zinc might improve healing of these lesions. Details: Clinical research shows that taking zinc sulfate 2.5-10 mg/kg orally in three divided doses daily, improves the cure rate of cutaneous leishmania lesions after 45 days when compared with no treatment (86935). Other clinical research shows that intralesional injections of zinc sulfate 2% solution for 6 weeks improves cure rates of cutaneous leishmania lesions when compared with no treatment (6587). However, intralesional injections with zinc sulfate solution does not appear to be more effective than intralesional injections of meglumine antimoniate (Glucantime), hypertonic saline, or sodium stibogluconate (6587,86996,87008).
• Leprosy. Oral zinc seems to be beneficial when used in combination with anti-leprosy drugs. Details: Zinc levels appear to be reduced in people with leprosy. Early clinical research suggests that the addition of zinc improves tolerance of the anti-leprosy drug regimen and might allow for lowering or eliminating steroid doses in erythema nodosum leprosum, a severe form of leprosy (6534,6535,6536,6537).
• Low birth weight. Oral zinc supplementation seems to improve growth in low birth weight infants. Whether oral zinc can improve other outcomes, including mortality, is unclear. Taking oral zinc during pregnancy does not seem to reduce the risk of having a low birth weight infant. Details: While there is some mixed evidence regarding the effects of zinc supplementation on weight gain and length in infants born with low birth weight (87172,87452,90229), a meta-analysis of 14 clinical trials in preterm or low birth weight infants receiving breastmilk shows that zinc supplementation, typically 5-7 mg daily started at birth and continued for up to 12 months with or without other micronutrients, increases weight by around 380 grams, length by around 3 cm, and head circumference by around 0.6 cm when compared with control (109455). There is also mixed evidence regarding the effect of zinc supplementation on other outcomes in low birth weight infants. A large clinical trial in full-term, underweight infants aged 1-6 months in developing countries shows that adding zinc to nutritional supplementation reduces the risk of mortality by about 68% when compared with nutritional supplementation not containing zinc (8920). A small clinical trial in very low birth weight preterm infants born in an industrialized country shows that adding zinc to multivitamin supplementation appears to reduce the occurrence of necrotizing enterocolitis and mortality. However, adding zinc does not appear to prevent late-onset sepsis, bronchopulmonary dysplasia, or retinopathy of prematurity (90229). A meta-analysis of these trials and two other studies in low birth weight infants shows that supplementation with zinc reduces the risk of all-cause mortality by 52% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation (106239). Another small clinical study in low birth weight and preterm infants born in a developing country shows that zinc supplementation seems to improve alertness and attention when compared with placebo (97140). However, a meta-analysis of 14 clinical trials in preterm or low birth weight infants receiving breastmilk shows that zinc supplementation, typically 5-7 mg daily started at birth and continued for up to 12 months with or without other micronutrients, does not improve mental or psychomotor development or reduce the risk of mortality, hospitalization, acute respiratory infection, or sepsis when compared with control (109455). Some of these discrepant findings may be due to differences in patient populations (hospitalized, non-hospitalized), milk sources (breastfed, formula-fed, or both), and duration of follow-up. The effect of zinc intake or supplementation during pregnancy has also been evaluated. Population research has found that low dietary intake of zinc during pregnancy is associated with low birth weight in infants; similarly, zinc supplementation is associated with increased infant weight at birth (87471,105678). However, a meta-analysis and a large clinical study show that zinc supplementation during pregnancy does not reduce the risk of having a low birth weight infant (97142,105679). Reasons for the discrepancies may be due to differing zinc status prior to supplementation. Also, numerous factors contribute to the risk of low birth weight, which may confound research on the use of zinc supplementation alone.
• Peptic ulcers. Oral zinc seems to treat and prevent peptic ulcers. Details: Taking zinc orally seems to help treat and prevent peptic ulcers (6588,6589,6591). Some clinical research shows that zinc acexamate improves peptic ulcers when compared with placebo (6589,87285), and seems to be as effective as H2-receptor antagonist drugs (6589,87533). It is not known if other zinc salts are effective.
• Pneumonia. Oral zinc might reduce the risk for pneumonia in children, but it doesn't seem to improve symptoms in children that already have pneumonia. Details: A meta-analysis of four clinical studies shows that giving zinc supplements to children, ages 3 months to 5 years living in developing countries, some of whom were undernourished, reduces the risk of pneumonia incidence by 21% when compared with placebo (104047). Another meta-analysis of clinical research in children under the age of five years shows that supplementation with zinc reduces the risk of pneumonia mortality by 21% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation (106239). The research on TREATING existing pneumonia in children is inconsistent. Most meta-analyses and clinical studies in children ages 2 months to 5 years with severe pneumonia show that taking elemental zinc in addition to antibiotic therapy does not improve symptom resolution or the time to recovery when compared with antibiotic therapy alone. Zinc also does not seem to reduce mortality in these patients (87248,90197,96080,98131,104042). However, two clinical studies in children in the same age group with pneumonia suggest that adding zinc to standard antibiotic therapy improves symptom resolution and decreases hospital stay when compared with placebo (11052,87242). Reasons for these discrepancies are not clear, but may be related to zinc status prior to treatment.
• Prematurity. Analyses of clinical studies suggest that oral zinc improves growth in premature infants. Whether zinc improves development or reduces the risk of mortality in these patients is unclear. Details: A meta-analysis of small clinical trials in hospitalized infants born prematurely suggests that receiving enteral zinc supplementation at a dose of up to 10 mg daily reduces mortality and might improve short-term weight gain when compared with placebo (105687). Another meta-analysis of small clinical studies in preterm infants shows that adding zinc to formula or to a multivitamin seems to modestly increase infant weight and height and improve motor development when compared with control (105676). A larger meta-analysis of 14 clinical trials in preterm or low birth weight infants receiving breastmilk shows that zinc supplementation, typically 5-7 mg daily started at birth and continued for up to 12 months with or without other micronutrients, increases weight by around 380 grams, length by around 3 cm, and head circumference by around 0.6 cm when compared with control. However, zinc supplementation did not improve mental or psychomotor development or reduce the risk of mortality, hospitalization, acute respiratory infection, or sepsis when compared with control (109455). These analyses are limited by imprecision as well as a high risk of bias in some of the included studies. Some of the discrepant findings may be due to differences in patient populations (hospitalized, non-hospitalized), milk sources (breastfed, formula-fed, or both), and duration of follow-up.
• Pressure ulcers. Topical zinc paste seems to work as a skin barrier and improve pressure ulcer healing. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that applying zinc oxide paste to pressure ulcers daily for 8 weeks reduces necrotic tissue and decreases the surface area of skin pressure ulcers similarly to using a topical streptokinase-streptodornase product (Varidase) (87331). Other small clinical studies show that applying zinc oxide paste to pressure ulcers daily for 8-12 weeks improves healing similarly to a hydrocolloid dressing (Duoderm) (87181) or a specific barrier film product (Cavilon No Sting Barrier Film) (87017). Oral zinc has been evaluated in combination with other ingredients for the treatment of grade II-IV pressure ulcers. Two small clinical studies in hospitalized patients shows that administering an oral nutritional supplement enriched with zinc, L-arginine, and vitamin C 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, zinc, L-arginine, and vitamin C 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.
• Sickle cell disease. Oral zinc seems to improve symptoms of sickle cell disease in patients with zinc deficiency. Details: Taking zinc orally seems to help reduce symptoms of sickle cell disease in people with zinc deficiency (6594,6595,6596,8626,87343). Taking zinc supplements also seems to decrease the occurrence rate of sickle-cell crises and infections (6594,6596,90228). Additionally, zinc might reduce the number of hospitalizations for sickle cell crises, although the severity of the crises that do develop is not necessarily decreased by taking zinc supplements (6594,6596). In prepubertal children and adolescents with homozygous sickle cell disease, taking zinc seems to improve growth, height, and weight gain (8626,87403).
• Warts. Oral and topical zinc seem to improve the cure rate of cutaneous warts. Details: A small clinical study suggests that applying zinc sulfate 10% solution three times daily for 4 weeks improves plane warts, but not common warts, when compared with distilled water (87094). Another small clinical study suggests that applying topical zinc oxide 20% ointment twice daily for up to 3 months seems to have a similar cure rate as ointment containing salicylic acid 15% with lactic acid 15% (87082). Taking zinc orally may also be effective in treating warts (87227). A meta-analysis of low quality clinical studies shows that taking zinc sulfate orally improves the odds of curing cutaneous warts nearly 17-fold when compared with respective controls (87227). Preliminary clinical research in adults treated with cryotherapy for anogenital warts shows that taking zinc gluconate 30 mg orally three times daily for 2 months does not reduce the number of warts when compared with placebo (111445).

POSSIBLY INEFFECTIVE

• Alopecia areata. Oral zinc does not seem to improve symptoms of this condition. Details: Although there is preliminary evidence that suggests zinc in combination with biotin might be helpful for alopecia areata (6932), most studies indicate that zinc is not effective for alopecia areata, alopecia totalis, or alopecia universalis (6931,6932).
• Cystic fibrosis. Oral zinc does not improve cystic fibrosis symptoms or progression. Details: Clinical research shows that taking supplements providing 30-90 mg of elemental zinc for 6 weeks to one year does not improve lung function when compared with placebo in children and adolescents with cystic fibrosis (87066,87113,96079). One clinical study also shows that taking elemental zinc for one year does not reduce the number of days requiring oral or intravenous antibiotics for pulmonary infections (96079). However, one study shows that taking zinc can reduce the number of days of oral antibiotic use when compared with placebo (87113).
• HIV/AIDS. Oral zinc does not seem to improve outcomes in patients with HIV. Details: Clinical research in adult HIV patients with normal or low zinc levels shows that taking elemental zinc 12-15 mg daily orally for 18 months along with antiretroviral therapy does not improve viral load, CD4/8 counts, or mortality when compared with placebo (87036,87216,105686). In children with HIV-1, clinical research shows that administering zinc sulfate, providing 10 mg elemental zinc, daily for 6 months does not improve mortality, viral load, or CD4 counts when compared with placebo (82377).
• HIV/AIDS-related pregnancy complications. Oral zinc does not prevent pregnancy complications related to HIV infection. Details: Adding zinc 25 mg orally during pregnancy does not seem to reduce parent-to-child vertical transmission of HIV, infant mortality, birth weight, or gestational period in HIV-infected females with low zinc levels (11054,87034). Also, one clinical study in HIV-1-infected pregnant patients suggests that supplemental zinc can increase the risk of wasting, as assessed by weight and mid-upper arm circumference, by 170% when compared with placebo (87034).
• HIV/AIDS-related wasting. Oral zinc does not seem to improve HIV-related wasting syndrome. Details: A clinical study in patients with HIV-related wasting syndrome shows that taking zinc orally in combination with vitamins and albendazole does not seem to improve diarrhea or mortality when compared with taking albendazole alone (6564).
• Infant development. Oral zinc does not seem to improve infant mental and psychomotor development. Details: Clinical research, including a meta-analysis of eight studies, shows that giving zinc to infants or children at high risk for zinc deficiency does not improve mental and psychomotor development when compared with placebo (87013,90209). In another meta-analysis of studies in children whose baseline zinc status was not specified, there was no beneficial effect of zinc supplementation on mental or psychomotor development at 6 or 12 months of age (104817).
• Inflammatory bowel disease (IBD). Oral zinc does not improve symptoms of IBD. Details: Some clinical research shows that taking zinc orally does not seem to help treat IBD (6913,6915,6916).
• Influenza. Oral zinc does not seem to reduce the risk for influenza. Details: Supplemental zinc seems to improve cell-mediated immune response in elderly people (824), but it does not seem to have a significant effect on antibody response and incidence of influenza infection after the vaccine (6553,6563). Additionally, zinc supplementation in patients on hemodialysis, who have a high risk of zinc deficiency, does not seem to improve response to influenza vaccine (10809). Taking zinc supplements orally is unlikely to improve immune function in people without risk factors for zinc deficiency (10789). However, there is preliminary evidence that suggests zinc along with selenium might reduce the incidence of infections in institutionalized older patients (8921).
• Otitis media. Oral zinc does not prevent otitis media in children. Details: A meta-analysis of clinical research shows that taking elemental zinc 3-70 mg daily for up to 24 months does not prevent the occurrence of ear infections in children from low- or middle-income countries (87258).
• Pre-eclampsia. Oral zinc taken prenatally does not seem to be beneficial for pre-eclampsia prevention. Details: A meta-analysis and a large clinical study show that zinc supplementation during pregnancy does not reduce the risk of pre-eclampsia when compared with placebo (97142,105679).
• Prostate cancer. Oral zinc does not reduce the risk for prostate cancer or prostate cancer-related mortality. Details: Some epidemiological research has found an inverse relationship between dietary zinc intake and prostate cancer (96075). Also some clinical research shows that taking zinc 20 mg in combination with vitamin C 120 mg, vitamin E (alpha-tocopherol) 30 mg, beta-carotene 6 mg, and selenium 100 mcg daily for an average of 8 years might reduce the risk of prostate cancer in men with normal PSA levels; however, it does not seem to be beneficial for reducing the risk of prostate cancer in patients with PSA levels above 3 mcg/L (14135). However, some evidence raises concern that zinc might actually INCREASE the risk of prostate cancer. A large-scale population study found that taking more than 100 mg of supplemental zinc daily or taking supplemental zinc for 10 or more years doubles the risk of developing prostate cancer (10306). Another large-scale population study shows that men who take a multivitamin more than seven times per week and who also take a separate zinc supplement have a significantly increased risk of prostate cancer-related mortality (15607). Despite these studies suggesting the potential for adverse effects of zinc, a meta-analysis of mainly population research has found that there is no association between zinc intake and the risk of prostate cancer (96075).
• Psoriasis. Oral zinc does not reduce the severity of psoriasis symptoms. Details: Zinc epidermal levels are reportedly lower in people with psoriasis (6509). However, taking zinc orally does not seem to help treat psoriasis (6513,6514,6912,87363). Zinc supplementation has no effect on the psoriasis area and severity index (6513,6514).
• Rheumatoid arthritis (RA). Oral zinc does not treat symptoms of RA. Details: Multiple clinical studies in patients with RA show that taking zinc orally does not improve function or symptoms when compared with baseline or control (6517,6518,6519,87406).
• Sexual dysfunction. Oral zinc does not improve sexual function in males with chronic kidney disease (CKD). Details: Clinical research shows that zinc supplementation does not improve sexual activity or libido when compared with placebo in males with sexual dysfunction secondary to CKD (6708,6568,87220,87386,87416). In fact, one clinical study shows that taking zinc can decrease the frequency of intercourse by 76% when compared with placebo in patients with CKD-related sexual dysfunction (87220).
• Tinnitus. Oral zinc does not improve severity of tinnitus or reduce tinnitus-related disability. Details: A meta-analysis of three small clinical trials in adults with tinnitus shows that taking elemental zinc 50 mg daily for up to 16 weeks does not improve tinnitus severity, or disability from tinnitus when compared with placebo (104051).

LIKELY INEFFECTIVE

• Malaria. Oral zinc does not prevent or treat malaria in undernourished children or pregnant adults in developing countries. Details: A meta-analysis of clinical research in children or pregnant adults shows that taking zinc orally, alone or in combination with other supplements, for does not reduce the risk of malaria parasitemia (111444). A large multi-country study in zinc-deficient preschool children with acute malaria shows that taking zinc supplements does not affect fever, parasitemia, or hemoglobin when compared with placebo (10246). An even larger clinical study of over 40,000 children with malaria aged 1-36 months shows that taking zinc 5-10 mg daily orally for approximately 17 months does not reduce mortality when compared with placebo (87078). Zinc supplements also do not appear to protect against infection by Plasmodium falciparum (8638,87235,86937). However, one small study in children with low and high levels of parasitemia shows that taking zinc 10 mg daily for 46 weeks may lower the incidence of fever episodes by 38% and 69%, respectively, when compared with placebo (86937).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral zinc is beneficial in patients with age-related cognitive decline. Details: An epidemiological study based on elderly adults enrolled in the National Health and Nutrition Examination Survey (NHANES) has found that taking zinc may improve cognition in a non-linear manner. Daily doses below 9 mg and 8 mg in males and females, respectively, showed a positive association with cognitive function, but doses above that level showed no association. Additionally, high intake of both zinc and selenium was associated with improved cognition in females, but not in males (108446). Dietary intake was collected from two patient-reported 24-hour recalls and cognition was only measured once, limiting the validity of these findings.
• Alcohol-related liver disease. It is unclear if oral zinc is beneficial in patients with alcoholic-related liver cirrhosis. Details: A small clinical study in patients with alcoholic liver cirrhosis shows that taking zinc sulfate 600 mg daily for 6 weeks improves liver function, based on increased alkaline phosphatase activity and reduced serum bilirubin, when compared to baseline (87325).
• Anorexia nervosa. Oral zinc seems to improve weight gain in people with anorexia nervosa. Details: Anorexia nervosa might be linked with zinc deficiency. Small clinical trials in adolescents and adults with anorexia nervosa show that oral zinc supplements might help increase weight gain and improve depressive symptoms when compared with placebo (6905,6906).
• Arsenic poisoning. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that taking zinc 4 mg in combination with spirulina extract 500 mg daily for 16 weeks can decrease skin manifestations and reduce arsenic levels in the urine and in hair of patients with chronic arsenic poisoning (18301).
• Asthenopia (eye strain). Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in adults without dry eye disease shows that taking a specific combination product containing zinc 10 mg, L-carnitine 50 mg, elderberry fruit extract 300 mg, currant 100 mg, and Eleutherococcus root 50 mg (Meramirt CM) orally once daily for 1 month improves measures of eye strain and contrast sensitivity when compared to baseline. Improvements in these measures were lacking in the control group (111295). Statistical comparison between the two groups was not reported. It is unclear if these effects are due to zinc, other ingredients, or the combination.
• Athletic performance. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in sleep-deprived recreational athletes shows that taking a combination of zinc 90 mg, magnesium 1350 mg, and vitamin B6 31.5 mg orally for 3 nights at bedtime does not improve grip strength, squat, or bench press performance when compared with placebo (113655).
• Atopic dermatitis (eczema). It is unclear if oral zinc is beneficial for alleviating eczema in children. Details: A small clinical study in children with eczema shows that taking zinc sulfate 185.4 mg orally daily for 8 weeks does not appear to improve the surface area affected and degree of erythema, symptom scores of itch and sleep disturbance, or topical steroid use when compared with placebo. Also, plasma zinc levels appear to be normal in children with eczema (6911).
• Attention deficit-hyperactivity disorder (ADHD). Oral zinc might improve certain symptoms in children with ADHD. Details: Observational research has found that lower serum zinc levels are both more prevalent in children with ADHD and are linked to worsened response to stimulant therapy (9965,9966,9967). Based on this evidence, there is some interest in using zinc to improve symptoms in children with ADHD. A meta-analysis of six small clinical trials shows that although taking zinc modestly improves overall symptoms of ADHD when compared with placebo, there is no effect on hyperactivity or inattention when these outcomes are examined separately. The sub-analyses conducted for these two separate outcomes included only 3 studies. Most, but not all, of the included studies were conducted in children also receiving methylphenidate treatment (106240). Elemental zinc, usually as sulfate, was typically used in doses of 10-40 mg daily for 6-12 weeks (11350,12060,106240). There is some evidence that zinc could be most helpful in children with a high body mass index (BMI), low zinc levels, and low free fatty acid levels (11350). It is unclear if zinc is beneficial in children who are not already taking stimulant medications. One clinical guideline also provisionally recommends against use of oral zinc to treat patient with ADHD based on low-quality evidence (110318).
• Autism spectrum disorder. It is unclear if oral zinc is beneficial in children with autism spectrum disorder. Details: One small clinical study conducted in children with autism spectrum disorder shows that taking zinc 15-30 mg orally, alone or as add-on therapy to amphetamine, does not improve attention deficit hyperactivity disorder (ADHD) symptoms when compared with placebo (98711). However, the optimal mg/kg dose of amphetamine was shown to be 37% lower for those children also taking zinc 15 mg twice daily when compared with those taking placebo (98711).
• Autoimmune thyroiditis. It is unclear if oral zinc is beneficial in children with autoimmune thyroiditis. Details: A small clinical study in children aged 3-18 years with autoimmune thyroiditis shows that taking zinc acetate 25 mg daily in addition to standard therapy for 12 weeks does not change thyroid auto-antibody levels, thyroid function tests, or oxidative stress markers when compared with standard therapy alone. However, subjects taking zinc did not require escalation in levothyroxine doses when compared with the control group control group, which did require levothyroxine dose escalation (113661).
• Behcet disease. It is unclear if oral zinc is beneficial in patients with Behcet disease. Details: A small clinical trial in patients with Behcet disease shows that taking zinc gluconate 30 mg daily for 12 weeks does not improve disease activity scores, quality of life, or measures of inflammation when compared with placebo (109453).
• Benign prostatic hyperplasia (BPH). Although there is interest in using oral zinc for BPH, there is insufficient reliable information about the clinical effects of zinc for this condition.
• Beta-thalassemia. It is unclear if oral zinc is beneficial in patients with beta-thalassemia major. Details: A small clinical study in children recently diagnosed with beta-thalassemia major shows that initiating zinc sulfate in addition to standard blood transfusions increases linear growth rate when compared with transfusions alone (87329). Another small clinical study in adult and pediatric patients with thalassemia major and low bone mass shows that taking zinc 25 mg daily (as zinc sulfate) for 18 months improves whole-body bone mineral content, as well as hip and spine bone mineral density, by small amounts when compared with placebo (90208).
• Brain tumor. It is unclear if dietary zinc is beneficial for reducing the risk for brain cancer. Details: Population research has found that zinc intake is not associated with a reduced risk of developing brain cancer (87098).
• Breast cancer. It is unclear if increased dietary zinc intake is beneficial for reducing the risk for breast cancer. Details: Population research has found that neither zinc intake nor blood levels of zinc are associated with a reduced risk of breast cancer (106229).
• Bronchiolitis. It is unclear if oral zinc is beneficial for viral bronchiolitis in infants and children. Details: A small clinical study in children 2 years or younger with acute viral bronchiolitis shows that taking elemental zinc 10-20 mg as zinc sulfate for 5 days improves clinical recovery and reduces the duration of hospital stay by almost one day when compared with placebo. After 72 hours, 98% of infants and children taking zinc were considered fully recovered, compared to only 52% of infants taking placebo (96076).
• Burning mouth syndrome. Topical zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with burning mouth syndrome shows that taking zinc 15 mg and vitamin C 35 mg once daily, along with a vitamin B complex twice daily, for 30 days modestly decreases pain and burning when compared to baseline (105195). The validity of this finding is limited by the lack of a comparator group. Furthermore, it is unclear if the benefit is due to zinc, other vitamins, or the combination.
• Burns. Intravenous zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. The effects of oral zinc for burn healing are unclear. Details: Administering zinc intravenously in combination with other minerals seems to improve the outcomes of burn patients. Supplementation with zinc, copper, and selenium appears to improve wound healing, reduce pulmonary infections, and shorten intensive care unit stay in patients with serious burns (6520,87085). The effect of supplementation with zinc alone is unclear.
• Canker sores. It is unclear if oral zinc is beneficial in patients with canker sores. Details: Evidence for the use of zinc in canker sores is conflicting. A small clinical crossover study in patients with recurrent canker sores shows that taking zinc sulfate 660 mg daily for 3 months does not improve the size or frequency of canker sore ulcers when compared with control (6592). However, another clinical study in patients with recurrent sores and low or normal zinc levels shows that taking zinc sulfate 220 mg daily for 1 month reduces recurrence of sores when compared with placebo (86964). Reasons for conflicting results are unclear. Zinc might be beneficial when used in a muco-adhesive formulation. A small clinical study in patients with canker sores shows that taking a muco-adhesive zinc sulfate 5 mg tablet three times daily for 7 days reduces pain and speeds up healing when compared with placebo (104048).
• Cataracts. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking zinc orally in combination with antioxidant vitamins does not seem to help treat or prevent cataracts. Taking elemental zinc 80 mg plus vitamin C 500 mg, vitamin E 400 IU, and beta-carotene 15 mg daily does not seem to have any effect on the development or progression of age-related lens opacities (cataracts) or the need for cataract surgery in well-nourished people 55-80 years of age. However, it is unknown whether earlier intervention and/or a longer period of treatment with supplements would have any effect on cataracts (7304).
• Chemotherapy-induced acral erythema. It is unclear if oral zinc reduces the severity of acral erythema induced in patients treated with the vascular endothelial growth factor receptor-tyrosine kinase inhibitors (VEGFR-TKIs) treatment regorafenib. Details: A small study in patients with metastatic colorectal cancer undergoing treatment with regorafenib shows that taking zinc gluconate 78 mg twice daily reduces the proportion of patients with more severe acral erythema when compared with control. Though there is no association in the zinc treatment group, lower serum zinc levels seem to correlate with more severe acral erythema in the control group, suggesting a possible role of zinc deficiency in the pathogenesis of acral erythema (112472). The validity of this study is limited by the lack of blinding.
• Chemotherapy-related fatigue. It is unclear if oral zinc improves symptoms in patients with fatigue due to chemotherapy. Details: A small clinical study in patients undergoing 4 or more cycles of chemotherapy for colorectal cancer shows that taking zinc 70 mg daily for 16 weeks does not improve fatigue or quality of life when compared with placebo (97141).
• Chronic fatigue syndrome (CFS). Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in females with CFS shows that taking zinc 10 mg as zinc sulfate plus melatonin 1 mg daily for 16 weeks modestly reduces self-reported symptoms of physical fatigue when compared with placebo. However, there was no effect on cognitive or psychological symptoms, sleep, or symptoms of anxiety or depression (106241). This study may not have been adequately powered to detect differences between groups.
• Cirrhosis. It is unclear if zinc is beneficial for reducing cirrhosis-related mortality. Details: A meta-analysis of four small clinical trials shows that zinc supplementation does not seem to reduce mortality in patients with cirrhosis when compared with control (104054). This finding is limited due to the heterogeneity and small size of the available studies.
• Cognitive function. It is unclear if zinc is beneficial for cognitive function. Details: A very small clinical study in adults with overweight and obesity shows that taking supplemental zinc 30 mg daily for 12 weeks improves some measures of cognitive function and executive processing but does not improve verbal fluency when compared with placebo (112471). Zinc has also been evaluated in combination with other ingredients. A small clinical trial in healthy adults shows that taking a specific product containing a combination of zinc 9 mg, Lactobacillus helveticus, Lactiplantibacillus plantarum, Bifidobacterium longum, and other ingredients (Puraflor, GSK Consumer Healthcare, Milano, Italy) orally daily for 4 weeks does not affect cognitive performance during acute stress when compared with placebo (110923).
• Colorectal adenoma. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large clinical study shows that taking a combination supplement containing zinc 30 mg, selenium 200 mcg (as l-selenomethionine), vitamin A 2 mg (as retinol), vitamin C 180 mg, and vitamin E 30 mg (as D-a-tocopherol acetate) by mouth daily for 5 years or until the recurrence of an adenoma reduces the risk of recurrent large-bowel adenomas by approximately 40% when compared with placebo (92903). It is not clear if the benefit is due to zinc, other supplements, or the combination.
• Colorectal cancer. It is unclear if oral zinc is beneficial for reducing colorectal cancer risk. Details: Population research has found that increased intake of zinc is associated with a 17% to 20% reduced risk of colorectal cancer (90213,90220).
• Congenital heart disease. It is unclear if oral zinc is beneficial for reducing the risk of congenital heart defects. Details: An observational study in pregnant adults has found that consuming the recommended nutritional intake of zinc may be associated with a lower risk of total congenital heart defects in infants, including atrial and ventricular septal defects, when compared with low zinc intake. This association appears to persist despite copper or selenium intake (108445).
• Critical illness (trauma). It is unclear if oral zinc is beneficial for critically ill patients. Details: A meta-analysis of two small randomized clinical trials in adults with head trauma shows that supplementing zinc, given as 120 mg elemental zinc orally daily or 12 mg elemental zinc intravenously daily for 15 days to 3 months, regardless of serum zinc levels, does not improve the risk of 30-day mortality when compared with control (111290). However, the study may have been inadequately powered to detect a difference between groups.
• Dementia. Although there is interest in using oral zinc for dementia, there is insufficient reliable information about the clinical effects of zinc for this condition.
• Diabetic foot ulcers. Although there is interest in using oral zinc for diabetic foot ulcers, there is insufficient reliable information about the clinical effects of zinc for this condition.
• Diabetic neuropathy. It is unclear if oral zinc is beneficial in patients with diabetic neuropathy. Details: A small clinical study in patients with poorly-controlled diabetic neuropathy shows that taking zinc sulfate 660 mg daily for 6 weeks improves motor nerve conduction velocity and reduces fasting and postprandial blood sugar when compared to baseline (86933). The validity of this finding is limited by the lack of statistical comparison to the control group.
• Down syndrome. It is unclear if oral zinc is beneficial for improving immune function in people with this condition. Details: A very small clinical study in Down syndrome patients with zinc deficiency shows that taking zinc sulfate 1 mg/kg daily for 2 months seems to improve immune function and reduce recurrent infections when compared with baseline (87289). The validity of this finding is limited by the lack of a control group. Another small clinical study in children with Down syndrome shows that zinc 25-50 mg daily for 6 months does not improve immune function when compared with placebo (87278). Reasons for the discrepancies may be related to the dose of zinc or zinc status at baseline.
• Dysmenorrhea. It is unclear if oral zinc is beneficial in patients with dysmenorrhea. Details: Preliminary clinical research in females aged 13 to 21 years with primary dysmenorrhea shows that taking zinc sulfate 40 mg orally daily for the first 3 days of menstruation for three cycles reduces mean pain scores by 51% when compared with placebo (111446).
• Epilepsy. There is limited evidence on the oral use of zinc in children with intractable seizures. Details: A small clinical study in children with intractable epilepsy shows that taking elemental zinc 1 mg/kg daily as zinc sulfate heptahydrate for 6 months reduces seizures when compared with placebo. About 31% of children taking zinc experienced a 50% decrease in seizure frequency, compared to only 5% of children taking placebo (96078).
• Erectile dysfunction (ED). It is unclear if oral zinc is beneficial in patients with erectile dysfunction. Details: A moderate-sized, open-label clinical study in adults with mild-to-moderate ED shows that taking a specific combination supplement (Icarifil, Anvest Health S.p.A) containing zinc 15 mg, L-carnitine, L-citrulline, tribulus, and other ingredients daily for 3 months improves patient-reported erectile function when compared to baseline. Additionally, taking the supplement with tadalafil improves some, but not all, patient-reported assessments of erectile function when compared with taking tadalafil alone (114989). It is unclear if this effect is due to zinc, other ingredients, or the combination. Additionally, the interpretation of these results is limited by poor methodology, including the use of per-protocol analysis and lack of a placebo group.
• Esophageal cancer. It is unclear if oral zinc is beneficial for esophageal cancer prevention. Details: Population research in Chinese and Iranian patients has found that low intake of zinc is associated with an increased risk of esophageal squamous cell cancer (17205,87059). However, other population research in patients from America, Europe, or Asia has found that dietary zinc intake is not associated with esophageal cancer risk (90213).
• Fatigue. It is unclear if oral zinc is beneficial for reducing fatigue in older individuals. Details: A clinical study in adults 50 years and older, some with below-normal levels of zinc at baseline, shows that taking zinc 30 mg daily for 70 days improves subjective fatigue when compared with no intervention (105675). The validity of this finding is limited due to a lack of placebo control and potential performance bias. Additionally, it is unclear whether baseline zinc status alters the benefits of zinc supplementation.
• Fecal incontinence. Topical zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in females with fecal incontinence shows that topically applying an ointment containing zinc sulfate 1% and aluminum sulfate 5% to the anal canal mucosa three times daily for 4 weeks improves symptoms approximately twice as much as a placebo ointment. Quality of life related to the incontinence also improved (90219).
• Gastric cancer. It is unclear if dietary zinc is beneficial for gastric cancer prevention. Details: Population research has found that increased dietary zinc intake is not associated with a decreased risk of gastric cancer (90213).
• Head and neck cancer. It is unclear if oral zinc improves survival in patients with head and neck cancers. Details: Preliminary clinical research in patients with head and neck cancers shows that zinc supplementation does not improve disease-free or metastasis-free survival rates after 3 years when compared with placebo (87103).
• Hepatic encephalopathy. It is unclear if oral zinc is beneficial for reducing the severity of hepatic encephalopathy or preventing recurrence. Details: A meta-analysis of small clinical studies, as well as some individual clinical studies, show that short-term zinc supplementation improves cognitive function and possibly quality of life in patients with hepatic encephalopathy. These findings are based on results from the number connection test and other tests (87377,90202,106227). One study in patients with minimal hepatic encephalopathy used zinc bisglycinate 75 mg three times daily, providing elemental zinc 45 mg daily for 12 weeks (106227). However, other preliminary clinical research shows that short-term zinc supplementation does not improve hepatic encephalopathy severity when compared with placebo when assessed using Conn's index, which includes evaluation of mental state, asterixis (flapping tremor), number connection test, electroencephalogram (EEG) record, and plasma ammonia (87144). Also, a meta-analysis of clinical research shows that zinc sulfate supplementation does not reduce encephalopathy recurrence (90202). Based on these results, zinc supplementation may marginally improve cognitive function in hepatic encephalopathy patients, but it does not appear to improve disease severity or reduce the risk of recurrence.
• HIV/AIDS-related diarrhea. It is unclear if oral zinc is beneficial for preventing diarrhea in adult HIV patients. Details: Short-term zinc supplementation does not appear to TREAT diarrhea in adult HIV patients with persistent diarrhea. Clinical research shows that taking zinc 50 mg twice daily for 7 days does not reduce the duration of HIV-related diarrhea when compared with placebo (87055). However, zinc supplementation may help PREVENT HIV-related diarrhea when administered long-term. Clinical research shows that taking elemental zinc 12-15 mg daily for 18 months reduces the rate of diarrhea by about half when compared with placebo in adult HIV patients with zinc deficiency (87216). In HIV-infected children, clinical research shows that taking elemental zinc 10 mg daily for 6 months can reduce the occurrence of diarrhea by 49% when compared with placebo (82377). However, administering zinc in combination with vitamin A until 2 years of age does not reduce the occurrence of diarrhea when compared with vitamin A alone in HIV-infected children (82417).
• HIV/AIDS-related opportunistic infections. It is unclear if oral zinc is beneficial in opportunistic infections in patients with HIV/AIDs. Details: A small clinical study in patients with AIDS shows that taking zinc supplements orally in combination with zidovudine (AZT, Retrovir) might reduce opportunistic infections of Pneumocystis carinii and Candida when compared with taking zidovudine without zinc (6566).
• Human papillomavirus (HPV). It is unclear if oral zinc is beneficial for preventing relapse in patients with vulvar warts or for treating HPV infections and cervical lesions in patients with abnormal cervical cytology. Details: One small clinical study in patients with vulvar warts shows that taking zinc sulfate 400 mg daily for 8 weeks in addition to topical treatments including podophyllin 20%, imiquimod 5%, or cryotherapy, does not affect the duration of response, but does reduce the relapse rate by approximately 66% after 6 months, when compared with topical treatments alone (90190). Additionally, a small, open-label study in zinc-sufficient females with HPV shows that taking zinc sulfate 220 mg twice daily for 3 months reduces the odds of persistent HPV infection by 87% and improves the resolution of pre-existing cervical lesions when compared with no treatment (109456).
• Hypertension. It is unclear if oral zinc reduces blood pressure in normotensive or hypertensive patients. Details: A meta-analysis of small clinical trials shows that taking zinc reduces systolic blood pressure by about 1.5 mmHg, but does not reduce diastolic blood pressure, when compared with placebo. Response did not differ with the dosage of zinc or duration of supplementation. Only one study evaluated patients with hypertension; other patient populations included those with type 2 diabetes, diabetic retinopathy, pre-diabetes, obesity, polycystic ovary syndrome (PCOS), and patients on dialysis (104052). More research in patients with hypertension is needed to determine if zinc is beneficial in this population.
• Impaired glucose tolerance (prediabetes). While some conflicting evidence exists, several small clinical studies suggest that oral zinc may improve glycemic control in patients with prediabetes. Details: A meta-analysis of three low-quality studies in patients with prediabetes suggests that taking zinc sulfate 20-30 mg, alone or in combination with lysine and vitamin C, for 6-12 months reduces fasting blood glucose and postprandial glucose when compared with control (105682). Furthermore, a small clinical study in patients with prediabetes shows that taking zinc gluconate 30 mg daily for 90 days improves glycemic parameters when compared with placebo. All study participants were also instructed to increase physical activity and start a calorie-restricted diet (105391). However, another small clinical study in patients with prediabetes shows that taking zinc gluconate 30 mg daily for 12 months does not improve glycemic parameters when compared with placebo (109454). The available research has been conducted in Sri Lanka, Bangladesh, Iran, and Australia; it is unclear if these findings are generalizable to other geographic locations.
• Intestinal parasite infection. It is unclear if oral zinc is beneficial in patients with intestinal parasitic infections. Details: Zinc supplementation may help TREAT infection from Schistosoma mansoniin, but not other parasites, in children in developing countries. Results from one clinical study show that taking oral zinc sulfate 30-50 mg for 12 months reduces the intensity of Schistosoma mansoniin infection in children, as measured by number of eggs per gram in feces, when compared with placebo (87495). However, supplementation with zinc does not appear to reduce the intensity of Ascaris lumbricoides, Trichiuris trichura, nor Giardia lamblia infection in children (6586). Furthermore, preliminary clinical research suggests that supplementation with zinc may increase the duration of Entamoeba histolytica infection in children (87099). There are also inconsistent results regarding the effects of zinc in PREVENTING intestinal parasite infections. Some clinical research shows that taking zinc in combination with vitamin A reduces the incidence of Giardia lamblia infections when compared with placebo (87099). However, zinc supplementation does not appear to prevent intestinal infections by Ascaris lumbricoides, Schistosoma haematobium, nor Schistosoma mansoniin (87099,87495).
• Kidney failure. It is unclear if oral zinc is beneficial for patients on hemodialysis who have resistance to erythropoiesis-stimulating agents (ESAs). Details: Zinc deficiency is thought to play a role in ESA-resistant anemia in patients with kidney failure. A small clinical trial in patients on hemodialysis with low zinc levels shows that taking zinc acetate hydrate, usually 25mg or 50 mg daily, for 12 months increases plasma levels of zinc and modestly reduces the required weekly dose of ESAs when compared with placebo. However, there was no effect on hemoglobin levels (109781).
• Leukemia. It is unclear if oral zinc is beneficial for improving weight maintenance in children and adolescents with leukemia. Details: A small clinical study in children and adolescents with acute leukemia shows that taking zinc 2 mg/kg (as an amino acid salt) in two divided doses daily for 60 days doubles weight gain and reduces infection rate by approximately 60% when compared with placebo. However, zinc supplementation does not appear to improve nutritional status (90204).
• Liver cancer. It is unclear if oral zinc is beneficial for preventing hepatocellular carcinoma (HCC). Details: In patients treated for hepatitis C, the presence of hepatic fibrosis increases the risk for development of HCC, and is also associated with low plasma zinc levels. In a retrospective analysis of patients with a sustained virological response to hepatitis C therapy, those taking oral zinc supplements for at least 6 months had approximately half the risk of developing HCC when compared with those not taking zinc. Maintaining a serum zinc level above 90 mcg/dL seems to reduce the risk for HCC (106904).
• Lung cancer. It is unclear if increased dietary zinc intake is beneficial for reducing the risk of lung cancer. Details: Population research suggests that the highest dietary intake of zinc is associated with a 32% reduced risk of lung cancer when compared with the lowest intake (106235). Additionally, another large epidemiological cancer screening trial with a mean follow-up of 12.2 years suggests that dietary intake of zinc is protective against lung cancer, with the highest quartile of dietary intake showing the greatest benefit. However, this protective effect was not found for supplemental intake of zinc (112096).
• Male infertility. It is unclear if oral zinc is beneficial for infertility in males. Details: Some preliminary clinical research shows that taking zinc sulfate 66 mg daily increases sperm count, testosterone levels, and the incidence of pregnancy in idiopathic infertile men with low testosterone levels (9334,87430). Another clinical study shows that taking zinc sulfate 66 mg daily can improve sperm morphology by approximately 33% when compared to baseline in men with a grade III varicocele (90194). However, not all research agrees. One clinical study shows that taking elemental zinc 30 mg with folic acid 5 mg daily for 6 months does not improve sperm morphology or pregnancy rates when compared with placebo in infertile men (102085). It is possible the lower dose used in this study was insufficient to produce the beneficial effects observed in earlier research. Zinc supplementation has also been studied as part of combination therapy. A retrospective study in males with or without varicocele-related infertility has found that taking a specific combination product containing zinc 10 mg, L-carnitine fumarate 1725 mg, acetyl-L-carnitine 500 mg, vitamin C 90 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. Improvements 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). There is also interest in using zinc to improve results of in vitro fertilization (IVF). A small clinical study in couples undergoing IVF suggests that infertile male partners who take a specific combination product (Menevit) containing zinc and other antioxidants seem to have an increased rate of viable pregnancies when compared with placebo (87087). However, it's unclear if the benefit can be attributed to zinc, other antioxidants, or the combination.
• Melasma. It is unclear if topical zinc reduces melasma severity. Details: A small clinical study shows that applying a topical solution containing zinc sulfate 10% once daily for 2 months is less effective at reducing melasma severity when compared with hydroquinone 4% (90232).
• Menopausal symptoms. It is unclear if oral zinc improves sexual function after menopause. Details: A single clinical trial shows that taking zinc sulfate 110 mg daily for 6 weeks modestly improves testosterone levels and sexual function, including desire, arousal, satisfaction, and pain, after menopause when compared with placebo (106228).
• Migraine headache. It is unclear if oral zinc is beneficial in patients with migraine. Details: Two small clinical studies in patients with migraine show that taking zinc sulfate 200 mg or zinc gluconate 15 mg daily for 8-12 weeks modestly reduces migraine severity and frequency when compared with placebo (104040,105684). Both studies were conducted in Iran; it is unclear if these findings are generalizable to other geographic locations.
• Nasopharyngeal cancer. It is unclear if oral zinc is beneficial in patients with this type of cancer. Details: A small clinical study in patients with locally advanced nasopharyngeal cancer shows that zinc supplementation 75 mg daily for 2 months may improve disease-free survival rates after 5 years when compared with placebo (87163).
• Neonatal jaundice. It is unclear if oral zinc is beneficial for neonatal jaundice. Details: There is contradictory evidence about the effects of oral zinc in infants with hyperbilirubinemia. Two small clinical studies in infants with idiopathic neonatal hyperbilirubinemia show that receiving oral zinc sulfate 5 mg twice daily for 5-7 days does not affect levels of total bilirubin, the required duration of phototherapy, or the duration of hospitalization, when compared with placebo (90212,104814).However, a larger clinical trial in preterm infants receiving phototherapy and zinc 1.2 mg/kg daily as zinc sulfate heptahydrate, via either orogastric or nasogastric tube for 10 days, serum bilirubin levels were modestly decreased only on days 8-10 when compared with phototherapy alone (106242). Additionally, a second larger clinical trial in infants with idiopathic hyperbilirubinemia shows that receiving oral zinc sulfate (Zinc sulfate, Ramofarmin Company) 1 mg/kg daily for 3 days reduces total bilirubin levels and duration of phototherapy when compared with placebo; additionally length of hospitalization is reduced by less than 1 day (115631). The reason for these discrepant findings is unclear but may be attributed to variations in baseline characteristics, treatment duration, and dose.
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral zinc is beneficial in patients with NAFLD. Details: A small clinical study in patients with NAFLD shows that following a calorie-restricted diet and taking zinc 30 mg daily for 12 weeks reduces certain liver enzymes, but does not improve steatosis or reduce weight, when compared with taking placebo and following a calorie-restricted diet (104046).
• Non-Hodgkin lymphoma. It is unclear if oral zinc is beneficial for non-Hodgkin lymphoma prevention. Details: Population research has found that higher dietary intake of zinc is associated with a 42% decreased odds of developing non-Hodgkin lymphoma (87048).
• Obesity. Small studies suggest that oral zinc does not reduce weight or calorie intake in people with overweight or obesity. Details: A very small clinical study in adults with overweight or obesity shows that taking supplemental zinc 30 mg daily for 12 weeks does not reduce body weight, body mass index (BMI), calorie intake, or macronutrient intake when compared with placebo (112471). Additionally, clinical research in adults with overweight or obesity shows that taking zinc gluconate 25 mg and L-selenomethionine 200 mcg once daily for 8 weeks does not improve BMI, total body fat, or fat free mass when compared with placebo (111448).
• Obsessive-compulsive disorder (OCD). It is unclear if oral zinc reduces symptoms in patients with OCD. Details: A small clinical study in patients with OCD shows that taking zinc sulfate 200 mg twice daily with fluoxetine 20 mg daily for 8 weeks modestly reduces the severity of OCD symptoms when compared with taking placebo with fluoxetine (90223).
• Oral mucositis. It is unclear if oral or topical zinc prevents oral mucositis due to chemotherapy. Some small clinical studies suggest that oral zinc might prevent mucositis due to radiotherapy. Details: Two small clinical studies in adults with leukemia and other cancers shows that taking zinc sulfate 220 mg three times daily for 14 days or until the end of chemotherapy treatment reduces oral mucositis and pain intensity when compared with placebo (90191,98132). However, smaller doses have not shown benefit. A small clinical study in children and adolescents with leukemia shows that taking zinc 2 mg/kg daily (up to 60 mg daily) in two divided doses does not affect chemotherapy-induced mucositis when compared with placebo (90204). An unblinded clinical study in children and adolescents aged 8-16 years with recently diagnosed leukemia shows that taking zinc gluconate 50 mg (7 mg elemental zinc) daily does not significantly reduce the incidence or duration of oral mucositis when compared with a control group not receiving zinc (104816). Zinc also doesn't seem to be beneficial with high-dose chemotherapy. A small clinical study in adolescents and adults receiving high-dose chemotherapy prior to undergoing hematopoietic stem cell transplantation (HSCT) suggests that taking zinc sulfate 220 mg (50 mg elemental zinc) twice daily, beginning one day prior to the chemotherapy regimen and continuing for 3 weeks, does not affect the severity, duration, or onset of mucositis when compared with placebo (90215). Other preliminary clinical research in children aged 3-18 years receiving chemotherapy for leukemia or other cancer also shows that taking zinc 1 mg/kg orally daily for 14 days, beginning on the first day of chemotherapy, does not reduce the incidence or severity of mucositis when compared with placebo (111447). Topical zinc has also been investigated for radiation-induced or chemotherapy-induced oral mucositis. In two clinical studies, using 7.5 mL of a mouthwash containing zinc chloride 0.2% twice for 2 minutes every 8 hours for 3 weeks modestly reduces the incidence and severity of oral mucositis, and improves quality of life, when compared with a placebo mouthwash (106232,109690). In one study, the average patient weight was higher in the group using the mouthwash containing zinc (106232). Other preliminary clinical research in adults with head and neck cancer undergoing radiotherapy treatment, consisting of at least 30 Gy radiation exposure shows that using zinc sulfate 1% mouthwash, 5 mL three times daily for 6 weeks, beginning on the first day of radiation therapy, moderately improves oral mucositis severity and pain scores when compared with chlorhexidine 0.2% or placebo mouthwash (111291). Taking zinc orally might be beneficial in radiation-induced oral mucositis. A small clinical study in patients with head and neck tumors shows that taking zinc sulfate, providing 150 mg elemental zinc, daily starting at the first day of radiation therapy and ending at 6 weeks, reduces the severity of mucositis and prolongs the onset of mucositis when compared with placebo (86981). Another clinical study in patients with head and neck cancer shows that taking zinc sulfate 150 mg daily during and after chemoradiotherapy treatment, consisting of a total 69.5 Gy radiation exposure and cisplatin 40 mg/m2 weekly, is associated with less severe mucositis when compared with placebo (105677).
• Osteoporosis. It is unclear if oral zinc improves bone density in patients with osteoporosis. Details: Population research has found that reduced zinc intake and lower zinc serum levels seem to be associated with lower bone mineral density (BMD) (6920,14410). In elderly patients with at least marginal zinc deficiency who are taking standard therapy for osteoporosis, preliminary clinical research shows that taking zinc acetate dihydrate (Nobelzin, Nobelpharma) providing elemental zinc 25 mg twice daily for 12 months increases BMD when compared with baseline. Increases in serum zinc were associated with improvements in BMD. However, it is unclear if increases in BMD were significant when compared with placebo (106230). It is also unclear if zinc improves BMD in patients without zinc deficiency. A small clinical study in healthy postmenopausal adults suggests that taking zinc in combination with copper, manganese, and calcium might slow bone loss when compared with placebo (1994). It is not clear if this effect is due to zinc, other ingredients, or the combination.
• Overall mortality. It is unclear if oral zinc reduces overall mortality in young children. Details: A meta-analysis of clinical research in children under the age of five years shows that supplementation with zinc in daily doses of at least 10 mg reduces the risk of all-cause mortality by 16% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation. The risk of mortality was reduced by 54% when children took zinc for up to one year, but overall mortality was not reduced in studies lasting at least one year (106239).
• Periodontitis. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with moderate or advanced periodontitis shows that taking a combination supplement containing zinc 3.75 mg, alpha-lipoic acid, coenzyme Q10, cranberry extract, grapeseed extract, selenium, vitamin C, and vitamin E twice daily for 8 weeks in addition to standard nonsurgical therapy does not reduce periodontal indices including bleeding on probing, gingival recession, plaque index, or inflammation when compared with placebo (111708).
• Polycystic ovary syndrome (PCOS). It is unclear if oral zinc is beneficial in patients with PCOS. Details: A small clinical study in adults taking metformin for PCOS shows that also taking zinc sulfate 220 mg (50 mg elemental zinc) daily for 8 weeks improves hair loss and facial growth, but not acne, when compared with placebo (96071).
• Postoperative sore throat. It is unclear if oral zinc is beneficial for postoperative sore throat. Details: Clinical research shows that dissolving a lozenge containing zinc 40 mg as zinc sulfate in the mouth in the 30 minutes before surgery involving endotracheal intubation reduces the incidence of postoperative sore throat by 58% when compared with placebo lozenges. It also seems to reduce the severity of postoperative sore throat that does occur (97138). Other clinical research in adults undergoing a procedure that required endotracheal intubation shows that using a preoperative 30-mL gargle containing zinc 40 mg does not affect sore throat scores when compared with magnesium sulphate 250 mg or budesonide 200 mcg gargles (114763).
• Postpartum depression. It is unclear if oral zinc prevents postpartum depression after a Cesarean section (C-section). Details: A small observational study in pregnant patients with anemia who underwent C-section has found that taking zinc sulfate 100 mg daily for 4 days after surgery is associated with a 75% reduction in the odds of developing postpartum depression when compared with no supplementation (109452).
• Premenstrual syndrome (PMS). It is unclear if oral zinc improves symptoms in patients with PMS. Details: A small clinical study in female college students shows that taking elemental zinc 30 mg daily for 3 months improves quality of life, but not quality of sleep, when compared with placebo (104049).
• Preterm labor. It is unclear if oral zinc reduces the risk of preterm labor. Details: Observational research has found that low dietary intake of zinc during pregnancy is associated with an increased likelihood of preterm deliveries (87471). Also, most meta-analyses of clinical research show that taking zinc supplements during pregnancy modestly reduces the risk of preterm birth (106231). However, one large meta-analysis of 22 clinical studies shows that zinc supplementation during pregnancy seems to have little or no benefit for reducing the risk of preterm birth when compared with control (105679). Zinc supplementation also does not seem to reduce the risk of stillbirth, neonatal death, spontaneous abortion, or premature rupture of membranes (97142,105679,106231).
• Prostatitis. It is unclear if oral zinc improves symptoms in men with chronic prostatitis. Details: A clinical study in men with chronic prostatitis shows that taking zinc sulfate 220 mg daily along with prazosin 2 mg daily for 12 weeks does not improve difficulty urinating or quality of life, but does seem to improve pain, when compared with prazosin alone (90210). The validity of this study was limited by a significant dropout rate.
• Pruritus. There is limited evidence on the oral use of zinc for reducing pruritis in hemodialysis patients. Details: A small clinical study in end-stage renal disease patients with hemodialysis-associated pruritus shows that taking zinc sulfate 220 mg twice daily for 2 months reduces pruritus severity when compared with placebo (90218).
• Psoriatic arthritis. It is unclear if oral zinc improves psoriatic arthritis symptoms. Details: Two small clinical trials in patients with psoriatic arthritis show that taking zinc orally, alone or in combination with nonsteroidal anti-inflammatory drugs (NSAIDs), does not seem to reduce pain or improve function when compared with control (6514,6515).
• Respiratory tract infections. It is unclear if oral zinc reduces respiratory tract infections in children. Details: An open-label study in children aged 6 months to 5 years with zinc deficiency shows that taking zinc sulfate 20 mg orally once daily for 2 weeks reduces the number of episodes and the mean duration of upper and lower respiratory tract infections over 6 months of follow-up when compared with the 6 months prior to zinc supplementation (104815). The validity of this finding is limited by the lack of a comparator group.
• Rosacea. It is unclear of oral zinc improves symptoms of rosacea or quality of life. Details: A small clinical trial shows that taking zinc sulfate 440 mg in two divided doses daily for 90 days does not improve quality of life or symptoms associated with rosacea when compared with placebo (90195).
• Seizures. It is unclear if oral zinc reduces recurrent febrile seizures in children. Details: Although some individual preliminary clinical research disagrees (96069), a meta-analysis of generally low-quality research in children under 5 years of age with a previous febrile seizure shows that taking zinc sulfate 1-2 mg/kg or 20 mg daily for 6-12 months does not reduce febrile seizure recurrence when compared with placebo (106237). Also, a small clinical study shows that taking zinc does not increase the time to first febrile seizure recurrence (96069).
• Sepsis. It is unclear if oral zinc is beneficial in pediatric or adult patients with sepsis. Details: A meta-analysis of clinical research in children under the age of five years shows that supplementation with zinc reduces the risk of sepsis mortality by 57% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation (106239). Also, a small clinical study in newborns with sepsis shows that giving zinc sulfate monohydrate 3 mg/kg twice daily for 10 days along with antibiotics reduces the likelihood of neurological abnormalities, such as those related to posture, behavior, and reflexes, by 70% when compared with antibiotics alone. Mortality and length of hospital stay were not improved, but the study may have been inadequately powered to detect a difference in these parameters (96077). Another study in preterm infants with late-onset sepsis (developing at least 72 hours after birth), shows that giving 1.4 mg/kg elemental zinc daily orally for 10 days in addition to antibiotics reduces the number of infants with unresolved sepsis at 10 days, and reduces C-reactive protein and procalcitonin levels, when compared with giving antibiotics alone (104819). A meta-analysis of small clinical studies in infants less than 4 months old shows that administering zinc 1-3 mg/kg daily for 1-18 weeks may reduce the rate of infant mortality and treatment failure when compared with placebo or control, but does not seem to prevent sepsis or improve sepsis-related mortality (108444). Additionally, zinc has been evaluated in adults. A single-center observational study in adults with sepsis found that administering zinc orally or enterally in various doses, ranging from less than 15 mg to greater than 50 mg daily, does not improve survival rates or reduce the length of stay in the intensive care unit (115630).
• Shigellosis. It is unclear if oral zinc is beneficial in patients with acute shigellosis from food poisoning. Details: A small clinical study in malnourished children with acute shigellosis (food poisoning) shows that administering a multivitamin syrup containing elemental zinc 20 mg daily for 2 weeks, in addition to standard treatment, can improve recovery time and reduce the number of diarrhea episodes when compared with multivitamin syrup without elemental zinc (87088).
• Sleep deprivation. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in sleep-deprived recreational athletes shows that taking a combination of zinc 90 mg, magnesium 1350 mg, and vitamin B6 31.5 mg orally for 3 nights at bedtime does not change sleep quality, subjective sleepiness, mood, or fatigue when compared with placebo (113655).
• Substance use disorder. It is unclear if oral zinc is beneficial for substance use disorder. Details: Preliminary clinical research in adults with opioid use disorder that were being treated with methadone shows that taking zinc sulfate, containing 12 mg zinc, orally daily for 3 months moderately improves relapse prevention scores, including drug use and drug craving scores, when compared with control. Taking zinc also modestly improved stress and anxiety scores (111293).
• Tonsillopharyngitis. It is unclear if oral zinc is beneficial in patients with tonsillopharyngitis. Details: A moderate-sized, open-label clinical study in pediatric patients aged 3 to 10 years with acute tonsillopharyngitis shows that taking a specific combination solution (PediaFlù, Pediatrica S.r.l.) containing zinc (age dependent doses ranging from 2 to 4 mg), honey, propolis, and pelargonium sidoides daily for 6 days along with standard of care reduces tonsilitis severity scores when compared with standard care alone; however, this improvement is not clinically significant. (115632). It is not clear if these effects are due to zinc, other ingredients, or the combination.
• Traumatic brain injury (TBI). There is limited evidence on the parenteral use of zinc for closed head injury. Details: A small clinical study shows that administering zinc parenterally immediately following severe closed head injury seems to improve the rate of neurological recovery when compared with standard therapy (2696).
• Tuberculosis. It is unclear if oral zinc can improve outcomes in patients receiving tuberculosis treatment. Details: Low levels of zinc are common in patients with tuberculosis. In patients newly diagnosed with tuberculosis and using anti-tuberculosis treatment, some clinical research shows that taking zinc 50 mg daily as zinc sulfate for 6 months increases the number of patients with negative sputum smears by 50% to 80% within the first 6 weeks of treatment when compared with placebo. However, there were no differences in the number of patients with negative smears after this time point. There were also improvements in some liver function enzyme levels after 2 months, but not 6 months, when compared with placebo (106238). However, other clinical research shows that taking zinc 15-90 mg daily for 2-6 months does not improve cure rates or sputum smear conversions when compared with placebo. However, when combined with vitamin A, serum levels of vitamin A, zinc, and hemoglobin were modestly improved and there was a modest increase in sputum smear conversions (109754).
• Urinary tract infections (UTIs). It is unclear if oral zinc is beneficial in children with UTI. Details: A low-quality, clinical study in children aged 3-12 years hospitalized for a UTI and receiving intravenous antibiotic treatment shows that taking zinc 1 mg/kg daily for 14 days reduces the duration of dysuria, urinary frequency, and urgency when compared with intravenous antibiotics alone. Zinc does not improve fever or the time to negative urine culture (96081). However, this study did not demonstrate that treatment groups were equal at baseline.
• Venous leg ulcers. It is unclear if oral or topical zinc is beneficial for leg ulcer healing. Details: Two small studies in elderly patients with leg ulcers suggest that using a zinc saline solution on a wound dressing or applying zinc oxide to a dressing might improve healing of leg ulcers (2694,6901). However, oral zinc supplementation does not seem to be beneficial. A meta-analysis of four small clinical trials in patients with venous leg ulcers shows that taking zinc orally does not improve healing when compared with placebo (104079).
• Vertigo. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults with benign paroxysmal positional vertigo with serum 25-hydroxyvitamin D levels less than 20 ng/mL shows that taking a specific combination product containing zinc 7.5 mg, alpha-lipoic acid 600 mg, L-carnosine 165 mg, curcumin 100 mg, piperine 1 mg, cholecalciferol 800 units, vitamin B2 0.8 mg, and vitamin B6 1 mg (Vertistop D, Difass) orally daily for 6 months moderately reduces the number of vertigo relapse episodes when compared with control. However, in patients with serum 25-hydroxyvitamin D levels greater than 20 ng/mL that took a specific combination product containing zinc 7.5 mg, alanine 600 mg, L-carnosine 165 mg, curcumin 100 mg and piperine 1 mg (Vertistop L, Difass) orally daily for 6 months there was no difference in relapse episodes when compared with control (111294). It is unclear if this effect is due to zinc, other ingredients, or the combination.
• Water warts. It is unclear if oral zinc is beneficial for the treatment of water warts in children. Details: In children with water warts, preliminary clinical research shows that taking zinc sulfate heptahydrate (as Zinco syrup) for 2 months results in lesion resolution in 70% of patients when compared with baseline. Lesion resolution occurred in an additional 13% of patients in the month after treatment completion, with no recurrence in any of these children over the next 9 months. Zinc 3 mg daily was used in children up to 3 years of age, and 5 mg daily was used in older children (106234). Due to the lack of a comparator group, it is unclear if these outcomes are due to zinc or the natural resolution of the condition.
• Wound healing. Topical zinc might be beneficial for the healing of uncomplicated wounds. Details: A small clinical study shows that applying zinc chloride solution, standardized to contain zinc 20 mcg/mL, twice daily improves wound healing when compared with saline solution in patients with uncomplicated, skin wounds. However, when zinc is administered as a component of an insulin product (Humulin, Eli Lilly and Company), it seems to be more effective than zinc chloride alone (90192).
• Wrinkled skin. Topical zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A topical preparation containing 10% vitamin C as L-ascorbic acid and acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (Cellex-C High Potency Serum) applied to photo-aged facial skin for 3 months seems to improve fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone when compared with placebo (6155). More evidence is needed to rate zinc for these uses.

(Read more about ZINC)

LIKELY SAFE ...when used orally in amounts commonly found in foods. Centaury has Generally Recognized As Safe status (GRAS) for use in foods and beverages in the US (4912). The maximum permitted concentration of centaury for use in beverages in the US is 0.0008% (4).

POSSIBLY SAFE ...when used orally in medicinal amounts, short-term (12). Centaury herb 36 mg daily, in combination with lovage and rosemary (Canephron N, Bionorica), has been used with apparent safety for 6 months (91726).

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

(Read more about CENTAURY)

LIKELY SAFE ...when used orally in amounts commonly found in foods. Eyebright is listed by the Council of Europe as a natural source of food flavoring (4).

POSSIBLY UNSAFE ...when applied into the eyes. Avoid using due to hygienic concerns; eyebright ophthalmic products may be subject to contamination (8,11). There is insufficient reliable information available about the safety of eyebright when used orally in medicinal amounts.

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

(Read more about EYEBRIGHT)

LIKELY SAFE ...when used orally and appropriately. Consuming up to 20 mg of lutein daily from both dietary and supplemental sources appears to be safe (3219,3220,60167). Lutein supplements have been safely used in clinical trials at doses of up to 20 mg daily for up to 10 years (11798,60133,60177,94703,94701,100986,104570,107107,108615,109763).

CHILDREN: LIKELY SAFE
when used orally and appropriately. A specific product containing lutein (LUTEINofta, SOOFT Italia SpA) has been used with apparent safety in infants at a dose of 0.14 mg daily for 36 weeks (91163).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately in amounts found in foods. The high end of dietary lutein intake ranges from 6.9-11.7 mg/day (3219,3220).

(Read more about LUTEIN)

LIKELY SAFE ...when used in amounts found in foods. Typical daily intakes for adults range from 40-400 mg (101471).

POSSIBLY SAFE ...when used orally and appropriately in medicinal amounts. Taurine 2-4 grams daily in two or three divided doses has been used safely in studies lasting up to 3 months (5248,5271,8217,8221,10454,77147,95612,98337,104165,104167). Higher doses of taurine 6 grams daily have been used safely in studies lasting up to 4 weeks (98336,98337). A risk assessment of orally administered taurine has identified an Observed Safe Level (OSL) of up to 3 grams daily for healthy adults (31996).

CHILDREN: LIKELY SAFE
when used in amounts found in foods.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately in medicinal amounts. Taurine 2.4-4.8 grams daily in three divided doses has been safely used in children 6-16 years of age for up to 12 weeks (103210).

PREGNANCY AND LACTATION: LIKELY SAFE
when used in amounts found in foods. There is insufficient reliable information available about the safety of taurine when used in medicinal amounts during pregnancy and lactation; avoid using.

(Read more about TAURINE)

LIKELY SAFE ...when used orally and appropriately in doses of up to 2 mg daily. Zeaxanthin supplements have been safely used in clinical trials at doses of up to 2 mg daily for up to 10 years (94701,94702,94703,108615).

POSSIBLY SAFE ...when used orally and appropriately in amounts greater than 2 mg daily. Zeaxanthin supplements in doses of 8-10 mg daily for up to 12 months have been used with apparent safety in clinical trials (60175,60245).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately. A specific product containing zeaxanthin (LUTEINofta, SOOFT Italia SpA) has been used with apparent safety in infants at a dose of 0.0006 mg daily for 36 weeks (91163). There is insufficient reliable information available about the safety of zeaxanthin at higher doses or in older children.

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately in amounts found in foods. Zeaxanthin is found in breast milk and levels correlate with infant status (106365). There is insufficient reliable information available about the safety of supplemental zeaxanthin.

(Read more about ZEAXANTHIN)

LIKELY SAFE ...when used orally and appropriately. Zinc is safe in amounts that do not exceed the tolerable upper intake level (UL) of 40 mg daily (7135). ...when used topically and appropriately (2688,6538,6539,7135,8623,11051,111291).

POSSIBLY SAFE ...when used orally and appropriately in doses higher than the tolerable upper intake level (UL). Because the UL of zinc is based on regular daily intake, short-term excursions above 40 mg daily are not likely to be harmful. In fact, there is some evidence that doses of elemental zinc as high as 80 mg daily in combination with copper 2 mg can be used safely for approximately 6 years without significant adverse effects (7303,8622,92212). However, there is some concern that doses higher than the UL of 40 mg daily might decrease copper absorption and result in anemia (7135).

POSSIBLY UNSAFE ...when used intranasally. Case reports and animal research suggest that intranasal zinc might cause permanent anosmia or loss of sense of smell (11155,11156,11703,11704,11705,11706,11707,16800,16801,17083). Several hundred reports of anosmia have been submitted to the US Food and Drug Administration (FDA) and the manufacturer of some intranasal zinc products (Zicam) (16800,16801). Advise patients not to use intranasal zinc products.

LIKELY UNSAFE ...when taken orally in excessive amounts. Ingestion of 10-30 grams of zinc sulfate can be lethal in adults (7135). Chronic intake of 450-1600 mg daily can cause multiple forms of anemia, copper deficiency, and myeloneuropathies (7135,17092,17093,112473). This has been reported with use of zinc-containing denture adhesives in amounts exceeding the labeled directions, such as several times a day for several years (17092,17093). Advise patients to follow the label directions on denture adhesives that contain zinc.

CHILDREN: LIKELY SAFE
when used orally and appropriately (7135). Zinc is safe in amounts that do not exceed the tolerable upper intake level (UL). The UL for children is based on age: 4 mg daily for 0-6 months, 5 mg daily for 7-12 months, 7 mg daily for 1-3 years, 12 mg daily for 4-8 years, 23 mg daily for 9-13 years, and 34 mg daily for 14-18 years (7135,97140).

CHILDREN: POSSIBLY UNSAFE
when used orally in high doses. Taking amounts greater than the UL can cause sideroblastic anemia and copper deficiency (7135). ...when used topically on damaged skin. An infant treated with 10% zinc oxide ointment for severe diaper rash with perianal erosions developed hyperzincemia. Absorption seemed to occur mainly via the erosions; plasma levels dropped after the erosions healed despite continued use of the ointment (106905).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. Zinc is safe in amounts that do not exceed the tolerable upper intake level (UL) of 34 mg daily during pregnancy in those 14-18 years of age and 40 mg daily in those 19-50 years of age (7135).

PREGNANCY: LIKELY UNSAFE
when used orally in doses exceeding the UL (7135).

LACTATION: LIKELY SAFE
when used orally and appropriately. Zinc is safe in amounts that do not exceed the tolerable upper intake level (UL) of 34 mg daily during lactation in those 14-18 years of age, and 40 mg daily for those 19-50 years of age (7135).

LACTATION: POSSIBLY UNSAFE
when used orally in doses exceeding the UL. Higher doses can cause zinc-induced copper deficiency in nursing infants (7135).

(Read more about ZINC)

(Read more about CENTAURY)

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, eyebright might increase the risk of hypoglycemia when taken with antidiabetes drugs.  Details Animal research suggests that eyebright lowers blood glucose levels (49393).

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(Read more about LUTEIN)

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, taurine might increase the risk of hypotension when taken with antihypertensive drugs.  Details Some clinical evidence suggests that taurine can reduce both systolic and diastolic blood pressure (77229,95614,104166).

LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, taurine might reduce excretion and increase plasma levels of lithium.  Details Taurine is thought to have diuretic properties (3647), which might reduce the excretion of lithium.

(Read more about TAURINE)

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking zeaxanthin with antidiabetes drugs might increase the risk of hypoglycemia.  Details In an animal diabetic model, zeaxanthin has hypoglycemic effects (106363). However, population research has found that increasing intake of dietary zeaxanthin plus lutein does not decrease the risk of developing type 2 diabetes (14004,97227).

(Read more about ZEAXANTHIN)

AMILORIDE (Midamor) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Probable •  Level of Evidence = B Amiloride can modestly reduce zinc excretion and increase zinc levels.  Details Clinical research shows that amiloride can reduce urinary zinc excretion, especially at doses of 10 mg per day or more. This zinc-sparing effect can help to counteract zinc losses caused by thiazide diuretics, but it is unlikely to cause zinc toxicity at usual amiloride doses (830,11626,11627,11634). The other potassium-sparing diuretics, spironolactone (Aldactone) and triamterene (Dyrenium), do not seem to have a zinc-sparing effect.

ATAZANAVIR (Reyataz) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Probable •  Level of Evidence = B Zinc modestly reduces levels of atazanavir, although this effect does not seem to be clinically significant.  Details Clinical research shows that zinc might decrease serum atazanavir levels by chelating with atazanavir in the gut and preventing its absorption (93578). Although a single dose of zinc sulfate (Solvazinc tablets) 125 mg orally does not affect atazanavir concentrations in patients being treated with atazanavir/ritonavir, co-administration of zinc sulfate 125 mg daily for 2 weeks reduces plasma levels of atazanavir by about 22% in these patients. However, despite this decrease, atazanavir levels still remain at high enough concentrations for the prevention of HIV virus replication (90216).

CEPHALEXIN (Keflex) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Zinc might decrease cephalexin levels by chelating with cephalexin in the gut and preventing its absorption.  Details A pharmacokinetic study shows that zinc sulfate 250 mg taken concomitantly with cephalexin 500 mg decreases peak levels of cephalexin by 31% and reduces the exposure to cephalexin by 27%. Also, taking zinc sulfate 3 hours before cephalexin decreases peak levels of cephalexin by 11% and reduces the exposure to cephalexin by 18%. By decreasing cephalexin levels, zinc might increase the risk of treatment failure. This effect does not occur when zinc is taken 3 hours after the cephalexin dose (94163). To avoid an interaction, advise patients take zinc sulfate 3 hours after taking cephalexin.

CISPLATIN (Platinol-AQ) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, zinc might interfere with the therapeutic effects of cisplatin.  Details Animal research suggests that zinc stimulates tumor cell production of the protein metallothionein, which binds and inactivates cisplatin (11624,11625). It is not known whether zinc supplements or high dietary zinc intake can cause clinically significant interference with cisplatin therapy. Cisplatin might also increase zinc excretion.

INTEGRASE INHIBITORS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking zinc along with integrase inhibitors might decrease the levels and clinical effects of these drugs.  Details Zinc is a divalent cation. Pharmacokinetic studies have shown that other divalent cations such as calcium and iron can decrease blood levels of the integrase inhibitor dolutegravir through chelation (93578,93579).

PENICILLAMINE (Cuprimine, Depen) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Zinc might reduce the levels and clinical effects of penicillamine.  Details By forming an insoluble complex with penicillamine, zinc interferes with penicillamine absorption and activity. Zinc supplements reduce the efficacy of low-dose penicillamine (0.5-1 gram/day), but do not seem to affect higher doses (1-2.75 gram/day), provided dosing times are separated (2678,4534,11605). Advise patients to take zinc and penicillamine at least 2 hours apart.

QUINOLONE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Zinc can decrease the levels and clinical effects of quinolones antibiotics.  Details Quinolones form complexes with zinc in the gastrointestinal tract, reducing absorption of both the quinolone and zinc if taken at the same time (828,2682,3046,11600). Advise patients to take these drugs at least 2 hours before, or 4-6 hours after, zinc supplements.

RITONAVIR (Norvir) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Zinc modestly reduces levels of ritonavir.  Details Clinical research shows that zinc might reduce serum ritonavir levels by chelating with ritonavir in the gut and preventing its absorption (93578). In patients with HIV, ritonavir is taken with atazanavir to prevent the metabolism and increase the effects of atazanavir. A pharmacokinetic study shows that, in patients being treated with atazanavir/ritonavir, co-administration of zinc sulfate (Solvazinc tablets) 125 mg as a single dose or as multiple daily doses for 2 weeks reduces plasma levels of ritonavir by about 16% (90216). However, atazanavir levels still remains high enough to prevent HIV virus replication. Therefore, the decrease in ritonavir levels is not likely to be clinically significant.

TETRACYCLINE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Zinc might reduce levels of tetracycline antibiotics.  Details Tetracyclines form complexes with zinc in the gastrointestinal tract, which can reduce absorption of both the tetracycline and zinc when taken at the same time (3046,4945). Taking zinc sulfate 200 mg with tetracycline reduces absorption of the antibiotic by 30% to 40% (11615). Demeclocycline and minocycline cause a similar interaction (4945). However, doxycycline does not seem to interact significantly with zinc (11615). Advise patients to take tetracyclines at least 2 hours before, or 4-6 hours after, zinc supplements to avoid any interactions.

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General ...No adverse effects have been reported. However, a thorough evaluation of safety outcomes has not been conducted.

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General ...Orally, eyebright is generally well tolerated when used in food amounts. Topically, eyebright might be unsafe due to the potential for contamination.

Gastrointestinal ...Orally, eyebright has been reported to cause nausea and constipation (4).

Genitourinary ...Orally, eyebright has been reported to cause polyuria (4).

Neurologic/CNS ...Orally, eyebright has been reported to cause confusion and headache (4).

Ocular/Otic ...Topically, eyebright has been reported to cause increased ocular pressure, lacrimation, pruritus, redness, swelling of eyelid margins, vision changes, and photophobia when applied to the eyes (4). Ophthalmic eyebright products should be used with caution due to the potential for contamination (8,11).

Pulmonary/Respiratory ...Orally, eyebright has been reported to cause cough, dyspnea, and nasal congestion (4).

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General ...Orally, dietary and supplemental lutein is generally well tolerated. Doses up to 20 mg daily have not resulted in adverse effects.

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General ...Orally, taurine is generally well-tolerated when used in typical doses for up to one year.
Most Common Adverse Effects:
Orally: Constipation, diarrhea, and dyspepsia.
Serious Adverse Effects (Rare):
Orally: Hypersensitivity reactions in sensitive individuals. Case reports raise concerns for serious cardiovascular adverse effects, but these reports have involved energy drinks containing taurine and other ingredients. It is unclear if these adverse effects are due to taurine, other ingredients, or the combination.

Cardiovascular ...Changes in heart rate and increased blood pressure have been reported following the co-administration of taurine and caffeine, although the effects of taurine alone are unclear (77088). In healthy individuals, consumption of energy drinks containing taurine increased platelet aggregation and decreased endothelial function (77151,112268,112741). A case of cardiac arrest following strenuous exercise and an excessive intake of energy drinks containing caffeine and taurine has been reported (77136). In another case report, a 28-year-old male without cardiovascular risk factors presented to the hospital with radiating chest pain, shortness of breath, and diaphoresis after excessive intake of an energy drink containing taurine, caffeine, sugar, and glucuronolactone. Electrocardiogram findings confirmed myocardial infarction, and subsequent catheterization confirmed thrombotic occlusion (112741).

Endocrine ...Orally, taurine has been reported to cause hypoglycemia (77153).

Gastrointestinal ...Orally, constipation has been reported following the administration of taurine (77231). Dyspepsia has also been reported after oral taurine use (104165).

Hematologic ...In clinical research, taurine reduced platelet aggregation (77245). A case of massive intravascular hemolysis, presenting with confusion, dark urine, dyspnea, emesis, and fever, has been reported following the administration of a naturopathic vitamin infusion containing taurine, free amino acids, magnesium, and a vitamin B and D complex (77177). However, the effects of taurine alone are unclear.

Immunologic ...A case report describes a hypersensitivity reaction in a female patient with a history of allergies to sulfonamides, sulfites, and various foods, after ingestion of taurine and other sulfur-containing supplements. The amount of taurine in the products ranged from 50-500 mg per dose. The allergic reaction recurred upon rechallenge with taurine 250-300 mg (91514).

Neurologic/CNS ...In a case study, encephalopathy occurred in a body-builder who took approximately 14 grams of taurine in combination with insulin and anabolic steroids. It is not known if this was due to the taurine or the other drugs taken (15536).
Cases of seizures following the consumption of energy drinks containing taurine have been reported (77105,77196). In clinical research, taurine has been reported to cause drowsiness and ataxia in epileptic children (77241).

Psychiatric ...In a case report, a 36-year-old male with adequately controlled bipolar disorder was hospitalized with symptoms of mania after consuming several cans of an energy drink containing taurine, caffeine, glucuronolactone, B vitamins, and other ingredients (Red Bull Energy Drink) over a period of four days (14302). It is unknown if this effect was related to taurine.

Pulmonary/Respiratory ...In human research, an exacerbation of pulmonary symptoms of cystic fibrosis has been associated with taurine supplementation, although this could also be caused by progression of the disease (77231).

Renal ...A case of acute kidney failure has been reported following the concomitant intake of 1 liter of vodka and 3 liters of an energy drink providing taurine 4. 6 grams, caffeine 780 mg, and alcohol 380 grams (77185).

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General ...Orally, dietary and supplemental zeaxanthin are generally well tolerated. No adverse effects have been reported in clinical research.

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General ...Orally, zinc is well tolerated in doses below the tolerable upper intake level (UL), which is 40 mg daily for adults. Topically, zinc is well tolerated.
Most Common Adverse Effects:
Orally: Abdominal cramps, diarrhea, metallic taste, nausea and vomiting (dose-related).
Topically: Burning, discoloration, itching, stinging, and tingling when applied to irritated tissue.
Intranasally: Bad taste, dry mouth, headache, irritation, reduced sense of smell.
Serious Adverse Effects (Rare):
Orally: There have been cases of acute renal tubular necrosis, interstitial nephritis, neurological complications, severe vomiting, and sideroblastic anemia after zinc overdose.
Intranasally: There have been cases where intranasal zinc caused permanent loss of smell (anosmia).

Dermatologic ...Topically, zinc can cause burning, stinging, itching, and tingling when applied to inflamed tissue (6911,8623,87297). Zinc oxide can be deposited in the submucosal tissue and cause dark discoloration of the skin. This can occur with prolonged topical application to intact skin, application to eroded or ulcerated skin, or penetrating traumatic exposure, and also parenteral administration (8618).
In rare cases, oral zinc has resulted in worsened acne (104056), skin sensitivity (6592), a leishmanial reaction with a macular rash that occurred on exposed parts of the body (86935), eczema (104055), systemic contact dermatitis (109457), and the development of severe seborrheic dermatitis (86946).

Gastrointestinal ...Orally, zinc can cause nausea (338,2663,2681,6592,6700,18216,106230,106233,106227,113661), vomiting (2663,2681,6519,6592,96069,96074), a metallic or objectionable taste in the mouth (336,338,6700,11350,18216,106902,113661), abdominal cramping (6592,96069), indigestion (87227), heartburn (96069), dry mouth (87533), and mouth irritation (336,2619). When used orally in amounts above the tolerable upper intake level, zinc may cause irritation and corrosion of the gastrointestinal tract (331,86982,87315,106902), watery diarrhea (1352), epigastric pain (2663,2681), and severe vomiting (2663,2681).
Intranasally, zinc can cause bad taste, dry mouth, and burning and irritation of the throat (8628,8629).
When used topically as a mouth rinse, zinc may cause tooth staining (90206).

Hematologic ...There is concern that high daily doses of zinc, above the tolerable upper intake level (UL) of 40 mg per day, might increase the risk of copper deficiency, potentially leading to anemia and leukopenia (7135,112473). To prevent copper deficiency, some clinicians give a small dose of copper when zinc is used in high doses, long-term (7303).

Hepatic ...There are two cases of liver deterioration in patients with Wilson disease following initiation of treatment with zinc 50-200 mg three times daily. The mechanism of action is not understood, and the event is extremely uncommon (86927,87470).

Immunologic ...Daily doses of 300 mg of supplemental zinc for 6 weeks appear to impair immune response (7135). A case of erythematosus-like syndrome, including symptoms such as fever, leg ulcers, and rash, has been reported following intake of effervescent tablets (Solvezink) containing zinc 45 mg (87506). In another case, severe neutropenia was reported after taking supplemental zinc 900 mg daily for an unknown duration (112473).

Musculoskeletal ...Orally, zinc may cause body aches in children (113661).

Neurologic/CNS ...Zinc-containing denture adhesives can cause toxicity if used more frequently than recommended for several years. Case reports describe hyperzincemia, low copper levels, blood dyscrasias, and neurological problems, including sensory disturbances, numbness, tingling, limb weakness, and difficulty walking in patients applying denture adhesive multiple times daily for several years (17092,17093,90205,90233). Due to reports of zinc toxicity associated with use of excessive amounts of zinc-containing denture adhesives for several years, GlaxoSmithKline has reformulated Polygrip products to remove their zinc content (17092,17093).
Intranasally (8628) and orally (87534), zinc can cause headache. When used orally in amounts above the tolerable upper intake level (UL), zinc may cause central nervous system (CNS) symptoms including lethargy, fatigue, neuropathy, dizziness, and paresthesia (2663,2681,87369,87470,87533,87534,112473).

Oncologic ...There is concern that zinc might worsen prostate disease. For example, some preliminary evidence suggests that higher dietary zinc intake increases the risk for benign prostatic hyperplasia (6908). Epidemiological evidence suggests that taking more than 100 mg of supplemental zinc daily or taking supplemental zinc for 10 or more years doubles the risk of developing prostate cancer (10306). Another large-scale population study also suggests that men who take a multivitamin more than 7 times per week and who also take a separate zinc supplement have a significantly increased risk of prostate cancer-related mortality (15607). However, a large analysis of population research suggests that there is no association between zinc intake and the risk of prostate cancer (96075).

Pulmonary/Respiratory ...There are several hundred reports of complete loss of sense of smell (anosmia) that may be permanent with use of zinc gluconate nasal gel, such as Zicam (11306,11155,11707,16800,16801,17083,86999,87535). Loss of sense of smell is thought to be dose related but has also been reported following a single application (11306,11155,11707,16800). Patients often report having sniffed deeply when applying the gel, then experiencing an immediate burning sensation, and noticing anosmia within 48 hours (17083). On June 16, 2009, the US Food and Drug Administration (FDA) advised patients not to use a specific line of commercial zinc nasal products (Zicam) after receiving 130 reports of loss of smell (16800). The manufacturer of these products had also received several hundred reports of loss of smell related to its intranasal zinc products (16801). Zinc sulfate nasal spray was used unsuccessfully for polio prophylaxis before the polio vaccine was developed. It caused loss of smell and/or taste, which was sometimes permanent (11713). Animal studies suggest that zinc sulfate negatively affects smell, possibly by damaging the olfactory epithelium and neurons (11156,11703,11704,11705,11706). Zinc gluconate nasal spray has not been tested for safety in animals or humans. The clinical studies of intranasal zinc have not described anosmia as an adverse effect, but testing was not done to see if zinc use adversely affected sense of smell (6471,8628,8629,10247). Also, these clinical studies reported tingling or burning sensation in the nostril, dry nose, nose pain, and nosebleeds.
When used in amounts above the tolerable upper intake level (UL), zinc may cause flu-like symptoms including coughing (2663).

Renal ...In overdose, zinc can cause acute renal tubular necrosis and interstitial nephritis (331,1352,87338).

Other ...Occupational inhalation of zinc oxide fumes can cause metal fume fever with symptoms including fatigue, chills, fever, myalgias, cough, dyspnea, leukocytosis, thirst, metallic taste, and salivation (331).

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