Best Eye Vitamins: What the Clinical Evidence Actually Shows in 2026
The best-evidenced vitamins for eye health are the AREDS2 formula nutrients — lutein (10 mg), zeaxanthin (2 mg), vitamin C (500 mg), vitamin E (400 IU), and zinc (80 mg with 2 mg copper) — which together reduced the risk of advanced age-related macular degeneration (AMD) by approximately 25% in the NIH-funded AREDS2 clinical trial. As a Registered Dietitian Nutritionist, I want to be direct about what “best eye vitamins” actually means in clinical terms: the evidence applies primarily to specific conditions (AMD progression, dry eye disease), not to general vision improvement in healthy eyes. This guide gives you the clinical evidence hierarchy, the real dosing numbers, and the context needed to evaluate whether eye vitamin supplementation makes sense for your situation.
The global market for vision supplements is projected to exceed $4 billion by 2027, with thousands of products claiming to “support eye health.” Most contain either the wrong ingredients, sub-therapeutic doses, or formulations built on older research that AREDS2 has since refined. Getting the dose and ingredient selection right is as important as choosing to supplement at all.
TL;DR
- Strongest evidence: AREDS2 formula (lutein 10 mg + zeaxanthin 2 mg + vitamin C 500 mg + vitamin E 400 IU + zinc 80 mg + copper 2 mg) — reduces AMD progression risk by ~25% in intermediate AMD.
- Best evidence for dry eyes: Omega-3 DHA + EPA — reduces inflammatory mediators in tear film; earlier meta-analyses positive, though the DREAM trial (2018, NEJM) had a null result vs. olive oil placebo.
- Lutein dose matters critically: Most multivitamins contain 0.15–0.25 mg lutein; AREDS2 uses 10 mg. Verify milligrams, not just ingredient presence.
- For healthy eyes: Limited prevention evidence — dietary optimization (dark leafy greens, fatty fish) is better supported than supplementation for primary prevention.
- Beta-carotene replaced by lutein/zeaxanthin: AREDS2 made this switch after the CARET trial demonstrated increased lung cancer risk in smokers with beta-carotene supplementation.
- Product quality matters: Verify individual ingredient milligrams, not just ingredient names, and prefer third-party tested formulas.
The Evidence Standard: What Eye Vitamin Research Can and Can’t Show
Clinical research on eye vitamins spans three types: observational/epidemiological studies tracking dietary intake and disease rates, randomized controlled trials (RCTs) testing specific supplements against placebo, and mechanistic studies explaining biological pathways. These are not equivalent in evidentiary weight.
Observational studies are hypothesis-generating. They show that populations eating more lutein-rich vegetables have lower AMD rates, but cannot prove that taking isolated lutein supplements produces the same benefit — nutrition exists in a dietary matrix difficult to disaggregate from lifestyle, socioeconomic, and other nutritional factors. The landmark Women’s Health Initiative trials found that several nutrients protective in epidemiological studies failed to replicate when tested in RCTs.
The AREDS and AREDS2 trials are the highest-quality evidence in this space precisely because they are large, long-duration, NIH-funded RCTs with hard clinical endpoints: progression to advanced AMD and vision loss. They enrolled thousands of participants, ran for years, and used validated ophthalmologic outcome measures. This is why the AREDS2 formula has consensus support from the American Academy of Ophthalmology — the evidence quality distinguishes it from most supplement marketing claims.
What these trials cannot tell you: whether supplementation prevents AMD from developing in healthy eyes (they enrolled people with existing AMD), whether benefits extend to non-AMD eye conditions, or whether individual supplements in isolation replicate the combination effect.
Lutein and Zeaxanthin: The Core of Modern Eye Supplement Evidence
Lutein and zeaxanthin are carotenoids that concentrate specifically in the macula — the central region of the retina responsible for detail and color vision. They form the yellow macular pigment that filters high-energy blue light and neutralizes oxidative stress in this metabolically active tissue. The macula has the highest metabolic activity of any tissue in the body per unit weight, making antioxidant protection mechanistically plausible.
The AREDS2 trial replaced the original AREDS formula’s beta-carotene with lutein (10 mg/day) and zeaxanthin (2 mg/day). Published in JAMA Ophthalmology (2013), the AREDS2 results showed:
- In participants with low dietary lutein/zeaxanthin intake at baseline, supplementation reduced the risk of advanced AMD by 26% compared to the original beta-carotene formula
- Lutein/zeaxanthin showed no increased lung cancer risk (unlike beta-carotene), making it the preferred AREDS formulation for smokers and former smokers
- The lutein/zeaxanthin combination was superior to beta-carotene in subgroup analyses stratified by baseline dietary intake
The dosing reality check: The clinical dose is 10 mg lutein + 2 mg zeaxanthin daily. A 2019 systematic review by Eisenhauer et al. confirmed that supplemental lutein meaningfully increases macular pigment optical density (MPOD) at doses ≥6 mg/day. Standard multivitamins typically contain 150–250 micrograms of lutein — 40–65 times below the therapeutic threshold. Checking a multivitamin’s label for “lutein” tells you almost nothing about whether the dose is clinically relevant. The milligram number is everything.
For a comprehensive review of the mechanism and evidence base specifically for these two carotenoids — including MPOD measurement methodology, food sources, and bioavailability factors — see our lutein and zeaxanthin for vision guide.
The AREDS and AREDS2 Studies: The Gold Standard
Understanding the AREDS2 formula requires understanding what the trials were designed to measure and who they enrolled.
AREDS (2001): The original Age-Related Eye Disease Study enrolled 4,757 participants with varying AMD severity. After an average of 6.3 years, the combination of vitamin C (500 mg), vitamin E (400 IU), beta-carotene (15 mg), and zinc (80 mg with 2 mg copper) reduced the risk of progressing from intermediate to advanced AMD by 25% and reduced vision loss from advanced AMD by 19%. Published in Archives of Ophthalmology (2001).
AREDS2 (2013): The follow-up enrolled 4,203 participants and tested modifications to the original formula. Key findings:
- Replacing beta-carotene with lutein/zeaxanthin reduced AMD risk comparably, without the lung cancer signal seen with beta-carotene in smokers — lutein/zeaxanthin is now the standard recommendation
- Adding omega-3 fatty acids (DHA 350 mg + EPA 650 mg) to the AREDS formula did not further reduce AMD progression in the primary analysis
- Reducing zinc from 80 mg to 25 mg did not significantly change outcomes in the primary analysis, suggesting a lower dose may be sufficient for most people
- Eliminating beta-carotene is strongly recommended for current or former smokers
Critical limitation: Both AREDS and AREDS2 enrolled people with existing AMD. They were not primary prevention trials in healthy eyes. The evidence supports AREDS2 supplementation for people with documented intermediate AMD; it does not demonstrate benefit for healthy eyes without AMD signs.
The full clinical landscape of supplements for AMD specifically — including geographic atrophy progression, anti-VEGF treatment context, and neovascular AMD considerations — is detailed in our macular degeneration supplements guide.
Vitamin C for Eye Health: Antioxidant Protection and Cataract Research
Vitamin C (ascorbic acid) is concentrated in the aqueous humor of the eye at levels 15–20 times greater than plasma — a physiological priority suggesting significant biological importance in the ocular environment. The retinal pigment epithelium is particularly vulnerable to oxidative damage given the retina’s high metabolic rate and constant light exposure.
In AMD: Vitamin C at 500 mg/day is a component of the AREDS2 formula. Its primary proposed mechanism is quenching reactive oxygen species generated by high retinal metabolic activity and light exposure. As with other AREDS2 components, the evidence supports the combination formula, not vitamin C in isolation.
In cataracts: Observational evidence is stronger for cataracts than for AMD. The Iowa Women’s Health Study found that women with the highest vitamin C intake from food had significantly lower rates of nuclear cataracts over 10 years. Several RCTs testing vitamin C supplementation for cataract prevention have shown mixed results, with benefits appearing more consistently in people with initially poor vitamin C status or low dietary intake.
Dosing and safety: The AREDS2 dose (500 mg/day) is well tolerated by virtually all adults. At doses above 2,000 mg/day, vitamin C can cause gastrointestinal distress and, in individuals with a history of oxalate kidney stones, potentially increase stone risk due to oxalate conversion. The 500 mg/day AREDS2 dose is approximately 6x the RDA (75–90 mg) but far below doses that produce adverse events in clinical populations.
Vitamin E: Antioxidant Synergy in the AREDS2 Formula
Vitamin E (alpha-tocopherol) at 400 IU/day is the fourth component in the AREDS2 formula. Fat-soluble vitamin E concentrates in cell membranes, where it interrupts lipid peroxidation chain reactions — a mechanism particularly relevant in the lipid-rich photoreceptor outer segments of the retina, where polyunsaturated fatty acids are abundant and vulnerable to oxidative damage.
Evidence context: No independent vitamin E RCT has demonstrated AMD prevention or progression benefit when vitamin E is studied in isolation. The AREDS2 benefit derives from the combination of nutrients. This is a critical framing point: the evidence supports the full AREDS2 formula, not individual components supplemented selectively.
Safety and interactions: Vitamin E at 400 IU/day has antiplatelet activity. Patients taking warfarin should have INR monitored when adding AREDS2-dose vitamin E. At doses above 400 IU/day, some meta-analyses have suggested increased all-cause mortality risk in at-risk populations — the AREDS2 dose (400 IU) is a guideline ceiling, not a starting point for dose escalation.
Zinc: Retinal Health and the Mineral Backbone of AREDS
Zinc is the most abundant trace mineral in the retina, concentrated in the retinal pigment epithelium (RPE) — the layer of cells that sustains photoreceptor function and processes vitamin A. Zinc deficiency is associated with impaired dark adaptation and AMD-like retinal changes in animal models. It acts as a cofactor for multiple antioxidant enzymes in the RPE, including superoxide dismutase.
AREDS2 dose and the 80 mg vs. 25 mg question: The original AREDS used 80 mg elemental zinc per day. AREDS2 tested 25 mg zinc and found comparable primary AMD outcomes, suggesting the high zinc dose may not be necessary. The 25 mg dose has a cleaner safety profile for long-term use: 80 mg/day zinc over years can impair copper status (which is why AREDS2 includes 2 mg copper throughout), reduce HDL cholesterol, and affect immune function. Many ophthalmologists now recommend the lower zinc formulation for patients without specific evidence the higher dose adds benefit.
Beyond AMD: Zinc plays roles in vitamin A metabolism — it is required for converting retinol to retinal for rhodopsin synthesis — and zinc deficiency has been associated with night vision impairment in deficient populations. Supplementing zinc above adequacy in people with normal zinc status has not been shown to improve night vision in RCT settings.
Omega-3 Fatty Acids: Dry Eye Disease and Retinal Support
DHA (docosahexaenoic acid) is the most abundant long-chain omega-3 in the retina, comprising approximately 50–60% of the fatty acid content of photoreceptor outer segment membranes. EPA (eicosapentaenoic acid) is the primary anti-inflammatory precursor to specialized pro-resolving mediators (SPMs) including resolvins and protectins. Together these fatty acids have been studied for both dry eye disease and AMD.
Dry Eye Disease: Evidence and Nuance
The DREAM trial (Dry Eye Assessment and Management) published in NEJM (2018) was a well-powered RCT of 3,000 mg omega-3 (2,000 mg EPA + 1,000 mg DHA) vs. olive oil placebo over 12 months in 535 patients with symptomatic moderate-to-severe dry eye disease. The primary outcome (OSDI symptom score improvement) showed no statistically significant difference vs. placebo — a null result that surprised many clinicians given earlier meta-analytic findings.
Earlier systematic reviews, including Liu et al. (PLoS ONE, 2014), found statistically significant improvements in Schirmer test scores and OSDI in omega-3-treated groups across multiple smaller RCTs. The discrepancy between these positive results and DREAM may reflect the olive oil control’s own anti-inflammatory properties, differences in baseline omega-3 status between populations, or the heterogeneity of dry eye subtypes. The DREAM trial enrolled participants with more severe disease, while earlier positive trials often studied milder presentations.
Current clinical position: omega-3 supplementation is a reasonable first-line adjunctive intervention for dry eye disease given its excellent safety profile, even accounting for the DREAM null result. A 3–6 month trial at 2,000–3,000 mg/day is a low-risk, evidence-consistent approach to evaluate individual response. For a comprehensive dry eye supplement review — including meibomian gland dysfunction, anti-inflammatory diet approaches, and alternative interventions — see our dry eye supplements evidence guide.
Omega-3 and AMD
AREDS2 included an omega-3 arm (DHA 350 mg + EPA 650 mg) and found no additional AMD progression benefit beyond the base AREDS formula. Despite this null result, the biological importance of DHA in photoreceptor membrane composition and EPA’s role in anti-inflammatory signaling support omega-3 as part of a broader eye-protective dietary pattern — even if the supplementation signal in established AMD was not demonstrated in AREDS2’s primary analysis.
Vitamin A and Beta-Carotene: Necessary Cautions
Vitamin A (retinol) is essential for vision — specifically for rhodopsin synthesis in rod cells, which enables dim-light and night vision, and for the maintenance of corneal and conjunctival epithelium. Severe vitamin A deficiency causes night blindness and, in extreme cases, xerophthalmia (corneal ulceration leading to blindness), which remains the leading preventable cause of childhood blindness in developing countries.
In Western populations consuming varied diets with adequate animal protein (providing preformed retinol from liver, dairy, and eggs) and colorful produce (providing beta-carotene), true vitamin A deficiency is rare. The body regulates beta-carotene conversion to retinol based on status, providing a self-limiting safety feature not present with preformed retinol supplementation.
The CARET trial warning: The Carotene and Retinol Efficacy Trial (CARET) was stopped early when high-dose beta-carotene supplementation (30 mg/day) combined with vitamin A was found to increase lung cancer incidence by 28% and total mortality by 17% in current and former heavy smokers compared to placebo. This finding — replicated in the ATBC trial — is why AREDS2 eliminated beta-carotene from its formula and substituted lutein/zeaxanthin. Current and former smokers must not supplement beta-carotene.
Vitamin A toxicity: Preformed vitamin A (retinol) is teratogenic at high doses and should not exceed 3,000 mcg/day in women of childbearing age. Chronic high-dose supplementation can cause liver toxicity, pseudotumor cerebri, and bone mineral loss. These risks do not apply to dietary beta-carotene from food.
B Vitamins and Eye Health: Emerging AMD Evidence
B vitamins — specifically folate (B9), pyridoxine (B6), and cobalamin (B12) — have an emerging evidence base for AMD prevention through homocysteine-lowering pathways. Elevated plasma homocysteine is an independent risk factor for AMD, and these three B vitamins are essential cofactors in the methylation cycle that metabolizes homocysteine.
The Women’s Antioxidant and Folic Acid Cardiovascular Study (WAFACS) published in Archives of Internal Medicine (2009) found that daily supplementation with folate (2.5 mg), B6 (50 mg), and B12 (1 mg) reduced AMD development risk by 34% over 7.3 years in women with cardiovascular disease or risk factors. The proposed mechanism — homocysteine reduction improving endothelial function and reducing vascular oxidative stress in the choroid — is biologically coherent.
This is suggestive evidence, not definitive. The WAFACS enrolled a cardiovascular high-risk female population, limiting generalizability. No large AREDS-scale B vitamin AMD trial has been conducted. However, given that B12 and folate insufficiency are common in older adults (particularly those on metformin, proton pump inhibitors, or with reduced stomach acid), and that deficiency carries independent risks beyond eye health, ensuring B vitamin adequacy through diet or a standard B-complex supplement is a low-risk, evidence-consistent approach for older adults concerned about AMD risk.
Eye Supplement Products: Do They Deliver Clinical Doses?
The clinical evidence reviewed above requires specific doses. The gap between what the research studied and what most commercial eye supplements provide is often significant — and the marketing often obscures this gap.
What to verify on a label before purchasing:
- Lutein: minimum 6 mg, ideally 10 mg per serving (not “lutein complex” without stated milligrams)
- Zeaxanthin: 2 mg per serving
- Vitamin C: 500 mg per serving
- Vitamin E: 400 IU (268 mg alpha-tocopherol) per serving
- Zinc: 25–80 mg elemental zinc; 2 mg copper included
- For dry eyes: DHA + EPA combined ≥2,000 mg/day from triglyceride-form fish oil for superior bioavailability vs. ethyl ester forms
Products that list lutein without specifying milligrams, that bundle dozens of ingredients at trace doses, or that use proprietary blends concealing individual ingredient weights cannot be evaluated for clinical relevance. “Contains AREDS2 nutrients” is not the same as “provides AREDS2 doses.”
iGenics is one of the more extensively marketed vision supplements with clinical positioning — the full ingredient panel, dose verification against AREDS2 standards, and independent review of its formulation is covered in the iGenics review. TheYaVue takes a similar clinical approach; the TheYaVue review examines its ingredient transparency and dose accuracy against published trial standards. Vision 20 uses a different formulation architecture emphasizing zinc and antioxidant synergy; the Vision 20 review evaluates whether its zinc and carotenoid dosing meets clinical thresholds. VisiFlora takes an unusual gut-vision angle based on emerging microbiome-retinal axis research — the VisiFlora review evaluates its probiotic and prebiotic matrix against what the emerging evidence supports.
Who Benefits from Eye Vitamin Supplementation
Based on the clinical evidence, the following populations have the clearest benefit-to-risk rationale for specific eye vitamin interventions:
Intermediate AMD (one or both eyes): AREDS2 formula supplementation is supported by the strongest clinical evidence — level I RCT data with 25% relative risk reduction in progression to advanced AMD. Ophthalmologists routinely recommend AREDS2 for this population. This is the best-evidenced use case for eye supplements in any formulation.
Advanced AMD in one eye: AREDS2 supplementation to protect the fellow eye is a standard American Academy of Ophthalmology recommendation. AMD is the leading cause of central vision loss in adults over 60 in developed countries, and slowing fellow-eye progression is a meaningful outcome.
Dry eye disease (moderate to severe): Omega-3 supplementation is a reasonable first-line adjunctive intervention with a favorable safety profile. Assessing individual response over 3–6 months is the evidence-consistent approach given the mixed trial results. The full dry eye supplement landscape — including lipid layer support, anti-inflammatory approaches, and prescription options — is reviewed in our dry eye supplements evidence guide.
Older adults with low dietary lutein intake: For adults who consume little to no dark leafy greens and have a family history of AMD, lutein/zeaxanthin supplementation (10 mg/2 mg) has a favorable benefit-to-risk profile given the safety data and biological plausibility of macular pigment support. This population-risk approach is reasonable even without AMD diagnosis, particularly for individuals aged 50+ with AMD family history.
Individuals with known vitamin A deficiency: Supplementation restores night vision and prevents xerophthalmia — this is the most direct vitamin-to-vision relationship in the evidence base, with a centuries-long clinical history.
Who Probably Doesn’t Need Eye Vitamin Supplementation
Healthy adults under 50 with no AMD signs and good dietary patterns: The evidence for primary AMD prevention through supplementation in this group is weak. Diet-pattern approaches — high intake of dark leafy greens, fatty fish, and colorful vegetables consistent with a Mediterranean dietary pattern — are more broadly supported for eye disease prevention based on consistent observational evidence. The AREDS2 study authors themselves noted that the evidence applies to those with existing intermediate AMD, not healthy-eyed primary prevention.
People expecting to reverse established vision loss: No eye vitamin has demonstrated reversal of established vision loss from AMD, cataracts, or other conditions in RCT settings. The evidence is for slowing progression in people at high risk, not recovering sight already affected.
Smokers or former smokers taking beta-carotene: This combination increases lung cancer risk as demonstrated in the CARET trial. Smokers who need AREDS-formula supplementation should use the AREDS2 version (lutein/zeaxanthin substituted for beta-carotene) exclusively.
People expecting vision improvement from a standard multivitamin: Most multivitamins contain lutein at 0.1–0.25 mg, zinc at 8–11 mg, and vitamin C at 60–90 mg — all substantially below AREDS2 doses. A standard multivitamin is not a substitute for AREDS2-formula supplementation in people with AMD.
Frequently Asked Questions
What are the best vitamins for eye health?
The best-evidenced eye vitamins are the AREDS2 formula: lutein (10 mg), zeaxanthin (2 mg), vitamin C (500 mg), vitamin E (400 IU), and zinc (80 mg with 2 mg copper). This combination reduced AMD progression risk by approximately 25% in the NIH-funded AREDS2 trial. For dry eye disease, omega-3 DHA and EPA have the strongest evidence. For general prevention without existing disease, dietary optimization with dark leafy greens and fatty fish is better supported than supplementation alone.
Does taking eye vitamins actually improve your vision?
Eye vitamins slow deterioration in people with AMD — they do not improve normal vision. The AREDS2 formula reduced AMD progression risk by 25%; it did not restore vision already affected. In people with healthy eyes and no AMD signs, supplementation has not been shown to improve visual acuity in RCT settings. Expectation calibration is important: eye vitamins are a deceleration strategy for high-risk eyes, not a vision-enhancement tool for healthy ones.
What dose of lutein should I take for eye health?
The clinically studied dose is 10 mg lutein + 2 mg zeaxanthin daily (AREDS2). Most multivitamins contain 0.15–0.25 mg lutein — far below the therapeutic range. Look for supplements specifying “10 mg lutein” not just “lutein extract.” For more detail on dosing thresholds and MPOD response, the lutein and zeaxanthin for vision guide covers the pharmacokinetic data.
Are AREDS2 supplements worth taking if I don’t have macular degeneration?
The clinical trial evidence is for people with intermediate AMD, not healthy-eyed primary prevention. If you have intermediate AMD, AREDS2 is strongly supported. If you have no AMD signs, discuss with your ophthalmologist — there may be rationale based on family history and genetic risk (complement factor H, ARMS2 variants), but it’s an individual decision without RCT support for primary prevention.
What is the best eye vitamin for dry eyes?
Omega-3 fatty acids (DHA + EPA from fish oil) have the most clinical evidence for dry eye disease, though the 2018 DREAM trial returned a null primary outcome vs. olive oil placebo. Given the excellent safety profile, a 3–6 month trial of 2,000–3,000 mg omega-3 daily is a reasonable first step. Full evidence review, including alternative interventions, is in the dry eye supplements evidence guide.
Can vitamin A improve night vision?
Vitamin A supplementation restores night vision in people with true deficiency — meaningful in populations with inadequate dietary protein or absorption disorders, rare in North American and European adults eating varied diets. In well-nourished individuals, supplementation beyond adequacy does not further improve night vision. Smokers must avoid beta-carotene.
Do eye supplements interact with medications?
Yes, meaningfully. High-dose vitamin E (400 IU) increases bleeding risk with anticoagulants. High-dose zinc (80 mg) impairs copper absorption and affects antibiotic absorption timing. Omega-3 at high doses has mild antiplatelet effects. Always disclose AREDS2-dose supplements to your physician and ophthalmologist, particularly if anticoagulated.
What foods naturally contain the most lutein and zeaxanthin?
Cooked kale (~18 mg/100g), cooked spinach (~12 mg/100g), Swiss chard (~11 mg/100g), and frozen peas (~2.5 mg/100g). Egg yolks contain lower total amounts but in a highly bioavailable lipid-matrix form. Reaching 10 mg/day lutein through diet requires approximately one cup of cooked leafy greens daily — achievable with deliberate meal planning but inconsistent for many adults.
The Bottom Line
The clinical evidence for eye vitamins is more specific and more rigorous than most of the supplement category, thanks primarily to the NIH-funded AREDS2 trial. That specificity is both the strength and the limitation: the evidence applies to intermediate AMD progression at specific doses that most multivitamins do not provide.
If you have intermediate AMD, AREDS2-formula supplementation is one of the best-supported supplement interventions across all health categories. If you have dry eye disease, omega-3 supplementation is worth a 3–6 month trial given the risk-benefit profile. If your eyes are healthy and your diet includes regular dark leafy greens and fatty fish, the additional prevention benefit from supplementation is probably marginal.
The questions to ask any eye supplement: what is the lutein dose in milligrams (not just “contains lutein”), does it match the AREDS2 formula if AMD is your concern, and has the manufacturer provided third-party testing verification for potency and purity? Matching the AREDS2 dose profile — not just the ingredient list — is what separates clinically relevant formulations from label marketing.
Ophthalmologist oversight is essential for anyone with diagnosed AMD. Self-selecting AREDS2 supplementation without baseline fundus photography to confirm AMD stage means supplementing without knowing if you are in the population the evidence actually addresses. Start with an eye exam.
Our methodology and reviewer credentials are described on the About page. Our product review methodology and disclosure practices are detailed on our disclosure page.
These statements have not been evaluated by the FDA. These products are not intended to diagnose, treat, cure, or prevent any disease. The information in this article is for educational purposes only and does not constitute medical advice. Consult a qualified healthcare professional — including a board-certified ophthalmologist for eye health concerns — before starting any supplement program, especially if you have a diagnosed eye condition, are pregnant, or take prescription medications.