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Vitamin A

Evidence Level
Moderate
7 Clinical Trials
7 Documented Benefits
3/5 Evidence Score

Vitamin A is a fat-soluble nutrient essential for vision, immune defense, reproduction, and epithelial cell differentiation. It exists as preformed vitamin A (retinol and retinyl esters) from animal sources — liver, dairy, eggs — and as provitamin A carotenoids (primarily beta-carotene) from orange and dark green plants. Deficiency is the leading cause of preventable childhood blindness worldwide and substantially increases child mortality from measles, diarrhea, and respiratory infections. Modern intake is measured as Retinol Activity Equivalents (RAE) to account for the lower conversion efficiency of plant carotenoids. Important framing for readers in the US and other high-income countries: deficiency here is rare, and the large mortality benefits described on this page were measured in vitamin A-deficient children in low- and middle-income countries. They do not transfer to a well-nourished adult. Randomized trials in well-nourished adults have found no mortality benefit from vitamin A or beta-carotene supplements, and two large trials found increased lung cancer in smokers. For most people the useful question is not how much vitamin A to supplement, but whether they are deficient at all.

Studied Dose RDA: 700 mcg RAE/day for women, 900 mcg RAE/day for men (NIH ODS). Tolerable Upper Intake Level: 3,000 mcg/day of PREFORMED vitamin A (retinol and retinyl esters) - per NIH ODS the UL 'applies only to products from animal sources and supplements whose vitamin A comes entirely from retinol or its ester forms', not to beta-carotene. Pediatric mortality trials used a supervised public-health dose of 200,000 IU (60 mg retinol) every 4-6 months in children 12-59 months, and 100,000 IU (30 mg) in infants 6-11 months. These are mass-campaign doses for deficient populations, not a self-supplementation regimen for anyone reading this page.
Active Compound Retinol (preformed, animal) and beta-carotene (provitamin A, plants). 1 mg retinol = 1,000 mcg RAE. For beta-carotene the conversion depends on the source: 12 mcg of DIETARY beta-carotene = 1 mcg RAE, but only 2 mcg of SUPPLEMENTAL beta-carotene = 1 mcg RAE (NIH ODS). Beta-carotene in a capsule is roughly six times more potent per microgram than beta-carotene in food - which is why supplement doses reach exposures that diet never does.
Deficiency information View details

Vitamin A deficiency is rare in the US but remains the world's leading preventable cause of childhood blindness in developing countries. WHO estimates 250,000-500,000 children become blind from vitamin A deficiency each year, with about half dying within 12 months. The first sign is usually night blindness; severe deficiency causes irreversible eye damage.

Common symptoms

  • Night blindness (nyctalopia) — difficulty seeing in low light
  • Dry eyes, reduced tear production (xerophthalmia)
  • Bitot spots — foamy, white patches on the whites of the eyes
  • Corneal drying, ulceration, or scarring (advanced)
  • Permanent blindness (severe, untreated cases)
  • Frequent infections, especially respiratory and diarrheal
  • Dry, rough skin or follicular hyperkeratosis
  • Slow growth in children
  • Anemia

At-risk groups

  • Children in low-income countries with limited dietary variety
  • Pregnant women in developing countries (maternal night blindness affects 5-10% in some regions)
  • Premature infants (limited liver stores at birth)
  • People with fat malabsorption (cystic fibrosis, celiac disease, pancreatic insufficiency, biliary disease)
  • People who've had bariatric surgery, especially biliopancreatic diversion
  • People with chronic alcohol use disorder
  • People with very limited diets or anorexia
When to see a doctor: Difficulty seeing at night or in dim light — especially after gradually worsening over weeks — should be evaluated promptly, particularly in pregnant women or anyone with fat malabsorption. Important: vitamin A is fat-soluble and accumulates in the body. Do NOT take high-dose vitamin A (>10,000 IU/day) without medical guidance — toxicity causes liver damage, and excess during pregnancy causes severe birth defects.
Explore related deficiencies →
Sources: NIH ODS — Vitamin A Health Professional Fact Sheet · Xerophthalmia — StatPearls (NBK431094)

Benefits

Childhood Mortality Reduction in Vitamin A-Deficient Populations (Not a Benefit for Well-Nourished Adults)

Vitamin A supplementation in regions with endemic deficiency reduces all-cause childhood mortality by approximately 12% (risk ratio 0.88, 95% CI 0.83-0.93), with diarrhea-specific mortality also reduced by about 12% (RR 0.88, 95% CI 0.79-0.98). The Cochrane evidence synthesis covered 47 trials in roughly 1.2 million children aged 6-59 months. The effect is largest in children 6-59 months and is primarily driven by reduced deaths from diarrhea and measles. This 'one-third' figure carries no citation and is not supported by the trial evidence. DEVTA (Awasthi et al., Lancet 2013), a cluster-randomised trial in roughly 1 million pre-school children in north India that recorded 25,000 deaths, found no significant mortality benefit on its own: mortality ratio 0.96 (95% CI 0.89-1.03, p=0.22). Its authors wrote that DEVTA 'contradicts the expectation from other trials that vitamin A supplementation would reduce child mortality by 20-30%.' Those same authors, pooling DEVTA with eight earlier trials, still found a real but modest average reduction of 11% (95% CI 5-16, p=0.00015), which they described as reliably contradicting the hypothesis of no effect - close to Cochrane's 12%. The honest summary is therefore a roughly 10-12% mortality reduction in deficient children, not a third. The Cochrane review also found NO reduction in measles mortality (RR 0.88, 95% CI 0.69-1.11), respiratory-disease mortality (RR 0.98, 95% CI 0.86-1.12), or hospitalisation for diarrhea or pneumonia. None of this evidence comes from a well-nourished adult population.

Supported by Trial 1, Trial 3

Measles Treatment: A WHO Clinical Protocol for Deficient or High-Fatality Settings, Not a Consumer Supplement Use

WHO recommends high-dose vitamin A (200,000 IU on two consecutive days) for all children with measles in regions with vitamin A deficiency or high case-fatality. In the systematic review behind this recommendation (D'Souza & D'Souza 2002, five trials, 445 vitamin A vs 478 placebo), the POOLED effect on overall measles mortality across all trials was NOT statistically significant: RR 0.61, 95% CI 0.32-1.12. Only in the subgroup given 200,000 IU on two consecutive days, in hospital, in areas of high case fatality, was mortality reduced - by 64% (RR 0.36, 95% CI 0.14-0.82), with pneumonia-specific mortality reduced 67% (RR 0.33, 95% CI 0.08-0.92). Note separately that PREVENTIVE vitamin A supplementation did not reduce measles mortality in the 2022 Cochrane review (RR 0.88, 95% CI 0.69-1.11, 6 studies, 1,088,261 children). Effects are most pronounced in children under 2 years. A single 200,000 IU dose alone showed no mortality benefit — the two-dose protocol is essential.

Supported by Trial 2, Trial 1

Night Blindness and Xerophthalmia Treatment

Night blindness is the earliest symptomatic sign of vitamin A deficiency, progressing to xerophthalmia (corneal drying), Bitot's spots, keratomalacia, and ultimately permanent blindness. Vitamin A supplementation rapidly reverses night blindness and halts progression of xerophthalmia. An estimated 250,000-500,000 vitamin A-deficient children become blind annually worldwide, with half dying within 12 months. Sommer's Indonesian trials established that even subclinical deficiency causing night blindness is a late-stage sign of severe systemic deficiency.

Supported by Trial 3, Trial 1

Vision and Retinal Function

Retinal is the form of vitamin A directly used by photoreceptors. In rod cells, 11-cis-retinal combines with opsin protein to form rhodopsin — the visual pigment responsible for low-light vision. When a photon hits rhodopsin, 11-cis-retinal isomerizes to all-trans-retinal, triggering the visual cascade. Adequate vitamin A intake is required to regenerate the cycle. Deficiency manifests first as night blindness because rod-mediated dim-light vision fails before cone-mediated daylight vision.

Supported by Trial 3, Trial 1

Immune Function and Mucosal Barrier Integrity

Vitamin A maintains the integrity of mucosal epithelia in the respiratory, gastrointestinal, and genitourinary tracts — the body's first physical barriers against pathogens. Retinoic acid also directs T-cell differentiation toward gut-homing phenotypes and supports regulatory T-cell function via the gut-associated lymphoid tissue. This explains why vitamin A DEFICIENCY increases susceptibility to mucosal infections. What supplementation actually delivers is narrower than the mechanism suggests: in the 2022 Cochrane review of deficient children it reduced diarrhoea incidence (RR 0.85, 95% CI 0.82-0.87) and measles incidence (RR 0.45, 95% CI 0.30-0.69, but on only 2 trials and 1,982 children, low-certainty), while showing NO effect on respiratory-disease incidence (RR 0.99, 0.92-1.06), respiratory-disease mortality (RR 0.98, 0.86-1.12), measles mortality (RR 0.88, 0.69-1.11) or hospitalisation for diarrhoea or pneumonia. There is no evidence that supplementing an already-replete adult improves immune outcomes.

Supported by Trial 1

Epithelial Cell Differentiation and Skin Health

All-trans retinoic acid, the active metabolite of vitamin A, binds nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs) to regulate gene transcription for cellular differentiation, growth, and apoptosis. This is the mechanism behind pharmaceutical retinoids (tretinoin, isotretinoin) used for acne and photoaging. Dietary vitamin A supports normal skin keratinization, sebaceous gland function, and epithelial turnover — though supplemental doses for cosmetic effects in adequately nourished people show modest benefit and carry toxicity risk.

Supported by Trial 4, Trial 3

Reproductive and Embryonic Development

Vitamin A is essential for spermatogenesis in men and for embryonic development of the heart, eyes, ears, limbs, and central nervous system. Deficiency during pregnancy increases risk of maternal night blindness, anemia, and infant mortality. However, excess preformed vitamin A during pregnancy is teratogenic — particularly during the first trimester — and is a strict contraindication. The therapeutic window is narrow: pregnant women should not exceed 3,000 mcg/day of preformed vitamin A.

Supported by Trial 1, Trial 3

Mechanism of action

1

Nuclear Receptor Activation (RAR and RXR)

The active metabolite all-trans retinoic acid binds retinoic acid receptors (RARα, β, γ) and 9-cis retinoic acid binds retinoid X receptors (RXRα, β, γ). These nuclear receptors form heterodimers that bind retinoic acid response elements (RAREs) in DNA, regulating transcription of hundreds of genes involved in differentiation, immune function, and metabolism. This is the primary signaling mechanism through which vitamin A controls cellular identity and tissue homeostasis.

2

Rhodopsin and the Visual Cycle

Vitamin A is converted to 11-cis-retinal, which combines with the protein opsin in retinal rod photoreceptors to form rhodopsin — the visual pigment of dim-light vision. Photon absorption isomerizes 11-cis-retinal to all-trans-retinal, triggering the phototransduction cascade. The retinal is then reduced, transported back to the retinal pigment epithelium, re-isomerized, and reused. Inadequate vitamin A breaks this cycle, producing night blindness as the first deficiency symptom.

3

Mucosal Epithelial Differentiation

Retinoic acid drives normal differentiation of mucus-secreting epithelial cells throughout the respiratory, GI, and genitourinary tracts. Deficiency causes squamous metaplasia — the replacement of mucus-secreting cells with keratinized squamous cells that lose barrier function and antimicrobial defense. This histological change underlies the increased susceptibility to mucosal infections (diarrhea, pneumonia, measles complications) characteristic of vitamin A deficiency.

4

Immune Cell Differentiation and Gut Homing

Retinoic acid produced by intestinal dendritic cells imprints gut-homing receptors (α4β7 integrin and CCR9) on T-cells and B-cells, directing them to mucosal sites. It also promotes regulatory T-cell differentiation in the gut, supporting oral tolerance and mucosal homeostasis. This explains why vitamin A status particularly affects gut and respiratory immunity, and why deficiency leads to disproportionate mucosal infection mortality.

5

Carotenoid Conversion via BCO1

Dietary beta-carotene is enzymatically cleaved by beta-carotene oxygenase 1 (BCO1) in intestinal mucosal cells to produce two molecules of retinal. Conversion is regulated by vitamin A status — efficiency drops when retinol stores are adequate, providing a natural safety mechanism against carotenoid-mediated hypervitaminosis. Common BCO1 polymorphisms reduce conversion by 30-70% in some individuals, explaining why plant-source-only diets may not provide adequate vitamin A despite high beta-carotene intake.

6

Hepatic Storage and Plasma Transport

Roughly 80-90% of body vitamin A is stored in hepatic stellate cells as retinyl esters. The liver releases retinol bound to retinol-binding protein 4 (RBP4) and transthyretin, maintaining tight homeostatic control of circulating concentrations across a wide range of dietary intakes. This storage buffer means clinical deficiency develops slowly — months of inadequate intake — but also means hepatic toxicity from chronic excess builds gradually before symptoms appear.

Clinical trials

1
Vitamin A Supplementation and Childhood Mortality — Cochrane Evidence Synthesis

Cochrane systematic review and meta-analysis (NOT a single clinical trial) of vitamin A supplementation in children aged 6 months to 5 years; Imdad et al. 2022, CD008524.pub4, PMID 35294044. Its all-cause mortality meta-analysis is dominated by one trial, DEVTA (~1 million children, itself null), whose inclusion cut the pooled estimate roughly in half versus the pre-2017 versions of this review. Pooled 47 randomized clinical trials, 40 placebo-controlled and 7 comparing to usual treatment. Outcomes included all-cause mortality, cause-specific mortality, and ophthalmologic signs of deficiency.

Approximately 1.2 million children aged 6 months to 5 years across 47 trials in developing countries.

All-cause mortality reduced by 12% (RR 0.88, 95% CI 0.83-0.93; 19 trials, 1,202,382 children; high-certainty evidence). Diarrhea-specific mortality reduced by 12% (RR 0.88, 95% CI 0.79-0.98; 9 trials; high-certainty). Night blindness (RR 0.32), Bitot's spots (RR 0.42), vitamin A deficiency (RR 0.71) and diarrhoea incidence (RR 0.85) were reduced; measles incidence was reduced (RR 0.45) but on only 2 trials and 1,982 children, low-certainty. IMPORTANTLY, the review found NO evidence of a difference for measles mortality (RR 0.88, 95% CI 0.69-1.11), respiratory-disease mortality (RR 0.98, 95% CI 0.86-1.12), respiratory-disease incidence (RR 0.99, 95% CI 0.92-1.06), meningitis, or hospitalisation for diarrhea or pneumonia. A 24% figure appears only as a random-effects sensitivity estimate (RR 0.76) and was the headline of the superseded pre-DEVTA 2010 version of this review. Vomiting in the 48 hours following supplementation was the only common adverse effect. Quality of evidence rated high for all-cause and diarrhea mortality outcomes. The foundational evidence supporting WHO and UNICEF global supplementation programs.

2
Vitamin A for Measles Treatment — Pooled Pediatric Analysis

Systematic review and meta-analysis (NOT a single clinical trial): D'Souza RM & D'Souza R, J Trop Pediatr 2002;48(6):323-7, PMID 12521271. Compares vitamin A vs placebo in children with measles. Five trials met inclusion criteria, four conducted in African hospitals and one in a community setting. Stratified by dose (single 200,000 IU vs two-day 200,000 IU protocol) and age.

923 children aged 6 months to 13 years (445 vitamin A, 478 placebo).

Across all five trials pooled, the effect on overall mortality was NOT statistically significant (RR 0.61, 95% CI 0.32-1.12; a 39% reduction that could not be distinguished from chance). In the subgroup given two-day 200,000 IU in hospital in high-case-fatality areas, overall mortality fell 64% (RR 0.36, 95% CI 0.14-0.82) and pneumonia-specific mortality 67% (RR 0.33, 95% CI 0.08-0.92). Effect strongest in children under 2 (RR 0.17). Single 200,000 IU dose alone did not reduce mortality — the two-dose protocol is essential. Forms the basis of WHO's current measles treatment protocol.

3
Sommer Indonesian Childhood Mortality Trial

Landmark community trial in northern Sumatra, Indonesia (Sommer et al., Lancet 1986, PMID 2871418). 450 villages were cluster-randomised - 229 to a vitamin A distribution scheme, 221 to serve as controls for one year. The report describes no placebo: control villages simply received no capsule, so the trial was unmasked and randomisation was by village, not by individual child. 25,939 preschool children were examined at baseline; children over 1 year received 200,000 IU capsules from local volunteers, repeated at 6 months. Re-examination was at 11-13 months. Established the relationship between subclinical vitamin A deficiency and child mortality independent of blindness outcomes.

Approximately 26,000 preschool-aged children in rural Indonesia.

Vitamin A supplementation reduced mortality by approximately one-third in children with subclinical deficiency. Demonstrated that even 'mild' vitamin A deficiency (presenting as night blindness or Bitot's spots) was associated with roughly 4-times-higher mortality and with at least 16% of all deaths in children aged 1-6 years - though these two figures come from a SEPARATE observational cohort by the same group (Sommer et al., Lancet 1983, ~3,481 children re-examined every 3 months for 18 months, PMID 6136744), not from this randomized trial. The 1986 trial itself rested on a small absolute number of deaths: 75/10,231 in control villages versus 53/10,919 in supplemented villages over about one year. Reframed vitamin A from a vision nutrient to a mortality-reducing intervention.

4
Age-Related Eye Disease Study (AREDS) for Macular Degeneration

Multi-center randomized placebo-controlled trial conducted by the US National Eye Institute; AREDS Report No. 8, Arch Ophthalmol 2001;119(10):1417-36, PMID 11594942. Four arms: antioxidants (vitamin C 500 mg, vitamin E 400 IU, beta-carotene 15 mg); zinc 80 mg + copper 2 mg; both; or placebo. Mean follow-up 6.3 years. Tested whether daily nutritional supplementation could slow progression of age-related macular degeneration (AMD). Original AREDS formula contained 15 mg beta-carotene alongside vitamins C, E, zinc, and copper.

3,640 participants aged 55-80 years with varying stages of AMD.

Over a mean 6.3 years, the ANTIOXIDANTS-PLUS-ZINC arm reduced the odds of progression to advanced AMD (odds ratio 0.72, 99% CI 0.52-0.98). Critically, the antioxidant-only arm - the arm that isolates beta-carotene, C and E - was NOT statistically significant (OR 0.80, 99% CI 0.59-1.09), and zinc alone was OR 0.75 (99% CI 0.55-1.03). AREDS therefore does not establish an eye benefit for beta-carotene or vitamin A on their own; the significant result came from the combination that included zinc. However, beta-carotene was later linked to increased lung cancer risk in smokers, leading to AREDS2 — which replaced beta-carotene with lutein/zeaxanthin and showed equivalent or superior AMD protection without the lung cancer risk. Current AREDS2 formula is the standard of care for intermediate AMD.

5
Beta-Carotene and Retinol Efficacy Trial (CARET)

Large randomized placebo-controlled clinical trial of high-dose beta-carotene (30 mg/day) plus retinyl palmitate (25,000 IU/day) for lung cancer chemoprevention in smokers and asbestos-exposed workers. Stopped early due to harm signal.

18,314 high-risk adults — current/former smokers and asbestos-exposed workers; 4-year intervention.

Unexpected 28% increase in lung cancer incidence and 17% increase in all-cause mortality in the intervention group vs placebo. Trial terminated 21 months early. Established that high-dose supplemental beta-carotene is harmful in current and former smokers. Critical safety finding informing current supplement guidance against high-dose beta-carotene in smokers.

6
Alpha-Tocopherol Beta-Carotene (ATBC) Lung Cancer Prevention Trial

Large-scale Finnish randomized placebo-controlled clinical trial in male smokers. 2×2 factorial design testing alpha-tocopherol (50 mg/day), beta-carotene (20 mg/day), both, or placebo for lung cancer prevention. Mean follow-up 5-8 years.

29,133 Finnish male smokers aged 50-69.

Beta-carotene arm showed 18% increase in lung cancer incidence and 8% increase in total mortality vs no beta-carotene. Independently confirmed the CARET safety signal. Effect not seen with alpha-tocopherol. These two trials together established that high-dose supplemental beta-carotene is contraindicated in current/former smokers — a finding that reshaped supplement formulation across the industry.

7
AREDS2 10-Year Follow-Up on Beta-Carotene Substitution

Epidemiologic follow-up of the AREDS2 clinical trial; Chew EY et al., AREDS2 Report 28, JAMA Ophthalmol 2022;140(7):692-698, PMID 35653117. Conducted Dec 2012 - Dec 2018. Compared 10-year lung cancer and advanced AMD outcomes in participants originally randomized to beta-carotene vs lutein/zeaxanthin in the AMD supplementation formula. Self-reported lung cancer validated with medical records.

3,882 AREDS2 participants (mean age 72; 57.7% women), 6,351 eyes.

10-year lung cancer odds ratio 1.82 (95% CI 1.06-3.12) for beta-carotene vs 1.15 (0.79-1.66) for lutein/zeaxanthin. Risk persisted even after participants stopped beta-carotene in the last 5 years of follow-up. Lutein/zeaxanthin was equivalent or superior for AMD progression without lung cancer signal. Confirmed long-term safety concern with supplemental beta-carotene in current/former smokers.

Side effects and drug interactions

Common Potential side effects

Acute hypervitaminosis A from very high single doses (>660,000 IU adults, >300,000 IU children) — nausea, vomiting, vertigo, headache, blurred vision.
Chronic hypervitaminosis A from prolonged daily intake above 10,000 IU (3,000 mcg) of PREFORMED vitamin A — dry skin, hair loss, cheilitis (cracked lips), bone pain, fatigue, and elevated liver enzymes.
Teratogenic at high doses — supplemental preformed vitamin A above 3,000 mcg/day during pregnancy increases risk of birth defects, especially in the first trimester. Strict contraindication.
Reduced bone mineral density and increased hip fracture risk associated with long-term high intake of PREFORMED retinol in observational studies - not randomized trials, so causation is not established. Melhus 1998 (Sweden; 247 women with a first hip fracture vs 873 age-matched controls, drawn from a cohort of 66,651): every 1 mg/day increase in retinol raised hip-fracture risk 68% (95% CI 18-140%), and intake above 1.5 mg/day versus below 0.5 mg/day roughly doubled hip-fracture risk (OR 2.1, 95% CI 1.1-4.0) with 10% lower femoral-neck and 14% lower lumbar-spine bone density. Feskanich 2002 (Nurses' Health Study; 72,337 postmenopausal women, 18 years, 603 hip fractures): highest quintile of total vitamin A intake (>=3,000 mcg RE/day) RR 1.48 (95% CI 1.05-2.07), driven by retinol (RR 1.89, 95% CI 1.33-2.68). Beta-carotene was NOT associated with fracture risk (RR 1.22, 95% CI 0.90-1.66). Note the signal was present for retinol from FOOD as well as supplements, so it is not a supplement-specific effect.
Bulging fontanel (transient intracranial pressure increase) reported rarely in infants given high-dose vitamin A.
Beta-carotene from plant FOOD does not cause hypervitaminosis A — conversion is down-regulated when stores are adequate, and carotenodermia (a harmless orange skin tint) is the only common effect of very high dietary intake. This does NOT mean beta-carotene SUPPLEMENTS are harmless: in the ATBC trial (29,133 male smokers, 20 mg/day) beta-carotene raised lung cancer incidence 18%, and in CARET (18,314 smokers and asbestos-exposed workers, 30 mg/day plus retinyl palmitate) it raised lung cancer 28% and all-cause mortality 17%, with the trial stopped early for harm. The AREDS2 10-year follow-up found lung cancer odds still elevated (OR 1.82, 95% CI 1.06-3.12) years after beta-carotene was stopped. Anyone who currently smokes or has smoked should not take beta-carotene supplements.
Vomiting within 48 hours of high-dose supplementation in young children — the most consistent adverse effect in the 2022 Cochrane pediatric supplementation analysis (RR 1.97, 95% CI 1.44-2.69; 4 trials, 10,541 children).

Important Drug interactions

Retinoids (isotretinoin, acitretin, tretinoin) — strict contraindication; combining pharmaceutical retinoids with supplemental vitamin A creates additive toxicity including severe hypervitaminosis.
Orlistat — reduces absorption of all fat-soluble vitamins including vitamin A; users on long-term orlistat should take a multivitamin containing vitamin A several hours apart from medication.
Warfarin — very high doses of vitamin A have been reported to enhance anticoagulant effect, though the evidence is old and thin and the NIH Office of Dietary Supplements does not list anticoagulants among vitamin A drug interactions; tell your prescriber about high-dose supplements so INR can be checked. This does NOT apply to direct oral anticoagulants such as dabigatran, apixaban or rivaroxaban, which are not monitored by INR at all.
Bile acid sequestrants (cholestyramine, colestipol) — reduce fat-soluble vitamin absorption; separate doses by 4+ hours.
Tetracycline antibiotics (minocycline, doxycycline) — combining with vitamin A may increase intracranial pressure (pseudotumor cerebri); avoid concurrent high-dose use.
Hepatotoxic medications — combining chronic high-dose vitamin A with medications that stress the liver (acetaminophen, methotrexate, amiodarone) may compound hepatic toxicity risk.
Pregnancy — preformed vitamin A above 3,000 mcg/day during pregnancy is teratogenic; beta-carotene from food is safe; check prenatal vitamins for retinol content vs beta-carotene form.

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Frequently asked questions about Vitamin A

How much vitamin A should I take?

The RDA is about 900 mcg RAE for men and 700 mcg for women (roughly 3,000 and 2,300 IU). Many multivitamins use a mix of preformed vitamin A (retinol) and beta-carotene. Most people in the US already meet the RDA from food (liver, dairy, eggs, and orange/dark-green vegetables), so supplementation is usually unnecessary unless you have a documented deficiency or a condition that impairs fat absorption. Avoid high-dose preformed vitamin A long-term, since it accumulates in the liver; the tolerable upper limit is 3,000 mcg/day of preformed vitamin A (about 10,000 IU) for adults.

What is the difference between retinol and beta-carotene?

Preformed vitamin A (retinol or retinyl palmitate), from animal foods, is used directly and can build to toxic levels if overdone. Beta-carotene from food is converted to vitamin A only as needed, so it does not cause hypervitaminosis A. But 'no hypervitaminosis' is not the same as 'safe at any dose': in the ATBC and CARET trials, high-dose supplemental beta-carotene (20-30 mg/day) increased lung cancer incidence by 18-28% in smokers and former smokers, and CARET was halted early for harm. Beta-carotene in a capsule is also absorbed far more efficiently than beta-carotene in food (2 mcg = 1 mcg RAE supplemental, versus 12 mcg = 1 mcg RAE dietary), so supplement doses create exposures diet does not. Many supplements blend the two forms.

What is vitamin A good for?

Vitamin A is essential for vision (especially night vision), immune function, skin, and cell growth. Essential, however, means you need ENOUGH - not that more is better. The dramatic benefits in the research literature (fewer child deaths, reversal of night blindness, fewer measles complications) were all measured in populations that were deficient. In well-nourished adults, randomized trials of vitamin A and beta-carotene supplements have not shown a mortality or disease-prevention benefit, and some found harm. It is fat-soluble, so it is stored in the body and absorbed best with dietary fat.

Can you take too much vitamin A?

Yes, preformed vitamin A is one of the more toxic vitamins in excess, causing headache, liver issues, and bone problems over time, and birth defects in pregnancy. Beta-carotene does not cause hypervitaminosis A, but calling it 'much safer' is too simple: supplemental beta-carotene increased lung cancer in smokers in both the ATBC and CARET trials, and the AREDS2 follow-up found the risk persisted for years after stopping. If you smoke or used to smoke, avoid beta-carotene supplements. Pregnant women should not take high-dose retinol without medical guidance. Chronic excess preformed retinol has also been linked to lower bone density and higher hip-fracture risk in observational studies.

What is Vitamin A?

Vitamin A is a fat-soluble nutrient essential for vision, immune defense, reproduction, and epithelial cell differentiation. It exists as preformed vitamin A (retinol and retinyl esters) from animal sources — liver, dairy, eggs — and as provitamin A carotenoids (primarily beta-carotene) from orange and dark green plant…

What is Vitamin A used for?

Vitamin A is researched primarily for Immune Support and Eye Health. Vitamin A supplementation in regions with endemic deficiency reduces all-cause childhood mortality by approximately 12% (risk ratio 0.88, 95% CI 0.83-0.93), with diarrhea-specific mortality also reduced by about 12% (RR 0.88, 95% CI 0.79-0.

What are the signs of Vitamin A deficiency?

Vitamin A deficiency is rare in the US but remains the world's leading preventable cause of childhood blindness in developing countries. WHO estimates 250,000-500,000 children become blind from vitamin A deficiency each year, with about half dying within 12 months.

What is the recommended dosage of Vitamin A?

The clinically studied dose is RDA: 700 mcg RAE/day for women, 900 mcg RAE/day for men (NIH ODS). Tolerable Upper Intake Level: 3,000 mcg/day of Preformed vitamin A (retinol and retinyl esters) - per NIH ODS the UL 'applies only to products from animal sources and supplements whose vitamin… Always follow the product label and check with a healthcare provider for personal advice.

Is Vitamin A safe, and does it have side effects?

For most healthy adults, Vitamin A is well tolerated at studied doses. Reported effects can include: Acute hypervitaminosis A from very high single doses (>660,000 IU adults, >300,000 IU children) — nausea, vomiting, vertigo, headache, blurred vision. It may also interact with some medications. Vitamin A is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Vitamin A interact with any medications?

Possible interactions include: Retinoids (isotretinoin, acitretin, tretinoin) — strict contraindication; combining pharmaceutical retinoids with supplemental vitamin A creates additive toxicity including severe hypervitaminosis. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Vitamin A?

NutraSmarts rates the evidence for Vitamin A as Moderate (3 out of 5). It is backed by 7 clinical trials and 13 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(13 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Sommer A, Tarwotjo I, Djunaedi E, West KP Jr, Loeden AA, Tilden R, Mele L. Impact of vitamin A supplementation on childhood mortality. A randomised controlled community trial. Lancet. 1986;1(8491):1169-73. doi: 10.1016/s0140-6736(86)91157-8.PubMedUsed to support: Community trial in northern Sumatra, Indonesia. 450 villages cluster-randomised: 229 to a vitamin A distribution scheme, 221 to serve as OPEN CONTROLS for one year (there was no placebo and no individual randomisation). 25,939 pre-school children examined at baseline and again at 11-13 months; 200,000 IU capsules given to children over 1 year by local volunteers, repeated at 6 months. Among children 12-71 months, mortality was 75/10,231 (7.3 per 1000) in control villages versus 53/10,919 (4.9 per 1000) in supplemented villages, p<0.05 - a ~34% relative reduction resting on 128 total deaths. Foundational for the deficient-child mortality hypothesis, but it is a single one-year open-control cluster trial in a severely deficient 1980s Indonesian population, and its result was not reproduced by DEVTA in ~1 million children.
  2. Imdad A, Mayo-Wilson E, Haykal MR, Regan A, Sidhu J, Smith A, Bhutta ZA. Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age. Cochrane Database Syst Rev. 2022;3(3):CD008524. doi: 10.1002/14651858.CD008524.pub4.PubMedUsed to support: Cochrane systematic review, 47 studies, ~1,223,856 children aged 6-59 months, almost all in low- and middle-income countries. HEADLINE RESULT: all-cause mortality reduced 12% (RR 0.88, 95% CI 0.83-0.93; 19 trials, 1,202,382 children; high-certainty). Diarrhoea mortality also 12% (RR 0.88, 0.79-0.98). Deficiency signs improved markedly: night blindness RR 0.32, Bitot's spots RR 0.42, vitamin A deficiency RR 0.71, diarrhoea incidence RR 0.85. EQUALLY IMPORTANT NULLS: no evidence of a difference for measles mortality (RR 0.88, 0.69-1.11), respiratory-disease mortality (RR 0.98, 0.86-1.12), respiratory-disease incidence (RR 0.99, 0.92-1.06), meningitis, or hospitalisation for diarrhea/pneumonia. Vomiting within 48 hours was increased (RR 1.97, 1.44-2.69). The 24% figure that appears elsewhere is the random-effects sensitivity estimate (RR 0.76) and was the headline of the superseded pre-DEVTA 2010 version. The 2022 update identified NO new eligible RCTs. Population caveat: this is deficient children in LMICs and does not generalise to a well-nourished adult.
  3. The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med. 1994;330(15):1029-35. doi: 10.1056/NEJM199404143301501.PubMedUsed to support: ATBC: randomized, double-blind, placebo-controlled, 2x2 factorial trial in 29,133 Finnish male smokers aged 50-69, 5-8 years follow-up. Beta-carotene 20 mg/day did NOT prevent lung cancer and was associated with an 18% increase in lung cancer incidence and an 8% increase in total mortality. Alpha-tocopherol showed no such effect. NOTE THE POPULATION: these were well-nourished adults in a high-income Western country - the closest match on this page to the reader of a US supplement label - and the direction of the result is harm, not benefit. Together with CARET this is the primary evidence base for the standing advice that current and former smokers should not take beta-carotene supplements.
  4. Omenn GS, Goodman GE, Thornquist MD, Balmes J, Cullen MR, Glass A, Keogh JP, Meyskens FL, Valanis B, Williams JH, Barnhart S, Hammar S. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med. 1996;334(18):1150-5. doi: 10.1056/NEJM199605023341802.PubMedUsed to support: CARET: randomized, double-blind, placebo-controlled trial in 18,314 current/former smokers and asbestos-exposed adults; average 4 years of intervention. THE INTERVENTION INCLUDED PREFORMED VITAMIN A - beta-carotene 30 mg/day PLUS retinyl palmitate 25,000 IU/day - which makes it the largest randomized test of supplemental preformed vitamin A in Western adults on this page. Result: 28% more lung cancer and 17% higher all-cause mortality in the intervention group; the trial was stopped 21 months early for harm. Direction of evidence is harm.
  5. Rothman KJ, Moore LL, Singer MR, Nguyen US, Mannino S, Milunsky A. Teratogenicity of high vitamin A intake. N Engl J Med. 1995;333(21):1369-73. doi: 10.1056/NEJM199511233332101.PubMedUsed to support: Prospective cohort of 22,748 pregnancies (NOT a randomized trial). Intake of more than 10,000 IU/day of preformed vitamin A from SUPPLEMENTS was associated with a markedly increased risk of cranial-neural-crest birth defects; among babies born to women taking >10,000 IU/day, about 1 in 57 had a defect attributable to the supplement. The study examined preformed vitamin A only; carotenoids were not assessed. This is the basis for the preformed-vitamin-A teratogenicity warning in pregnancy and for keeping the upper limit at 3,000 mcg/day of preformed vitamin A. Observational design, so residual confounding cannot be fully excluded, but the finding is the foundation of current regulatory guidance.
  6. Sommer A, Tarwotjo I, Hussaini G, Susanto D. Increased mortality in children with mild vitamin A deficiency. Lancet. 1983;2(8350):585-8. doi: 10.1016/s0140-6736(83)90677-3.PubMedUsed to support: This is the study behind the widely quoted figures that mildly deficient children (night blindness or Bitot's spots) had roughly four times the mortality of children with normal eyes, and that about 16% of deaths in children aged 1-6 were attributable to vitamin A deficiency. It is an observational cohort, not a randomized trial. OBSERVATIONAL COHORT, NOT A TRIAL: an average of 3,481 preschool-age rural Indonesian children re-examined every 3 months for 18 months. Mortality among children with mild xerophthalmia (night blindness and/or Bitot's spots) averaged about 4 times the rate among children without it, and 8 to 12 times the rate in some age groups. Mortality rose almost linearly with the severity of mild xerophthalmia, and the relationships persisted after stratification for respiratory disease, wasting, gastroenteritis, pedal oedema and childhood exanthems. Mild vitamin A deficiency was directly associated with at least 16% of all deaths in children aged 1 to 6 years. Because the design is observational, this establishes an association between deficiency STATUS and mortality - it does not measure the effect of supplementation.
  7. Melhus H, Michaëlsson K, Kindmark A, Bergström R, Holmberg L, Mallmin H, Wolk A, Ljunghall S. Excessive dietary intake of vitamin A is associated with reduced bone mineral density and increased risk for hip fracture. Ann Intern Med. 1998;129(10):770-8. doi: 10.7326/0003-4819-129-10-199811150-00003.PubMedUsed to support: Primary source for the previously uncited hip-fracture side effect. OBSERVATIONAL, NOT RANDOMIZED: a cross-sectional study of 175 Swedish women aged 28-74 plus a nested case-control study of 247 women with a first hip fracture versus 873 age-matched controls, drawn from a mammography cohort of 66,651 women aged 40-76. Retinol intake was estimated from dietary records and a food-frequency questionnaire. Each 1 mg/day increase in retinol intake was associated with a 68% higher hip-fracture risk (95% CI 18% to 140%, p for trend 0.006). Intake above 1.5 mg/day versus below 0.5 mg/day was associated with 10% lower femoral-neck density (p=0.05), 14% lower lumbar-spine density (p=0.001), 6% lower total-body density (p=0.009), and roughly doubled hip-fracture risk (OR 2.1, 95% CI 1.1-4.0). Because the design is observational and the exposure is DIETARY retinol in a high-liver-consumption Northern European population rather than a randomized supplement, confounding cannot be excluded and causation is not established.
  8. Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol. 2001;119(10):1417-36. doi: 10.1001/archopht.119.10.1417.PubMedUsed to support: The uncited source behind clinicalTrials[3]. 3,640 participants aged 55-80, an 11-centre double-masked randomised placebo-controlled trial, average follow-up 6.3 years, four arms: antioxidants (vitamin C 500 mg, vitamin E 400 IU, beta-carotene 15 mg); zinc 80 mg plus copper 2 mg; both; or placebo. BORROWED EVIDENCE - this tests a multi-nutrient formula, not vitamin A. The only significant progression result was antioxidants PLUS zinc (OR 0.72, 99% CI 0.52-0.98); the antioxidant-only arm containing the 15 mg beta-carotene was NOT significant (OR 0.80, 99% CI 0.59-1.09), nor was zinc alone (OR 0.75, 99% CI 0.55-1.03). The only significant reduction in at-least-moderate visual acuity loss was likewise in the antioxidants-plus-zinc arm (OR 0.73, 99% CI 0.54-0.99). AREDS therefore does not demonstrate an eye benefit for beta-carotene or vitamin A in isolation, and the beta-carotene component was subsequently replaced in AREDS2 over lung-cancer risk.
  9. Feskanich D, Singh V, Willett WC, Colditz GA. Vitamin A intake and hip fractures among postmenopausal women. JAMA. 2002;287(1):47-54. doi: 10.1001/jama.287.1.47.PubMedUsed to support: Second primary source for the hip-fracture side effect, and the largest. PROSPECTIVE OBSERVATIONAL COHORT, NOT A TRIAL: 72,337 postmenopausal US women aged 34-77 in the Nurses' Health Study, followed 18 years (1980-1998), with 603 incident low- or moderate-trauma hip fractures. Highest quintile of total vitamin A intake (>=3,000 mcg RE/day) had RR 1.48 (95% CI 1.05-2.07, p for trend .003) versus the lowest quintile (<1,250 mcg RE/day). The risk was attributable primarily to RETINOL: RR 1.89 (95% CI 1.33-2.68, p for trend <.001) comparing >=2,000 with <500 mcg/day. Beta-carotene did NOT contribute significantly (RR 1.22, 95% CI 0.90-1.66). IMPORTANTLY FOR HOW THIS IS PRESENTED ON A SUPPLEMENT PAGE: women currently taking a vitamin A supplement had only a NON-significant 40% higher risk (RR 1.40, 95% CI 0.99-1.99), while among women NOT taking supplemental vitamin A, retinol from FOOD was significantly associated with fracture (RR 1.69, 95% CI 1.05-2.74, p for trend .05, >=1,000 vs <400 mcg/day). The signal therefore tracks total preformed retinol rather than supplement use specifically. The association was attenuated among women using postmenopausal estrogens. Observational design means causation is not established; the authors conclude only that high dietary retinol 'may promote' osteoporotic hip fractures and that amounts in fortified foods and supplements 'may need to be reassessed.'
  10. D'Souza RM, D'Souza R. Vitamin A for the treatment of children with measles--a systematic review. J Trop Pediatr. 2002;48(6):323-7. doi: 10.1093/tropej/48.6.323.PubMedUsed to support: The uncited source behind clinicalTrials[1]. SYSTEMATIC REVIEW, NOT A TRIAL: five randomised trials conducted in Africa (four in hospitals, one in a community), 445 children given vitamin A versus 478 given placebo, ages 6 months to 13 years - matching the site card's stated numbers exactly. The POOLED effect on overall mortality was a 39% reduction that was NOT statistically significant (RR 0.61, 95% CI 0.32-1.12). Only the subgroup given 200,000 IU on two consecutive days, in hospital, in areas of high case fatality, showed benefit: overall mortality RR 0.36 (0.14-0.82), pneumonia-specific mortality RR 0.33 (0.08-0.92), children under 2 years RR 0.17 (0.03-0.61). A single 200,000 IU dose was not associated with reduced mortality (RR 1.25, 0.48-3.1), and no trial directly compared one dose with two. The authors note there were not enough studies to separate the individual effects of age, dose, formulation, hospitalisation and local case fatality. This is inpatient treatment of active measles under medical supervision, not a consumer supplement use.
  11. Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. 2012;2012(3):CD007176. doi: 10.1002/14651858.CD007176.pub2.PubMedUsed to support: THE DIRECT ANSWER TO 'DOES THIS HELP A WELL-NOURISHED ADULT?' - AND IT IS NO. 78 randomised trials, 296,707 adults, mean age 63, mean supplementation duration 3 years; all antioxidants administered ORALLY; 26 trials included 215,900 HEALTHY participants and 52 trials included 80,807 patients with stable disease. Antioxidant supplements had no significant effect on mortality under a random-effects model (RR 1.02, 95% CI 0.98-1.05) and SIGNIFICANTLY INCREASED mortality under a fixed-effect model (RR 1.03, 95% CI 1.01-1.05). In the 56 trials at low risk of bias, mortality was significantly increased (RR 1.04, 95% CI 1.01-1.07), rising to RR 1.10 (95% CI 1.05-1.15) in the 38 low-risk-of-bias trials remaining after potentially confounded factorial trials were excluded. Among low-risk-of-bias trials, beta-carotene significantly increased mortality (RR 1.05, 95% CI 1.01-1.09; 26 trials) as did vitamin E; vitamin A alone did not reach significance (RR 1.07, 95% CI 0.97-1.18; 12 trials), but in univariate meta-regression the DOSE of vitamin A was significantly associated with increased mortality (RR 1.0006, 95% CI 1.0002-1.001, p=0.002). Authors' conclusion, verbatim: 'We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A.' This is the basis for removing the Antioxidant category and for capping the evidence level.
  12. Awasthi S, Peto R, Read S, Clark S, Pande V, Bundy D; DEVTA (Deworming and Enhanced Vitamin A) team. Vitamin A supplementation every 6 months with retinol in 1 million pre-school children in north India: DEVTA, a cluster-randomised trial. Lancet. 2013;381(9876):1469-77. doi: 10.1016/S0140-6736(12)62125-4.PubMedUsed to support: THE LARGEST VITAMIN A TRIAL EVER CONDUCTED, AND ON ITS OWN IT WAS NULL. Cluster-randomised, roughly 1 million pre-school children across 8,338 state-staffed village child-care centres in north India, 25,000 deaths recorded at ages 1-6 over 5 years. 200,000 IU retinyl acetate every 6 months, estimated compliance 86%. The supplement demonstrably worked biologically - mean plasma retinol rose from 0.62 to 0.72 micromol/L and Bitot's spots fell from 3.5% to 1.4% - but mortality was 3.01 versus 3.15 deaths per centre, mortality ratio 0.96 (95% CI 0.89-1.03, p=0.22), and 'No specific cause of death was significantly affected.' The authors state DEVTA 'contradicts the expectation from other trials that vitamin A supplementation would reduce child mortality by 20-30%, but cannot rule out some more modest effect.' CRUCIALLY, THE SAME AUTHORS CONCLUDE A REAL EFFECT EXISTS: their meta-analysis of DEVTA plus eight previous randomised trials gave a weighted average mortality reduction of 11% (95% CI 5-16, p=0.00015), 'reliably contradicting the hypothesis of no effect.' That 11% is close to Cochrane's 12% and is the honest magnitude - roughly a tenth, not a quarter and not a third. DEVTA's inclusion is why the pooled child population rose to 1.2 million and why the pre-DEVTA 24% headline no longer stands. Note this is a cluster-randomised open-control trial (the fourth arm was 'neither'), not placebo-controlled, and the population is deficient LMIC children, not Western adults.
  13. Chew EY, Clemons TE, Agrón E, Domalpally A, Keenan TDL, Vitale S, Weber C, Smith DC, Christen W; AREDS2 Research Group. Long-term Outcomes of Adding Lutein/Zeaxanthin and ω-3 Fatty Acids to the AREDS Supplements on Age-Related Macular Degeneration Progression: AREDS2 Report 28. JAMA Ophthalmol. 2022;140(7):692-698. doi: 10.1001/jamaophthalmol.2022.1640.PubMedUsed to support: The uncited source behind clinicalTrials[6]; every figure on that card is confirmed correct. Multicenter epidemiologic follow-up of the AREDS2 trial conducted 1 December 2012 to 31 December 2018: 3,882 participants (mean baseline age 72.0, SD 7.7; 2,240 women, 57.7%) and 6,351 eyes. At 10 years the odds ratio for lung cancer was 1.82 (95% CI 1.06-3.12, p=.02) for those originally randomised to beta-carotene versus 1.15 (95% CI 0.79-1.66, p=.46) for lutein/zeaxanthin - and the elevation persisted even though all participants received a beta-carotene-free formula throughout the 5-year follow-up period. In the authors' own words, beta carotene usage 'nearly doubled the risk of lung cancer.' Direct comparison of lutein/zeaxanthin versus beta-carotene gave HR 0.85 (95% CI 0.73-0.98) for late-AMD progression, favouring lutein/zeaxanthin. NOTE THIS IS AN OBSERVATIONAL FOLLOW-ON ANALYSIS, NOT THE RANDOMIZED PHASE.