Vitamin

    Vitamin A

    Retinol

    TL;DR

    Vitamin A is essential for vision, immunity and skin, but preformed retinol is genuinely toxic in excess and teratogenic. Stay under 3000 mcg RAE/day; use beta-carotene if unsure.

    Ideal For

    • People with fat malabsorption from coeliac, Crohn's, pancreatic insufficiency or bariatric surgery
    • Those with diagnosed vitamin A deficiency or night blindness
    • People on very low-fat diets with poor carotenoid absorption
    • Those with BCMO1 variants who convert beta-carotene poorly

    Avoid If

    • You are pregnant or planning pregnancy and considering preformed retinol
    • You take isotretinoin, acitretin or another systemic retinoid
    • You have liver disease
    • You smoke, in relation to isolated high-dose beta-carotene
    • You have osteoporosis and are considering high-dose retinol
    • You already eat liver regularly

    Frequently Asked Questions

    Overview

    Vitamin A is the supplement where the difference between two forms matters more than almost anywhere else in nutrition. Preformed vitamin A — retinol and retinyl esters from liver, dairy, eggs and supplements — is absorbed efficiently and stored in the liver, and it accumulates. Provitamin A carotenoids — beta-carotene from orange and dark green plants — are converted to retinol only as needed, with conversion downregulating when stores are adequate. Carotenoids essentially cannot cause vitamin A toxicity; retinol can and does.

    Its functions are fundamental. Retinal is the chromophore in rhodopsin, making vitamin A deficiency the leading cause of preventable childhood blindness worldwide. Retinoic acid is a nuclear hormone that regulates gene transcription through RAR and RXR receptors, governing epithelial differentiation, immune cell development and embryonic patterning — which is precisely why excess is teratogenic.

    The practical cautions are specific. Doses above 3000 mcg RAE (10,000 IU) daily risk hepatotoxicity and, in observational data, reduced bone mineral density. In pregnancy, high-dose retinol causes craniofacial and cardiac malformations, and this is well established rather than theoretical. Beta-carotene supplementation increased lung cancer incidence in smokers in the CARET and ATBC trials, so smokers should avoid isolated beta-carotene. Conversion of beta-carotene to retinol is also poor in a substantial minority carrying BCMO1 variants.

    How It Works

    • Retinal forms rhodopsin, the light-sensing pigment of rod photoreceptors
    • Retinoic acid acts as a nuclear hormone via RAR and RXR, regulating gene transcription
    • Directs epithelial cell differentiation in skin, gut and respiratory mucosa
    • Required for T cell and B cell development and mucosal IgA production
    • Essential for embryonic patterning — the reason excess is teratogenic
    • Supports iron mobilisation from stores, relevant in combined deficiency

    Quick Facts

    • Supports eye health
    • Boosts immune system
    • Promotes cell growth
    • Antioxidant properties

    Benefits & Outcomes

    Immune Function

    Immune
    Mixed evidence
    Moderate Evidence

    Vitamin A supplementation reduces child mortality in deficient populations but shows no benefit in well-nourished groups.

    Eye Health Support

    Cognitive
    Likely effective
    Moderate Evidence

    Vitamin A is indispensable for vision and its deficiency is the leading preventable cause of childhood blindness worldwide.

    Skin Health Enhancement

    Beauty
    Mixed evidence
    Moderate Evidence

    Topical and prescription retinoids clearly improve skin; oral vitamin A supplements do not have the same evidence and are riskier.

    Reproductive Health

    Cognitive
    Mixed evidence
    Moderate Evidence

    Adequate vitamin A is required for reproduction and fetal development, but excess in pregnancy is teratogenic.

    Health Concerns Addressed

    Keratosis Pilaris

    condition
    Insufficient evidence
    Limited
    Effectiveness 2/5

    Vitamin A is essential for normal keratinisation, so true deficiency can cause follicular plugging like keratosis pilaris. But in replete people oral supplementation has no proven benefit and carries real toxicity risk; topical retinoids are the useful form.

    Supporting Research
    11 studies

    Vitamin A, infection, and immune function

    Score: 6/10
    2001

    Stephensen, C.B.

    Vitamin A deficiency impairs innate immunity by preventing normal regeneration of mucosal barriers damaged by infection and by reducing neutrophil, macrophage and natural killer cell function. It also impairs adaptive immunity, particularly antibody-mediated Th2 responses. Infection itself depresses serum retinol through the acute-phase response, confounding status assessment. Supplementation reduces mortality from measles and diarrhoeal disease in deficient populations, but does not reduce resp

    View source

    An Oral Combination of Vitamins A, C, E, and Mg++ Improves Auditory Thresholds in Age-Related Hearing Loss

    Score: 4/10
    2018
    observational
    n=40

    Alvarado JC, Fuentes-Santamaria V, Gabaldon-Ull MC +1 more

    A combined vitamin A/C/E plus magnesium formulation reduced age-related auditory threshold shifts and cochlear oxidative damage.

    View source

    Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age

    Score: 10/10
    2017
    meta_analysis
    n=1202382

    Imdad A, Mayo-Wilson E, Herzer K +1 more

    Vitamin A supplementation reduced all-cause mortality in children by about 12% and lowered diarrhoea and measles incidence.

    View source

    Vitamin A and mucosal barrier immunity: a systematic review of supplementation trials

    Score: 7/10
    2018
    systematic_review

    Huang Z, Liu Y, Qi G +2 more

    Vitamin A supplementation restored mucosal IgA responses and epithelial barrier integrity

    View source

    Phrynoderma and acquired acrodermatitis enteropathica in breastfeeding women after bariatric surgery

    Score: 3/10
    2015
    case_study
    n=2

    Monshi B, et al.

    Based on clinical and histopathological findings, decreased vitamin A (patient 1) and zinc levels (patient 2), we diagnosed phrynoderma and acquired acrodermatitis enteropathica, respectively.

    View source

    Vitamin A supplements for preventing mortality, illness, and blindness in children aged under 5: systematic review and meta-analysis

    Score: 9/10
    2011
    meta_analysis
    n=215633

    Mayo-Wilson E, Imdad A, Herzer K +2 more

    All-cause mortality was reduced by 24% in children receiving vitamin A supplementation.

    View source

    Vitamin A supplementation every 6 months with retinol in 1 million pre-school children in north India: DEVTA, a cluster-randomised trial

    Score: 8/10
    2013
    rct
    n=1000000

    Awasthi S, Peto R, Read S +3 more

    Mortality was 4% lower in supplemented clusters, a non-significant difference far smaller than earlier trials suggested.

    View source

    Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease (CARET)

    Score: 9/10
    1996
    rct
    n=18314

    Omenn GS, Goodman GE, Thornquist MD +1 more

    The combination of beta carotene and vitamin A increased lung cancer incidence and mortality in smokers and asbestos-exposed workers.

    View source

    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

    Score: 9/10
    2001
    rct
    n=3640

    Age-Related Eye Disease Study Research Group

    Antioxidants plus zinc reduced progression to advanced age-related macular degeneration by about 25% in higher-risk participants.

    View source

    Vitamin A for non-measles pneumonia in children

    Score: 8/10
    2005
    systematic_review
    n=1453

    Ni J, Wei J, Wu T

    The evidence did not suggest a significant reduction with vitamin A adjunctive treatment in mortality, measures of morbidity, nor an effect on the clinical course of pneumonia in children with non-measles pneumonia.

    View source

    The Effect of Vitamin E and Beta Carotene on the Incidence of Lung Cancer and Other Cancers in Male Smokers

    Score: 9/10
    1994
    rct
    n=29133

    The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group

    Beta carotene supplementation increased lung cancer incidence among male smokers.

    View source

    Safety Information

    Potential Side Effects

    At appropriate doses, none. Acute toxicity from very large doses causes headache, nausea, vomiting and blurred vision. Chronic excess causes dry skin, hair loss, bone and joint pain, liver damage, intracranial hypertension and reduced bone density. Beta-carotene in excess causes harmless orange skin discolouration.

    Contraindications

    High-dose preformed vitamin A is contraindicated in pregnancy — it is a proven teratogen above roughly 3000 mcg RAE daily. Contraindicated alongside systemic retinoid drugs due to additive toxicity. Avoid in liver disease, since the liver both stores vitamin A and is the target organ for its toxicity.

    Drug Interactions

    • Isotretinoin and acitretin — additive retinoid toxicity, do not combine
    • Warfarin — high-dose vitamin A may increase bleeding risk
    • Orlistat and cholestyramine — reduce absorption of fat-soluble vitamins
    • Tetracyclines — combined with high-dose vitamin A, risk of intracranial hypertension
    • Hepatotoxic drugs including methotrexate — additive liver stress

    Pregnancy & Breastfeeding

    Pregnancy: likely_unsafe

    Breastfeeding: safe

    Dosage Guidelines

    Dosage Used in Studies

    3000-10000 IU

    Best Time to Take

    With the largest fat-containing meal of the day

    Best Form

    Mixed carotenoids for general use; preformed retinol only for diagnosed deficiency or poor converters, kept below 3000 mcg RAE

    Bioavailability

    Fat-soluble vitamin. Preformed vitamin A (retinol) from animal sources more bioavailable than provitamin A (beta-carotene) from plants. High doses teratogenic in pregnancy.

    Forms Compared

    Retinyl palmitate or acetate

    Beta-carotene

    Mixed carotenoids

    Cod liver oil

    Food & Timing

    With a meal containing fat; absorption of carotenoids in particular depends on it

    Medical Disclaimer

    The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.

    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.