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
Is beta-carotene safer than retinol?
How much is too much?
Can I take it in pregnancy?
Why do some people not convert beta-carotene well?
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
Vitamin A supplementation reduces child mortality in deficient populations but shows no benefit in well-nourished groups.
Eye Health Support
Vitamin A is indispensable for vision and its deficiency is the leading preventable cause of childhood blindness worldwide.
Skin Health Enhancement
Topical and prescription retinoids clearly improve skin; oral vitamin A supplements do not have the same evidence and are riskier.
Reproductive Health
Adequate vitamin A is required for reproduction and fetal development, but excess in pregnancy is teratogenic.
Health Concerns Addressed
Vitamin A Deficiency
Replacing vitamin A corrects the deficiency and reverses early eye signs; the open questions are dose, form and supervision, not whether it works.
Keratosis Pilaris
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 Research28 studies
Vitamin A, infection, and immune function
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
An Oral Combination of Vitamins A, C, E, and Mg++ Improves Auditory Thresholds in Age-Related Hearing Loss
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.
Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age
Imdad A, Mayo-Wilson E, Haykal MR +4 more
VAS is associated with a clinically meaningful reduction in morbidity and mortality in children
Vitamin A or beta-carotene supplementation reduces but does not eliminate maternal night blindness in Nepal
Christian P, West KP, Khatry SK +4 more
Vitamin A supplementation reduced the incidence of night blindness during pregnancy
Double blind, cluster randomised trial of low dose supplementation with vitamin A or beta carotene on mortality related to pregnancy in Nepal. The NNIPS-2 Study Group
West KP, Katz J, Khatry SK +4 more
vitamin A or beta carotene lowered mortality by 44%
Recovery from impaired dark adaptation in nightblind pregnant Nepali women who receive small daily doses of vitamin A as amaranth leaves, carrots, goat liver, vitamin A-fortified rice, or retinyl palmitate
Haskell MJ, Pandey P, Graham JM +3 more
Improvement in dark adaptation did not differ significantly
A randomised controlled trial to test equivalence between retinyl palmitate and beta carotene for vitamin A deficiency
Carlier C, Coste J, Etchepare M +2 more
the two treatments were statistically equivalent
No improvement in suboptimal vitamin A status with a randomized, double-blind, placebo-controlled trial of vitamin A supplementation in children with sickle cell disease
Dougherty KA, Schall JI, Kawchak DA +4 more
failed to improve serum retinol values
Prevalence, Ocular Manifestations, and Treatment Response in Post-Bariatric Vitamin A Deficiency: A Systematic Review and Meta-Analysis
Abdel-Sayyed A, Bigam S, Alizada A +2 more
13 (93%) improved or resolved
Vitamin A for treating measles in children
Huiming Y, Chaomin W, Meng M
two doses were associated with a reduced risk of mortality
Vitamin A supplementation during pregnancy for maternal and newborn outcomes
McCauley ME, van den Broek N, Dou L +1 more
antenatal vitamin A supplementation reduces maternal night blindness
Teratogenicity of high vitamin A intake
Rothman KJ, Moore LL, Singer MR +3 more
High dietary intake of preformed vitamin A appears to be teratogenic
Impact of vitamin A supplementation on xerophthalmia. A randomized controlled community trial
Djunaedi E, Sommer A, Pandji A +2 more
distribution was associated with a dramatic decline in xerophthalmia prevalence
Effects of vitamin A or beta carotene supplementation on pregnancy-related mortality and infant mortality in rural Bangladesh: a cluster randomized trial
West KP, Christian P, Labrique AB +4 more
Vitamin A compared with either placebo or beta carotene supplementation increased plasma retinol concentrations
Daily consumption of Indian spinach (Basella alba) or sweet potatoes has a positive effect on total-body vitamin A stores in Bangladeshi men
Haskell MJ, Jamil KM, Hassan F +4 more
0.065 mmol for retinyl palmitate (P < 0.001)
Responsiveness of dark-adaptation threshold to vitamin A and beta-carotene supplementation in pregnant and lactating women in Nepal
Congdon NG, Dreyfuss ML, Christian P +4 more
improved significantly in response to vitamin A supplementation
Vitamin A and retinol-binding protein deficiency among chronic liver disease patients
Chaves GV, Peres WA, Gonçalves JC +1 more
vitamin A supplementation may trigger harmful effects in CLD patients
Vitamin A and beta (β)-carotene supplementation for cystic fibrosis
de Vries JJ, Chang AB, Bonifant CM +2 more
no conclusion on the supplementation of vitamin A in people with CF can be drawn
Rethinking Vitamin A Deficiency: Its Causes, Ophthalmologic Presentation, and Management Gaps at a New England Tertiary Hospital
Fearon KH, Dameron CM, Kelleher SL +2 more
Vitamin A supplementation was documented in just over half of symptomatic patients
Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age
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.
Role of Vitamin A in the Immune System
Huang Z, Liu Y, Qi G +2 more
Vitamin A supplementation restored mucosal IgA responses and epithelial barrier integrity
Phrynoderma and acquired acrodermatitis enteropathica in breastfeeding women after bariatric surgery
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.
Vitamin A supplements for preventing mortality, illness, and blindness in children aged under 5: systematic review and meta-analysis
Mayo-Wilson E, Imdad A, Herzer K +2 more
All-cause mortality was reduced by 24% in children receiving vitamin A supplementation.
Vitamin A supplementation every 6 months with retinol in 1 million pre-school children in north India: DEVTA, a cluster-randomised trial
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.
Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease (CARET)
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.
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
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.
Vitamin A for non-measles pneumonia in children
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.
The Effect of Vitamin E and Beta Carotene on the Incidence of Lung Cancer and Other Cancers in Male Smokers
The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group
Beta carotene supplementation increased lung cancer incidence among male smokers.
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: Considered 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.
Dosing by Goal
| Goal | Dose | Notes |
|---|---|---|
| RDA (men) | 900 mcg RAE/day | |
| RDA (women) | 700 mcg RAE/day | |
| Pregnancy | 770 mcg RAE/day — do not exceed 3000 mcg RAE | |
| Beta-carotene | No upper limit set; 6-15 mg/day is typical in supplements | |
| Upper limit | 3000 mcg RAE (10,000 IU) daily from preformed vitamin A | |
| Notes | Fat-soluble — take with a meal containing fat. Conversion factor: 1 mcg RAE = 12 mcg dietary beta-carotene |
Forms Compared
Retinyl palmitate or acetate
Preformed vitamin A; potent, storable and the form that can cause toxicity
Beta-carotene
Provitamin A with regulated conversion; cannot cause vitamin A toxicity but avoid isolated high doses if you smoke
Mixed carotenoids
Beta-carotene alongside lutein, zeaxanthin and lycopene; the safest default
Cod liver oil
Supplies retinol plus vitamin D and omega-3; watch cumulative retinol intake
Food & Timing
With a meal containing fat; absorption of carotenoids in particular depends on it
Articles on Vitamin A
All articlesVitamin A Foods: Best Sources (Plus Vitamin D)
The richest vitamin A foods are liver, sweet potato, spinach and carrots. Amounts per serving, foods with vitamin D too, absorption tips and safety limits.
14 min readFat-Soluble vs Water-Soluble Vitamins Explained
Vitamins A, D, E and K dissolve in fat and are stored; C and the B vitamins are not. See how fat affects absorption and where the limits sit.
16 min read
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.