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Moderate evidenceVitamins & minerals

Vitamin A (Retinol)

Preformed vitamin A is essential and supplementation dramatically cuts child mortality and blindness where deficiency is endemic. In well-nourished adults there is no demonstrated benefit from supplementing, and high doses are genuinely dangerous — especially in pregnancy.

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What the science says

  • Reduces child mortality in deficient populations Strong evidence

    A Cochrane review of 47 trials in over 1.2 million children aged 6 months to 5 years found periodic high-dose vitamin A reduced all-cause mortality by about 12% (RR ~0.88) and cut incidence of diarrhoea and measles. This is one of the best-evidenced public health interventions in nutrition — but the effect exists because baseline deficiency exists.

  • Prevents xerophthalmia and night blindness Strong evidence

    The same trial base shows roughly 50-70% reductions in night blindness and Bitot's spots with supplementation. Vitamin A is a direct precursor to rhodopsin, so replacement in deficiency restores function; this is treatment of a deficiency state, not a general vision enhancer.

  • Improves skin, immunity, or general health in well-nourished adults Limited evidence

    No RCT has shown meaningful benefit from retinol supplementation in populations with adequate intake. Antioxidant meta-analyses have if anything found a signal toward increased mortality with vitamin A supplements. Topical and oral retinoids for acne are prescription drugs, not the same thing as a retinol supplement.

  • Safe at high doses Limited evidence

    A prospective cohort of over 22,000 pregnancies found women consuming more than 10,000 IU/day of preformed vitamin A from supplements had roughly 1 in 57 excess cranial-neural-crest birth defects attributable to the supplement. Chronic intake above ~25,000 IU/day in adults causes hepatotoxicity and intracranial hypertension.

Dosage & safety

Studied doseRDA is 900 mcg RAE/day for men and 700 mcg RAE/day for women (roughly 3,000 and 2,300 IU). Public health programs use single high doses of 100,000 IU (6-11 months) or 200,000 IU (12-59 months) every 4-6 months. Tolerable upper limit for adults is 3,000 mcg RAE (10,000 IU)/day of preformed vitamin A. Supplementing beyond the RDA has no established benefit in non-deficient adults.
SafetyTeratogenic above ~10,000 IU/day — pregnant women and those who may become pregnant should not take preformed retinol supplements and should avoid liver-heavy diets. Chronic excess causes hypervitaminosis A: liver fibrosis, raised intracranial pressure (headache, papilloedema), bone loss and increased hip fracture risk, dry skin, hair loss. Acute megadoses cause nausea, vomiting, vertigo and skin peeling. Additive toxicity with isotretinoin, acitretin and other retinoids. Impaired liver function and alcohol use increase risk. Smokers should be particularly careful with combined vitamin A/beta-carotene products (see beta-carotene).

How to take it

TimingTiming does not matter.
With food?With a meal containing fat — it is fat-soluble and absorbs poorly otherwise.
Worth knowingOnly preformed retinol counts toward the toxic ceiling; if the label says beta-carotene, the hypervitaminosis risk does not apply (the smoking risk does).

Interactions

With medications

  • isotretinoin, acitretin and other oral retinoids

    Toxicity is fully additive — you are already taking a vitamin A analogue at pharmacological dose. do not take supplemental retinol during retinoid treatment

  • tetracycline antibiotics (including doxycycline and minocycline)

    Both can raise intracranial pressure; the combination has caused benign intracranial hypertension. do not combine high-dose vitamin A with a tetracycline

  • orlistat, cholestyramine and other bile acid sequestrants

    Fat absorption is blocked, and with it the absorption of vitamin A. separate by at least 4 hours; long-term users may need monitoring

With other supplements

  • cod liver oil and multivitamins

    Both commonly contain preformed retinol, and the toxic ceiling is your combined total. add up retinol from every product before supplementing separately

  • beta-carotene

    Beta-carotene converts to vitamin A, and combined products are the exact formulation implicated in increased lung cancer among smokers. if you smoke or have smoked, avoid products containing beta-carotene

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Is vitamin A worth taking as a supplement?

For well-nourished adults, no — there is no demonstrated benefit from vitamin A supplements, and antioxidant meta-analyses have hinted at higher mortality. The strong evidence for vitamin A is in children in deficient populations, where it cut mortality by about 12%.

How much vitamin A per day is too much?

The adult upper limit is 3,000 mcg RAE (10,000 IU)/day of preformed vitamin A. Chronic intake above about 25,000 IU/day of vitamin A causes liver toxicity and raised intracranial pressure.

Is vitamin A safe during pregnancy?

Preformed vitamin A (retinol) supplements are not: above about 10,000 IU/day, vitamin A causes birth defects. Pregnant women and those who may become pregnant should avoid retinol supplements and liver-heavy diets.

Does beta-carotene carry the same risk as vitamin A retinol?

No, only preformed retinol counts toward the vitamin A toxic ceiling. Beta-carotene carries a different risk: combined vitamin A and beta-carotene products have been linked to more lung cancer in smokers.

Scientific references

Where to buy

NOW Foods, Vitamin A, 3,000 mcg (10,000 IU), 100 Softgels

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