Supplement analysis backed by scientific evidence · PT

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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.

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).

Scientific references

Where to buy

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

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