Vitamin A Benefits

How are the role in the body and the benefit of a supplement separated?

The NIH reports that vitamin A plays a role in many processes, including immune function, cell communication, growth, development, and reproduction. ^[1] This role shows that deficiency causes harm. Whether more intake in a person with an adequate level would improve the same processes is a separate question and is tested in separate studies. On this page, for each claim, whom was examined and what the result does not cover are given together.

What does vitamin A do for vision in deficiency?

Vitamin A is a component of rhodopsin, the light-sensitive protein in the retina, and supports the normal functioning of the conjunctiva and cornea. In deficiency the first symptom is night blindness, difficulty seeing in low light; xerophthalmia also affects the cornea and can eventually lead to permanent blindness. The NIH counts xerophthalmia among the leading causes of preventable blindness in children. ^[1]

The Cochrane 2022 review found that in children supplementation reduced the frequency of night blindness (2 studies, 22,972 children; RR 0.32; 0.21–0.50) and the frequency of Bitot spots (5 studies, 1,063,278 children; RR 0.42; 0.33–0.53); certainty was moderate for both. The results concern children; vitamin A is not the cause in every person with a vision problem. ^[2]

What does the evidence say for child deaths and infections?

Cochrane 2022 pooled randomized trials examining synthetic vitamin A supplementation in community-dwelling children aged 6 months to 5 years: 47 studies in 19 countries, about 1,223,856 children (63% of the studies in Asia, 16 in India). Hospitalized children and children with disease, food fortification, and beta-carotene studies were out of scope. ^[2]

The authors conclude that supplementation is associated with a clinically meaningful reduction in illness and death in children. The all-cause mortality result was calculated with a fixed-effect model. ^[2] The WHO’s 2011 guideline recommends high-dose supplementation for infants and children aged 6–59 months in regions where vitamin A deficiency is a public health problem, as a public health intervention aimed at reducing illness and death (strong recommendation); whether a region falls into this scope is determined by measuring the prevalence of deficiency in the population with biochemical and clinical indicators. ^[5] The NIH, for its part, states that overt deficiency is rare in the US and is still common in many developing countries. ^[1] Application doses and schedules are determined by health programs and physicians.

These findings do not show that giving a supplement to a child or adult with an adequate vitamin A level would provide the same benefit. The Cochrane authors also state that a placebo-controlled trial would be unethical in communities where deficiency is documented. ^[2]

Does a supplement strengthen immunity in a healthy adult?

The phrase “strengthens immunity” does not say which outcome is meant. Deficiency increases the severity of infections and the risk of death (particularly in measles and diarrhea); this is a correctable condition. ^[1] The results in Cochrane, however, belong to children aged 6 months to 5 years and to studies conducted mostly in Asia; they cannot be carried over to adults with adequate levels.

What can be said for macular degeneration?

Age-related macular degeneration (AMD) is the leading cause of significant vision loss in older adults. As reported by the NIH, in the AREDS randomized trial, people at high risk of developing advanced AMD (intermediate AMD or advanced AMD in one eye) used a mixture containing beta-carotene (15 mg), vitamin E, vitamin C, zinc, and copper for 5 years, and the risk of advanced AMD was found to be 25% lower than with placebo. AREDS2 (4,203 participants, aged 50–85, 5 years) confirmed the effect of this mixture; adding lutein-zeaxanthin or omega-3 provided no additional benefit, whereas when beta-carotene was removed, the protective effect remained the same. In AREDS2, more lung cancer was found in the group receiving beta-carotene (23 and 11 cases) and 31 of the 34 people affected were former smokers; the formula with beta-carotene had not been given to current smokers. ^[1]

This finding shows not that a vitamin A supplement alone prevents AMD, but that a specific combined formula reduced progression in high-risk people. The dose belongs to the formula in the study and is not a personal recommendation; in people who have macular degeneration or are at risk of developing it, formula choice is left to the ophthalmologist’s evaluation.

Does a vitamin A supplement work for skin and acne?

In skin care the words “retinol” and “retinoid” are frequently used; however, prescription retinoid medicines (for example, isotretinoin for severe acne and etretinate for severe psoriasis) are products separate from a vitamin A supplement and have been associated with birth defects. The NIH’s vitamin A health section does not address results of oral supplements for skin or acne; no study result for this claim appears there. High amounts of vitamin A, on the other hand, can cause symptoms of chronic excess such as dry skin. ^[1]

Does it prevent cancer?

The NIH reports that the relationship between serum vitamin A level or supplements and cancer risk is unclear. Some observational studies found a lower risk of some cancers in people with high intake of retinol, carotenoids, and fruits and vegetables; some found no association. An observational association does not mean a supplement would produce the same effect. ^[1]

Randomized trials tested this directly and the result was unexpected. In ATBC, 29,133 male smokers were followed for 5–8 years on 20 mg of beta-carotene per day; the incidence of lung cancer was 18% (95% CI 3–36) higher in those receiving beta-carotene and total mortality was 8% higher. ^[3] In CARET, in smokers, former smokers, and people exposed to asbestos (18,314 people), 30 mg of beta-carotene was given together with 25,000 IU of retinyl palmitate per day; RR 1.28 (1.04–1.57) for lung cancer and RR 1.17 (1.03–1.33) for all-cause mortality were found. The trial was stopped 21 months earlier than planned. ^[4]

The NIH adds that other studies testing similar doses in people who smoked less did not show this risk, and that beta-carotene and vitamin A supplements do not appear to affect cancer risk in nonsmokers. EFSA 2024, however, states that smokers should avoid food supplements containing beta-carotene. ^{[1] [6]}

Summary of the evidence

This guide does not recommend personal doses. The limits in pregnancy and upper intake values for high-risk groups are in the main guide.