Vitamin A, RAE

Vitamin A, RAE (retinol activity equivalents) is USDA's standardized measure of a food's total vitamin A activity — combining preformed vitamin A (retinol) from animal foods with the smaller vitamin-A contribution of plant carotenoids like beta-carotene. It supports vision, immune defense, and the health of cells lining the skin, lungs, and gut.

What is vitamin A, RAE

"Vitamin A, RAE" is the retinol activity equivalent value — the unit USDA and NIH use to express how much usable vitamin A a food actually delivers, since preformed vitamin A (retinol) and plant-derived provitamin A carotenoids convert to active vitamin A at very different efficiencies. Preformed vitamin A comes mostly from animal-source foods — organ meats, fortified dairy, and eggs — and is absorbed and used directly. Provitamin A carotenoids, chiefly beta-carotene, alpha-carotene, and beta-cryptoxanthin, come from orange, yellow, and dark-green produce and must be converted to retinol in the body, a much less efficient process — roughly 12 mcg of dietary beta-carotene is needed to yield 1 mcg RAE. In the body, vitamin A is stored mainly in the liver and used to make retinal, the retina's light-sensitive pigment, and retinoic acid, a hormone-like compound that regulates gene expression in skin, immune, and reproductive tissue. Beef liver, kale, and carrots are among the food sources most concentrated in vitamin A activity, per this site's ranked data.

Health benefits of vitamin A, RAE

• Immune function. The Harvard T.H. Chan School of Public Health, The Nutrition Source notes that vitamin A stimulates the production and activity of white blood cells that help the body trap and clear pathogens.
• Vision. The same source describes vitamin A's structural role in the retina; inadequate intake is the best-documented cause of preventable night blindness worldwide (see Deficiency, below).
• Epithelial and bone health. Harvard's Nutrition Source also credits vitamin A with maintaining the health of cells lining body surfaces (skin, lungs, gut) and with a role in bone remodeling.
• Vitamin-A-rich dietary patterns. Harvard notes that diets varied in vitamin-A-rich produce — including provitamin A carotenoids such as alpha-carotene — have been associated with better memory and learning performance in observational research, though this has not translated into a specific intake target for cognitive benefit.

How much vitamin A you need

The Recommended Dietary Allowance (RDA), per the NIH Office of Dietary Supplements, Vitamin A and Carotenoids Health Professional Fact Sheet, is 900 mcg RAE/day for adult men and 700 mcg RAE/day for adult women (ages 19+). Requirements rise during pregnancy — 750 mcg RAE (ages 14–18) and 770 mcg RAE (ages 19–50) — and rise further during lactation, to 1,200 mcg RAE (14–18) and 1,300 mcg RAE (19–50). Infants 0–6 months have an Adequate Intake (AI) of 400 mcg RAE/day, based on the vitamin A content of human milk. The Tolerable Upper Intake Level (UL) for adults is 3,000 mcg/day of preformed vitamin A specifically — a limit that does not apply to the provitamin A carotenoids naturally present in fruits and vegetables, per Harvard's Nutrition Source (linked above).

Signs of deficiency and excess

Deficiency is rare in the United States but well documented globally. The earliest sign is typically night blindness — difficulty adjusting to low light — followed, if intake stays inadequate, by dry corneas, foamy Bitot's spots on the eye's surface, and in advanced cases corneal ulceration (xerophthalmia) that can cause permanent vision loss, per Cleveland Clinic and MedlinePlus. Dry, scaly skin and increased susceptibility to infection are also documented signs. People with liver disease, fat-malabsorption conditions (celiac disease, cystic fibrosis, chronic diarrhea), or a history of bariatric surgery are at higher risk, per Cleveland Clinic.

Excess/toxicity: because vitamin A is fat-soluble and stored in the liver, chronic high intake — placed above roughly 33,000 IU/day in adults, per MedlinePlus — can cause blurred vision, bone pain, nausea and vomiting, dry or peeling skin, and light sensitivity. Very large single doses (several hundred thousand IU) can cause acute poisoning. High preformed vitamin A intake has also been linked to reduced bone density and increased hip-fracture risk in observational research, per Harvard's Nutrition Source. These risks apply to preformed vitamin A (retinol and retinyl esters, mainly from supplements and liver); beta-carotene from food is not associated with this kind of toxicity — very high beta-carotene intake instead causes a harmless yellow-orange skin discoloration (carotenemia) that resolves when intake drops, per Harvard.

Warnings & interactions

People taking prescription retinoid medications — isotretinoin and acitretin, used for severe acne and psoriasis — should avoid additional vitamin A supplements, since combining the two raises the risk of hypervitaminosis A, including pseudotumor cerebri (elevated pressure around the brain causing headache and vision changes), per the NIH Office of Dietary Supplements' Vitamin A fact sheet (linked above). The same fact sheet notes that vitamin A supplements can also interact with orlistat (a weight-loss medication that reduces fat-soluble vitamin absorption) and with tetracycline antibiotics. Pregnant women are specifically cautioned against high-dose preformed vitamin A supplementation, linked to birth defects; food-based provitamin A carotenoids do not carry this risk. Separately, high-dose beta-carotene supplements — not dietary beta-carotene — have been associated with increased lung cancer risk in smokers, per Harvard's Nutrition Source. Anyone with liver disease or heavy alcohol use should discuss vitamin A supplementation with a clinician, since the liver stores most of the body's vitamin A reserve, per Cleveland Clinic.

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