Vitamin A

Fat-soluble · retinol & carotenoids

What does Vitamin A do in your body?

Needed for vision in dim light, healthy skin and mucous linings, immune function and growth.

How it works, step by step

Retinol or carotenoids are absorbed with fat into lymph.
The liver stores retinol and releases it bound to a carrier protein.
In the eye, retinal joins opsin to form rhodopsin.
Light changes retinal's shape, triggering a nerve signal.

What does Vitamin A do?

Forms part of rhodopsin, the light-sensitive pigment in the eye's rod cells. Also guides how cells specialize and helps maintain skin and the linings of the gut and airways.

Where does Vitamin A act in the body?

Eyes (retina), skin, gut and airway linings, immune cells. Stored mainly in the liver.

Which foods contain Vitamin A?

Preformed vitamin A: liver, fish oils, eggs, dairy. Provitamin A carotenoids: carrots, sweet potato, spinach, pumpkin, mango.

How much Vitamin A do adults need?

RDA: 900 mcg RAE (men), 700 mcg RAE (women). Upper limit for preformed vitamin A: 3,000 mcg/day. No upper limit for beta-carotene from food.

What happens with too little Vitamin A?

Deficiency is uncommon in high-income countries but a leading cause of preventable childhood blindness worldwide. Night blindness is an early sign.

Can you get too much Vitamin A?

High preformed vitamin A from supplements or very frequent liver intake can harm the liver and bones and can cause birth defects in pregnancy. Large beta-carotene intakes from food can turn skin orange — harmless.

What does Vitamin A interact with?

Absorbed best with some fat. Retinoid medications (e.g., for acne) add to vitamin A load.

What is known and unknown about Vitamin A?

Roles in vision and cell development are established. Beta-carotene supplements increased lung cancer risk in smokers in two large trials.

Evidence & sources

The adult RDA for vitamin A is 900 mcg RAE for men and 700 mcg RAE for women; the UL for preformed vitamin A is 3,000 mcg. Evidence: regulatory. Known: Set by the Institute of Medicine (2001). Unknown: Optimal intakes above deficiency prevention are uncertain. Source: NIH Office of Dietary Supplements, Vitamin A and Carotenoids — Health Professional Fact Sheet (Current revision).
High-dose beta-carotene supplements increased lung cancer risk in smokers. Evidence: strong. Known: Shown in the ATBC and CARET randomized trials. Unknown: Mechanism not fully understood. Source: NIH Office of Dietary Supplements, Vitamin A and Carotenoids — Health Professional Fact Sheet (Current revision).

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General education only, not medical advice. Drafted Oct 2026 · pending qualified expert review.