Vitamin A

Also known as retinol, retinyl palmitate, vitamin a palmitate, vitmain a.

Last reviewed October 9, 2026 · Jump to references

What is Vitamin A?

In plain words

Vitamin A is a vitamin found in animal foods and made by the body from certain plant pigments. The body stores much of it in the liver and converts it into forms that support vision, immune defenses, and normal growth. Researchers study its role in preventing deficiency and maintaining these functions. Too much preformed vitamin A, such as retinol or retinyl palmitate, can damage the liver and cause birth defects.

Technical definition

Vitamin A is a group of fat-soluble retinoids, including retinol and its storage esters such as retinyl palmitate; dietary sources provide preformed vitamin A or provitamin A carotenoids that can be converted to retinol. Retinal supports light detection in visual pigments, while retinoic acid binds nuclear retinoic acid receptors to regulate genes involved in cell differentiation, immune function, and development. Vitamin A is an essential nutrient available in foods and regulated as a dietary supplement in the United States, with certain formulations also used in approved medicines.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.