Vitamin A

Vitamin A is also known as retinol.

What does Vitamin A do?

Vitamin A helps cells reproduce normally—a process called differentiation. Cells that have not properly differentiated are more likely to undergo precancerous changes. Vitamin A, by maintaining healthy cell membranes, helps prevent invasion by disease-causing microorganisms. Vitamin A also stimulates immunity and is needed for formation of bone, protein, and growth hormone. Beta-carotene is a substance from plants that the body can convert to vitamin A.

Where is Vitamin A found?

Liver, dairy, and cod liver oil provide vitamin A. Vitamin A can also be found in supplements.

Who is likely to be deficient?

Individuals who limit their consumption of liver, dairy foods, and beta-carotene-containing vegetables can develop a vitamin A deficiency. The earliest deficiency sign is poor night vision. Deficiency symptoms can also include dry skin, increased risk of infections, and metaplasia (a precancerous condition). Severe deficiencies causing blindness are extremely rare in Western societies.

How much is usually taken?

In males and postmenopausal women, up to 25,000 IU (7,500 mcg) of vitamin A per day is considered safe. In women who could become pregnant, the safest intake level is being reevaluated; less than 10,000 IU (3,000 mcg) per day is widely accepted as safe. Whether the average person would benefit from vitamin A supplements remains unclear.