Two forms of vitamin A in food

Vitamin A exists in two forms: preformed vitamin A or retinol available only from animal sources, and provitamin A available from plant sources.

Active vitamin A is present in foods of animal origin. The richest sources are liver and fish oil but milk and milk products and other fortified foods such as cereal, to which active vitamin is added can also be good sources. Even better and eggs provide some vitamin A.

An active vitamin A or retinol is also stored in the intestinal walls of fish, in the body fat of eels, and in the eyes of certain species of shrimp.

Plants contain no active vitamin A, but many vegetables and fruits provide the vitamin A precursor, beta-carotene. Beta-carotene is the important because it has the highest vitamin A activity.

Because the body uses both the performed vitamin A and the beta-carotene in foods to make retinol, the amount o vitamin A that comes from foods is usually expressed in retinol activity equivalents (RAE).
Two forms of vitamin A in food