vitamin A

Last reviewed 04/2022

Vitamin A is a fat-soluble aliphatic alcohol vitamin occurring in nature in two forms, retinol and dehydroretinol.

Vitamin A is found in fish liver oils, liver, butter, egg yolk, cheese and most yellow and orange fruits and vegetables, in most of which it exists in its precursor form, carotene. In the developing world, most vitamin A comes from vegetable sources whereas in the developed world, animal sources are the main dietary source. Vitamin A is formed from carotene (and other provitamins) in the small intestine. Bile salts and fat are required for absorption.

After absorption vitamin A is transported in chylomicrons to the liver, where it is either stored as an ester, or re-exported to critical tissue sites in combination with retinol binding protein.