also called retinol
Fat-soluble alcohol , most abundant in fatty fish and especially in fish-liver oils.
It is not found in plants, but many vegetables and fruits contain beta-carotene (see carotene ), which is readily converted in the body to vitamin A. It functions directly in vision, especially night vision. A derivative, retinaldehyde, is a component of the visual pigment s, including rhodopsin , in the retina . Humans require vitamin A in very small amounts. Unlike carotenes, it is toxic in large amounts and is readily destroyed by exposure to heat, light, or air.