Abstract

Vitamin A is a fat-soluble vitamin obtained from two classes of compounds: preformed natural vitamin A: retinol and its compounds; and precursors of vitamin A (provitamin A): beta carotene and related compounds or vitamin A (retinol, retinyl esters), and provitamin A carotenoids such as alpha-carotene and beta-carotene that are converted to retinol. Food sources of vitamin A are represented by: liver (in high concentration in fish and polar bear), dairy products, egg yolk - for retinol; green, yellow, orange fruits and vegetables (broccoli, melon, potatoes, carrots, tomatoes, spinach) – for beta carotene. Retinol is indispensable for vision (especially twilight vision); it is also necessary for tissue growth and differentiation, bone growth, reproductive process, embryonic development, glycoprotein synthesis, prevention of cancer and cardiovascular diseases. Together with certain carotenoids, vitamin A increases immunity, reducing the risk of infections.