There are strong circumstantial evidences to suspect that in many tissues (notably in the epithelium) of our body

The animals take B carotene along with their foods. In the intestinal wall the P carotene is converted into Vit A Vit A thus produced, is earned to the liver where it is stored. The reason as to why the sea fish liver oils [e.g. halibut, cod, shark) in rich sources of vit A is as follows sea plants containing P carotene are eaten by very small fishes; these very small fishes in turm, are eaten by bigger fishes who store the vit A (obtained from their victims' liver) in their own liver and thus a high concentration of vil A is found in their liver Two terms should bo clearly differentiated vit A' and1 'vit A activity' Vit A means the compound 'retinol' and its close chemical relatives whersas Vit A activity is obtainable from vit A as welI as from p carotene, Because of poor absorption of pcarotene in the intestine as well as incomplete conversion into vit A, vit A activity of B carotene is less than that of vit A Retinoic acid (vrt A acid) is an oxidized product of retinol [recall, retinol = the naturally occurring vit A). It is possible that retinoic acid has some anticancer effects and this has lead to a tremendous spurt of research on various aspects of retinoic acid since the 1980s. There are strong circumstantial evidences to suspect that in many tissues (notably in the epithelium) of our body, retmoic acid is the active form and retinol (vit A) is the provitamin Stability carotene can withstand the heat of cooking fairly well but frying of vit A in fat or oil reduces the vit A to considerible extent. Daily requirement In adults the daily requirement of vit A is about 7,50 p gms Children require less During lactation, the requirement is almost double