Vitamin A is a fat-soluble vitamin that exists in the form of free aldehydes or esters in animal foods and is abundant in fat, protein, milk and liver. Vitamin A is not found in plants, but A precursor of vitamin A (provitaChemicalbookminA) is found in vegetables such as carrots and tomatoes, which can be converted into vitamin A when absorbed by animals. Vitamin A is essential for growth, development, reproduction and the stability of cell membranes, and plays an important role in vision.