Vitamin A or preformed vitamin A and also known as provitamin A is a fat soluble vitamin. It was first identified in 1914 and its structure elucidated in 1930. It is found only in animals, although a number of plants contain carotene, from which vitamin A can be produced in the body once the plants containing carotene are eaten.
Vitamin A may be formed in the body from the yellow pigments (containing carotene) of many fruits and vegetables, especially carrots. Vitamin A is also found in the fats and especially in the liver oils many saltwater fish.
Vitamin A is required for several essential life processes, including metabolism, haematopoiesis, bone development, pattern formation, during embryogenesis, the maintenance of differentiated epithelia, and immune-competence. It is of critical importance for reproduction.
Vitamin A is required for vision. Epithelial cells (those cells present in the lining) of body cavities and in the skin and glands) require vitamin A. Vitamin A is converted to light-sensitive pigments in receptor cells of the retina, the light sensitive layer of the eye.
This vitamin also required for resistance to infection.
Vitamin A exerts considerable influence on body function through its regulation of the activities of the genes. Genes direct the synthesis of proteins, including enzymes and enzymes perform the metabolic work of the tissues.
Loss of night vision is an early sign of vitamin A deficiency and clinical features of well developed deficiency include epidermal lesions, ocular changes, growth retardation, glandular degeneration, increased susceptibility to infection, and sterility.
Why is vitamin A important?
