Vitamin A is a fat-soluble vitamin, also known as retinol. As any other fat-soluble vitamin, vitamin A does not dissolve in water. This vitamin is stored in the body fat and in the liver. On the other hand, water-soluble vitamins are excreted from the body in the process of urination, and humans need them every day in the diet. In some cases, a buildup of vitamins in the body is extremely abundant and leads to vitamin overdose or toxicity. However, vitamin toxicity usually occurs as a result of vitamin supplementation. It is nearly impossible to eat enough food and actually overdose on fat-soluble vitamins. Fat-soluble vitamin deficiency is more likely to occur, and they may result in numerous complications. The good news is that most fat-soluble vitamin deficiencies are preventable if recognized early and treated appropriately.
Vitamin A, in its purest form, is found only in foods from animal sources. However, certain fruits and vegetables are loaded with carotenoids, health-beneficial compounds that can be transformed to vitamin A by the human body. Another name for vitamin A is “retinol”. A name is given in reference to the eye-protective compounds and beneficial effect on the functions of the retina. Retinol occurs only in foods of animal origin. Carotenoids, on the other hand, occur in plants, and they are chiefly responsible for red, orange and yellow color of fruits and vegetables. Human body is able to convert beta-carotene, alpha-carotene, and gamma-carotene into vitamin A. Another name for carotenoids is “provitamin A”.
Functions of vitamin A
Vitamin A plays an important role in vision, supports the immune system, maintains epithelial and mucosal tissues, growth, reproduction and bone development. Vitamin A improves the function of white blood cells, boosts the response of antibodies to antigens, and their anti-viral properties.
Vitamin A deficiency
Deficiency of vitamin A is a common health problem in developing countries. Severe deficiency is linked with the high incidence of blindness, viral infections and child mortality. The symptoms of deficiency are usually noticeable on the skin, hair, eyes and the immune system. An inadequate intake of vitamin A usually causes loss of appetite, bone deformities and growth retardation. Individuals deficient on vitamin A will usually have increased susceptibility to bacterial and viral infections.
Most prominent sign of vitamin A deficiency is a skin condition known as hyperkeratosis. Hyperkeratosis is a thickening of the outermost layer of the epidermis, often associated with a qualitative abnormality of the keratin. Hyperkeratosis first occurs on the forearms and thighs, where the skin becomes dry, scaly, and rough. In severe cases, it affects the whole body, causing hair loss. Prolonged vitamin A deficiency can lead to night blindness.