Vitamin A is a fat-soluble Vitamin
Vitamin A is a collective term for retinol, retinal, retinoic acid and B- carotene.
Retinol is pre-vitamin and B-carotene is a pro-vitamin.
B-carotene is present in plant foods.
Sources of Vitamin A:
1. Animal foods- Liver, egg, milk and fish are sources of Vitamin A (Retinol).
Fish and liver oil are the richest sources of Vitamin A (Retinol).
2. Plant foods- Yellow and dark green vegetables and fruits.
e.g. spinach, papaya, mango, and carrots, etc.
Daily requirements of Vitamin A:
The RDA for an adult is 1000 retinol equivalents (RE) for males and 800 RE for females.
(1RE =1ųg of retinol or 6ųg of B-carotene).
Functions of Vitamin A:
The main functions of Vitamin A are as follows:
1. Vision: It is necessary for normal vision.
Vitamin A is a component of visual pigments of rod cells(e.g. rhodopsin) and cone cells (iodopsin) of the retina.
Rhodopsin is essential for night vision and iodopsin is essential for colour vision and daytime vision.
2. Growth: It is essential for the normal growth of body especially skeletal growth.
3. Epithelial integrity: Vitamin A is essential for the maintenance of integrity and functioning of the epithelial and glandular tissue of intestinal, respiratory and urinary tracts as well as skin and eyes.
4. Reproduction: Retinol and retinal are essential for normal reproduction.
They help in spermatogenesis.
5. Anti-infective: Vitamin A is essential for the prevention of infection by modulating the immune system.
Deficiency of Vitamin A:
1. Deficiency of Vitamin A causes night blindness and Xerophthalmia (dry eye).
2. It causes retardation in skeletal growth.
3. Impotence, anorexia and follicular hyperkeratosis.
Hypervitaminosis A results in yellow, dry and pruritic skin, weight loss, bone pain, nausea and vomiting, etc.
Prevention from Vitamin A:
Prevention from Vitamin A is possible by increasing the dietary intake of Vitamin A and by giving Vitamin A capsules.
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