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Functions of Vitamin AVitamin A is essential for red blood cell production. It also helps the immune system to prevent and combat infections. It does so by creating white blood cells that destroy incoming viruses or bacteria. Vitamin A works on the surface linings of the eyes, the respiratory tract, the urinary tract and the intestines. When these linings deteriorate, the body becomes more susceptible to bacteria and infection. Vitamin A works against this deterioration by assisting the body's mucous membranes to serve as a barrier against bacteria and viruses. There are two kinds of Vitamin A based on whether the food source is plant or animal. The Vitamin A found in animal foods is called pre-formed Vitamin A. It gets absorbed as retinol, the most active and usable form of Vitamin A for our bodies. The Vitamin A that is found in plants is termed ProVitamin A carotenoid. This is available as beta-carotene, alpha-carotene and beta-cryptoxanthin. Of these, beta-carotene is the most efficient in terms of retinol conversion. Some of these carotenoids work in a secondary capacity as antioxidants. Antioxidants protect cells from compounds called free radicals. Free radicals damage the by-products of oxygen metabolism and may contribute to chronic disease development. The recommended daily allowance (RDA) of Vitamin A varies according to age and gender. Pregnant women have a separate RDA. For children aged one and 13 years, the RDA is anywhere between 300 and 600 mcg. For adult males, the RDA is 900 mcg. For adult non-pregnant women, the RDA is 700 mcg. The dosage increases to 750 mcg during pregnancy. An adult lactating woman has an RDA of 1,200 mcg. The Institute of Medicine recommends meeting these RDA by following a diet that is rich in beta-carotenes. This means eating plenty of fruits and vegetables. Also Read:
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