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A fat-soluble vitamin that occurs in two forms. In animal foods, such as fish oils and liver, it occurs as retinal - which is readily used by the body or stored in the liver. In vegetable foods, it occurs as beta carotene and other carotenoids - which must first be converted by the body into retinal, before becoming usable as vitamin A.
It's an antioxidant, and important for growth, boosting the immune system, maintaining healthy-looking skin and with beta carotene ensuring good vision, by forming a photosensitive pigment called visual purple.
Deficiencies generally only occur in dieters, especially those on low-fat regimes and vegans - since only a small part of the beta caratene is converted to retinal if the fat intact is low. Supplements are recommended for those on these unbalanced diets.
The Recommended Daily Allowance for adults is 5,000 i.u, and for children 3,000 i.u. See 'Antioxidant', 'Beta Carotene', 'Carotenoids', 'Retinol','Vegans', 'Vitamin', 'Vitamin B Complex', 'Vitamin B1', 'Vitamin B2', 'Vitamin B3', 'VitaminB5', 'Vitamin B6', 'VitaminB12', 'VitaminB15', 'Vitamin C', 'Vitamin D', 'Vitamin E', 'Vitamin K', 'Vitamin P', 'Vitamin Supplements'