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| Healthy adults produce vitamin A from vegetable carotenes, but many people, particularly infants, diabetics and individuals with poor thyroid function, do so less efficiently. Vitamin supplements can be an important source of vitamin A for such people, yet many vegetarian and prenatal products contain only beta carotene, which appears to convert to vitamin A at a fixed rate. Preformed vitamin A delivers the desired dosage more reliably; it is found naturally in foods such as yellow and dark-green vegetables, fruits, dairy foods, eggs and cod liver oil. One retinol equivalent is defined as 1mcg of retinol. One U.S.P. unit (and also the International unit IU) is equivalent to 0.3mcg of retinol. That means that 3 IUs equals 1 retinol equivalent. That said, 6mcg of beta-carotene is considered to be equal to 1mcg of retinol or 3 IU. Both synthetic and natural sources of Vitamin A are available. Vitamin A helps the body overcome the problem of thickening and hardening of the artery walls (dissimilated sclerosis) in the circulatory system. It helps reduce blood cholesterol, and is essential for the normal structure and function of epithelial cells which protect the body from all kinds of environmental contamination. In fact, as far back as ancient Egypt night blindness and some eye disorders were treated with topical application of the juice of cooked livers (high in vitamin A). The World Health Organization recommends large doses of vitamin A to treat measles - a leading killer in developing countries. Therapeutic doses also help treat glaucoma and conjunctivitis (an inflammation of the mucous membrane that lines the eyelids). In this instance, topical, sterile vitamin A is used. Side-Effects There is no question that, when taken in excess, fat-soluble vitamins can accumulate in tissues and cause symptoms of toxicity. A 1995 study reported that women who take more than 10,000 IU of preformed vitamin A daily during the first three months of pregnancy run an increased risk of having a child with birth defects. |