The History Use And Effectiveness Of Medicinal — страница 7

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during cooking. Unlike other water-soluble vitamins, folic acid is stored in the liver and need not be consumed daily. Pantothenic acid, another B vitamin, plays a still-undefined role in the metabolism of proteins, carbohydrates, and fats. It is abundant in many foods and is manufactured by intestinal bacteria as well. Biotin, a B vitamin that is also synthesized by intestinal bacteria and widespread in foods, plays a role in the formation of fatty acids and the release of energy from carbohydrates. Its deficiency in humans is unknown. This well-known vitamin is important in the formation and maintenance of collagen, theprotein that supports many body structures and plays a major (Pg 22)role in the formation of bones and teeth. It also enhances the absorption of iron from

foodsof vegetable origin. Scurvy is the classic manifestation of severe ascorbic acid deficiency. Its symptoms are due to loss of the cementing action of collagen and include hemorrhages,loosening of teeth, and cellular changes in the long bones of children. Assertions thatmassive doses of ascorbic acid prevent colds and influenza have not been borne out bycarefully controlled experiments. In other experiments, however, ascorbic acid has beenshown to prevent the formation of nitrosamines which are compounds found to produce tumorsin laboratory animals and possibly also in humans. Although unused ascorbic acid is quicklyexcreted in the urine, large and prolonged doses can result in the formation of bladder andkidney stones, interference with the effects of blood-thinning drugs,

destruction of B12,and the loss of calcium from bones. Sources of vitamin C include citrus fruits, freshstrawberries, cantaloupe, pineapple, and guava. Good vegetable sources are broccoli,Brussels sprouts, tomatoes, spinach, kale, green peppers, cabbage, and turnips. This vitamin is necessary for normal bone formation and for retention of calcium and phosphorus in the body. It also protects the teeth and bones against the effects of low calcium intake by making more effective use of calcium and phosphorus. Also called the sunshine vitamin, vitamin D is obtained from egg yolk, liver, tuna, and vitamin-D fortified milk. It is also manufactured in the body when sterols, which are commonly found in many foods, migrate to the skin and become irradiated. Vitamin D deficiency, or

rickets, occurs