Vitamin is a chemical compound that the human body needs in small amounts. Vitamins make up one of the major groups of nutrients (food substances necessary for growth and health). Vitamins regulate chemical reactions by which the body converts food into energy and living tissues. There are 13 vitamins. Five of them are produced in the body itself. These vitamins are biotin, niacin, pantothenic acid, vitamin D, and vitamin K. Biotin, pantothenic acid, and vitamin K, which are made by bacteria in the human intestine, are usually produced in sufficient quantities to meet the body's needs. In addition, sunlight on the skin can produce an adequate amount of vitamin D. But the other nine vitamins must be supplied in a person's daily diet.
Each vitamin has such specific uses that one of the compounds cannot replace, or act for, another. But the lack of one vitamin can interfere with the function of another. The continued lack of one vitamin in an otherwise complete diet results in a vitamin deficiency disease. Such diseases include beriberi, pellagra, rickets, and scurvy. Investigators first discovered vitamins while searching for the causes of such diseases. In order to be considered a vitamin, a substance must be required in the diet to prevent a deficiency disease.
The best way for a healthy individual to obtain vitamins is to eat a balanced diet. A daily diet that includes a variety of foods from each of the basic food groups provides an adequate supply of all the vitamins (see NUTRITION [vitamins]). A Recommended Dietary Allowance (RDA) has been established for most vitamins. In order to provide a margin of safety, the RDA is considerably greater than the amount of a vitamin needed daily for good health. The RDA is established by the Food and Nutrition Board of the National Academy of Sciences.
Some people take daily vitamin supplements, mostly in the form of vitamin tablets. Most supplements contain doses of one or more vitamins in the range of their RDA's. The vitamins in such preparations are equivalent to those in food. But a healthy person who eats a balanced diet has no need for such supplements.
A person with a vitamin deficiency disease may be helped by taking one or more preparations that contain large doses of a certain vitamin or of a combination of vitamins. But people should use such preparations only if they are prescribed by a physician. Self-diagnosis and treatment with megadoses (doses five to ten or more times larger than the RDA) can be dangerous.
Source: World Book of Encyclopedia
Each vitamin has such specific uses that one of the compounds cannot replace, or act for, another. But the lack of one vitamin can interfere with the function of another. The continued lack of one vitamin in an otherwise complete diet results in a vitamin deficiency disease. Such diseases include beriberi, pellagra, rickets, and scurvy. Investigators first discovered vitamins while searching for the causes of such diseases. In order to be considered a vitamin, a substance must be required in the diet to prevent a deficiency disease.
The best way for a healthy individual to obtain vitamins is to eat a balanced diet. A daily diet that includes a variety of foods from each of the basic food groups provides an adequate supply of all the vitamins (see NUTRITION [vitamins]). A Recommended Dietary Allowance (RDA) has been established for most vitamins. In order to provide a margin of safety, the RDA is considerably greater than the amount of a vitamin needed daily for good health. The RDA is established by the Food and Nutrition Board of the National Academy of Sciences.
Some people take daily vitamin supplements, mostly in the form of vitamin tablets. Most supplements contain doses of one or more vitamins in the range of their RDA's. The vitamins in such preparations are equivalent to those in food. But a healthy person who eats a balanced diet has no need for such supplements.
A person with a vitamin deficiency disease may be helped by taking one or more preparations that contain large doses of a certain vitamin or of a combination of vitamins. But people should use such preparations only if they are prescribed by a physician. Self-diagnosis and treatment with megadoses (doses five to ten or more times larger than the RDA) can be dangerous.
Source: World Book of Encyclopedia
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