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A large dose of a particular vitamin. Megavitamins are sometimes used under medical supervision to treat specific diseases. Generally, they are not recommended for use except by those suffering from a vitamin deficiency. Some vitamins, for example, vitamin B6, niacin, and the fat-soluble ones like vitamins A and D, can be poisonous in high doses. However, Linus Pauling, the Nobel Prize winning biochemist, suggested everyone would benefit from taking megadoses of vitamin C. He recommended 1 or 2 grams per day, 20–40 times the Recommended Daily Amount, to protect the body from cold viruses and other diseases. Preliminary tests of Pauling's claims indicate that there are only a few instances in which taking more than 100–300 milligrams per day is beneficial; when more than 100 mg is taken in one day, most of the vitamin is excreted unchanged in the urine. Doses of more than 1000 milligrams (1 gram) per day may be harmful to certain people causing nausea, abdominal cramps, and diarrhoea. Pauling's most controversial suggestion was that megadoses of vitamin C might be effective against certain cancers. There is no doubt that adequate amounts (i.e. between 30 and 100 milligrams per day) of vitamin C are needed to defend the body against the onset of cancer, but there is no evidence that megadoses of vitamin C act as a cancer cure.

Subjects: Medicine and Health.

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