Niacin and Pelkgra
Pellegra, a disease characterized by dermatitis, diarrhea, and dementia, has been known for centuries. It was once prevalent in the southern part of the United States and is still a common problem in some parts of Spain, Italy, and Romania. Pellegra was once thought to be an infectious disease, but Joseph Goldberger showed early in this century that it could be cured by dietary actions. Soon thereafter, it was found that brewer's yeast would prevent pellegra in humans. Studies of a similar disease in dogs, called blacktongue, eventually led to the identification of nicotinic acid as the relevant dietary factor. Elvehjem and his colleagues at the University of Wisconsin in 1937 isolated nicotin-amide from liver, and showed that it and nicotinic acid could prevent and cure blacktongue in dogs. That same year, nicotin-
amide and nicotinic acid were both shown to be able to cure pel-legra in humans. Interestingly, plants and many animals can synthesize nicotinic acid from tryptophan and other precursors, and nicotinic acid is thus not a true vitamin for these species. However, if dietary intake of tryptophan is low, nicotinic acid is required for optimal health. Nicotinic acid, which is beneficial to humans and animals, is structurally related to nicotine, a highly toxic tobacco alkaloid. In order to avoid confusion of nicotinic acid and nicotinamide with nicotine itself, niacin was adopted as a common name for nicotinic acid. Cowgill, at Yale University, suggested the name from the letters of three words—nicotinic, acid, and vitamin.
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