NIACIN

also called Nicotinic Acid, or Vitamin B3 water-soluble vitamin of the B complex; it is also called the pellagra-preventive vitamin, or vitamin PP, because an adequate amount in the diet prevents pellagra, a chronic disease characterized by skin lesions, gastrointestinal disturbance, and nervous symptoms. Niacin is interchangeable in metabolism with its amide, niacinamide (nicotinamide). Like vitamin B1 (thiamine) and vitamin B2 (riboflavin), it is a coenzyme involved in the metabolism of carbohydrates and acts to catalyze the oxidation of sugar derivatives and other substances. Niacin, which was identified as a pellagra preventive in 1937, is widely distributed among plants and animals. Lean meat is generally a good source. Approximately 10 to 20 milligrams per day (1 milligram = 0.001 gram) of nicotinic acid is required by humans. In the intestinal tract, the amino acid tryptophan can be converted to niacin by bacterial action and thus can serve as a source for part of the niacin required by the animal. This explains scientists' early observation that the protein in such foods as eggs and milk, both poor sources of niacin, can nevertheless prevent or cure pellagra in humans. Niacin is one of the most stable vitamins, resisting most cooking and preserving processes. It is prepared commercially from b-picoline or from quinoline, which are both obtainable from coal tar.