Niacin, or nicotinic acid, is a member of the water-soluble vitamin B family. For the most part, niacin functions as part of two important coenzymes. Both enzymes play vital roles in a number of metabolic pathways, in particular, those pathways concerned with cellular respiration (the process by which tissue cells "burn" carbohydrates and proteins in order to release energy) and, to a lesser extent, those pathways involved in the synthesis (blending) of fatty acids and steroids.
A deficiency of niacin causes pellagra, a serious disease which has plagued mankind for centuries. In most cases pellagra strikes people whose diet consists mainly of corn and cornmeal. Until fairly recently, pellagra was a major health problem in the United States. In the 1920s the disease killed thousands of people in poor rural areas. At that time, pellagra patients filled both hospitals and, because mental confusion was one of its symptoms, mental institutions as well.
Although no one knew the exact cause of the disease, by the beginning of the twentieth century more and more researchers began to suspect that a dietary deficiency was responsible. The search for an "anti-pellagra factor" intensified in both Europe and the United States. In 1912, Casimir Funk (1884-1967), the Polish-born biochemist who coined the term vitamin, managed to isolate the right factor—nicotinic acid—from rice polishings. Unfortunately, at the time Funk was actually hunting for a substance that would cure beriberi, another serious deficiency disorder. When he found that nicotinic acid had only a minimal effect on beriberi, Funk pushed the compound aside. In the years that followed, the compound was largely ignored.
Niacin and Vitamins
In the 1930s, a number of researchers—among them Hans Euler-Chelpin, Otto Warburg, and Arthur Harden—began reporting that nicotinic acid appeared to be part of quite a few vital coenzymes. Perhaps, the researchers suggested, the compound was a lot more important than was originally supposed.
Niacin wasn't fully established as a vitamin until 1937. It was then that a team of researchers headed by American biochemist named Conrad Arnold Elvehjem (1901-1962) administered 30 miligrams of nicotinic acid to a dog suffering from blacktongue (the canine equivalent of pellagra). The dog improved immediately and, with further doses, was soon completely cured.
Other biochemical researchers quickly confirmed that niacin was the anti-pellagra vitamin for humans. They also confirmed that adding foods high in niacin to the diet, such as meat, green vegetables, yeast, and most grains, dramatically cured the disease. Moreover, since tryptophan is converted by the body into niacin, adding milk and other tryptophan-rich foods to the diet worked equally well.
Very quickly, pellagra cases began declining. In 1941 breads and cereals routinely began to be fortified with the vitamin. It was then that pellagra ceased to be a problem in the United States. The disease does crop up occasionally in other parts of the world, usually where poor diet is a problem.