Pellagra, a niacin deficiency disease, begins unremarkably, usually with weakness, skin rash, mouth sores, and loss of appetite. Unless checked, however, it gradually worsens, producing severe inflammation of the skin, mental disturbances, and diarrhea--followed all too often by death. The word pellagra is Italian for "rough skin," a description of the rough, scaly skin seen in most pellagra patients.
The disease was first noticed by scientists in Europe around 1720, just about the time that maize (or Indian corn) was beginning to be heavily imported from the Americas and planted in many countries. In 1735, the symptoms of pellagra were described by Spanish physician Gaspar Casal (1679-1759), who correctly observed that the disease seemed to be associated with maize-based diets. At the time, however, most scientists believed the disease was caused by a toxin somehow produced by maize, particularly by wet or spoiled maize, and spent many wasted years hunting for the elusive germ. Pellagra had always been troublesome in the American South where both corn and cornmeal were dietary staples. However, it was not until 1907 when a major epidemic began that the government launched a number of serious investigative studies. (The epidemic peaked in 1928, when close to 7,000 deaths were attributed to pellagra, and roughly 20,000 pellagra sufferers were seen in Georgia alone.) One of those investigating the problem was Joseph Goldberger (1874-1929), a doctor who from 1913 on devoted himself to finding a solution.
A few researchers, such as Casimir Funk (1884-1967), had already suggested that pellagra might be caused by an inadequate diet, and Goldberger and his associates agreed. Pellagra, they found, attacked people who, largely because of poverty, had diets that were often restricted to corn meal, salt pork, lard, and molasses. Milk, meat, and eggs were conspicuously absent but, when these were added to the diet, the patients' conditions dramatically improved. To test whether a limited diet could really cause pellagra, Goldberger conducted an experiment in 1915 in which volunteer prisoners in the study were placed on a typical meat-and milk-free cornmeal diet. Within six months, when virtually all prisoners developed pellagra--a pellagra that showed no signs of being infectious--Goldberger restored the meat and milk and promptly saw his patients restored to health. Goldberger concluded that pellagra was a dietary deficiency disease that could be cured by a "P-P factor" (pellagra preventive) that was clearly lacking in corn, but that could probably be found in meat or milk. Goldberger and his associates suspected that the high tryptophan, or amino acid, level in milk was involved in the cure of pellagra.
More than thirty years later, Conrad Arnold Elvehjem (1901-1962), an American biochemist, finally proved that the P-P factor was nicotinic acid, or niacin, one of the B vitamins, which was indeed involved in tryptophan metabolism.
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