Pellagra is a vitamin deficiency disease caused by dietary lack of niacin and protein. A deficiency in the essential amino acid lysine can result in a deficiency in niacin (which is a B vitamin) and can result in pellagra.

Symptoms of pellagra are red skin lesions, diarrhea, dermatitis, weakness, mental confusion, and eventually dementia. This disease can be common for persons who obtain most of their food energy from maize, as maize is a poor source of lysine, and any lysine it contains is chemically bound. Therefore this disease can be common amongst people who live in rural South America where — during winter — they live off maize. Usually the symptoms show during spring, and disappear over summer, to return the next spring, after another long winter. It is also one of several diseases of malnutrition common in Africa.

The traditional food preparation method of maize by native new world cultivators, who had domesticated maize, required treatment of the grain with lime, an alkali. It has now been shown that the lime treatment makes lysine nutritionally available and reduces the chance of developing pellagra. When maize cultivation was adopted worldwide, this preparation method was not accepted because the benefit was not understood. The original cultivators, who often depended heavily on maize, did not suffer from pellagra. Pellagra became common only when maize became a staple that was eaten without the traditional treatment.

In the early 1900s, when pellagra appeared in the American south, the scientific community held that pellagra was probably caused by a germ or some unknown toxin in maize. However, in 1915 Joseph Goldberger , assigned to study pellagra by the Surgeon General, showed that pellagra was linked to diet by inducing the disease in prison volunteers. By 1926, Goldberger established that a balanced diet or a small amount of baker's yeast prevented pellagra. Still, skepticism in the medical community persisted until in 1937 Conrad Elvehjem showed that the vitamin niacin cured pellagra (manifested as black tongue) in dogs. Later studies by Tom Spies, Marion Blankenhorn and Clark Cooper established that niacin also cured pellagra in humans, for which Time Magazine called them its 1938 Men of the Year in comprehensive science.