Pellagra sufferer with skin lesions
Pellagra is a deficiency disease caused by lack of the B complex vitamin niacin (B3, or nicotinic acid), either from a dietary lack of niacin and the essential amino acid tryptophan, or from an inability to properly absorb or metabolize niacin. Because tryptophan can be converted into niacin, foods with tryptophan but without niacin, such as milk, prevent pellagra. However, if dietary tryptophan is diverted into protein production, niacin deficiency may still result.
Pellagra is an endemic disease in Africa, Mexico, Indonesia, and China. In affluent societies, a majority of patients with clinical pellagra are poor, homeless, alcohol dependent, or psychiatric patients who refuse food (Jagielska et al. 2007).
As a nutritional disorder, pellagra is a preventable disease, requiring a diet adequate in niacin-rich foods or appropriate supplementation (Carson-DeWitt 2004). However, in many areas of the world, pellagra is a condition of poverty, as such niacin-rich foods are unavailable to some people.
A vitamin deficiency disease, pellegra generally is brought about by dietary lack of niacin (B3) and protein, especially proteins containing the essential amino acid tryptophan, which can be converted into niacin (Pitche 2005).
However, there are two types of pellagra. Primary pellagra involves a diet extremely deficient in niacin-rich foods or niacin being present in a form that cannot be absorbed. For example, this type of pellagra is common in areas where maize is the dietary staple, because while it contains niacin, it cannot be absorbed unless treated with alkali (as is done in the preparing tortillas) (Carson-DeWitt 2004). Secondary pellagra occurs when there are adequate quantities of niacin in the diet, but other conditions or diseases interfere with its absorption or processing, such as in cases of prolonged diarrhea, cirrhosis of the liver, alcoholism, and with use of the anti-tuberculosis drug isoniazid (Carson-DeWitt 2004). Also Hartnup disease results in disordered absorption of amino acids from the intestine and kidney (Carson-DeWitt 2004).
Niacin is part of the B vitamins or the vitamin B complex, a group of water-soluble vitamins. Niacin is found in foods such as yeast, liver, meat, fish, legumes, and whole-grain cereals (Carson-DeWitt 2004).
Tryptophan is an amino acid found in most proteins. It is classified as an "essential amino acid" since it cannot be synthesized by the human body from other compounds through chemical reactions and thus has to be taken in with the diet. Tryptophan is found in soybeans, meat, poultry, fish, and eggs. If one's diet contains these foods, one's need for niacin from other sources will be reduced (Haas 1992). Conversion of tryptophan to niacin is insufficient by itself to fully meet the demands for this vitamin, but it can help forestall pellagra. Lack of tryptophan, however, such as dependence on food of low tryptophan content such as maize (corn), can contribute to this niacin-deficiency disease.
Pellagra can be common in people who obtain most of their food energy from corn, since untreated corn is a poor source of niacin. Corn is also a poor source of tryptophan. This disease can be common among people who live in rural South America where corn is a staple.
It is one of several diseases of malnutrition common in Africa. It was also endemic in the poorer states of the U.S. South, like Mississippi and Alabama, as well as among the inmates of jails and orphanages, where it was studied by Joseph Goldberger who conducted experiments in the penal colony in Rankin. Alkali treatment of the corn corrects the niacin deficiency, and this was a common practice in Native American cultures that grew corn. Pellagra was common among prisoners of Soviet labor camps, the infamous Gulag. It can be found in cases of chronic alcoholism.
The relationship between leucine and pellagra is unclear (Bapurao and Krishnaswamy 1978).
Pellagra causes a number of symptoms affecting the skin, mucous membranes, central nervous system, and gastrointestinal tract. Common sympto