Pellagra is a chronic disease that can affect men, women, and – very rarely – children. The onset is insidious. At first, the afflicted experience malaise but have no definite symptoms. This is followed by the occurrence of a dermatitis on parts of the body exposed to sunlight. A diagnosis of pellagra is strongly indicated when the dermatitis appears around the neck and progresses from redness at the onset to a later thickening and hyperpigmentation of the skin in affected areas. The dermatitis appears during periods of the year when sun exposure is greatest. Other symptoms, including soreness of the mouth, nausea, and diarrhea, begin either concurrently with the skin changes or shortly thereafter. Diarrhea is associated with impaired nutrient absorption, and as a result of both dietary inadequacies and malabsorption, pellagrins frequently show clinical signs of multiple nutritional deficiencies.

Late signs of pellagra include mental confusion, delusions of sin, depression, and a suicidal tendency. Occasionally, these psychiatric signs are accompanied by a partial paralysis of the lower limbs. In the final stages of the disease, wasting becomes extreme as a result of both a refusal to eat (because of nausea) and pain on swallowing (because of fat malabsorption). Death is from extreme protein–energy malnutrition, or from a secondary infection such as tuberculosis, or from suicide (Roe 1991).

Pellagra as a Deficiency Disease

Since 1937, it has been known that pellagra is the result of a deficiency of the B vitamin niacin (Sydenstricker et al. 1938), and that the deficiency usually arises as a consequence of long-term subsistence on a diet lacking in animal protein or other foods that would meet the body’s requirement for niacin (Carpenter and Lewin 1985). However, a sufficient quantity in the diet of the amino acid tryptophan – identified as a “precursor” of niacin (meaning that the body can convert tryptophan into niacin) – has also been found to cure or prevent the disease (Goldsmith et al. 1952). This explains why milk, for example, helps combat pellagra: Milk contains relatively little niacin but is a good source of tryptophan. Pellagra is most strongly associated with diets based on staple cereals, especially maize. This grain has historically been the daily fare of those who develop the disease: Maize is high in niacin content, but much of this niacin is in a chemically bound form that prevents absorption of the vitamin by the body (Goldsmith 1956).