Nutritional disorder caused largely by a deficiency of niacin, marked by skin lesions and digestive and neurological disturbances. Dermatitis usually appears first, with abnormal sensitivity to sunlight. It may look like a severe sunburn, later becoming reddish brown, rough, and scaly. Diarrhea usually alternates with constipation, along with mouth and tongue inflammation and cracking and dry scaling of the lips. Later, mental abnormalities may include nervousness, depression, and delirium. Mild cases of niacin deficiency respond to a well-balanced diet alone. Pellagra still occurs where diets consist mostly of corn, which is low in both niacin and tryptophan (converted to niacin in the body), with little or no protein-rich food. It can also be a side effect of chronic alcoholism.

This entry comes from Encyclopædia Britannica Concise.
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