What disease is caused by a lack of niacin?

Pellagra is the disease caused by severe deficiency of niacin, also called vitamin B3.

Niacin is needed to form NAD and NADP, coenzymes involved in energy production, cellular repair, and many metabolic reactions. When niacin or its precursor tryptophan is insufficient, tissues with high energy demands—especially skin, the digestive system, and the nervous system—can be affected.

Classic descriptions emphasize the “four Ds”: dermatitis, diarrhea, dementia, and, when untreated, death. The dermatitis often affects sun-exposed skin, where it can become dark, thickened, scaly, or cracked. Pellagra may result from poor nutrition, malabsorption, alcoholism, certain medicines, or disorders such as Hartnup disease.

Pellagra has an important food-history connection. Corn treated by nixtamalization—a traditional alkaline preparation—makes its niacin nutritionally available. Eating untreated maize as a staple can therefore contribute to deficiency. The condition is treatable with nicotinic acid or nicotinamide and dietary improvement.