What disease is caused by a deficiency of niacin (vitamin B3)?

The disease caused by a deficiency of niacin, or vitamin B3, is pellagra. Niacin is needed to make NAD and NADP, molecules that help cells transfer energy and carry out essential chemical reactions.

Untreated pellagra is classically associated with the “three Ds”: dermatitis, diarrhea, and dementia. The skin inflammation often affects sun-exposed areas and may become dark, thickened, or scaly. Severe disease can also cause mouth sores, weakness, neurological symptoms, and death.

Pellagra can result from inadequate dietary niacin, but the body also makes niacin from the amino acid tryptophan. Conditions that impair absorption or metabolism, including alcoholism, prolonged diarrhea, Hartnup disease, carcinoid syndrome, and some medicines, can produce secondary pellagra.

The condition was historically common in populations reliant on untreated maize. In 1937, Conrad Elvehjem’s experiments showed that niacin could cure pellagra in dogs, helping establish the nutritional cause. Pellagra is distinct from beriberi, which results from vitamin B1 deficiency.