Pellagra is due to a lack of the vitamin niacin and/or its precursor tryptophan, an essential amino acid.

 Food sources of niacin and/or tryptophan include nutritional yeast, eggs, bran, peanuts, meat, poultry, fish with red meat, cereals (especially fortified cereals), legumes, and seeds.

Niacin, also known as nicotinic acid, is an organic compound and a form of vitamin B₃, an essential human nutrient.