Niacin, also called nicotinic acid or vitamin B3, is a vitamin of the vitamin B complex. Niacin plays an essential role in the activities of various enzymes involved in the metabolism of carbohydrates and fat, the functioning of the nervous and digestive systems, the manufacture of sex hormones, and the maintenance of healthy skin.
Important dietary sources of niacin include liver, lean meat, poultry, fish, nuts, and dried beans. Niacin can also be manufactured in the body from the amino acid tryptophan.
Most cases of niacin deficiency are due to malabsorption disorders or to severe alcohol dependence. Prolonged niacin deficiency causes pellagra, a potentially fatal condition symptoms of which include inflamed skin, digestive problems, and mental impairment.
Large doses of niacin can cause liver damage, peptic ulcers, and skin rashes. Even normal doses can be associated with skin flushing. It can be prescribed as a treatment for elevated total cholesterol and other types of lipid disorders, but it should only be used with medical supervision due to its potential for severe side effects.