DefinitionNiacin is a type of B vitamin. It is water-soluble, which means it is not stored in the body. Water-soluble vitamins dissolve in water. Leftover amounts of the vitamin leave the body through the urine. That means you need a continuous supply of such vitamins in your diet.Alternative NamesDiet - niacin; Nicotinic acid; Vitamin B3FunctionNiacin assists in the functioning of the digestive system, skin, and nerves. It is also important for the conversion of food to energy.Food SourcesNiacin (also known as vitamin B3) is found in dairy products, poultry, fish, lean meats, nuts, and eggs. Legumes and enriched breads and cereals also supply some niacin.Side EffectsA deficiency of niacin causes pellagra. The symptoms include inflamed skin, digestive problems, and mental impairment.Large