Niacin 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.
Niacin assists in the functioning of the digestive system, skin, and nerves. It is also important for the conversion of food to energy.