Vitamin B3, also called niacin, is one of the water-soluble B vitamins. The term niacin refers to nicotinic acid and nicotinamide (also called niacinamide). This nutrient helps the body convert food into glucose, used to produce energy Niacin contributes to the normal function of the nervous system and normal psychological function. It also contributes to the reduction of tiredness and fatigue. Niacin is used to fortify grain, including corn and bran breakfast cereals and wheat flour. Multivitamin and B-complex vitamin infusions, tablets and capsules also contain nicotinamide.