||A nutrient that is needed by the body to make energy from food, and for a healthy digestive tract, nervous system, and skin. Niacin is found in some foods, including dairy products, lean meats, poultry, fish, eggs, nuts, whole grains, and enriched breads and cereals. In medicine it is used as a drug to lower high blood pressure and cholesterol. It is one of the B vitamins. Also called nicotinamide and nicotinic acid.