Niacin (B3) 250 mg (90 capsules) is also known as nicotinic acid. Niacin is an essential vitamin and a B complex vitamin found in a many foods such as liver, poultry, fish, nuts and dried beans. It is needed for the nervous system and gastrointestinal tract function. Vitamin B3 is made up of niacin (nicotinic acid) and niacinamide. Although niacin deficiency (pellagra) was common in the early 20th Century, it has now been virtually eliminated in the United States due to the niacin fortification of foods.