Vitamin B3 is made up of niacin (nicotinic acid) and its amide, niacinamide,and can be found in many foods, including yeast, meat, fish, milk, eggs,green vegetables, and cereal grains. Dietary tryptophan is also converted to niacin in the body. Vitamin B3 is often found in combination with other B vitamins including thiamine, riboflavin, pantothenic acid, pyridoxine,cyanocobalamin, and folic acid.