Niacinamide is a form of vitamin B3 that forms when the body absorbs more niacin than it actually needs. This chemical can be found in many different kinds of foods including green vegetables, beans, whole wheat, barley, fish, eggs, and meat. Niacinamide is also a common ingredient in many oral vitamins. It is often used in place of niacin because both are essentially the same nutrient, but niacinamide is believed to have fewer side effects. Doctors recommend taking a vitamin containing niacinamide because if you were to try to get the proper amount of niacin in your diet through the food you ate, you would end up being deficient in other vitamins.