Vitamin B3 of nicotinic acid (niacin) and nicotinamide (niacinamide) are generally termed as niacin. Niacinamide is part of coenzymes NAD/P (nicotinamide adenine dinucleotide/phosphate) connected with glycolysis, tissue respiration and synthesis of macromolecules. Niacin is also derived from the essential amino acid tryptophan as its metabolic end product and thus dietary tryptophan can spare the requirements of niacin. In considering the dietary adequacy of niacin, contribution of both is taken into account. The intakes of both energy and protein are known to regulate the efficiency of conversion of tryptophan to niacin.