Relationship of tryptophan to niacin
The amino acid tryptophan can be converted to niacin in the body. Research studies have indicated that approxima tely 60 mg of tryptophan are equivalen t to 1 mg of niacin. Animal and vegetable proteins contain about 1.4% and 1% of tryptophan, respectively.Illustrates how an approximate amount of niacin can be calculated from protein. Total niacin equals the preformed niacin plus the niacin available from protein. The accepted ratio of 60:1 is not applicable under a variety of conditions. The conversion is less efficient on very low intakes of niacin and tryptophan and is increased during pregnancy and in the users of oral contraceptive agents Estrogen apparently raises the level of corticosteroids, which, in turn, stimulates tryptophan mygenase, the first enzyme in the pathway. Earlier suggestions tha t amino acid imbalance caused by high intake of leucine impairs the utiliza tion of dietary tryptophan as a source of niacin were not confirmed in a metabolic studv in adult men.
