Efficiency of D-tryptophan as niacin in rats

L-Tryptophan is a very important precursor of niacin in mammals, Food prepa ration in which proteins the exposed to an alkali and/or high temperature f or a long period generate appreciable amounts of D-amino acids from racemiz ation. The efficiency of D-tryptophan as niacin was thus investigated by us ing weaning rats. The availability of a-tryptophan was almost the same as t hat in L-tryptophan as the precursor of niacin and was 1/6 as active as nia cin.