Tryptophan-Niacin Relationships in Pregnancy

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Abstract
The effect of tryptophan supplementation on the urinary excretion of “free” and total tryptophan, nicotinic acid, N1-methylnicotinamide, N1-methyl-6-pyridone-3-carboxylamide, and quinolinic acid have been reported for a group of women in the pregnant and in the nonpregnant state. All the urinary metabolites studied were excreted in higher amounts in pregnancy than in the postpartum period. During the 14-day period of daily supplementation with 500 mg of DL-tryptophan in late pregnancy, the excretion of all metabolites with the exception of “free” tryptophan increased. The excretion of “free” tryptophan decreased significantly. During supplementation in the nonpregnant period, there was an increase in the excretion of total tryptophan, N1-methylnicotinamide, and N1-methyl-6-pyridone-3-carboxylamide. In the pregnant period, the increase in the excretion of niacin metabolites after the usual diet was supplemented with tryptophan was higher than in the postpartum period. The data support the view that the conversion of tryptophan to niacin is more efficient in the pregnant than in the nonpregnant state.