Abstract
This study was conducted to evaluate conversion ratio of tryptophan to niacin in healthy young women. Five healthy young women served as the experimental subjects.
The basal diet (tryptophan 0.41g, niacin 2.5mg; determined) prepared from twenty-one food stuffs (tryptophan 0.47g, niacin 5.1mg; calculated from Standard Tables of Food Composition in Japan) was given to the subjects for 5 days as a control period. Just after the control period, a certain amount of tryptophan or niacin was additionaly given for 5 days at a test period to the subjects eating the basal diet.
Urinary N1-methylnicotinamide and N1-methyl-2-pyridone-5-carboxamide, as niacin metabolites, of the latter 2 days at each period, were determined. The value of the niacin metabolites in a control period of each subject was subtrated from that of the corresponding test period.
The conversion ratio of tryptophan to niacin was calculated by comparison between the niacin metabolites per 1mg niacin given and the amount of niacin metabolites after administration of 500mg or 1000mg tryptophan.
The calculated ratio of tryptophan was from average of 21.4 to 60.1mg per 1mg niacin for four subjects except one, whose value was extremely high. The average value obtained from the four subjects was 44.7±17.6mg.
