Method for evaluation of the requirements of B-group vitamins using tryptophan metabolites in human urine

Abstract

Tryptophan metabolism is directly involved with B-group vitamins such as vitamin B 2, niacin, and vitamin B 6, and indirectly with vitamin B 1 and pantothenic acid. We evaluated the validity of requirements of B-group vitamins set by the Dietary Reference Intakes for the Japanese (DRI-J). We investigated the fate of dietary tryptophan in 10 Japanese adult men who ate the same diet based on DRI-J during a 4-week study. Vitamin mixtures were administered based on the amounts in the basal diet during weeks 2, 3, and 4. Daily urine samples were collected eight times (days 1 and 5 in each week). Administration of vitamin mixtures had no effect on tryptophan metabolites such as anthranilic acid, kynurenic acid, xanthurenic acid, 3-hydroxyanthranilic acid, and quinolinic acid within individuals. Surplus administration of B-group vitamins against DRI-J requirements did not elicit beneficial effects on tryptophan metabolism. Our findings supported the requirements of B-group vitamins set by the DRI-J.