title: Time-dependent effects of L-tryptophan administration on urinary excretion of L-tryptophan metabolites.
abstract: We have previously reported that dietary supplementation with up to 5.0 g/d of L-tryptophan (L-Trp) for 21 d has no adverse effects, judging from the levels of general blood variables, in healthy women. We performed a randomized, double-blind, placebo-controlled, crossover intervention study in 17 apparently healthy Japanese women. The subjects were randomly assigned to receive a placebo (0 g/d) or 1.0, 2.0, 3.0, 4.0, or 5.0 g/d of L-Trp for 21 d each with a 5-wk washout period between trials. We examined the 24-h urine profiles on days -1 (1 d before starting L-Trp), 7, 14, and 21 to determine whether administration of L-Trp at doses of up to 5.0 g/d affects time-dependent urinary excretion of L-Trp or its metabolites in healthy women. The urinary excretion of L-Trp, kynurenic acid, 3-hydroxykynurenine, xanthurenic acid, 3-hydroxyanthranilic acid, quinolinic acid, N(1)-methylnicotinamide, N(1)-methyl-2-pyridone-5-carboxamide, and N(1)-methyl-4-pyridone-3-carboxamide increased in an L-Trp dose-dependent manner on day 7. The amount of urinary excretion of these compounds was unchanged on days 14 and 21. The urinary excretion of serotonin, 5-hydroxyindole-3-acetic acid, 2-oxoadipic acid, and nicotinamide was unaffected by L-Trp at any of the doses tested. L-Trp doses had weak effects on the urinary excretion of kynurenine and anthranilic acid. Based on these findings, we conclude that there are no time-dependent effects of L-Trp administration in urinary excretion of L-Trp metabolites. Additionally, L-Trp and its metabolites do not accumulate in the body.
authors.affiliation: Department of Nutrition, School of Human Culture, The University of Shiga Prefecture.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Hiratsuka
authors.forename: Mitsue
authors.initials: M
authors.lastname: Sano
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Fukuwatari
authors.forename: Katsumi
authors.initials: K
authors.lastname: Shibata
mesh_terms: D000293:Adolescent; D000328:Adult; D044466:Asian People; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007564:Japan; D014364:Tryptophan / Q000031:analogs & derivatives / Q000378:metabolism / Q000493:pharmacokinetics*; D055815:Young Adult
chemical_list: D014364:Tryptophan