title: Influence of tryptophan supplementation of soy-based infant formulas on protein quality and on blood and brain tryptophan and brain serotonin in the rat model.
abstract: A 2-wk feeding study with weanling rats was conducted to investigate the effects of tryptophan supplementation of soy-based infant formulas on protein quality and on the levels of blood and brain tryptophan and brain serotonin and 5-HIAA (5-hydroxyindole-3-acetic acid), a metabolite of serotonin. The powder and liquid concentrate forms of soy-based infant formulas obtained from four manufacturers were tested. The tryptophan contents of the test soy-based formulas (10.0-12.3 mg/g protein) were considerably lower compared to those of human milk (17-19 mg/g protein). The infant formulas were fed as the sole source of protein in diets containing 8% protein, 20% fat, 5% cellulose and adequate amounts of minerals and vitamins. In general, supplementation of the diets containing test formulas with graded levels of L-tryptophan (0.1 or 0.2%) had no effect on protein quality indices based on rat growth such as PER (protein efficiency ratio), NPR (net protein ratio) and relative NPR (RNPR), but resulted in significant (p < 0.05) increases in the concentrations of tryptophan in the plasma and brain, and serotonin and 5-HIAA in brain of rats. The increased concentrations of brain tryptophan and 5-hydroxyindoles (serotonin + 5-HIAA) in rats fed tryptophan-supplemented formulas compared to those fed unsupplemented formulas support the need for further research to investigate the influence of tryptophan supplementation of soy-based infant formulas on tryptophan metabolites and their potential related effects on sleep latency and neurobehavioral developments in infants.
authors.affiliation: Nutrition Research Division, Health Canada, Ottawa, Ontario.
authors.forename: G
authors.initials: G
authors.lastname: Sarwar
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D004032:Diet; D004044:Dietary Proteins / Q000592:standards*; D019587:Dietary Supplements / Q000009:adverse effects / Q000032:analysis; D006801:Humans; D007223:Infant; D007225:Infant Food / Q000032:analysis; D008297:Male; D008895:Milk, Human / Q000737:chemistry; D009753:Nutritive Value; D011208:Powders; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D012890:Sleep; D013025:Glycine max; D014364:Tryptophan / Q000008:administration & dosage* / Q000009:adverse effects / Q000378:metabolism*; D015430:Weight Gain
chemical_list: D004044:Dietary Proteins; D011208:Powders; D012701:Serotonin; D014364:Tryptophan