QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sarwar, G. Articles by Botting, H. G. Search for Related Content PubMed PubMed Citation Articles by Sarwar, G. Articles by Botting, H. G.

---

Articles

Liquid Concentrates Are Lower in Bioavailable Tryptophan than Powdered Infant Formulas, and Tryptophan Supplementation of Formulas Increases Brain Tryptophan and Serotonin in Rats

Health Canada, Nutrition Research Division, Bureau of Nutritional Sciences, Health Protection Branch, Banting Research Centre (AL: 2203 C), Tunney's Pasture, Ottawa, Ontario, Canada K1A OL2

¹To whom correspondence should be addressed.

The bioavailability of tryptophan in powdered and/or liquid concentrate forms of milk-based infant formulas was determined by studying rat growth response by using a slope ratio method (food conversion efficiency: weight gain/food consumed vs. tryptophan consumed). A gelatin basal diet formulated to be adequate in all nutrients, except tryptophan (0.03%), for rat growth was supplemented with graded levels of crystalline L-tryptophan (0.02, 0.04, 0.06, 0.08, 0.10, 0.12 and 0.14%, standard diets) or infant formulas providing 0.04 and 0.08% supplemental tryptophan (test diets). These diets were fed to weanling rats for 2 wk. Tryptophan bioavailabilities of various formulas varied from 83 to 95%, with some of the liquid concentrates having the lowest values. The levels of bioavailable tryptophan in the liquid concentrate forms (9.7–12.6 mg/g protein) and the powdered forms (11.1–13.1 mg/g protein) were considerably lower than those of human milk (17–19 mg/g protein). Supplementation of the liquid concentrates with graded levels of L-tryptophan (0.1, 0.5 and 1.0%) had no effect on protein quality indices, based on rat growth, but resulted in a dose-related increase in the concentrations of tryptophan in the plasma and brain and of serotonin and 5-hydroxyindole-3-acetic acid in the brains of rats. This study supports further research to investigate the influence of tryptophan supplementation of infant formulas, to more closely simulate tryptophan composition of human milk, on tryptophan metabolites and their potential related effects on sleep latency and neurobehavioral developments in infants.

KEY WORDS: • infant formulas • tryptophan bioavailability • rat growth • brain serotonin