Infant regulation of intake: the effect of free glutamate content in infant formulas1234

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Background: We recently discovered that infants randomly assigned to a formula high in free amino acids (extensive protein hydrolysate formula; ePHF) during infancy consumed less formula to satiation and gained less weight than did infants fed an isocaloric formula low in free amino acids (cow milk formula; CMF).

Objective: Because ePHF and CMF differ markedly in concentrations of free glutamate, we tested the hypothesis that the higher glutamate concentrations in ePHF promote satiation and satiety.

Design: In this counterbalanced, within-subject study, infants <4 mo of age (n = 30) visited our laboratory for 3 sets of 2 consecutive infant-led formula meals over 3 test days. Infants were fed 1 of 3 isocaloric formulas during each first meal: CMF, ePHF, or CMF with added free glutamate to approximate concentrations in ePHF (CMF+glu). When infants signaled hunger again, they were fed a second meal of CMF. From these data, we calculated satiety ratios for each of the 3 formulas by dividing the intermeal interval by the amount of formula consumed during that particular first meal.

Results: Infants consumed significantly less CMF+glu (P < 0.02) and ePHF (P < 0.04) than CMF during the first meals. They also showed greater levels of satiety after consuming CMF+glu or ePHF: satiety ratios for CMF+glu (P < 0.03) and ePHF (P < 0.05) were significantly higher than for CMF.

Conclusion: These findings suggest a role of free glutamate in infant intake regulation and call into question the claim that formula feeding impairs infants’ abilities to self regulate energy intake. This trial was registered at http://clinicaltrials.gov as NCT00957892.

Abbreviations used:

CMF
cow milk formula
CMF+glu
cow milk formula with added free glutamate
ePHF
extensive protein hydrolysate formula
FAA
free amino acid
gLMS
general labeled magnitude scale
MSG
monosodium glutamate
WIC
Special Supplemental Nutrition Program for Women, Infants, and Children

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From the Monell Chemical Senses Center, Philadelphia, PA.

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The content is solely the responsibility of the authors and does not necessarily represent the official views of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

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Supported by grant R01HD37119, an American Recovery and Reinvestment Act supplement to this grant (3R01HD037119-10S1), National Research Service Award F32HD063343 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and an investigator-initiated grant from Ajinomoto Inc.

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Address correspondence and reprint requests to JA Mennella, 3500 Market Street, Philadelphia, PA 19104-3308. E-mail: [email protected]

Copyright © 2012 American Society for Nutrition. Published by Elsevier Inc. All rights reserved.