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Infant regulation of intake: the effect of free glutamate content in infant formulas
Alison K Ventura1, Gary K Beauchamp, Julie A Mennella
1Monell Chemical Senses Center, Philadelphia, PA, USA.
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.
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