Cow-Milk Formula-Fed Infants May Have Accelerated Weight Gain

Infants fed cow milk formula (CMF) have accelerated weight gain, whereas infants fed protein hydrolysate formula (PHF) have normative weight gain, according to the results of a randomized controlled trial reported in the January 2011 issue of Pediatrics.
"Infant formulas differ considerably in composition and sensory profiles," write Julie A. Mennella, PhD, from the Monell Chemical Senses Center in Philadelphia, Pennsylvania, and colleagues. "In this randomized study, we examined whether healthy infants fed an extensively ...PHF would differ in feeding behavior and growth from those fed ...CMF."
Infants were randomly selected to feeding with CMF (n = 35) or PHF (n = 29) from ages 0.5 to 7.5 months. Infants were weighed, measured, and then videotaped while being fed their assigned formula monthly during the 7-month study period. Using World Health Organization growth standards, the investigators calculated anthropometric z scores, and they compared trajectories for growth measures and formula acceptance using multilevel linear growth and piecewise mixed-effects models.
Although PHF-fed infants had significantly lower weight-for-length z scores across ages 2.5 to 7.5 months vs CMF-fed infants, length-for-age z scores were similar in both groups, suggesting that group differences could be attributed to gains in weight rather than length. Compared with infants fed CMF, those fed PHF also had significantly slower weight gain velocity. Monthly evaluations across the study period revealed that infants fed PHF rather than CMF consumed less formula to satiation. At all ages tested, infants' acceptance of formula was similar in both groups, based on maternal ratings.
"[Z]-score trajectories indicate that CMF-fed infants' weight gain was accelerated, whereas PHF-fed infants' weight gain was normative," the study authors write. "Whether such differences in growth are because of differences in the protein content or amino acid profile of the formulas and, in turn, metabolism is unknown."
Limitations of this study include small sample size and inability to determine the exact mechanisms underlying the different weight-gain trajectories between CMF and PHF.
"Longer-term effects of hydrolyzed protein diets, which are relatively new in the human food supply and are growing in use, also need to be investigated," the study authors conclude. "Because dietary and nutritional programming can have long-term consequences in terms of later development of obesity, diabetes, and other diseases, it is imperative that we learn more about the long-term consequences of the early growth differences caused by environmental triggers, such as those associated with infant formulas, and how and why they differ from breastfeeding, which is the optimal mode of feeding."
The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health supported this study. Mead Johnson Nutritionals supplied the formulas. The study authors have disclosed no relevant financial relationships.