Infants fed cow's milk-based infant formula gain more weight

It's been known that babies fed infant formula are more likely than those breastfed to become obese.  But a new study suggests babies fed a cow's milk based infant formula gain weight faster than those fed a protein hydrolysate infant formula.

Julie Mennella, Ph.D. of Monell Chemical Senses Center  and colleagues found the association, but did not know how explain why infants who were fed a cow's milk-based infant formula were more likely to gain weight.

The researchers did observe that infants tended to use less of infant formulas made of pre-digested proteins than cow's milk-based infant formulas.

A health observer speculated that it is possible that pre-digested proteins/peptides taste more satisfying than cow's milk or simply cow's milk tastes better than the digested proteins.

The study was meant to examine how infant formulas influence weight gain in infants.

For the study published in the journal Pediatrics, Mennella et al. let parents feed their babies either a cow's milk based formula or a protein hydrolysate formula, starting at two weeks of age for seven months.

The hydroplysate formula had more protein, and higher amounts of small peptides and free amino acids.  Both formulas contained the same amount of calories.

The meal would discontinue when infants showed signs that they were full.  Body weight was measured for each infant each month.

The researchers found the infants fed protein hydrolysate ate less of their meal and gained weight at a slower rate, compared with those fed cow's milk-based formula.

Mennella said "One of the reasons the protein hydrolysate infants had similar growth patterns to breast-fed infants, who are the gold standard, is that they consumed less formula during a feed as compared to infants fed cow's milk formula."

"The next question to ask is: Why do infants on cow's milk formula overfeed?"

The researchers had no answer for that.

Infants who are formula-fed are at higher risk for infectious morbidity, childhood obesity, type 1 and 2 diabetes, leukemia and sudden infant death syndrome among others, according to a report by Stuebe A of the University of North Carolina at Chapel Hill Chapel Hill, NC. and published in the Fall 2009 issue of Reviews in Obstetrics and Gynecology.

The U.S. physicians recommend that infants should be breast-fed from day one for at least six months or more than one year if both the mother and infant desire to do so. 

By David Liu