Cow Milk Formula Leads to Quicker Weight Gain in Infants

In Study, Babies Fed Protein Hydrolysate Formula Gained Weight at a Normal Pace

Reviewed by Louise Chang, MD on December 26, 2010

Dec. 27, 2010 -- Researchers report that infants fed cow milk formula gained more weight more quickly than infants fed protein hydrolysate formulas, which are also known as hypoallergenic formulas meant for babies that have problems digesting certain proteins. The proteins in the formula have already been broken down to make digestion easier.

Investigators led by Julie Mennella, PhD, from the Philadelphia-based Monell Chemical Senses Center, a research institute dedicated to studying the chemistry behind taste and smell, compared the benefits of drinking cow milk formula vs. protein hydrolysate formula.

Sixty-four healthy infants aged 0.5 months to 7.5 months were randomly assigned to one of the formulas for seven months. Infants were weighed and measured once a month to assess their growth. The two groups of infants were similar in birth weight and length at birth. Feeding time lengths were also similar between the two groups; the infants were also introduced to solid foods at about the same time.

Differences in the rate of weight gain appeared as early as two months after starting the study. Although infants fed the protein hydrolysate formula gained weight at a normal pace, infants fed the cow's milk formula gained more weight more quickly. Overall, the protein-hydrolysate-formula-fed infants had lower weight-for length scores than those children given cow’s milk formula.

Possible Hypotheses

The researchers proposed a few theories to explain the differences in weight gain between the two groups.

“Infants may dislike the taste of protein hydrolysate formula and consequently consume less, thereby gaining weight more slowly,” the authors wrote. It’s also possible the higher-protein content of this particular formula made infants feel fuller quicker, so they didn’t need to eat as much. Researchers also question whether the amino acids in protein hydrolysate formula may play a role in absorption and metabolism. All of these theories would require further evaluation.

“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 researchers write. “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.”