Cow’s milk-based formula led to higher weight gain in babies

Mennella JA. Pediatrics. 2011;127:110-118.

Issue: February 2011

Babies who were fed cow’s milk-based formula had accelerated weight gain over a 7-month period compared with babies who were fed a protein hydrolysate-based formula, according to researchers from the Monell Chemical Senses Center in Philadelphia.

Women who had recently given birth were recruited for the study. The researchers enrolled women who had chosen to feed their newborn cow’s milk. Sixty-four infants starting at about aged 0.5 months of age were randomly assigned to receive either a cow’s milk-based formula or a protein hydrolysate-based formula for 7 months. Thirty-five infants were assigned cow’s milk and 29 were assigned to a protein hydrolysate-based formula. Both formulas had the same number of calories per ounce, but the cow’s milk-based formula had less protein per ounce.

In this double-blind study, the mother and child pairs completed monthly visits to the researchers’ outpatient laboratory. On each visit, the infants were weighed and measured and also videotaped while being fed their formula. When the feeding ended, the researchers recorded the amount of formula that was consumed. They also measured how long the infants spent attached to the bottle’s nipple and the mothers’ perception of their infant’s enjoyment of the formula. For the 2 days before each monthly visit, the mothers recorded what they fed their infants.

At study entry, the z scores for weight-for-age, weight-for-length and length-for-age did not differ. Infants who were fed the protein hydrolysate-based formula had significantly lower z scores for weight-for-age from age 3.5 to 7.5 months vs. infants who were fed cow’s milk-based formula. They also had lower z scores for weight-for-length from age 2.5 to 7.5 months. The groups did not differ for z scores for length-for-age. In addition, infants who received protein hydrolysate consumed less formula during their monthly assessments than infants who received the cow’s milk.

“Additional research into the exact mechanisms underlying these differences is needed both for practical concerns of optimizing infant feeding and for theoretical concerns focusing on understanding mechanisms underlying hunger and satiation,” the researchers wrote.

This small study shows some intriguing preliminary findings about the use of protein hydrolysate formula vs. cow milk formulas. Although the height growth was similar for both infant groups, the protein hydolysate group consumed 1 oz to 2 oz less per feeding in the first 5 months of life. They subsequently had a lower weight over each of the first 2 to 7 months of life.

I have three comments:

Having performed numerous research studies on new formulas in newborns years ago, these data suggest we may need a major change in the duration of these FDA monitored studies. Nearly all formula studies have been terminated after only 1 or 2 months of study. Perhaps, they should be conducted over a full 9-to 12-month period to monitor for potential weight growth deficiencies.
If these data are confirmed, pediatricians should consider recommending protein hydrolysates for newborns with a strong family history of moderate, severe or morbid obesity. Earlier data have demonstrated that overweight babies have a tendency towards being overweight in adulthood. This could be our first preventive step for obesity.
By contrast, any newborn, who is growing poorly or who is a marginal or poor feeder should probably not be placed on protein hydrolysates without very significant medical reasons. Protein hydrolysates are often nonchalantly prescribed for constipation, colic and spitting up, etc.

—Stan L. Block MD
Infectious Diseases in Children Editorial Board member

Disclosure: Dr. Block reports no relevant disclosures.

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