Cow’s Milk Infant Formula Has Greater Weight Gain Effect than Protein Hydrolysate
For some babies, such as low birth weight or premature infants, promoting early rapid weight gain is important. The type of infant formula a baby drinks has a major impact on that weight gain, finds a group of researchers from Monell Chemical Senses Center in Philadelphia.
Infants on Cow's Milk Gained More Weight
Newborn infants usually gain about two-thirds of an ounce each day, or between 4 to 7 ounces a week during the first month. Between the second month of life and six months – typically the time when babies are introduced to solid foods – weight gain is slowed slightly to an average of one to two pounds per month. But not all weight gain is positive. Excessive weight in infancy affects the child’s future risk of developing obesity, diabetes, and other diseases.
"Events early in life have long-term consequences on health, and one of the most significant influences is early growth rate," says study author Julie Mennella, a developmental psychobiologist at Monell.
Mennella and colleagues assigned two-week old bottle-fed infants to one of two formula types. One group (35 infants) received a formula based on cow’s milk and the second group (24 babies) received a protein hydrolysate formula containing pre-digested proteins. The infants drank the formula, which both contained an equal amount of calories, for seven months.
The infants who drank the cow’s milk-based formula gained weight faster. The infants on the protein hydrolysate formula had a weight gain more typical of breast-fed babies. Infant length (linear growth) was not affected by the choice of formula.
Between four and six months of age, formula-fed babies tend to gain weight faster than those that are breastfed. The extra weight is thought to be due to excess water retention and a difference in the composition of body fat. Breast-fed babies are often leaner and gain an average of one pound less than formula fed babies during the first twelve months.
Protein hydrolysate formulas contain more protein than cow’s milk and the babies consumed less of the liquid during a feed compared to those on cow’s milk-based formula. “The next question to ask is: Why do infants on cow’s milk formula overfeed?” says Mennella.
Julie A. Mennella, Alison K. Ventura, and Gary K. Beauchamp. Differential Growth Patterns Among Healthy Infants Fed Protein Hydrolysate or Cow-Milk Formulas. Pediatrics, 2010; DOI: 10.1542/peds.2010-1675