A new study by CU School of Medicine researchers has determined that protein intake from solid foods has a significant impact on infant growth during the first year of life.

The study tested whether dairy-based or meat-based protein in an infant's diet contributed to growth and weight gain. Sixty-four infants were involved in the study, with the group evenly divided between those who ate dairy and those who ate meat in addition to their formula and fruits and vegetables.

"We found that the source of protein may have an important role in regulating growth," said Minghua Tang, PhD, assistant professor of pediatrics, who led the study. "The infants had distinct growth patterns, especially for length, depending on whether they ate meat- or dairy-based complementary foods."

The study, published this month in the American Journal of Clinical Nutrition, is perhaps the first of its kind to evaluate the effect of protein from sources other than formula on infant growth during the first year of life. Such studies can provide evidence-based feeding guidance that can yield long-term benefits for optimal growth and obesity prevention.

To conduct the study, the investigators recruited families in metro Denver with full-term, formula-fed infants who were three to five months old. If eligible, they were screened with a baseline visit and once enrolled they were randomized into dairy-based and meat-based groups. Those on the meat-based diet complemented their usual eating with commercially available pureed meats, while the dairy-based added infant yogurt, cheese and a powdered concentrate of whey protein.

From five to 12 months, the infants were measured for length, weight and head circumference. Blood samples were collected at baseline visit and again at the end of the study. Sources of protein did not seem to affect intake because both groups reported similar amounts of total calories, protein and fat consumption.

Based on the measurements, meat-based complementary foods promoted linear growth. The analysis showed the length-for-age increased in the meat group and declined in the dairy group. At the same time, the weight-for-length measurements significantly increased in the dairy group compared with the meat group.