Serum insulin and blood glucose levels in breast-fed and formula-fed infants in the first week of life.

Serum insulin and blood glucose levels were measured in newborns aged four to eight hours and those aged seven days who were either breast fed or formula fed. With both types of feeding, the maximum serum insulin levels occurred 60 minutes postprandially in four- to eight-hour-old infants and 30 minutes postprandially in seven-day-old babies. Between breast-fed and formula-fed groups, no statistically significant difference was found in postprandial serum insulin levels or (except for the 90-minute values on the seventh day) in blood glucose levels. It may be necessary to examine the metabolic-endocrine responses to formula administered as the only feeding over a long period to determine whether formula feeding alters such physiologic mechanisms as pancreatic function and immunity in early life and thereby affects the development of the child.