Acute and chronic intestinal motor activity responses to two infant formulas

Denser infant formulas with more calories may cause reduced intestinal motor activity and explain early feeding intolerance in premature infants. Researchers evaluated the intestinal motor activity in 26 premature infants who received small amounts of slowly infused preterm formulas. The formula with lower caloric content was Similac 20 and the richer formula was Similac Special Care 24 with higher contents of fat, carbohydrates, and protein. Normal increased movement in the intestines occurred in infants who received Similac 20, but the denser formula was associated with lower intestinal motor activity. Seven children on the richer formula and two patients on the lighter formula developed feeding intolerance. After 10 days, this difference disappeared. Infants who fail to tolerate formula initially may respond well after the introduction of heavier milk products somewhat later.
Objective. Preterm formulas are nutritionally better for preterm infants; however, it has been observed that these formulas cause more feeding intolerance than do regular formulas. Because intestinal motor activity is responsible for the aboral movement of intraluminal nutrients, the purpose of this study was to evaluate intestinal motor activity responses to two infant formulas: 84 and 100.8 J/oz. Study Design and Results. Intestinal motor activity was recorded in 52 preterm infants who had never been fed and who were randomly assigned to receive small enteral feedings (24 mL/kg per day) for 10 days with one of two commonly used infant formulas. In a subset of 26 of these infants, acute motor responses to both formulas were also evaluated. At the end of the study period, motor activity during fasting did not differ between the two groups of infants. However, motor responses during feeding to the two formulas differed significantly. When infants were fed for the first time, their motor activity increased compared with fasting when they were fed the 84-J/oz formula but decreased when they were fed the 100.8-J/oz formula. These differences in motor responses to the two formulas were not present 10 days later. These differences in motor responses to the 100.8- and 84-J/oz formulas were even more pronounced among the 7 infants who subsequently developed feeding intolerance to the 100.8-J/oz formula during the 10-day study period. Conclusion. Inhibition of motor responses to calorically denser formulas during active feeding in a subset of preterm infants may underlie the feeding intolerance they experience when they are fed these formulas. However, this inhibitory response diminishes with age, suggesting that denser formulas can be reintroduced later in life to these infants. Pediatrics 1995; 96:331--335; preterm formulas, feeding intolerance, gastrointestinal motility.
ABBREVIATION. NICU, neonatal intensive care unit. As survival of preterm infants has increased, so has morbidity related to immaturity of the gastrointestinal tract.(1)(2) Although a variety of enteral feeding regimens [...]