Energy expenditure in human milk- versus formula-fed preterm infants

Objective: We compared energy expenditure (EE) of preterm infants fed their mother's milk versus preterm infant formula. Study design: A prospective, randomized crossover study of 13 healthy, appropriate weight for gestational age, gavage-fed, preterm infants. Before the study and according to our feeding protocol, infants uniformly received alternate feeds of human milk and formula. Each infant was randomly assigned to 24 hours of formula feeding followed by 24 hours of breast milk or the reverse. Infants were studied asleep, at the end of each 24-hour period. EE was measured by indirect calorimetry 1 hour before feeding, 20 minutes during feeding, and 1 hour after feeding in a servo-controlled convective incubator. Energy content of human milk was analyzed by bomb calorimetry. Results: EE was significantly lower in breast milk-fed infants during prefeeding (52 ± 6 vs 57 ± 10 kcal/kg per 24 hours) (P < .05), per feeding (55 ± 6 vs 60 ± 10 kcal/kg per 24 hours) (P < .05), and at the postfeeding measurement (60 ± 7 vs 65 ± 7 kcal/kg per 24 hours) (P = .059). After correction of the results for the actual measured energy intake, all statistical differences reached the < .05 level. Conclusions: Preterm infants have lower EE when they are fed breast milk than when they are fed preterm infant formula.