Gastric Proteolysis in the Preterm Infant: Protein Digestion is Limited and Is Not Affected by Diet, Human Milk or Formula † 580

Abstract

Pepsin activity and postprandial output are significantly lower in premature infants (125 U/ml and 589 U/Kg body wt) than adults (600 U/ml and 3352 U/Kg) (Pediatr Res 1996; 40:429 and Am J Clin Nutr 1995; 62:74). In vitro hydrolysis of isolated milk proteins by gastric aspirates of newborns is minimal (Early Hum Dev 1989; 19:127). In this study we have measured gastric proteolysis after feeding preterm infants mother's milk (n=11, gestational age(GA) 29.5±0.6 wks) or formula (SMA; n= 9, GA = 29.1±0.9, or Similac; n= 8, GA = 28.9±1.4 wks). Proteolysis%*/Time(min) 0 10 30 50 Human milk 14.5±5 29±7 29±7 28±7 Similac 8.6±3 24±5 24±5 25±7 SMA 8.9±4 15±5 27±12 24±8 * Quantified after separation from unhydrolyzed protein (Pediatrics 1996; 97:492.) The data show that 1. Gastric proteolysis amounts to 15% of total ingested protein. 2. Proteolysis is lower than lipolysis and, contrary to the latter, is not affected by the type of feeding. 3. High postprandial gastric pH (5.0-6.0) and low pepsin output are probably the reason for the limited extent of protein digestion in the newborn. 4. This might benefits the infant by preserving the structure of milk proteins, many with specific functions in the newborn.