Amino Acid Levels in the Critically ill Preterm Infant Given Mother's Milk Fortified with Protein from Human or Cow's Milk

Abstract

Twenty preterm infants undergoing neonatal intensive care were randomly allocated to one of two feeding regimens: human milk enriched with either human milk protein (HMP) or adapted cow's milk protein (CMP). The birthweights (1076 +/- 301 g; 1031 +/- 309 g) and the gestational ages (28.4 +/- 1.6 weeks; 27.7 +/- 2.1 weeks) were comparable. The amount of protein added to the milk was set at 0.7 g/100 ml in order to provide a total supply of 3.0-3.5 g/kg/24 h. All infants received additional amounts of carbohydrate, calcium, phosphorous, and sodium chloride. Capillary whole blood amino acids were measured with high pressure liquid chromatography (HPLC). The amino acid levels did not differ significantly when the feeding groups were compared week by week, but the glycine/valine ratio was higher (p less than 0.05) in the HMP group after three weeks of fortification. Longitudinal changes after protein enrichment could be demonstrated in both groups. Alanine and threonine increased after one week (p less than 0.01) in both groups. Glycine in the HMP group peaked after two weeks (p less than 0.02), and valine in the CMP group increased (p less than 0.02) after one week on the feeding regimen. However, the amino acids never reached levels above those seen after a meal in normal term newborns. Other variables related to protein intake, such as protein and urea in serum, did not vary between the groups. Growth, expressed as gains in weight, length, and head circumference was poor but comparable. The quality of the protein, whether a human milk protein isolate or a cow's milk whey protein product, used for the fortification of human milk up to a protein load of 3.0-3.5 g/kg/24 h, did not cause any alterations of significance in the amino acid profiles of peripheral blood.