Donor human milk is being used in neonatal intensive care units to feed preterm infants. Pasteurization is part of the process for preparing donor human milk for safe consumption. Pasteurized donor human milk is not as effective as mother's own breast milk in the prevention of necrotizing enterocolitis in preterm infants. In this study, we examine three factors that have been demonstrated to play a role in intestinal protection and assay their concentration in donor human milk samples pre- and postpasteurization. Seventeen paired pre- and postpasteurization samples were obtained from the Mother's Milk Bank of Austin. Samples were centrifuged to attain the aqueous phase of the milk. IL-10, erythropoietin (EPO), and transforming growth factor B1 (TGF-B1) were assayed in the aqueous phase using an enzyme-linked immunosorbent assay method. The concentrations of these factors were as follows (mean ± SEM):
Pasteurization significantly reduced the concentration of IL-10 and EPO but did not affect the concentration of TGF-B1 in paired donor breast milk samples. Concentrations of IL-10 and EPO were below the assay range in 7 of 17 samples, although not the same samples in each assay. However, our values were within the range of previously reported concentrations of IL-10 and EPO in human milk. We conclude that the pasteurization of human milk for use in feeding preterm infants significantly reduces the concentration of certain cytokines that have been demonstrated to play a role in intestinal protection. To our knowledge, this is the first report of the effect of pasteurization on the concentration of these cytokines in breast milk. We speculate that this may partially explain the clinical evidence that donor human milk is not as effective as the mother's own milk in the prevention of NEC in preterm infants.