Is fat content of human milk decreased by infusion?

Human milk (HM) is the optimum nutrition for preterm infants. Previous studies showed that tube infusion decreased the fat content in thawed HM. The aim of this study was to determine if freezing–thawing is the main reason for decrease of fat content. In neonatal intensive care units, thawed HM is used in general, therefore the aim of this study was to investigate fat loss during tube infusion with regard to changes in tube size, material, and infusion rate.

First, pre-infusion and post-infusion fat content was measured in 15 fresh HM, 10 thawed HM and 6 formula samples. We compared post-infusion and pre-infusion fat content as well as the percent decrease in fat concentration among fresh HM, thawed HM and formula samples. Second, we measured the fat content of 160 thawed HM samples infused via four different diameters (3–6 Fr), two types of material (DEHP-free and PVC-free), and two infusion rates (30 or 60 min). We compared the percent decrease in fat concentration among four different tube sizes, between DEHP-free and PVC-free tubes, and between 30 and 60 min infusion durations.

Post-infusion fat content was significantly decreased compared to before infusion in thawed HM and fresh HM but not in formula. Given that thawed HM resulted in larger decrease in fat content, we performed a second experiment and found no difference regarding differing size, materials or infusion rate.

There was a far greater decrease in the post-infusion fat content of thawed HM compared to fresh HM under all test conditions.