Comparison of the effects of two human milk fortifiers with different energy sources on the body composition of premature infants

Human milk fortification is recommended to meet the nutritional requirements of preterm infants. Most human milk fortifiers (HMFs) contain non-protein energy (NPE) predominantly as carbohydrate which may lead to high fat deposition relative to lean mass accretion. We hypothesized that fortifying human milk with a HMF containing NPE predominantly as fat (fatHMF) would result in a higher (1) lean mass accretion (percent lean mass) and (2) growth (anthropometry), compared to fortifying with an isocaloric, isonitrogenous HMF containing NPE predominantly as carbohydrate (carbHMF). In a double-blind randomized trial, 29 infants (≤32 weeks and appropriate for gestational age) admitted to the Neonatal Intensive Care Unit received either mother's milk fortified with the fatHMF (n = 14) or the carbHMF (n = 15). Body composition and growth measurements were performed at Baseline (at ≤10% of goal intake 150 ml/kg), Phase 1, and Phase 2 (3 weeks and 6 weeks, respectively, from starting HMF). Although neither percent lean (fat) mass nor growth were statistically different, by Phase 2 infants receiving fatHMF showed a 63% increase in percent fat mass, gained 1194 g in weight and 8.8 cm in length, whereas the carbHMF showed a 96% increase in percent fat mass, gained 1005 g in weight and 6.9 cm in length (p = 0.3586, 0.3815, and 0.1851 respectively). By Phase 2, the fatHMF infants gained 128 g in absolute dry lean tissue, whereas the carbHMF infants gained 99 g (p = 0.0362, Post hoc analysis). Differences of this magnitude are clinically important, but a larger study is required to demonstrate statistical significance.