Fat and Protein Variability in Donor Human Milk and Associations with Milk Banking Processes

Background: The impact of milk banking processes on macronutrient variability in donor human milk (DHM) is largely unknown. Objective: To gain a better understanding of fat and protein composition in DHM and assess potential relationships with modifiable milk bank processes. Methods: Samples of raw, pooled DHM were collected from 20 milk banks (n = 300) along with the following processing attributes: if macronutrient analysis was used to select donors for pooling (target pooling; yes/no), number of donors per pool, pooling container material (glass/plastic/other), and method for mixing during bottling (manual/mechanical). Fat and protein were assessed. Homoscedasticity was assessed and magnitude of the spread was quantified. Results: Fat ranged from 1.9 to 6.1 g/dL (n = 298) and protein ranged from 0.7 to 1.4 g/dL (n = 300). Variability in fat was significantly lower in samples that had been target pooled (p = 0.04), contained more donors per pool (p < 0.001), and had been mixed mechanically (p < 0.001). Variability in protein was significantly lower in samples that contained more donors per pool (p = 0.001). In a stratified analysis, increasing the number of donors per pool only reduced nutrient variability in samples that were not target pooled. Conclusion: For milk banks that do not target pool, using a greater number of donors in a pool may reduce fat and protein variability.