Medical Student University of Rochester School of Medicine and Dentistry Rochester, New York, United States
Background: Human milk-derived human milk fortifiers (HM-HMF) are commonly used to fortify the enteral feeds of extremely premature and low birth weight infants. Products exist for different levels of fortification. There are limited data on the variation in macronutrient content between lots of the same product type. Objective: To characterize the protein and lactose content of HM-HMF and compare detected concentrations between product types and between lots of the same product. Design/Methods: We analyzed the concentration of protein and lactose in 5-11 different lots of each HM-HMF product (20, 24, 26, 28, and 30 kcal/oz). A combination of ready-to-feed, and fortifier products were acquired. All concentrated fortifiers were reconstituted with the same lot of donor human milk before analysis. All samples were measured in duplicate with internal controls. The Bradford assay was used to measure total protein content (BioRad: 50000001, Hercules, CA), and a calorimetric enzymatic assay was used to measure total lactose (Sigma Aldrich: MAK017, St Louis MO). Average values were compared between product types using ANOVA and pairwise comparisons via Tukey-Kramer test. Linear regression was used to characterize the relationship between product type (kcal/oz) and protein content. Variability within a lot was calculated as the maximum value minus the minimum value, divided by the average value. Results: Average protein concentration increased from 0.905 ± 0.094 g/100mL in the 20kcal/oz product to 3.217 ± 0.231 g/100mL in the 30 kcal/oz product. Average lactose concentration varied from 7.296 ± 0.647 g/100mL in the 20kcal/oz product to 7.985 ± 0.606 g/100mL (n=10) in the 26kcal/oz product (see table). Average protein concentration was significantly different among product types (p < 0.0001), with protein concentration significantly increasing with each fortification level (p < 0.002). Using linear regression, protein content increased 0.22 g/100mL with every 1 kcal/oz increase in fortification level (p < 0.0001, R2 = 0.93) Average lactose concentration was not significantly different between product types (p=0.16). The maximum variability in protein content ranged between 17% (in the 30kcal/oz product) and 41% (in the 26kcal/oz). The maximum variability in lactose content ranged between 14% (in the 30kcal/oz product) and 30% (in the 24kcal/oz product).
Conclusion(s): Protein content of HM-HMF increases with each level of fortification. Variability in protein and lactose content between lots may be taken into consideration when tracking growth outcomes in recipient infants.
