Osmolality of fortified donor human milk: An experimental study

Background: We quantify the osmolality of human milk fortified with human milk fortifiers (HMFs), powder infant formulas and protein additives. Methods: Commercial liquid HMFs and powder infant formulas were added to pasteurized pooled donor human milk in triplicate and stirred. The osmolality of unfortified and fortified human milk at 22, 24, 26, 27, 28, and 30 kcal/oz (0.73, 0.8, 0.87, 0.9, 0.93, and 1 kcal/ml, respectively) was determined using freezing-point depression. Results: The osmolality of fortified human milk associated with energy density in a linear relationship regardless of the fortification strategies. Multiple liquid HMFs and every powder infant formula exceeded the osmolality threshold of 450 mOsm/kg H₂O within the energy densities tested. Conclusion: The osmolality of fortified human milk is highly variable and should be considered when selecting a fortifying agent for human milk.