A pilot study on nutrients, antimicrobial proteins, and bacteria in commerce-free models for exchanging expressed human milk in the USA.

Expressed human milk can be donated or sold through a variety of channels, including human milk banks, corporations or individuals, or peer-to-peer milk sharing. There is a paucity of research regarding the nutrient and bioactive profiles of expressed human milk exchanged through commerce-free scenarios, including peer-to-peer milk sharing. The study objective was to evaluate the macronutrient, antimicrobial protein, and bacteria composition in expressed human milk acquired via commerce-free arrangements. Expressed human milk samples were collected from the following commerce-free scenarios: milk expressed for a mother's or parent's own infant (MOM; N = 30); unpasteurized milk donated to a non-profit milk bank (BANKED; N = 30); milk expressed for peer-to-peer milk sharing (SHARED; N = 31); and health professional-facilitated milk sharing where donors are serologically screened and milk is dispensed raw (SCREENED; N = 30). Analyses were conducted for total protein, lactose, percent fat and water, lysozyme activity, immunoglobulin A (IgA) activity, total aerobic bacteria, coliform, and Staphylococcus aureus. No bacterial growth was observed in 52/121 samples, and 15/121 had growth greater than 5.0 log colony-forming units/mL. There was no evidence of differences by groups (p > .05) in lactose, fat, water, lysozyme activity, sIgA activity, aerobic bacteria, coliforms, and S. aureus. Mean protein values (95% confidence interval) were 1.5 g/dL (1.4, 1.6) for BANKED, 1.4 g/dL (1.3, 1.5) for MOM, 1.6 g/dL (1.5, 1.7) for SCREENED, and 1.5 g/dL (1.4, 1.6) for SHARED, which was not significantly different (p = .081). This research contributes to growing literature on the risks and benefits of uncompensated, peer-to-peer milk sharing.