A Longitudinal Quantification of Total Protein in Human Milk From Three Global Cohorts: a GEHM Study

Abstract

The quantity of protein in human milk is believed to be important for growth and development of breastfed infants. This study, in support of the Global Exploration of Human Milk (GEHM) collaboration, reports total protein concentration as a weight to weight percentage based on Dumas combustion in longitudinal samples collected from three global cohorts (Mexico, China, and USA) at 4, 13, 26, and 52 weeks lactation. Average total protein decreased rapidly from 4 to 13 weeks of lactation (1.40 ± 0.14% to 1.16 ± 0.16%) and then remained relatively stable to 52 weeks (1.17 ± 0.13%). Similar trends have been reported and are further strengthened by data generated from these samples collected using standardized techniques. Since some components of human milk, including protein, are known to vary diurnally, samples for the GEHM study were collected in the morning by emptying an entire breast via electric pump. Additionally, commercially available human milk standards (HMS) and NIST Standard Reference Material (SRM) 1849a were incorporated into analyses to further verify the accuracy of Dumas combustion for determination of total protein in human milk. The HMS analyzed by combustion all fell within protein certified ranges determined by Kjeldahl methodology. SRM was analyzed before, during, and after each analytical run as a check sample. These added assessments of accuracy, as well as the integration of samples from different geographical populations across multiple points of lactation, strengthen the foundation of knowledge into total protein concentration in human milk. This research was supported by Mead Johnson Pediatric Nutrition Institute.