Fucosylated human milk oligosaccharides vary between individuals and over the course of lactation

Specific human milk oligosaccharides, especially fucosylated neutral oligosaccharides, protect infants against specific microbial pathogens. To study the concentrations of individual neutral oligosaccharides during lactation, a total of 84 milk samples were obtained from 12 women at 7 time periods during weeks 1–49 postpartum. The neutral oligosaccharides from each sample were isolated, perbenzoylated, resolved, and quantified by reversed-phase highperformance liquid chromatography. The resultant oligosaccharide peaks, identified by co-elution with authentic standards and mass spectrometry, ranged in size from trito octasaccharides. The total concentration of oligosaccharides declined over the course of lactation; the mean concentration at 1 year was less than half that in the first few weeks postpartum. One of the 12 donors produced milk fucosyloligosaccharides that were essentially devoid of α1,2 linkages (but contained α1,3and α1,4-linked fucose) until late in lactation, consistent with the nonsecretor phenotype. In milk samples from the remaining 11 donors, fucosyloligosaccharides containing α1,2-linked fucose were prevalent, and their profiles were distinct from those of fucosyloligosaccharides devoid of α1,2-linked fucose. The ratio of α1,2-linked oligosaccharide concentrations to oligosaccharides devoid of α1,2-linked fucose changed during the first year of lactation from 5:1 to 1:1. Furthermore, the absolute and the relative concentrations of individual oligosaccharides varied substantially, both between individual donors and over the course of lactation for each individual. The patterns of milk oligosaccharides among individuals suggest the existence of many genotype subpopulations. This variation in individual oligosaccharide concentrations suggests that the protective activities of human milk could also vary among individuals and during lactation.