Breast Milk Seeds the Infant Gut with Bifidobacteria, Study Finds

A Nature Communications study of 507 milk and infant stool samples from 195 mother–infant pairs shows breast milk harbors a distinct microbiome dominated by bifidobacteria, with 12 cases of identical strains in milk and infant gut—strong evidence of vertical transmission via breastfeeding—and hints at retrograde transfer of oral bacteria, suggesting early milk microbes help shape the infant gut and health trajectory.