Gut Microbiome and Breast-feeding: Implications for Early Immune Regulation

Establishment of the gut microbiome during early life is a complex process with lasting implications on an individual’s health. Several factors influence microbial assembly; however, breastfeeding is recognized as one of the most influential drivers of gut microbiome composition during infancy, with potential implications for function. Differences in gut microbial communities between breastfed and formula-fed infants have been consistently observed and are hypothesized to partially mediate the relationships between breastfeeding and decreased risk for numerous communicable and non-communicable diseases in early life. Despite decades of research on the gut microbiome of breastfed infants, there are large scientific gaps in understanding how human milk has evolved to support microbial and immune development. This review will summarize the evidence on how breastfeeding broadly impacts early life gut microbiome composition and function and discuss mechanisms by which specific human milk components shape intestinal bacterial colonization, succession, and function.