Shaping of the Infant Gut Microbiome by Milk Oligosaccharides

The gut microbiome governs aspects of human growth and development. While human milk's primary purpose is metabolism, it also provides nonnutritious biologics and macromolecules. This mixture includes the human milk oligosaccharides (HMOs), which are indigestible and survive the low pH of the stomach and small intestine, reaching the large intestine intact. Here, HMOs serve as prebiotics for beneficial bacteria, providing a competitive growth advantage over potential pathogens. Upon metabolizing HMOs, commensals generate short-chain fatty acids and metabolites that enhance the gut community. Therefore, HMOs work to develop and sustain the gut microbial community as a living therapeutic that prevents illness from potential microbial pathogens and modulates development of the infant gut. The goal of this targeted review is to characterize the roles HMOs play in governing bacterial and viral members of the infant gut microbiome, describing how HMOs both define a healthy microbiota and prevent microbial dysbiosis.