Human Milk Oligosaccharides: Impact on Infant Gut Microbiome and Health

Breastfeeding protects the infant against diseases, although the mechanisms are not fully understood. Besides macro- and micronutrients, breast milk contains a range of bioactive components such as immunoglobulins, hormones and growth factors, cytokines, and anti-microbial compounds. In addition, breast milk contains a variety of human milk oligosaccharides (HMOs), which are small indigestible oligosaccharides that together comprise the third most abundant solid fraction of breast milk. HMOs directly enhance the gastrointestinal barrier function, protect against invading viral or bacterial pathogens by coating them and acting as decoys for receptors located on the gut epithelium, and suppress inflammatory signaling in intestinal epithelial cells. They also provide indirect effects by stimulating the growth of beneficial bacteria in the gastrointestinal tract. HMOs are strong contributors to the establishment of a healthy gut microbiota in early life, as they promote a community rich in specialized Bifidobacterium species, capable of consuming HMOs and in turn producing immune-regulatory metabolites, which may protect the infant against infectious and immune-related diseases. The use of this knowledge to support breastfeeding, but also develop Bifidobacterium-based probiotics and/or HMO-based formula milk may hold great promise to prevent infectious, inflammatory, and immune-related diseases in infants that cannot be breastfed or are lacking Bifidobacterium species in the gastrointestinal tract.