Dynamics of human milk oligosaccharide (HMO) composition during different lactation stages and correlation with the infant gut microbiota.

The gut microbiota influences host metabolism and synthesizes essential vitamins. Human Milk Oligosaccharides (HMOs), diverse non-conjugated polysaccharides, are the third major solid component in breast milk. We assessed maternal HMO composition expression over 0-6 months of lactation and its correlation with the infant gut microbiota. A total of 59 breast milk samples were collected monthly from mothers, and 30 fecal samples were obtained from their exclusively breastfed infants at 1, 2, 3, and 6 months. The relative abundance of eight HMO compositions in breast milk decreased significantly with lactation, while three bacterial genera and 10 metabolic pathways in fecal samples of exclusively breastfed infants varied significantly across lactation stages. Furthermore, certain HMO compositions in breast milk were found to be correlated with specific bacterial genera and metabolic pathways in the fecal samples of exclusively breastfed infants. This research provides a basis for future studies on HMOs' role in the infant gut microbiota.