A study published in Nature Communications has identified mechanisms by which sugars in breast milk influence the development of gut bacteria in infants during and after the transition to solid food. The research was conducted by scientists at the Technical University of Denmark (DTU), Rigshospitalet, and an international team that also analyzed samples from healthy mother-infant pairs in the Netherlands.
Two Key Mechanisms Identified
The research describes two separate but related processes by which human milk oligosaccharides (HMOs) shape the infant gut microbiome.
Transition to Solid Food
Researchers found that HMOs, which infants cannot digest, affect which bacteria thrive during weaning.
Scientists from DTU and Rigshospitalet identified a mechanism where certain gut bacteria can metabolize both HMOs from breast milk and dietary fibers from plant-based foods. This ability gives these bacteria a competitive advantage, promoting the maturation of the gut microbiota toward an adult-like community.
Cross-Feeding Between Bacteria
In a separate analysis of stool samples from 41 healthy mother-infant pairs in the Netherlands, researchers described a mutualistic relationship between Bifidobacterium and E. coli. In this process:
- First step: Bifidobacterium breaks down HMOs
- Second step: E. coli consumes the resulting simple sugars
- Third step: A byproduct of E. coli metabolism—the amino acid cysteine—serves as a nutrient source for Bifidobacterium
The researchers suggested this relationship may help maintain E. coli at low, stable levels while supporting a Bifidobacterium-rich gut ecosystem.
Clinical Implications
The findings indicate the weaning period is a critical developmental window for establishing a healthy gut microbiota. Lise Aunsholt, Consultant at Rigshospitalet's Department of Intensive Care for Newborns and Young Children, stated the findings support existing recommendations to promote mothers' own milk production and breastfeeding for infants in neonatal intensive care.
Bacterial Transmission Patterns
DNA sequencing revealed distinct patterns of bacterial transmission. Several Bifidobacterium strains were shared between mothers and infants, while E. coli strains typically originated from outside the family but persisted within an infant over time.
Potential Applications
Researchers stated the findings may:
- Inform the development of new nutritional solutions for infants
- Support targeted interventions to promote healthy gut microbiota establishment
- Lead to supplementary treatments for preterm infants or those without consistent access to breast milk
Researcher Statements
Professor Lindsay Hall, corresponding author of the Dutch cohort analysis, stated the research demonstrates how "HMOs consumed by Bifidobacterium also support E. coli, a relationship not previously shown."
Dr. David Seki, first author of the same analysis, commented that "fundamental gaps remain in understanding the ecology of E. coli and the factors determining its role as a commensal or pathogen."