Does More Early Human Milk Change the Preterm Gut Microbiome?

For very preterm infants, early nutrition is more than calories—it may help shape lifelong health. Human milk is known to protect against infections, improve growth, and shorten hospital stays. But could giving more milk earlier also change how the gut microbiome develops?

Our recent randomized trial of early enteral nutrition explored this question. Very preterm infants received either higher volumes of human milk (60–80 ml/kg/day) or lower volumes (20–30 ml/kg/day) within the first 36 hours after birth. We then analyzed stool samples on day 14 to see if early higher feeding volumes boosted microbial diversity.

The findings?
By two weeks of age, there were no significant differences between the groups in richness, diversity, or community structure of the gut microbiome. Both groups showed similar bacterial patterns—dominated early by bacteria commonly seen in preterm infants.

What does this mean?
Early, higher milk volumes are safe and nutritionally beneficial, but they may not be enough on their own to alter microbiome development in the first two weeks. Other factors like antibiotics, probiotics, mode of delivery, or the NICU environment likely play a bigger role in shaping microbial communities during this fragile period.

Why it matters:
While the study didn’t find early differences, it highlights the complexity of the preterm microbiome and raises important questions. Could longer-term follow-up reveal effects of early feeding strategies? How do nutrition and other interventions interact to influence health outcomes later in life?

For now, the take-home message is clear: early human milk feeding supports clinical stability and growth, but the microbiome story may take longer to unfold.

Read the full-text article published in Pediatric Research here.