Breastmilk Microbiome Develops Differently in Women with Type 1 Diabetes

Scientists compared breastmilk samples from 69 pregnancies in women with Type 1 diabetes to samples from 49 pregnancies in women without Type 1 diabetes. They collected milk at seven different times, starting at birth and continuing through 15 months after delivery. In total, they analyzed 174 samples from women with Type 1 diabetes and 123 samples from the comparison group.

Using genetic sequencing, the researchers identified and counted the different types of bacteria present in each milk sample. This allowed them to track how the bacterial communities—the microbiome—changed over time in both groups.

The study found a clear difference in how quickly the breastmilk microbiome matured. In women without Type 1 diabetes, the variety and richness of bacteria increased significantly within the first week after birth. However, in women with Type 1 diabetes, this early increase did not happen. Instead, the bacterial diversity increased later—between one week and three months postpartum.

The bacterial composition of milk also shifted more gradually in women with Type 1 diabetes. Women without Type 1 diabetes showed more dramatic and earlier changes in which bacteria were present and dominant in their milk.

Breastmilk microbiomes play an important role in shaping an infant's gut bacteria and immune system development during those critical early months. When the breastmilk microbiome develops differently, infants may be exposed to a different bacterial environment during a key window for immune development.

This study opens new questions: Does the slower development of the microbiome in women with Type 1 diabetes affect infant health outcomes? Are there ways to support healthy microbiome development in this population? Future research will be needed to answer these questions.

This study identified an important difference but did not determine why the delay occurs or what practical effects it might have on infants. The researchers also examined links to blood sugar control and immune factors in the milk, but the full picture of how these connect remains unclear.

More research is needed to understand whether this difference has long-term consequences for infant health and immunity, and whether any interventions could help support healthy microbiome development in women with Type 1 diabetes.

Source: Diabetologia. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.