- Researchers followed 887 children at high genetic risk of type 1 diabetes and analysed more than 12,000 stool samples.
- One pattern of slower, plateauing gut microbiome development was linked with more than three times the risk of type 1 diabetes.
- The study does not show that probiotics, dietary changes or altering gut bacteria can prevent type 1 diabetes.
The development of type 1 diabetes appears to involve more than genetics alone.
A new study suggests the way the gut microbiome develops during the first years of life may interact with a child’s genes to influence future risk.
Researchers used data from TEDDY, one of the world’s largest long-running studies into the environmental triggers of childhood type 1 diabetes.
The team analysed 12,151 gut microbiome samples collected from 887 children in Finland, Germany, Sweden and the United States.
All of the children already had a higher genetic risk of diabetes.
Samples were collected repeatedly during the first years of life, allowing researchers to look at how each child’s gut bacteria developed over time rather than taking a single snapshot.
Three broad microbiome patterns emerged.
Researchers labelled them Early Matured, Late Matured and Early Plateaued.
Children in the Early Plateaued group had a microbiome that changed less over time and remained less diverse.
They had more than three times the risk of developing persistent islet autoantibodies or clinical type 1 diabetes compared with children whose microbiome matured earlier.
The adjusted risk ratio was 3.21 compared with the Early Matured group.
That is a substantial association, but it is not evidence that the gut microbiome directly caused type 1 diabetes.
Type 1 diabetes is an autoimmune condition in which the immune system gradually destroys the pancreatic beta cells that produce insulin.
Genetics plays an important role, but researchers have long suspected that environmental influences help determine why one genetically susceptible child develops the condition while another does not.
The new study adds the gut microbiome to that picture.
Researchers also found that certain genetic variants involved in antiviral and antimicrobial immune responses changed the relationship between microbiome development and diabetes risk.
That fits with the growing understanding from gene research that diabetes susceptibility reflects an interaction between inherited biology and the environment.
But parents should not read this as evidence that they need to manipulate their child’s gut bacteria.
The study did not test probiotics, supplements or a particular diet as a way to prevent diabetes.
Breastfeeding, antibiotics, probiotic use, introduction of solid foods and delivery method were considered in the statistical analysis, but the research cannot tell families that changing any one of these factors will alter the outcome.
The children were also specifically selected because they had high genetic risk.
That means the findings cannot automatically be applied to every child in the population.
The importance may eventually lie in prediction.
Research into screening children for type 1 diabetes is already moving quickly, with blood tests looking for autoantibodies before symptoms appear.
New international screening guidance has proposed testing at several stages of childhood.
The TEDDY programme itself has already transformed understanding of how type 1 diabetes develops in children.
In time, microbiome information could potentially add another layer to those risk models.
For now, however, this remains research rather than a test parents can request from their GP.
It tells us something important about type 1 diabetes biology, but not yet how to stop the process.
Study link: https://doi.org/10.1038/s42255-026-01614-9
