# Are Bifidobacterium Species Key Players in the Progression of Type 1 Diabetes? A Systematic Review

## TL;DR

This review examines whether Bifidobacterium bacteria play a key role in type 1 diabetes development, finding mixed evidence of their presence in different disease stages.

## Contribution

The study systematically reviews Bifidobacterium's association with T1D across stages, revealing inconsistent patterns that challenge its role in prevention.

## Key findings

- Bifidobacterium abundance is higher in at-risk asymptomatic individuals with T1D.
- Bifidobacterium levels decrease after T1D diagnosis.
- Findings do not support Bifidobacterium loss as a key factor in early T1D development.

## Abstract

Type 1 diabetes (T1D) frequently develops in childhood and is preceded by a non‐symptomatic period of autoimmunity. Alterations in the gut microbiome are implicated in T1D pathogenesis. Bifidobacterium is a significant focus due to its positive health impacts, association with breastfeeding and presence in probiotics and infant milk‐formulas. This systematic review aims to investigate Bifidobacterium's association with T1D across disease stages.

A comprehensive electronic search was conducted in MEDLINE, EMBASE and Web of Science, from 2011 to 2024. The search used a combination of medical subject headings and keywords related to Bifidobacterium. Studies included individuals at risk of T1D (pre‐stage, stage 1 or 2 asymptomatic T1D) and with stage 3 symptomatic T1D while excluding T2D, clinical trials and animal studies.

The search initially retrieved 1120 articles. Of these, 25 papers met the inclusion criteria, covering 4533 individuals (842 cases with or at‐risk of T1D and 3691 healthy controls). The studies highlighted variability in Bifidobacterium abundance in T1D, with higher abundance found more often in at‐risk asymptomatic individuals and lower abundance frequently found in those with established T1D.

These findings do not support loss of Bifidobacterium as a key factor in the early development of T1D. Further studies are needed to explore Bifidobacterium's role in T1D progression and management.

Bifidobacterium are generally considered beneficial bacteria, and are found in probiotic formulations currently being trialled for type 1 diabetes (T1D) prevention. In this systematic review, we find that there is a reduction in Bifidobacterium species after T1D diagnosis and an increase or no change in Bifidobacterium abundance in those at risk of T1D. These findings do not support a role for Bifidobacterium in T1D prevention.