Exploring the relationship between gut microbiota and breast cancer risk in European and East Asian populations using Mendelian randomization.

Background: Several studies have explored the potential link between gut microbiota and breast cancer; nevertheless, the causal relationship between gut microbiota and breast cancer remains unclear.

Methods: We utilized summary statistics from genome-wide association studies (GWAS) of the gut microbiome from the MiBioGen project with summary data from GWAS on breast cancer from the FinnGen consortium and the IEU database, with the IEU data sourced from the Biobank Japan. Preliminary statistical analyses were conducted using inverse variance weighting (IVW), supplemented by various sensitivity analysis methods, including MR-Egger regression, weighted median, weighted mode, simple median, and simple mode, to ensure the robustness of our findings.