Cohabitation Accelerates Microbiome Sharing, Tied to Diabetes Risk

A study of 430 people in 207 households across Italy and Fiji shows that living under the same roof drives large-scale transfer of gut and oral bacterial strains, far exceeding genetic relatedness. Cohabitants share ~19% of gut and ~26% of oral strains, while romantically involved partners share about 44% of oral strains. Non-cohabiting individuals share markedly fewer strains. Importantly, the most transmissible gut bacteria correlate with biomarkers of Type 2 diabetes and poor cardiometabolic health, and certain oral strains linked to colorectal cancer. These findings could inform more effective probiotic and fecal microbiota transplant therapies by leveraging natural transmission traits.