Molecular Ecology, April 2026 | Chuen Zhang Lee et al., University of East Anglia
A study published in Molecular Ecology in April reports that cohabitation reshapes the gut microbiome in ways not accounted for by shared diet alone. The research team, led by Chuen Zhang Lee, tracked social interactions and gut microbiomes in a population of island birds, a rare setup that allowed them to observe lifelong microbial exchange among known individuals in stable social groups. The findings parallel existing human research, where cohabiting couples have been estimated to share 13%–30% of their gut microbiome—even when eating different diets.
The more time individuals spent together, the more similar their gut bacteria became. The effect was strongest among anaerobic bacteria, which struggle to survive exposure to open air and therefore spread primarily through direct, close contact.
Greater microbial diversity, a common outcome of that sharing, is associated in the broader literature with lower risk of irritable bowel syndrome, cardiovascular disease, and elevated blood sugar. Isolation works in the opposite direction. Increasingly common in modern life, prolonged solitary living reduces the microbial exchange that cohabitation provides. Animal studies and pandemic-era human research have linked isolation to lower gut microbial diversity and, in turn, to the health risks that accompany it. Even an imperfect household may offer biological advantages that solitary living does not.
Additionally, when one household member improves their diet or cuts ultra-processed foods, the microbial benefits may extend to everyone under the same roof.
