Living With Friends (Or Family) Impacts Gut Health — Here's Why
You've probably heard that your gut health is shaped by what you eat, how well you sleep, and your daily habits. But here's a twist: new research suggests the people you live with might also play a role.
Two recent animal studies—one on birds, one on rats—point to the same intriguing conclusion: living in close contact with others can influence your gut bacteria.
The bird study: social closeness matters
Researchers at the University of East Anglia studied Seychelles warblers, small songbirds living on a tiny island in the Indian Ocean. By collecting samples from birds with known social relationships—breeding pairs, helpers, and neighbors—they could compare the gut bacteria of birds that spent a lot of time together versus those that didn't.
The finding? Birds who spent more time together shared more similar gut bacteria—specifically, the anaerobic kind that can't survive in open air.
According to Chuen Zhang Lee, Ph.D., who led the research, "these anaerobic microbes can't survive in the open air, so they don't drift around in the environment. Instead, they move between individuals through intimate interactions and shared nests."
So it's about living in the same place, and about how much close contact you have.
The rat study: your genes can shape someone else's microbiome
A second study, published in December 2025 in Nature Communications1, took a different approach. Researchers at UC San Diego and the Centre for Genomic Regulation studied more than 4,000 genetically unique rats housed in different facilities across the U.S.
Because all the rats ate the same food, the team could focus on how genetics (not diet) affected gut bacteria. They discovered something surprising: a rat's gut microbiome wasn't just shaped by its own genes, but also by the genes of its cage-mates.
Here's how it works: certain genes encourage specific bacteria to thrive in the gut. When animals live together, those bacteria can spread between them through close contact.
The researchers found three consistent gene-bacteria connections:
- One gene (St6galnac1) adds sugar molecules to gut mucus, which feeds a bacterium called Paraprevotella—this was the strongest link
- A group of genes that build the gut's protective mucus layer was connected to Firmicutes bacteria
- A gene that produces an antibacterial peptide (Pip) was linked to Muribaculaceae, a bacterial family found in both rodents and humans
When the team accounted for this social sharing of bacteria, the genetic influence on the microbiome jumped four-to-eight times higher than previously thought.
What this means for humans
Before you start side-eyeing your roommate, spouse, or children, there are a few important caveats. Both studies were done in animals, not humans. The controlled conditions (identical diets, randomly assigned living partners) don't reflect real life, where we choose who we live with and eat very different foods.
Still, these findings raise interesting questions about how our living situations might subtly influence our gut bacteria over time. While more research is needed to understand exactly how this works in humans, the animal studies suggest that close contact and shared living spaces create opportunities for gut microbes to pass between individuals.
Diet, sleep, and lifestyle habits remain the biggest factors shaping your gut-brain connection and overall microbiome health, but the people around you may play a small supporting role.
The takeaway
While your diet, sleep, stress levels, and lifestyle habits are still the biggest factors shaping your microbiome, the people around you might have a subtle influence too. Looking to improve your gut? These two (easy) daily habits are crucial for supporting your gut microbiome.