Friendships are rooted in mutual interests and passions. Some sort of common ground sparks the friendship, from similar hobbies or being a part of the same fanbase. But what about the gut? Friends have similar gut microbe ecosystems. No wonder the gut feeling drives the first awkward small talk to become best friends soon later.

A noteworthy Yale-based study published in the journal Nature found a relation between social connection and the makeup of their microbiomes in the gut. The microbiome is the communities of bacteria, fungi and other microorganisms living in the digestive system. It’s an astonishing take on how social networks affect us, even at the most microscopic, microbial level.

More about the research

The research carried out a comprehensive examination of 18 isolated villages in Honduras, assessing the social connections and gut microbes of 1,787 adults, and inspecting 339,137 microbial strains. Surprisingly, people within the same social networks, whether they live together or not, show similarities in their microbiomes.

Co-lead author Francesco Beghini said, “We found substantial evidence of microbiome sharing happening among people who are not family and who don’t live together, even after accounting for other factors like diet, water sources, and medications. In fact, microbiome sharing was the strongest predictor of people’s social relationships in the villages we studied, beyond characteristics like wealth, religion, or education.”

Patterns

The similar microbiome makeup in the gut was seen the most in cohabitants, partners or other household members. But here’s where it gets fascinating, the high amount of microbial sharing was also high in friends, and even their friends’ friends (second-degree connections.) These similarities most likely originated from shared activities, including frequent meals together or physical interactions like hugs and handshakes, which led to the transfer of microbes in social circles. Those who are not a part of this social network don’t display similar microbial resemblances. Microbial sharing is far less among those who don't share any social relationships, despite living in the same place.

To further cement this revelation, the researcher again came back two years later after their initial assessment and reexamined the microbiomes of 301 participants from four villages. They found that those who were socially connected had become more alike in their microbiomes compared to those who weren’t connected.

And much like forming a group among friends, looks like microbiomes do the same. The research surprisingly found that groups of people in the villages shared specific types of microbes. It reflects that social networks foster similar microbiomes. There were clusters of microbial strains in social groups that were different.

Co-lead author Jackson Pullman said, “You have friend groups centred on things like theatre, or crew, or being physics majors. Our study indicates that the people composing these groups may be connected in ways we never previously thought, even through their microbiomes.”

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