More Than Just Gut Feelings : Friends Don't Just Share Secrets, They Share Microbes!

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Who can do without friends? And our large circle of friends are the ones who often bond over shared interests that range from music tastes to lifestyle choices. But it turns out their similarities could run deeper, right into their gut. A study spearheaded by Yale University has revealed that our microbiomes, the communities of microbes in our digestive systems, may align with those of our close companions. Let's see how.

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A Study In Yale

A Yale-led study, published in the journal Nature, reveals that similarities between friends can extend beyond shared interests and lifestyles to include the microbiomes in their guts.

Analysing social networks and microbiome data from 1,787 adults across 18 remote Honduran villages, researchers identified 2,543 microbial species and over 339,000 strains.

Remarkably, the findings showed that microbiome similarities are present even among non-relatives and those not living in the same household, suggesting a deeper, unexpected link between social connections and microbial ecosystems.

What The Researchers Had To Say

"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," explained Francesco Beghini, co-lead author and postdoctoral associate at Yale's Human Nature Lab.

He further noted, "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." These findings underscore a fascinating connection between gut microbes and social bonds, offering new insights into the role of microbiomes in human relationships.

What The Study Revealed

The highest levels of microbial sharing were observed between spouses and individuals living in the same household, but interestingly, the study also found notable sharing among other social connections, including friends and even second-degree relationships, such as friends of friends.

People at the centre of social networks showed more similar microbiomes to others in their village compared to those on the periphery, indicating that microbes flow across social ties within these communities.

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The frequency of interactions whether through shared meals, handshakes, hugs, or kisses was also linked to an increase in microbial sharing. However, less microbial sharing was observed between individuals with no social connection, and even less so among those living in separate villages.

Two years later, when the microbiomes of 301 participants from four villages were remeasured, those with social ties showed increased microbial similarity, reinforcing the idea that social connections help shape our microbiomes.

The study also revealed that microbial species and strains tend to cluster within social groups, suggesting that social networks create environments where people develop similar microbiomes.

The Negative And Positive Sides

Jackson Pullman, co-lead author, drew an interesting parallel: "Think of how different social niches form at a place like Yale... Our study indicates that people in these groups may be connected in ways we never thought, even through their microbiomes."

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While the findings could suggest that certain diseases linked to the microbiome are more easily transmitted through social networks, they also highlight the positive potential for microbiome benefits to spread within these connections.

"What's so fascinating is that we're so interconnected," said Pullman, who now runs an artificial intelligence startup in the health-technology sector. "Those connections go beyond the social level to the microbial level."

The Link Between Gut Bacteria And Social Relationships

This insight highlights the depth of our interconnectedness, showing how even our gut bacteria can reflect the bonds we share. Nicholas Christakis, senior author of the study and Sterling Professor of Social and Natural Science at Yale, directs the Human Nature Lab, which focuses on research at the crossroads of social, biological, and computational sciences.

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"My lab is very happy to publish this paper, as it builds on an idea we proposed in 2007, that phenomena like obesity could spread not just through social contagion, but also biological contagion, potentially via the bacteria in our guts," Christakis explained. This breakthrough marks an exciting step in understanding how biological factors, like our microbiomes, shape and are shaped by our social worlds.