The Role of Social Networks in Shaping Gut Microbiome Diversity

A recent Yale University study reveals that friends not only share similar interests, preferences, and lifestyles but may also have comparable gut microbial compositions.

The study, which was published in the journal Nature, looked at the connection between people's social networks and the microbiomes, the bacteria and other microbes that live in their gastrointestinal systems.

The researchers used detailed microbiome data from each participant and a thorough mapping of the social networks of 1,787 adults residing in 18 remote Honduran villages. The extensive database contained 2,543 microbial species and 339,137 distinct strains, which are close genetic variants of the same species that share certain characteristics.

They discovered that similarities in microbiomes between individuals connected through a range of relationship types, such as non-household and non-familial relationships, above what would be predicted by chance.

We found substantial evidence of microbiome sharing happening among people who are not family and who do not 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.”

Francesco Beghini, Postdoctoral Associate and Study Co-Lead Author, Human Nature Lab, Yale University

Although spouses and those who shared a home had the highest rates of microbial sharing, the researchers also found that other connections, such as friends or even second-degree social ties (such as friends of friends), had higher rates of sharing.

Additionally, in line with a social flow of microorganisms across network linkages within the villages, individuals at the heart of the social networks resembled the other villagers more than those at the social periphery.

An increase in microbial sharing was also linked to the frequency of social interactions, such as how often individuals share meals or greet one another through kisses, embraces, or handshakes.

At the same time, the researchers found that residents of the same hamlet who did not have social ties to one another shared fewer microbes. Additionally, they saw considerably less sharing between those who resided in other communities.

A group of 301 people from four of the villages had their microbiomes remeasured by the researchers two years after the original data collection. They discovered that the socially connected members of this subset had developed greater microbiological similarity than the unconnected members.

Additionally, the researchers found that clusters of microbial species and strains are found within villages and groups of people, indicating that social networks offer niches where people might establish similar microbiomes.

Think of how different social niches form at a place like Yale. You have friend groups centered on things like theater, 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.”

Jackson Pullman, Undergraduate Research Assistant and Study Co-Lead Author, Human Nature Lab, Yale University

The researchers stated that the results have both positive and negative ramifications. For instance, they imply that some illnesses or ailments linked to the microbiota are more contagious than previously believed. However, they also show that social networks can be used to spread the advantages of having a healthy microbiome.

“What is so fascinating is that we are so interconnected. Those connections go beyond the social level to the microbial level,” said Pullman, who now manages an artificial intelligence startup he founded in the health technology sector.

The Human Nature Lab, led by Study Senior Author Nicholas Christakis, Sterling Professor of Social and Natural Science in Yale's Faculty of Arts and Sciences, investigates issues at the nexus of the biological, computational, and social sciences.

My lab is very happy to publish this paper since it reflects the ongoing pursuit of an idea we articulated in 2007, namely, that phenomenon like obesity might spread not only by social contagion but also by biological contagion, perhaps via the ordinary bacteria that inhabit human guts.”

Nicholas Christakis, Project Principal Investigator and Study Senior Author, Yale University