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2 critical emotional states are influenced by gut health — study

New research takes the concept of a "gut feeling" to a whole other level.

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Wisdom is difficult to define. There are those who we know are wise — Gandalf, Obi-Wan Kenobi, Kermit the Frog — but why they are wise is more challenging to say. There’s no single, all-inclusive definition of wisdom, some scientists argue. But what they do know is one state of being has an inverse relationship to wisdom: loneliness.

Tanya Nguyen is an assistant professor of psychiatry at the University of California, San Diego. She’s very interested in the evidence suggesting people who are deemed to be wiser are less prone to feel lonely, and those who are lonelier are less wise. She also studies the gut-brain axis, and how the relationship between the gut microbiome and the brain influences healthy aging.

Nguyen’s new study combines these two interests, finding wisdom and loneliness influence the gut — or are influenced by the gut. Or maybe both. Either way, there’s a connection — a behavioral, biological link ready to be explored, with the potential to inspire new treatments for the mind and body.

“We cannot know for sure at this point, but my guess is that it is likely a bit of both,” Nguyen tells me. This was a cross-sectional study, meaning it can show a connection but cannot predict the “directionality of the relationship.”

“We know that being lonely can lead to other physiological changes in the body, so it is feasible that those changes could also involve, or perhaps even be caused by, the microbiome,” she says.

“Or conversely, perhaps having a specific microbiome might change social behaviors that lead to loneliness.”

The link between the gut and behavior

When it comes to how the gut influences the self, most of what we know comes from animals. Studies in different animal species, Nguyen explains, demonstrate microbes can create cues that are used in social interactions and communications. Rodent studies, for example, suggest alterations in gut microbiota can modulate emotional behaviors, including depression and anxiety.

We don’t have equivalent research in people just yet, but past research has associated gut microbial diversity and composition with certain personality traits and psychosocial constructs. For example, a study published in March 2020 in the Human Microbiome Journal found people who are more social have a more diverse gut microbiome, while people who are more anxious have a less diverse gut microbiome. But importantly, this is an observed association — not a cause-and-effect finding.

Nguyen and her colleagues’ study, published in March in the journal Frontiers in Psychiatry, is the first to show loneliness and wisdom are related to gut microbial diversity and composition.

What was discovered — The team analyzed the fecal samples of 184 study participants between the ages of 28 and 97 alongside their self-reported measures of loneliness, wisdom, compassion, social support, and social engagement. Those fecal samples helped the team measure microbial gut diversity.

They looked for alpha-diversity — which is the “ecological richness” of microbial species within a person — and beta-diversity, which are the differences in the microbial community between people.

“... aspects of mental health and well-being are very closely connected to our physical health.”

Overall, higher levels of wisdom, compassion, social support, and engagement were found to be associated with more diverse gut microbiomes. Loneliness, meanwhile, was associated with dampened microbial diversity, especially among older adults, which jibes with previous work suggesting older adults are especially vulnerable to the health-related consequences of loneliness.

Still, “the mechanisms by which loneliness, compassion, and wisdom may be related to gut microbial diversity is unknown,” the team writes. Other research has found a link between reduced alpha-diversity and worse physical and mental health, while low microbial diversity is also related to conditions like major depressive disorder.

There is, the study suggests, a possibility that lonely people “may be more susceptible to developing different diseases” while social support, compassion, and wisdom may confer “protection against loneliness-related instability of the gut microbiome.”

What’s next — Could warding off loneliness boost gut health and, in turn, help with healthy aging? It’s possible. One can increase wisdom through behavioral interventions. This study is a sign that’s a smart choice for overall wellness.

“The most important message [of the study] is that aspects of mental health and well-being are very closely connected to our physical health,” Nguyen says.

“Even seemingly ‘fuzzy’ concepts, like loneliness and wisdom, can be related to and perhaps even influenced by ‘hard’ biological entities. Loneliness contributes to real medical morbidity [even mortality], and the gut microbiome may be an important factor in this connection.”

This complex interplay between the gut and brain, Nguyen says, has been known for centuries. Some of the earliest reports linking gastrointestinal functioning and mental health go back to the late 18th and early 19th century. But the past five years have been witness to a renaissance in gut-brain research due to technological advances in sequencing microorganisms.

Next, she wants to study the gut microbiome over time in an effort to understand the chicken-and-the-egg connections here. Is the gut influencing behavior, driving loneliness, or is loneliness influencing the gut? The answer can help experts know how they can potentially intervene and develop “therapeutics to help improve mental health and aging,” Nguyen says.

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