Beneficial bacteria: A March 2020 study (“Gut microbiome composition and diversity are related to human personality traits”) in Human Microbiome Journal, by the University of Oxford’s Katerina Johnson, offers surprising insights about beneficial bacteria and human social behavior.
At a glance:
Oxford researcher links some personality traits to the presence of different types of bacteria in the gut.
The presence of “beneficial” bacteria or “harmful” bacteria is less important than how diverse your microbiome is.
If your microbiome is more diverse, you are likely to be more social and in better health.
Sociability and better linked to beneficial bacteria
Katerina Johnson is a researcher in experimental psychology at the University of Oxford. She studies how bacteria, beneficial bacteria and harmful bacteria, affect psychological health and behavior.
The biology of human life is complex. We cohabitate with billions of commensal species of bacteria. And Johnson’s experiment considers a number of variables.
Her study included 655 individuals from four different continents. Participants provided fecal samples. The microbiome in each sample was then sequenced. At the same time, participants answered questions about their behavior, lifestyle, diet, and health. They did this via a detailed on-line questionnaire.
The results: Several types of bacteria correlated with lower levels of sociability. Other bacteria were associated with neurotic tendencies. These correlations were statistically significant.
The genera Akkermansia, Lactococcus and Oscillospira were found to be more abundant in individuals with a higher sociability score.”
However, since many variables contribute to our personalities, the overall effect of any type of bacteria is difficult to quantify.
Furthermore, this was an observational study partly based on self-reporting. As Johnson herself points out, the gut-brain axis is known to be bi-directional. Yes, gut bacteria can influence behavior. But it’s also true that behavior can influence gut bacteria. Researchers have yet to determine which comes first: the bacteria or the behavior.
The bigger picture
We’ve known since at least the 1970s that not all bacteria are created equal. And that not all germs make us sick.
Sure, there are bacteria that can be deadly. Especially when they grow unchecked. These include the bacteria that cause salmonella and those that cause pneumonia. But, in part thanks to the discovery of penicillin and other antibiotics, bacterial infections like these are much less likely to kill us than they were a hundred years ago.
Right, so “germs” can and do make us sick. However, it turns out that some bacteria are beneficial to humans.
In fact, arguably the most important—and surprising!—biological discovery of the twenty-first century is that bacteria are necessary for human life. As adults, we humans have more bacterial cells than human cells in our bodies. We can’t live without our bacterial hitchhikers. As much as germs may make us sick, “germs” also help us be healthy.
We are a network of symbiotic species
My mother, Lynn Margulis, has been talking about symbiosis since the late 1960s. But it wasn’t until recently that biologists and medical doctors have finally started to listen. Microbiologists used to dismiss her ideas. And most medical doctors had no idea what the microbiome was. In fact, until recently, biologists focused on the idea of the body as a machine. But we aren’t machines. We are actually intricately interwoven networks of symbiotic species.
Beneficial bacteria help us digest our food. They produce important nutrients such as B vitamins and short-chain fatty acids. And there’s more: these beneficial bacteria even coordinate our nervous system through production of neurotransmitters, such as the “happiness hormones” serotonin and dopamine.
Depending upon which species predominate, our gut bacteria can help us keep lean or, conversely, pack on the pounds—independent of how many calories we consume! Gerard Mullin, M.D., explains this in his book, The Gut Balance Revolution.
Antibiotics kill beneficial bacteria
In what some might see as the ultimate irony, bacteria, especially beneficial bacteria, even help us fight infection.
At the same time, recent research indicates that good health is associated, not with the lack of any particular species of bacteria, but with the presence of a wide variety of bacterial species.
Consider this: the more types of bacteria we house in our guts and elsewhere, the less likely it is that any one particular species will grow unchecked. And remember it is unchecked growth that often leads to disease.
Our microbiome is our own personal collection of gut “bugs.” And it—the microbiome—is involved in our defense against both pathogenic bacteria and viral pathogens as well.
What this means is that bringing out the antibiotic big guns to annihilate every last strep or staph bacterium is likely leading to a host of negative consequences for human health.
Among these negative consequences: a disturbing rise in anxiety and mood disorders, autism, and other neurological challenges.
Fecal transplants improve brain health
Several scientific studies, including this one, have uncovered an association between autism and disturbed gut flora, known as “dysbiosis.” In fact, overgrowth of specific types of bacteria have been associated with autism (including Clostridium and Sutterella) as well as with certain mental illnesses.
Fecal transplants are the transfer of feces from a healthy donor with healthy gut microbes into the colons of patients suffering from neurological disorders. These fecal transplants can improve behavior in patients suffering from autism. This bolsters the idea bacteria influence the brain. It was the gut-brain connection that inspired Johnson to research the link between less extreme personality traits and our microbial symbionts.
Encouraging the growth of beneficial bacteria
Which brings us back to the Oxford research. Using two different measures of microbiome diversity, Katerina Johnson found a high correlation between microbiome diversity and general good health. Conversely, she found chronic infectious disease, immunodeficiency, and cancer correlated with a lack of microbiome diversity. This research supports a growing body of science that links good health with microbiome diversity.
Perhaps one of the best things we can do for our health is to behave in ways that encourage the growth of beneficial bacteria in our guts. The more humans we connect with, the more types of bacteria they transmit to us. These social interactions help diversify our microbiomes, which in turn may help us be healthier.
Wait, what? Social solidarity not social distancing?
Katerina Johnson’s work on microbiome diversity is especially important in light of public health strategies to stop or slow the spread of COVID-19.
Since March of 2020, public health officials in the United States and many other countries have exhorted us to stay home, keep our distance from others, and minimize contact.
But all of these behaviors are likely to reduce the diversity of our gut bugs. Social distancing may actually make us sicker than we are already. Avoiding all social interaction doesn’t just result in loneliness, despair, and self-harm. Extrapolating from this Oxford research, it may discourage the growth of beneficial bacteria and ultimately harm our health.