how your guts could define your personality, literally

There’s a non-zero chance that you’ve once seen a person pull off a bold stunt, stand up to intimidation, or overcome visible nerves to talk to their crush and appreciatively said “damn, they’ve got guts” or oversized genitals made out of much harder material than flesh. And you may have been right about that. Well, the guts part. According to research into the collection of 100 trillion microorganisms that call your body home and known as your microbiome, what’s in your guts could very well be responsible not just for your overall health but for how you handle stressful situations, personality, and sociability, opening up brand new ways to think about treatments of chronic conditions and mental health.

Decades of studies unearthed some very interesting relationships between various hormones used to control our basic bodily functions like regulating our blood pressure and affecting our nerve signaling pathways when we deal with fear and stress. If that seems weird, remember that our microbiome is symbiotic and evolved with us for millions of years, so it would actually be much more bizarre if we had guts full of microbes, viruses, fungi that just hung around and did absolutely nothing. Now, a new study tracking the habits, attitudes, and the composition of microbiomes of 655 adults says that these organisms could even affect our personality, with extroverts having a more diverse gut biome than introverts.

are there bacteria that make us more social and happier?

One of the biggest benefits of being able to analyze the makeup of people’s biomes is zeroing in on the differences between them, then mapping it to the traits to which we think they may be somehow linked. In particular, more bacteria in the Lactococcus and Osciollospira genera tend to correspond to more extroverted individuals with more friends, which having fewer bacteria in the Desulfovibrio and Sutterella genera hint at introversion. Even more curious, those whose diets included naturally probiotic foods — not supplements, which seemed to have absolutely no detectable effect — also reported less stress, anxiety, and mental health issues. In short, the healthier and more diverse your microbiome, the healthier and happier you’re likely to be.

Unfortunately, we’re still not sure exactly how all this works, just that it does. We’re also not sure whether changing the gut biome can make people happier and more extroverted. While we know that weight loss has positive effects on mental illness, specifically when it comes to depression, we know this is due to how fatty deposits interact with your brain and that if you have fewer such deposits, they leave your hypothalamus alone. But this research on our gut flora and personalities isn’t just some weird, random one off. It fits quite well with what we already know about our biomes and just how extensively they seem to affect us in all stages of life, and provides concrete answers to some pressing questions.

so, how do we use this knowledge?

By understanding how our gut biome interacts with our bodies, we can better understand what antibiotics do to it, especially at a young age because there’s research showing some disturbing side-effects from the overuse of antibiotics in childhood. It also gives us ideas for treatments which change up our diets to promote certain bacteria and general microbiome diversity rather than more pills and shots for a wide variety of both physical and mental ailments. Finally, this research shows us just how important it is to make sure we have a properly balanced diet and make healthy choices, and just how much neglecting our health and paying no attention to what we shove in our mouths can harm us in ways we wouldn’t even think.

And while this is definitely reaching well into the future, this knowledge will play an important part in space exploration and any attempts to augment humans with technology. If deep space radiation damages our microbiomes, or our new cyborg parts affect their diversity and makeup, there may be very serious long term implications for our health and sanity, and we need to take them into account when considering new medical interventions and technologies to take us to the Moon, Mars, and beyond. All this research and new information is a terrific reminder that our bodies aren’t just interacting parts working largely in isolation, but complicated systems that need to be treated as such, and by failing to do so, we suffer the consequences.

See: Katerina Johnson, (2020) Gut microbiome composition and diversity are related to human personality traits, Human Microbiome Journal, DOI: 10.1016/j.humic.2019.100069

Chu, Coco, et al., (2019) The microbiota regulate neuronal function and fear extinction learning, Nature 574, 543–548 (2019), DOI: 10.1038/s41586-019-1644-y

Raizada k. Mohan, et al., (2017) Report of the National Heart, Lung, and Blood Institute Working Group on the Role of Microbiota in Blood Pressure Regulation: Current Status and Future Directions, Hypertension, DOI: 10.1161/HYPERTENSIONAHA.117.09699