How soil microbes influence our emotions

When they come into contact with us, soil microbes can modulate key hormones and neurotransmitters such as dopamine, serotonin, and oxytocin, Australian researchers explain. This is how they influence our emotional states

by Matteo Cavallito

 

Everyday emotions are triggered by personal experiences and, of course, are influenced by many factors. Among these, one in particular stands out as the most original: the soil microbiome. This hypothesis was recently put forward by experts at Flinders University in Adelaide, Australia, who investigated the dynamics that would lead microbes present in the soil and surrounding environments to influence the human microbiota and the ‘gut-brain axis’. By shaping our emotional states and relationships in this way, soil microbes can modulate key hormones and neurotransmitters such as dopamine, serotonin, and oxytocin. In this way, they influence our emotional states.

Microbes modulate hormones and neurotransmitters

The study is still in progress but it already draws on some theoretical foundations summarized in an article published in mSystems, a journal of the American Society for Microbiology, which explains how microbes can modulate key hormones and neurotransmitters such as dopamine, serotonin, and oxytocin. With all the related consequences. “Emerging evidence suggests that the human gut microbiome plays a regulatory role in the endocrine system, influencing hormone activity and potentially shaping the emotional and physiological dimensions of behaviors such as aggression and emotional states, including love,” the paper notes.

This does not mean that microbes “cause” love,  Jake Robinson, a member of Flinders’ Restoration Genomics and Biodiversity-Health Connections research group and co-author of the study, said in a statement. “Our aim is to map plausible biological routes, grounded in microbiology and endocrinology, that researchers can now evaluate with rigorous human studies.”

Odi et amo

Scientists have found that the emotions typically associated with romantic love correspond to specific neuroendocrine processes. Psycho-endocrinological theory, for example, argues that the interaction between testosterone, estradiol, and other hormones drives the emotions associated with desire, and that serotonin and dopamine play a role in attraction, while oxytocin and vasopressin influence the modulation of attachment and social bonds. Some studies on animals have confirmed these hypotheses at least in part, but research on humans is still limited.

For this reason, they explain, “Investigating the evolutionary underpinnings of microbial-endocrine interactions could provide insights into how microbes influence emotions beyond love, including hate and aggression—with important societal implications.”

Understanding these mechanisms would have profound implications for human relationships, mental health, and therapeutic interventions targeting the microbiota-gut-brain axis. It would also help to discover whether manipulating microbial communities can modulate behavior. But what does all this have to do with soil?

Is soil a possible source of emotions?

These dynamics, as described and hypothesized, explain the researchers, would also apply to soil microbes and those in natural environments. By spreading into the air we breathe, the food we eat, and the nature we come into contact with, they could enrich the human microbiome. In other words, soil microbes can also temporarily colonize our bodies and modulate our immune system by influencing the endocrine and neurochemical pathways linked to emotions.

In short, the quality of soils and ecosystems could therefore influence our relational and emotional well-being in this way.

“As well as emitting important chemical and microbial signals, healthy soils support vegetation that improves air quality, buffer noise and moderate temperature to create immersive environments that affect our nervous, endocrine and immune system,” explained Martin Breed, associate professor at Flinders and co-author. “Conversely, soil degradation can increase unhealthy airborne particulates and reduce the richness of the aerobiome, with possible downstream effects on inflammation and mental wellbeing.”