Digging In: Soil Microbes and Our Health

Sink your hands into moist loam, feel the granules massage your fingertips, the heft of soil press against your skin. Lift a palmful to your nose and inhale the sweet, earthy scent, squeeze it into a ball, and then watch it crumble back apart. There’s something so satisfying and primal about the sensory experience of soil. Why is that?

A good part of my love affair with gardening is how it makes me feel. That’s why I was excited when I read research that offers some explanations for how dirt can lift my mood, and how contact with soil can treat anxiety, depression, and a host of inflammatory diseases.

We are interconnected beings. You are a large organism that is in reality a community of much tinier ones, all communicating and working together to create the functioning miracle of who you are. Just as in any ecosystem, when there’s an imbalance in one place, the whole community gets thrown out of whack.

What does this have to do with playing in the dirt, and anxiety and depression?

Let’s start here: This article from Psychology Today says various research has made it “now indisputable” that there is a link between inflammation and most elements of mental health (among them: anxiety, depression, stress, autoimmune conditions, Fibromyalgia, and PTSD). Perhaps the most well-known condition that demonstrates this link is “leaky gut,” where an imbalance in the gut microbiome damages the gut lining and allows toxins and bacteria to leak out and end up in places in the body where they cause all sorts of trouble. Wherever those unwanted intruders show up, the immune system kicks in, using inflammation as a defense, which often becomes chronic.

There’s a lot more we could talk about regarding this link between inflammation and mental health, but I want to get to the treatment you can find right outside your front door. This article from Vice.com discusses Chris Lowry, a behavioral neuro-endocrinologist at University of Colorado Boulder, and his work over the past decade. He and his team “have shown in animal models that a particular soil bacteria, Mycobacterium vaccae (or M. vaccae), can reduce inflammation and the troubling behavioral symptoms that come with it.”

Mice that received an injection of M. vaccae behaved less anxiously and got over being afraid quicker than other mice (when faced by an aggressive male), produced more serotonin (that feel-good hormone our bodies make), and were less likely to develop inflammation.

As I read this report, I thought of how listless one can feel when depressed. And I wondered if even that listlessness is a protective instinct meant to get us some good earth medicine. A century or two ago, if you felt listless, you’d probably lie down on the dirt floor of your hut or your field. While you were lying there, soil microbes like M. vaccae would work their magic to get you back on your feet. 

Which brings us to the question of why we citizens of affluent countries have so much chronic inflammation in our bodies. 

Over the past century-and-a-half, the transition to a more sanitary and sterile lifestyle has helped us control infectious diseases, but there’s been another cost to our immune systems. We develop strong and savvy immune systems by exposing them to challenges at an early age. If they haven’t been educated by encountering a series of threats, our immune systems don’t know what to do when they do encounter one, and they can overreact, with chronic inflammation. 

One of Lowry’s colleagues, Graham Rook, says this modern problem comes from: “an overuse of antibiotics, cesarean sections, the radical changes in the foods we eat, the loss of old infections (like TB, hepatitis A, helicobacter pylori, and parasitic worms), and from not coming into contact with organisms that live off dead and decaying matter found in the mud and soil.”

Earlier this year, Lowry, Rook, and others discovered that M. vaccae contains a lipid that mammals cannot produce that binds to a receptor in our immune systems and slows inflammation. The scientists hope to develop M. vaccae as a vaccine for humans that would reduce inflammation and support mental health. That could be great. 

But to me, these findings simply offer a further invitation to connect with the stuff that supports our feet and grows our food. M. vaccae is just one of many microbes in a complex community.

Maybe childrens’ mud play is actually wisdom of instinct, exposing them to sensory pleasure and to immune strengthening. Let them roll in it. We should let ourselves roll in it, too. 

When we’re depressed or anxious, it’s easy to get into a self-perpetuating cycle. Whether you’re over-busy or keeping yourself tucked away from the world, it can be hard to step out of that cycle. 

So: here’s some encouragement that you are worth it. You are part of a greater unseen world that’s working together to support your health, both physical and mental. It could just take a few minutes outside to start letting those microbes help you.

You could snuggle a pet who’s just taken a dirt bath. You could find a soft, shady spot, and stretch out for a nap on the ground, or lie on your belly and examine the workings of the insect world in its grass forest. You could dig your bare hands into a planting pot of soil, plant a seed. 

You could take your shoes off and scrunch your toes in the soil. There’s other exciting research about how the electrons on the earth’s surface help keep our bodies in optimal balance. In this area of study, researchers have found that walking barefoot or sleeping on the earth for as little as 30-40 minutes a day can positively affect autoimmune disorders, sleep troubles, chronic pain, chronic stress, heart rate variability, and blood pressure issues, to name a few.

It’s almost time to plant seeds for a winter cover crop where we live, and I’m dreaming of an early spring garden filled with dark reds and purples on a backdrop of deep green. Crimson clover and purple lupine, I think, will be just the thing for me to plant this fall. They’ll give nitrogen to the soil and a feast to the eyes. I’ll be sure to take off my garden gloves as I aerate the soil and scatter seeds, knowing the soil will be enriching me, too. 

2 Replies to “Digging In: Soil Microbes and Our Health”

  1. Morgan, Thank you! I just went to a permaculture workshop at the New Paradigm College and I want to learn more about composting and the soil! So much nutrient in healthy soil! From a mental health perspective — I love how composting turns something raw and smelly into something akin to black gold! Take care.

    1. Barbara,
      That sounds like a wonderful class, and yes, I’m astounded on a regular basis by the beautiful compost that comes from letting smelly stuff sit and be worked on by microbes over time. It seems a lovely reminder that we don’t necessarily have to always work so hard to create what we want in life–time and nature takes care of us in so many ways. Best wishes to you.

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