How Dirt Makes Us Smart And Happy

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Soil Microbes Boost Happy Hormones

A fascinating article by Sarah Agan posted on the Excellence in Government website ( posits health benefits from two of my favorite things; working in the garden and singing. Indeed, I always sing or hum while gardening, just because it feels terrific. As it turns out, there are excellent reasons for those feel-good moments. I am getting my hands “dirty” and in the process, my brain is getting a booster dose of serotonin.

Who knew? Turns out that, just as Bt, or Bacillus thuringiensis, is a naturally occurring soil bacteria with multiple applications (mostly as pesticides), another soil dweller, Mycobacterium vaccae, offers humans who dabble in dirt a lovely lift. Like so many health advances, the first recognition of mood elevating effects from M. vaccae came about accidentally, when a dose intended to boost immune response serendipitously created an antidepressant effect in advanced cancer patients.

Feel Mellow, Get Smart

You don’t need to be ill to enjoy similar benefits, which come naturally to those of us whose hands are often dipped in dirt. The serotonin-elevating effects, which increase happiness and decrease anxiety, can be achieved simply by gardening. Digging in the dirt and shoveling compost (or at least breathing while we do it) may also make us smarter, according to researchers Dorothy Matthews and Susan Jenks of The Sage Colleges in Troy, New York.

Matthews explains that the benefits are actually absorbed through our lungs, not our hands, so even those who stand by and breathe as we hands-on types actively garden may benefit. Indeed, breathing in M. vaccae may be responsible for our feelings of well being when we hike in natural settings. Matthews and Jenks found that mice injected with heat-killed M. vaccae experienced neural brain growth and displayed higher serotonin and lower anxiety levels. They wondered whether live M. vaccae might help mice learn, and indeed, their studies indicate that it does. “We found that mice that were fed live M. vaccae navigated the maze twice as fast and with less demonstrated anxiety behaviors as control mice,” said Matthews.

Don’t Stop Believing

The good news is we don’t need injections or heat-killed bacteria to benefit from exposure to M. vaccae. However, the effects seem to be temporary, lasting less than three weeks. To get the most from the magic, get back into the garden as often as possible. Even a weekly dose can keep the natural high going, but when times are tough, a daily dose of hands-on gardening will help keep you smart and smiling. On really rough days, we may need to go outside and breathe deeply for a few minutes every hour….

“This research suggests that M. vaccae may play a role in anxiety and learning in mammals,” says Matthews. “It is interesting to speculate that creating learning environments in schools that include time in the outdoors where M. vaccae is present may decrease anxiety and improve the ability to learn new tasks.” In simple terms, this means we need to get school kids outdoors more often, and preferably into the garden. Next time you garden, take a student along!

More Mysteries of the Soil

Poking around on the net, following article leads and links, I also learned about the scent of good earth, which scientists call ‘geosmin’ and we call delicious. It caught my attention because I’ve been thinking lately about what makes scents delicious or awful to us, assuming that health played a part. It seems likely that as we evolved, humans learned to avoid things that made certain kinds of smells we now identify as rank or foul, though from what we know about, say, the Middle Ages, it also seems likely that we would think the people themselves living then stank to high heaven. They did not know about dangerous smells like pesticide fumes, while we, thankfully, are less acquainted with the smell of rotting wounds or untreated sewage.

Similarly, we must have found the scents of ripe fruit and honey appealing from our earliest history, and doubtless the first farmers learned to judge soil quality at least in part by its rich, sweet smell. To this day, farmers feel, smell, and sometimes taste soil to learn about it. Watching my new grandson put everything he possibly can into his mouth, I wonder whether mouth receptors still function as guides to food safety (though thinking about what my own kids put in their mouths at tender ages, I’d guess the reception function is a lot less squeamish than our sophisticated brains).

Hands-On Benefits

Just breathing in M. vaccae when handling soil or compost helps our day improve, but it turns out that the hands-on part also contributes to a sense of well being. I have always found knitting soothing and meditative, and now I know why; it turns out that handwork triggers what’s called an ‘effort-driven rewards circuit’ in our brains. That circuit produces brain chemicals that promote well being and helps relieve depression and anxiety.

The rewarding effect is especially triggered by handwork that produces a pleasing result, such as growing and harvesting vegetables, knitting a baby hat, or cooking dinner for your family and friends. When we use our hands to make something that we find attractive, useful, or beautiful, it literally makes us feel good. In a day when much office work is anything but hands on and many people work all day without having anything concrete to show for it, it definitely seems wise to develop a hands-on hobby or two!

Think I’m nuts? Check out these links and see that I’m not alone:

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2 Responses to How Dirt Makes Us Smart And Happy

  1. Meredith says:

    What a life changing post. This completely resonates with me! So funny that there was a message in my inbox today, from our school district, promoting master composting classes from Seattle Tilth to be taught in our area. What do you think? Take the course or teach myself?

  2. Deirdre Mowat says:

    A fascinating and thought-provoking article. Thank you.

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