I love digging in the dirt. Something about the soil, and all that life teeming inside, makes me feel alive. I love to work in the garden with bare hands and feel all that moist, dark earth between my fingers. I love the smell of freshly turned compost after it’s been sitting for six months. (By the way, that sweet smell of dirt comes from an organic compound called geosmin — and it’s also what gives beets and carrots their earthy flavor.)
I don’t know what it is, but that sort of stuff makes me happy. I feel lighter and calmer, even when I haven’t crossed anything off my garden checklist.
As I’ve found out, sifting through soil is not only therapeutic, but also… pharmaceutic?!
Studies have shown that a bacterium in the earth, Mycobacterium vaccae, works like an antidepressant by releasing serotonin (the natural “happy drug”) in your brain, much in the same way that Prozac works. The mind-altering (but harmless) bacterium has been found to boost levels of serotonin and norepinephrine in both mice and humans. By simply taking a walk in the woods or digging in the dirt, you can dose yourself with nature’s happy pill just by breathing in the smell of clean earth. “High on life” has a totally new meaning now.
The effects of M. vaccae were accidentally discovered over a decade ago by Mary O’Brien, an oncologist at Royal Marsden Hospital in London. In an experimental treatment for lung cancer patients, Dr. O’Brien inoculated the patients with heat-killed M. vaccae. She observed that not only did the patients exhibit fewer signs of cancer, but they also reported less nausea and pain, and an overall greater sense of well-being and happiness.
Following Dr. O’Brien’s trials, Christopher Lowry, a neuroscientist at University of Bristol in England, conducted an experiment with mice and found that the immune response to an injection of M. vaccae induced the brain to produce serotonin. The results were significant because they offer the possibility that clinical depression could be treated with what is essentially a vaccine. Secondly, the vast effects of our natural immune response to this wonder bug could be further explored as a treatment for not only cancer and depression, but also Crohn’s disease and rheumatoid arthritis.
In a 2010 study by Dorothy Matthews and Susan Jenks of The Sage Colleges in New York, mice were fed live M. vaccae (smeared on little peanut butter sandwiches — mm mmm!) and found to have lower levels of stress and higher levels of learning. Their improved mood and performance continued for a few weeks, even after the bacterium was removed from their diet. Though the effects were temporary, they proved a link between M. vaccae boosting serotonin, and serotonin playing a role in learning.
In productive garden soil, there can be anywhere between 100 million and 3 billion bacteria in a gram (about a teaspoonful). These hard-working microbes do everything from fixing nitrogen to decomposing material in the soil. And now, they’re even responsible for lifting your mood and making you smarter.
This is not to say you should go out and start eating dirt (although a little dirt never hurts — I love to eat tomatoes and berries right off the vines). But do get outside, get a little dirty, and get stoned on soil — it’s good for you!