Digging in the Dirt Makes You Happy — Here’s Why

Contributing writer for Wake Up World

“It came to me while picking beans, the secret of happiness. I was hunting among the spiraling vines that envelop my teepees of pole beans, lifting the dark-green leaves to find handfuls of pods, long and green, firm and furred with tender fuzz. I snapped them off where they hung in slender twosomes, bit into one, and tasted nothing but August…” ~ from Braiding Sweetgrass: Indigenous Wisdom, Scientific Knowledge and the Teachings of Plants

For anyone who has spent time cultivating a garden — vegetable, landscaping with ornamentals or a bit of both — there’s no question about it’s mood-boosting quality. Even a potted plant or two can have an uplifting effect. During my most bleak times in dealing with depression and bone-crushing fatigue, the simple act of caring for an outdoor plant by watering and plucking the dead bits has had a near miraculous effect, with a tangible boost in energy and overall brighter outlook. Whether this shift is attributed to the fresh air, slowing down to appreciate a bit of greenery or nurturing another living thing, the entire experience tends to border on the mysterious. Whatever the reason, one aspect is clear: gardening is strong medicine.

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The Power of Soil-Based Organisms for Health and Happiness

Science has shown time and again that spending time in nature — along with playing in the dirt and gardening — has a powerful impact on our physiological and psychological health. Over the last decade, researchers have explored why soil microbes improve the nutritional value of our food and why rural children — like those who live on farms — are far healthier than their city-dwelling counterparts. Clean air, water, and fresh produce aside, one of the main factors for the health of farm-living kids boils down to soil microbes. As it turns out, these microbes help develop healthy human immune systems. Not only that, but soil organisms can boost our production of serotonin — a feel-good neurotransmitter that keeps anxiety and depression at bay.

Writes Daphne Miller in The Curious Case of the Antidepressant, Anti-Anxiety Backyard Garden:

“[Jill] Litt, a professor at the University of Colorado School of Public Health, was studying gardening’s impact on a variety of health outcomes — including mood disorders. She rattled off a list of possible explanations, including that gardens create community, encourage physical activity, offer a bounty of nutrient-rich food, and expose one to Vitamin D-producing sunshine, which helps regulate serotonin, the “happiness” neurotransmitter. But then Litt surprised me by adding, “Also there are the microbes themselves. We have no idea what they are doing.”’

It all began with a study where British researchers were testing to see if Mycobacterium vaccae — a benign microbe found in soil and water, along with unwashed vegetables — could help treat lung cancer in humans. While the life expectancy of the participants wasn’t affected, those who received the microbe reported enhanced mood and quality of life.

The torch was then taken up by Chris Lowry, a behavioral endocrinologist at the University of Colorado, Boulder. His research team found that rodents who were injected with heat-killed M.vaccae exhibited less depression and anxiety — and had more endurance — during a forced swim test. The control mice paddled on average for two and a half minutes, while the M. vaccae—injected animals swam for four. It’s already been established that antidepressants increase active swimming and decrease immobility. Interestingly, the soil organism “had the exact same effect as antidepressant drugs,” explained Lowry.

The researchers believe that an immune reaction to the microbe activates the release of brain serotonin. Low levels of this important neurotransmitter are linked with a range of disorders, including aggression, anxiety, depression, obsessive compulsive disorder (OCD), bipolar disorder, irritable bowel and fibromyalgia.

The results so far suggest that simply inhaling M. vaccae — you get a dose just by taking a walk in the wild or rooting around in the garden — could help elicit a jolly state of mind. “You can also ingest mycobacteria either through water sources or through eating plants — lettuce that you pick from the garden, or carrots,” Lowry says.

Graham Rook, an immunologist at University College, London and coauthor of the paper, points out that depression may partly be an inflammatory disorder. By triggering immune cells that diminish the inflammatory response to allergens, M. vaccae could actually ease inflammation and, in turn, depression.

Further studies on M. vaccae’s mood-boosting properties followed, one of which by Susan Jenks and Dorothy Mathews of Sage Colleges in Troy, New York. The team cultured the live organism and fed it to mice with Wonderbread and peanut butter.

“It was just amazing,” said Jenks about a stressful maze test used for the rodents. “We would place them in the maze and could clearly see that there were some mice doing better than others. We would think: ‘Is that the M. vaccae [mouse]?’ And sure enough it was.” She adds, “What our research suggests is that eating, touching, and breathing a soil organism may be tied to the development of our immune system and our nervous system.”

The takeaway from all this? If you struggle with depression or immune disregulation, gardening without gloves and spending time in nature may be just what the doctor ordered. Or, as Danielle Mariott writes in a piece for Backcountry magazine, “Get outside, get in the dirt, get happy.”

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