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LifestyleColumnistsJessica Damiano

Bacteria in soil has antidepressant effects

The soil-serotonin connection can help to explain feelings

The soil-serotonin connection can help to explain feelings of well-being in the garden. Credit: iStock

There’s something about the scent of soil and freshly mulched garden beds that makes me happy. My bohemian, Mother-Earthy side reacts to the smell of dirt the same way it does the scent of a baby or puppy breath. I inhale deeply and feel at peace with the world. All this time, I attributed that to my love of the trees, shrubs, perennials, annuals and vegetables that grow from it. But my reaction isn’t necessarily related to my green thumb. Inhaling soil has been found — scientifically — to have actual antidepressant effects.

Mycobacterium vaccae, a naturally occurring friendly bacteria found in soil, has been the focus of research in the United States, England and elsewhere for more than a decade, and the findings are impressive. In 2004, Mary O’Brien, an oncologist at Royal Marsden Hospital in London, discovered that lung cancer patients injected with the inactivated microbe reported less pain, less nausea, a higher quality of life and lower stress levels than those who were not inoculated. She concluded the microbe “significantly improved patient quality of life without affecting overall survival times.” Intrigued, other scientists dug deeper.

A 2007 article in the journal Neuroscience reported that researchers at the University of Bristol in the United Kingdom found that mice who were fed rewards containing the bacteria produced more serotonin, the mood-regulating neurotransmitter targeted by common antidepressants such as Prozac. And in 2013, the National Center for Biotechnology Information in Bethesda, Maryland, conducted multiple experiments in which mice were fed live M. vaccae bacteria before and during maze trials. Astonishingly, they demonstrated “a reduction in anxiety-related behaviors” and completed the maze twice as fast as those not given the bacteria. What’s more, these studies found that the benefits lasted up to three weeks after exposure.

It’s no big leap, then, to conclude that gardening, during which we regularly inhale and ingest soil dust, would yield similar effects.

We already knew that microbes in the soil contribute to the nutritional value of food and that being out in the sunshine, listening to birds chirp and watching an earthworm wriggle help quiet the mind. What we now know is that we have more than peace and quiet to thank.

When gardeners talk about their time digging and planting in terms of stress relief, the soil-serotonin connection becomes clear. We all just need to get out more, since merely walking through the woods, crunching on compacted leaves and breathing deeply was found to have similar effects. The research is in, and it shows inhaling soil organisms — even if not actively touching them — alters brain chemistry.

If nothing else, I now have a scientifically irrefutable explanation for why sipping iced tea while sitting on the deck and watching my husband pull weeds puts a smile on my face.

Four Long Islanders answer the question: What makes you happy in the garden?

“In addition to the mental relaxation, how the various perennials pop up and the annuals are constantly blooming throughout the season.”

— Angelina Mederos, Shirley

“Therapy. Anticipation. Escape.”

— Martha Rowan, East Rockaway

“The silence and solitude along with the satisfactory results of having worked with Mother Nature. The end result of a beautiful display and/or a tasty meal.”

— Linda Frohlinger, Massapequa

“Gardening helps me to feel close to those I learned from, even long-gone family members: my wife, my parents and my grandmother, who taught me to garden in her yard when I was 4 years old. I still feel them near, smiling over me while I tend my gardens.”

— Jeffrey Hirsch, Bay Shore

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