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Now that the weather has taken a spring-like turn, my friends and I, along with our dogs, pile into the one car amongst us every weekend and head out of Brooklyn to hike the trails in Harriman State Park—just an hour north of NYC. As soon as the scenery changes from concrete gray to green, we open our windows and breathe in the fresh air. The dogs wag their tails in anticipation, and I feel just as giddy and alert. There’s just something about getting out of the city and into nature that has a total rejuvenating effect. And that’s not just me speaking.
According to research presented at the 110th General Meeting of the American Society for Microbiology in San Diego, dirt may make us smarter. Exposure to mycobacterium vaccae, a type of bacteria found in soil, appears to increase levels of serotonin—a chemical in the brain that can boost mood, decrease anxiety and improve learning. According to one of the authors of the study, Dorothy Matthews, Ph.D., biology professor at Sage College of Albany and Russell Sage College, we very likely breathe in the bacteria when we spend time in nature. Perhaps that explains studies like this one, which suggest getting in touch with Mother Nature is good for your mood and self-esteem.
Drawing on past research that shows M. vaccae has an antidepressant-like effect in mice, Matthews and her colleague, Susan Jenks, wondered if it could also improve learning, since serotonin also plays a role in processing information. They found that mice exposed to the bacteria navigated a maze twice as fast with fewer signs of anxiety than the mice that were not given M. vaccae. Matthews and Jenks then removed the bacteria from their diet and retested them three weeks later. The mice that had initially eaten the bacteria still did slightly better than the mice who received none, but the difference was negligible. This, says Matthews, suggests that, like all good things in life, M. vaccae’s effects on learning and anxiety are likely temporary.
Still, their research does bolster the case for making sure students get time to play or do sports outside during the school day. According to Matthews, school environments that include spending time outdoors may help kids improve their learning skills—and, perhaps, even decrease their anxiety. (As I wrote last month, a recent study in the journal Pediatrics school reports that recess actually helps children behave better in the classroom too.)
Of course, adults could benefit from exposure too. Going for walks in the woods or park, rolling around in the grass, planting a garden, or eating produce you’ve plucked from your garden can all give you a small dose of M. vaccae. True, more research is needed to see if the bacteria found in dirt will have the same effect on humans as it does in mice. But I don't need more research to believe it does. I experience it firsthand every weekend. A day in the woods always leaves me feeling more clear-headed, joyful and calmer than when I walked in there. And, scientific or not, that’s the only evidence I need.
Do believe "dirt doesn’t hurt?" Chime in below!