Looking out over a scene like this, it's hard not to want to go roll in the dirt, dig your hands into the rich soil, and enjoy the earthy goodness of being outside. And it turns out that having dirty hands or a little grime under your fingernails isn’t always a bad thing. That contact with dirt has distinct health benefits.
Research over the last decade or so has shown the many ways in which the microbes and bacteria in dirt can help boost our immune systems, especially those of younger children.
Jack Gilbert, Ph.D., a scientist who studies microbial ecosystems at the University of Chicago and author of "Dirt is Good: The Advantage of Germs for Your Child's Developing Immune System," told NPR that most dirt exposures are beneficial. "So that dirty pacifier that fell on the floor — if you just stick it in your mouth and lick it, and then pop it back in little Tommy's mouth, it's actually going to stimulate their immune system. Their immune system's going to become stronger because of it."
Microbes in the dirt can be bad for us in large doses, but in small doses, our immune systems can learn what viruses or bacteria it needs to be able to fight off, storing that information and helping our bodies to quickly fight off illness later in life. The more parasites, viruses and bacteria our immune system is introduced to, the better chance we have of staving off infections as we age, including allergies and asthma! This is fairly well known, but there’s still more benefits that you might not be aware of.
Playing in dirt may actually play a role in lifting depression. Live Science reported on a 2007 study that showed "Exposure to friendly soil bacteria could improve mood by boosting the immune system just as effectively as antidepressant drugs." That friendly soil microbe is Mycobacterium vaccae.
This same microbe has another positive effect: it just may make you smarter. The Independent reported in 2010 on research looking into the effect of the microbe on mice, noting that, "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," though the benefits seem to be short lived, lasting only a few hours. Still, it could potentially mean kids may do better in school after coming in from a play ground not only because they burned off excess energy but also because they ingested a little M. vaccae.
Between dirt's beneficial microbes and being just plain fun to play in, it seems that getting your hands dirty fairly often is a wise idea. So the next time you head out to work in the garden or romp with your kids in the yard, pat yourself on the back for being smart and healthy.
Editor's note: This story has been updated since it was originally published in June 2015.