A good reason to get your hands dirty

Sage Colleges study points to possible beneficial psychological effects of bacteria found in soil

By BRIAN NEARING, Staff writer
First published in print: Tuesday, June 8, 2010
Playing in the dirt is actually good for you, with brain-boosting effects caused by naturally occurring bacteria in soil, according to recent research from The Sage Colleges.


By studying how quickly mice negotiate a maze, associate biology professor Dorothy Matthews found that mice did better and showed less stress after eating snacks containing the bacteria, which earlier research shows can increase levels of serotonin, a brain chemical linked in humans with increased learning ability and mood.

Matthews presented her research, assisted by Sage associate psychology professor Susan Jenks, last week at the annual meeting of the American Society of Microbiology in San Diego.

"When we look at our evolutionary history, we spent a lot of time as hunter-gatherers, or even more recently in agriculture, where we had lots of contact with the soil," Matthews said. "It's only been the last 100 years or so that we've become more urbanized and are eating our foods in a different way."

Her research focused on Mycobacterium vaccae, a strain of bacteria that occurs naturally in soil, and that was first scientifically isolated in cow dung.

The Sage study involved 20 lab mice and a maze where eight turns had to be made to reach food. Peanut butter snacks fed to some of the mice contained the bacteria.

Mice that ate the bacteria snacks consistently finished the maze almost twice as fast as those that ate untreated food.

And the faster mice also showed less visible anxiety behaviors, like hugging against the wall, freezing in place, excessive grooming, peering cautiously around corners, and defecating.

Even after the mice stopped snacking on the live bacteria, they still outperformed the other mice. Three weeks later, the effect seemed to taper off.

The Sage research builds on a 2007 study in England, which found mice that received a dead version of the bacteria showed behavioral changes similar to that produced by antidepressant drugs.

Researchers began looking more closely at the bacteria after human cancer patients being treated with it unexpectedly reported positive changes in mood and outlook.

Later, it was found that the bacteria were activating a group of neurons in the brain that produces the chemical serotonin. A lack of serotonin in the brain is thought to cause depression in people.

Matthews said her research suggests that bacteria may play a role in reducing anxiety and enhancing learning.

If that is true, she said, spending time outdoors and interacting with nature -- taking walks in the woods or gardening or playing -- may play a role in the way people learn -- and help reduce their anxieties as well.

And being too clean by disinfecting everything a person comes in contact with could reduce or eliminate exposure to helpful bacteria and it might be actually making people feel worse, not better, Matthews said.

Brian Nearing can be reached at 454-5094 or by e-mail at bnearing@timesunion.com.