Spending time outdoors has always offered health benefits for the body and the mind: fresh air, clean water, awe-inspiring vistas, peaceful quietude. Now, it turns out, even the dirt is good for you.
Scientists at the Sage Colleges of Troy, N.Y., have discovered that exposure to certain kinds of soil bacteria can reduce anxiety and increase learning capabilities when ingested or inhaled. (Dirt may actually make you smarter!)
The amazing bacterium in question is Mycobacterium vaccae, which occurs naturally in soil and is often breathed in innocuously when people spend time in nature. Previous studies had revealed that when the bacteria is injected into mice, it stimulates neuron growth and causes serotonin levels to increase. Since increased serotonin levels are known to decrease anxiety, researchers already suspected that the bacteria could have antidepressant benefits.
But decreased anxiety isn't the only effect of increased serotonin, and researchers wanted to investigate further. "Since serotonin plays a role in learning, we wondered if live M. vaccae could improve learning in mice," said Dorothy Matthews, who conducted the research.
After feeding the live bacteria to a group of mice, Matthews and her colleague Susan Jenks subjected the mice to a test of wits with a control group by having them run a maze.
"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," said Matthews.
Two subsequent experiments revealed that the mice fed the bacteria still ran the maze slightly faster than the control group once the bacteria was withheld from their diet, but the effect did not last for long — meaning the effect was a result of the presence of M. vaccae. If the bacteria had a similar effect on humans, it could mean that spending periods of time outdoors would need to be part of a regular routine for maximum neurological benefit.
"It is interesting to speculate that creating learning environments in schools that include time in the outdoors where M. vaccae is present may decrease anxiety and improve the ability to learn new tasks," noted Matthews.
