Dirty kids could be healthy kids

A little bit of dirt never hurt anyone, but new research now shows that it could actually be good for us, writes RAYMOND M LANE

‘I TOOK my Barbies out to play with me in the dirt,” says Candace Smyth, a lawyer in Takoma Park, Maryland, USA, remembering growing up near her grandparents’ farm in Alabama. “I was always outside, always in the dirt, until I got too old.

“I wish my girl could play in the dirt more,” says Smyth of her five-year-old daughter, Kate Oliphant.

But the family’s backyard is small, Kate’s day-care and after-school activities and visits with friends and family sometimes “keep her indoors too much, and maybe we parents are too organised, too clean”, the mother says with a laugh.

Now scientists are beginning to think there could be medical and educational reasons for parents and teachers to encourage kids to play in dirt.

That’s what Dorothy M Matthews and Susan M Jenks, biology professors at Sage College in Troy, New York, think they have discovered. This revelation came from feeding mice Mycobacterium vaccae, a harmless bacteria or germ found in dirt almost everywhere.

The professors made little sandwiches of white bread, with a little smear of the bacteria, topped with peanut butter.

“Mice love peanut butter,” says Matthews. “It was their reward when they ran through our tests.”

The professors gave one group of mice M vaccae (pronounced “vah-kay”) sandwiches and another group just little peanut butter sandwiches. Then they watched how quickly the animals could work their way through a difficult maze to the peanut butter reward at the end.

“The mice fed M vaccae navigated the maze twice as fast and showed far less anxiety than the other mice,” Matthews says. “We did a second test, and removed M vaccae from the first group’s diet, and they still maintained their learning edge. And testing three weeks later – which for mice is about the same as two and a half years for humans – showed that mice exposed once to M vaccae could remember what they learned for a long time.

“That’s pretty cool,” says Matthews, who remembers growing up in New York City, playing in the dirt of a back yard “with one little tree”.

Other scientists who injected M vaccae into mice found it stimulated neurons in the brain stem to start producing serotonin, says Matthews.

Humans make serotonin in their bodies naturally, and it is a well-known contributor to feelings of wellbeing.

So does that mean dirt sandwiches are a new vitamin for learning?

“Oh, no,” explains Matthews. “Please do not start eating dirt sandwiches!”

It will take years of studies to find out if there is a real benefit from M vaccae on children or adults, she says.

“But Mother Nature knows best,” she adds.

“It’s good for us to be outside on a lot of levels. People feel better when outside and active and, even on a chemical level, that exposure to the biologic world that in all likelihood we evolved with could help us live better lives.

“That’s why children should be free to play in the dirt,” she says.

“It may decrease their anxiety and improve their ability to learn new things.”

– ( Washington Post/Bloomberg)