by Heidi Green
February 08, 2009

I’ve heard it said, “everyone eats a peck of dirt before they die.”

This no-nonsense perspective about the grungy side of life has always seemed sensible and vaguely reassuring; it’s come to mind many times as I have watched other parents following their kids around with wet wipes and anti-bacterial goop. But, as Jane E. Brody explains in her column in The New York Times, “accumulating evidence strongly suggests that eating dirt is good for you.”

It seems that all the “stuff” that enters the body along with the dirt—bacteria, viruses and worms—stimulate the development of a healthy immune system.

The increasing tendency to avoid dirt may be why immune system disorders like multiple sclerosis, Type 1 diabetes, inflammatory bowel disease, asthma, and allergies have risen significantly in the U.S., as well as other developed countries.

Dirt is good
Proponents of the hygiene hypothesis have long argued that putting what they find in their mouths is a health-building activity for children. In her new book, microbiology and immunology instructor Mary Ruebush explains that such an activity “allows [the] immune response to explore [the] environment,” which allows not only for “‘practice’ of immune response, which will be necessary for protection, but … also plays a critical role in teaching the immature immune response what is best ignored.”

Gastroenterologist Dr. Joel Weinstock concurs, stating that the immune system at birth is similar to “an unprogrammed computer. It needs instruction.” Children who are raised in fastidiously clean environments and who lack exposure to dirt will lack exposure to the very organisms that help them develop appropriate immune response.

Dirt in moderation is good
It may sound like these researchers are calling for a return to the filth of long ago. Do they want a showerless, soap-less society free of laundry facilities and vacuum cleaners? Not at all. (Although, on laundry day, I might try to tell you otherwise!)

Instead, as Jane Brody explains, they recognize that “bacteria are everywhere: on us, in us and all around us … and many … are essential to good health.” And we’re not just talking about a few bacteria. “The typical human probably,” according to Mary Ruebush, “harbors some 90 trillion microbes [and the] very fact that you have so many microbes of so many different kinds is what keeps you healthy most of the time.”

Ruebush and like-minded researchers do want you to wash your hands “after using the bathroom, before eating, after changing a diaper, before and after handling food,” and any time they’re visibly dirty. However, children should be allowed to “go barefoot in the dirt and play in the dirt.” Alcohol-based sanitizers should be used sparingly and infrequently.

Get down and dirty
I have to admit that the idea of a dirt free-for-all makes me a little nervous. There are two reasons: lead and pesticides.

A few summers ago, we had the portions of our old brick-and-wood house re-painted. The painters were not careful about clean-up, and my husband and I were naïve. Chips of the old, lead-based paint remained in the yard. Although we never saw her do so, our toddler daughter must have ingested a small chip while playing outside. A routine blood test ordered by the pediatrician showed an elevated level of lead, and a subsequent investigation by the health department found the soil close to the house to be the only lead-containing substance around.

Luckily, Katie’s exposure was minimal, and she has shown no ill effects. But cleaning up paint chips from a yard is a difficult, painstaking task, and even a small amount of ingested lead can cause health problems for the child. I would like parents to be careful about their children’s exposure to soil at risk of lead contamination.

Environmental contaminants such as pesticides and weed killers are another topic of concern. The Environmental Working Group is a terrific resource for considering the “body burden” or chemicals in children today. Concerned about our children’s exposure to toxic chemicals, we have opted not to treat our yard; when I know the children have been playing somewhere that has been treated, I am more concerned about having them wash-up when they return home. Am I being overly cautious? Maybe.

I think what it all boils down to is to use common sense. Don’t be afraid of dirt; don’t be paranoid about germs. Recognize that, whether or not we all really do eat a peck of dirt before we die (which doesn’t sound too appetizing), a bit of a good, clean, organic dirt is probably good for us after all.

So, as spring approaches, make those mud pies! Don’t serve them up for dinner—but don’t agonize over the dirt, either.

Heidi Green has been researching and writing about women’s and children health since she moved to Pittsburgh more than 10 years ago. She is also a children’s book reviewer in her spare time. She is mom to Ben, Katie, Sam, and Max.