Dirt....it's what's for dinner?

Eat your dirt, honey     Ottawa CitizenFebruary 10, 2009    

Parents know that children should eat more fruits and vegetables, but probably don't know that there's something else missing from their kids' diets: dirt.

Children need to eat a little dirt now and then to develop healthy immune systems. Problem is, in many countries, people have be-come too clean for their own good.

In recent years, a greater percentage of children in developed nations have developed allergies or other immune system disorders, such as asthma. In October, the U.S. Centers for Disease Control reported that some three million American children have food or digestive allergies, an 18-per-cent increase from the decade before. In the mid-1990s, 11 per cent of Canadian children aged 11 and younger suffered from asthma. But by 2001, nearly 70,000 more had been diagnosed with the chronic condition, pushing that percentage up to 13 per cent.

A growing body of evidence suggests this is because of excessive hygiene -- the old too-much-of-a-good-thing problem. British epidemiologist David Strachan first suspected that cleanliness could lead to illness in 1989, dubbing his idea "the hygiene hypothesis."

In her new book Why Dirt is Good, immunology expert Mary Ruebush explains how recent research is proving Strachan's hypothesis. A baby's immune system is like a computer that hasn't been programmed. It needs to practise responding to bacteria and viruses and other things found in dirt to learn what it should fight and what it should ignore. It's not an evolutionary mistake that young children, regardless of what their parents tell them, keep putting icky things in their mouths.

Overall, of course, improved hygiene standards have been a good thing. Considering that 80 per cent of the diseases in the world still stem from water contamination, excessive cleanliness is a problem many countries can only dream of having. Sanitation is so importantthat the British Medical Journal last year awarded it a rather lofty title: best medical invention ever.

Still, a generation of children with poorly developed immune systems is not so minor a problem that it doesn't deserve attention. Scientists may one day develop a vaccine to kick-start young immune systems -- something that will mimic the positive effects of soil-borne stimulants -- but what are parents to do in the meantime? Sprinkle a little topsoil on the morning oatmeal? Toss a teaspoon of gravel into the baby's bottle?

Fortunately, parents don't have to do more of anything. They should just do less of some things. For instance, they should use fewer antibacterial products. Soap and water is all you need to clean dirty hands, immunology experts say, and not all bacteria are bad. The demonization of bacteria is largely a marketing ploy.

Parents should also just relax a tad -- allow kids to go barefoot outside, play in the dirt, even pet the occasional mangy-looking dog.

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