Dirt is Good for You.

Extracts from
Babies Know: A Little Dirt Is Good for You
by Jane E. Brody for the New York Times, January 26, 2009
When my young sons were exploring the streets of Brooklyn, I couldn't help but wonder how good crushed rock or dried dog droppings could taste when delicious mashed potatoes were routinely rejected.

Since all instinctive behaviors have an evolutionary advantage or they would not have been retained for millions of years, chances are that this one too has helped us survive as a species. And, indeed, accumulating evidence strongly suggests that eating dirt is good for you.

In studies of what is called the hygiene hypothesis, researchers are concluding that organisms like the millions of bacteria, viruses and especially worms that enter the body along with "dirt" spur the development of a healthy immune system. Several continuing studies suggest that worms may help to redirect an immune system that has gone awry and resulted in autoimmune disorders, allergies and asthma.

These studies, along with epidemiological observations, seem to explain why immune system disorders like multiple sclerosis, Type 1 diabetes, inflammatory bowel disease, asthma and allergies have risen significantly in the United States and other developed countries.

Training the Immune System

"What a child is doing when he puts things in his mouth is allowing his immune response to explore his environment," Mary Ruebush, a microbiology and immunology instructor, wrote in her new book, "Why Dirt Is Good" (Kaplan).

She points out that bacteria are everywhere: on us, in us and all around us. Most of these micro-organisms cause no problem, and many, like the ones that normally live in the digestive tract and produce life-sustaining nutrients, are essential to good health.

"The typical human probably harbors some 90 trillion microbes," she wrote. "The very fact that you have so many microbes of so many different kinds is what keeps you healthy most of the time."

She deplores the current fetish for the hundreds of antibacterial products that convey a false sense of security and may actually foster the development of antibiotic-resistant, disease-causing bacteria. Plain soap and water are all that are needed to become clean, she noted.

One leading researcher ... said the immune system at birth "is like an unprogrammed computer. It needs instruction... Children raised in an ultraclean environment are not being exposed to organisms that help them develop appropriate immune regulatory circuits. Children should be allowed to go barefoot in the dirt, play in the dirt, and not have to wash their hands when they come in to eat."

Children who grow up on farms and are frequently exposed to worms and other organisms from farm animals are much less likely to develop allergies and autoimmune diseases.