Are we doing our children a disservice by always insisting they wash their hands before eating?
Efforts to raise kids in an almost sterile environment can set them up for a life of asthma, irritable bowel disease, infections and even diabetes.
Evidence of soil as a major cause of disease in humans and other animals is limited. Many nonhuman animals regularly eat dirt, generally without ill effects and with some benefits.
Sure, there is a danger that Junior might ingest soils contaminated by industrial or human pollutants, animal feces or even heavy metals like lead, but the long-term benefits to health may be worth the risk.
Soil not overtaxed by overpopulation, industry and agriculture may be much different from the soil most of us encounter routinely.
The Environmental Protection Agency estimates that children in the United States consume, on average, 200 to 800 milligrams of dirt per day.
Children from large families with many older brothers and sisters are less likely to have asthma, hay fever, or eczema. Those raised in rural areas, especially on farms, have fewer allergies and autoimmune diseases than children raised in cities.
Children who have not had infections before their fifth birthdays are more likely to get Type I diabetes (an autoimmune disease) than healthy children the same age.
Our culture's obsessive attention to cleanliness, hygiene and sanitation may actually be having unintended consequences on our immune system. While a sanitary environment may be essential in areas such as hospitals and food production, our usual avoidance of dirt, bacteria and other infectious agents may be causing our under-stimulated immune system to overreact to simple antigens.
The "hygiene hypothesis" suggests that an increased incidence of inflammatory disorders is the result of a defective immune system brought on by reduced exposure to an adequate variety of microorganisms.
History repeatedly provides examples of isolated populations getting wiped out by disease when exposed to travelers or explorers. They had never been exposed to some microorganisms so they never developed a tolerance for them.
Researchers recently examined the immune system of "germ-free" mice that had been bred to lack gut bacteria. They compared them to mice with normal exposure to microbes and found that the germ-free mice had significantly more inflammation in the lungs and colon, similar to that found in humans with asthma and colitis. This inflammation is due to hyperactivity of certain immune T-cells associated with these conditions.
When the germ-free mice were exposed to microbes during the first few weeks of life, they gradually developed a normalized immune system and avoided inflammatory disease. The germ-free mice exposed later as adults never developed a fully functioning immune system.
It is not uncommon in some cultures to eat clay. The habit has often been associated with iron-deficiency in pregnant women and has been termed "pica." Perhaps there is more to it. Clay has also been used for medicinal purposes in local folklore, or by simple trial and error.
There are numerous companies promoting clay supplements for internal use primarily because of the high mineral content. These are even reputed to be helpful for topical use for skin infections.
Clay gathered from its original source deposit is refined and processed in various ways by manufacturers. This can include heating or baking the clay, since the raw clay tends to contain a variety of micro-organisms. Too much processing may reduce the clay's therapeutic potential.
While we may be worried about protecting our children from germs, perhaps we should actually encourage them to get a little dirty now and then.
Chuck Newcomb, MS, RD, CDE is a consulting registered dietitian providing medical nutrition therapy services for Memorial Hospital Los Banos. He has a masters of science in clinical nutrition from New York University. Email questions to the Attention of ChuckRD at: MHA LosBanos@SutterHealth.org or on his website MySmartRD.com.