Ah, the good old days. Remember when you played outside all day and didn’t come back to the house until your mother called for you? And even then, you only came in begrudgingly? You washed your hands with plain soap and water. You slid into your chair at the dinner table with dirt smudges on your clothes and knees and nobody panicked about that. Maybe you ate your meal without worrying about gluten or peanuts, and you didn’t have asthma or allergies.

If you can relate to this scenario, you are most likely over the age of forty. More recently, times have changed. We now live in a world where there are more trips to the hospital from kids falling out of bed than there are falls from trees. Diseases linked to immune disorders like asthma, obesity, and allergies are becoming ever more prevalent in the lives of our children, and signs of a decrease in these diseases are nowhere in sight.

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In Let Them Eat Dirt: Saving Our Children from an Oversanitized World, authors B.Brett Finlay and Marie-Claire Arrieta clean up our misconceptions about getting a little dirty and help us to understand what we are doing to contribute to our children’s susceptibility for developing immune related diseases. They lead us through our current practices of antibiotic overuse and obsession with germ-free living and help us understand the role that microbes play in establishing a healthy gut for our kids.

Although some parents may be surprised to learn that children depend on abundant microbial exposure to develop normally, the authors make a compelling case for exercising caution when cleaning up. Arrieta is currently an assistant professor at the University of Calgary where she studies microbiology and immunology—her recent study connecting asthma in very young babies to missing intestinal bacterial species was deemed a breakthrough in the field.

Professor of microbiology at the University of British Columbia, Finlay is a world leader in understanding how bacterial infections work. He has been studying microbes for over thirty years and received The Order of Canada for his efforts and achievements (Canada’s highest honor for civilians). Eartheasy caught up with him to discuss their exciting book, along with developments in the field of microbiology.

Cleaner Isn’t Necessarily Better

EE: If my grandmother were alive today, I just know she would love this book. One of her favorite sayings, if one of us scrunched up our kid faces over something that we thought was dirty or “gross” was, “Don’t worry about it. You need to eat a pound of dirt before you die anyway.” What happened? How have we gotten so unbalanced, that we, as parents, started to believe we have to over-sanitize the world of our children?

B.B.F: I call it the hygiene hangover. Once Koch and Pasteur showed that “germs” caused disease, and that killing them prevented it (Pasteurization), we went on a hygiene kick. It worked VERY well. Infectious diseases plummeted. So if clean is good, cleaner is better, right? This is where we realize we are wrong, and that we have eliminated the good microbes with the bad. We need a balance between microbial exposure and hygiene.

EE: You discuss many unfamiliar, and some would say, cutting edge concepts in your book. Some of these practices, like fecal transplants in humans, feeding peanuts to infants, seeding the newborn with mom’s vaginal fluids (if delivery is a C-section), may make people uncomfortable, angry, or squeamish. What kind of reaction does Let Them Eat Dirt get from your readers? Are you getting support or resistance from the medical community?

B.B.F: Once you get over the “gross” factor, most of what we say makes sense. The book was critically read by many pediatricians and naturopaths, and thus far the reception has been very positive. Everything we say is based on solid science. Most readers say “Yes, that is what my mom would have said.” Reception has been very positive from all camps.

EE: You are not afraid to take on some topics that are ripe with controversy. One such topic is about the safety of vaccines. I have seen parents almost come to blows over the topic of whether or not vaccines are safe for their children, and you say unequivocally, “Yes, do it.” What about those who say there are damaging ingredients in the vaccines such as mercury, formaldehyde, or SV40? Can you shed some light on this please?

B.B.F: The vaccine chapter is intentionally written based on science and fact. There has been much fraudulent science and claims around vaccines that have done tremendous damage to children. We just base the chapter on the science behind vaccines, and try and stay away from the emotional arguments. The problem is that most parents have not seen children die of polio, small pox, and the other scourges that have killed so many kids in the past.

EE: You discuss the role of diet and nutrition and how it can affect us, as well as what we put into our bodies in the way of medications, but I didn’t notice any discussion of what we give children to drink. Should we be paying attention to what kind of microbial life is in the drinking water that we are giving our children? How about tap water, for instance?

B.B.F: There are, no doubt, microbes in tap water (although chlorination would kill many). For the most part, these are harmless microbes growing in the pipes and plumbing, etc. There have been very few studies on how beneficial or not these are (I don’t know of any).


EE: So far, your discussions focus mainly on the diseases that we are seeing increase in such staggering proportions, such as asthma, allergies, celiac disease, diabetes, obesity, ADHD, and autism. It seems that our microbiota leads to inflammation if it is not balanced right. One of the more recent theories in disease research is that inflammation is a major contributor to cancer. Do you have any thoughts on the contribution of a balanced microbiome in the prevention of cancer?

B.B.F: Yes, this is a big area of research, and there are a lot of indications that microbes may play a role through immune modulation. Perhaps the most spectacular data is that microbes can influence the outcome of chemotherapy, although it is still early days.

I think we need a rethink in how we raise our kids… Realize that allowing them exposure to normal microbes is not bad, but balancing that with proper hygiene to prevent serious infections is a different way of raising kids.

EE: It is indeed an exciting time in the area of understanding the role that the microbiota play in our health overall, and there are doctors and researchers right now trying to figure out how to personalize an individual’s diet according to their microbiome. Can someone go today and get assessed to find out what their personal microbial environment is, and get some insight into what is ailing them or their child?

B.B.F: Yes, go to For $300 they will analyze your microbiota and suggest which foods are good for you (or not) based on your microbe composition. It really is personalized dieting based on your own microbes. and the American Gut Project also offer an analysis of the microbiome, but they give less information on what to do with that information.

EE: You cover many topics of concern that affect the healthy development of children, such as limiting or avoiding antibiotic use during pregnancy and delivery, making sure kids are exposed to outdoor microbial environments, and the unnecessary use of antibacterial agents in our soaps and other products. Is there a particular area of concern that really stands out as the most pressing or easiest change we can make for the health of our children today?

B.B.F: I think we need a rethink in how we raise our kids in terms of their microbes. Realize that allowing them exposure to normal microbes is not bad, but balancing that with proper hygiene to prevent serious infections is a different way of raising kids.

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