New Book Says Letting Kids Get Dirty Actually Makes Them Healthier

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"Let Them Eat Dirt" co-authors B. Brett Finlay and Marie-Claire Arrieta at the Here & Now studio. (Robin Lubbock/WBUR)
"Let Them Eat Dirt" co-authors B. Brett Finlay and Marie-Claire Arrieta at the Here & Now studio. (Robin Lubbock/WBUR)

Stores are awash in antibacterial cleaning products and parents often demand antibiotics when their children have an ear infection or a bad cough.

But a new book argues that an emphasis on cleanliness and overuse of antibiotics deprive children of microbes that, among other benefits, help develop their immune systems.

Co-authors B. Brett Finlay and Marie-Claire Arrieta join Here & Now's Meghna Chakrabarti to talk about "Let Them Eat Dirt: Saving Your Child from an Oversanitized World."

Interview Highlights: B. Brett Finlay & Marie-Claire Arrieta

On the importance of microbes for human health

Finlay: "Obviously we're not suggesting you shovel a bucket of dirt on a poor newborn's mouth. The concept is there and I think we all deep down know this. This is really a hanger we've had over the last century of cleaning up our world. In the 1900s, 30 percent of the kids in the U.S. cities died before the age of 1. Now, less than 0.1 percent die of infections... We have had a major success story and kids don't die of infections anymore. That's terrific.

But in the last 100 decades or so, we now start to realize that we're not only killing our bad microbes, we're killing the ones that actually we're starting to realize that are good for us. And so this really hypervigilance to sanitation has wiped out a whole microbial generation really. And so our kids are no longer exposed to the kids that humans have developed with. They're just not getting the bugs that Homo sapiens evolved with. And now this has real impact on what we called 'western society diseases,' like asthma, allergies, obesity, diabetes. These all have microbial links."

On why bacteria are important

Arrieta: "One of the main tasks that bacteria do for us is mature our immune system. We are born without microbes, but as soon as we are born, we get millions of them. And our immune system relies on them to complete the maturation process. And if they skip, or get depleted of some microbes, the immune system becomes sloppy — it doesn't do what it is supposed to do, which is trying to distinguish friend from foe. And later, it leads to these step of diseases like asthma.

Another thing that microbes do is that they're key decision makers on how we store or burn fat. So it's not surprising that these are the diseases that are growing so much in the society. "

On the balance between bacteria and cleanliness

Finlay: "There's not data to say that having infectious diseases actually improves you. So we don't have to infect our kids. But what we're sort of pointing forward is you need a balance between the risk of exposing your kids to an infection versus to the risks of exposing them just to the good microbes.

A final point I want to make which I find is very scary is that each generation gets cleaner and cleaner. Each generation we have less and less microbes. That means that our great grandparents's microbes are actually endangered species and we can't have them anymore even if they want them. So there's a lot of concern that each generation as we clean these up like any other endangered species, they'd go extinct, and we can't go back to where we were, which is really scary I think."

Book Excerpt: 'Let Them Eat Dirt'

The cover of "Let Them Eat Dirt," co-authored by B. Brett Finlay and Marie-Claire Arrieta. (Courtesy Algonquin Books of Chapel Hill)
The cover of "Let Them Eat Dirt," co-authored by B. Brett Finlay and Marie-Claire Arrieta. (Courtesy Algonquin Books of Chapel Hill)

By B. Brett Finlay and Marie-Claire Arrieta

We all want what is best for our kids. The problem is that there is no perfect handbook on how to raise them, nor is there any one best way, either. We read books and articles, talk to friends, and try to remember (or forget!) how our parents raised us. Both of us have children and have struggled and muddled through the parenting process the same way everyone does. We are also scientists who have worked with microbes for many years, and we couldn’t help but consider how these ever-present microbes influence development as we raised our children. At first we studied microbes that cause disease, and we feared them just like anyone else. But more recently we began taking notice of all other the microbes that live in and on us — our “microbiota.” As we continue to study the microbiota of humans, it is becoming clear that our exposure to microbes is most important when we’re kids. At the same time, modern lifestyles have made childhood much cleaner than ever before in human history, and this is taking a huge toll on our microbiota — and our lifelong health.

The genesis of this book came from the realization that the studies in our lab — and the labs of several other researchers — prove that microbes really do impact a child’s health. What shocked us most was how early this starts — the first one hundred days of life are critical. We knew microbes played a role in well-being, but we had no idea how soon this role began.

Several other factors converged to help convince us to write this book. Claire has young children, and all of her young parent friends were extremely interested in the concept of microbes and how they might affect their kids. Whenever we tell other parents about our work, the questions never cease — Do I need to sterilize their bottles every time? What kind of soap should I use? We realized that there are many questions out there about microbes . . . and a lot of wrong information.

Brett is married to a pediatric infectious disease specialist (Jane) who was constantly suggesting articles and findings about how microbes affect kids, which led us to realize that since this was such a new field, there was no one source parents could turn to if they wanted to learn more. Not to mention that scientific articles are usually dry, terse things with lots of jargon and, frankly, are terribly boring. However, this new area of research has a lot to offer to people raising children who are not likely to get this important information from dense scientific papers or from studies often misinterpreted by the press. There is a lot of information being produced by some of the best scientists in the world, which we consider extremely useful for the day-to-day decisions we make while raising our children, so we felt compelled to gather it all in one book and make it accessible to the everyday parent.

We start off by explaining a bit about microbes, and then explore what happens to a pregnant woman’s body in terms of her microbiota and how it affects her child(ren) for life. We then discuss the delivery process, breastfeeding, solid foods, and the first years of life from a microbial perspective. In the middle of the book we cover lifestyle issues (Should I get a pet? What do I do with a dropped pacifier?) and the use of antibiotics. The latter part of the book features chapters dealing with specific diseases that are growing by leaps and bounds in our society, and the microbes that seem to affect them. These include obesity, asthma, diabetes, intestinal diseases, behavioral and mental health disorders such as autism, and a whole array of diseases in which, even five years ago, we had no clue microbes might be involved. Readers may want to skip over particular chapters if you feel that they are not applicable to you. However, each one is full of information that will educate you about the processes involved in these health issues. We think the section on the gut — brain connection is particularly interesting in its exploration of how microbes might affect the brain and mental disorders. We finish the book with a discussion on vaccines and a futuristic view of what we can expect in terms of new therapies and medical interventions in the next few years. Each chapter ends with a few Dos and Don’ts — these are not meant to be comprehensive medical advice, but suggestions about things to do (or not do) that are based on current scientific evidence.

What we have learned in writing this book, and what we hope to convince readers of, is that microbes play a very large part in our children’s lives. Even as scientists in the field, we were stunned to discover some of the profound roles these microscopic bugs have in normal childhood development. No doubt many of these findings, and many more to come, will have a major impact in how we think about raising our children.

Excerpted from the book LET THEM EAT DIRT by B. Brett Finlay, Ph.D., and Marie-Claire Arrieta, Ph.D. Copyright © 2016 by B. Brett Finlay, Ph.D., and Marie-Claire Arrieta, Ph.D. Reprinted by Permission of Algonquin Books of Chapel Hill.


B. Brett Finlay, co-author of "Let Them Eat Dirt" and professor of microbiology at the University of Columbia. He tweets @finlaylab. The book tweets @kidsandmicrobes.

Marie-Claire Arrieta, co-author of "Let Them Eat Dirt" and assistant professor of physiology and pharmacology at the University of Calgary. She tweets @ArrietaLab.

This article was originally published on September 22, 2016.

This segment aired on September 22, 2016.



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