Let Them Eat Dirt


Saving Your Child from an Oversanitized World

  1. Brett Finlay and Marie-Claire Arrieta

Despite the catchy title, this book is written by serious scientists who specialize in studying our microbiota. They carefully distinguish between the information which has solid research backing at this time and that which only shows correlations. This is a relatively new field of inquiry (see Gut). While changing the microbiome in adults is more difficult, there are longitudinal studies which support the importance of nurturing a child’s microbiome in their early years and how this can be done.

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. mudjack

            Every form of life on Earth is covered in microbes in a complex yet usually harmonious relationship, making germophobia the most futile of phobias.

            For every single human cell in our bodies, there are ten bacterial cells inhabiting us; for every gene in our cells, there are one-hundred fifty bacterial genes, begging the question: Do they inhabit us or is it really the other way around?muddjack

            Microbes scare all of us, and rightly so since some of them are truly dangerous. However, only about one hundred species of microbes are known to actually cause diseases in human; the vast majority of the thousands of species that inhabit us do not cause any problems, and, in fact, seem to come with serious benefits.

            The prevalence of infectious diseases declined sharply after the emergence of antibiotics, vaccines, and sterilization techniques. However, there has been an explosion in the prevalence of chronic non-infectious diseases and disorders in developed countries. They include diabetes, allergies, asthma, inflammatory bowel diseases (IBDs), autoimmune diseases, autism, certain types of cancer, and even obesity. What we know now is that although all of these diseases have a genetic component to them, their increased pervasiveness cannot be explained by genetics alone.

            Giving cattle, pigs, and other livestock low doses of antibiotics causes significant weight gain in the animals. It seems that antibiotic overuse in humans, especially in children, in inadvertently mimicking what occurs in farm animals; increased weight gain.


            By cleaning up our children’s environments, we prevent their immune systems from maturing in the way they have for millions of years before us: with lots and lots of microbes.

            Helping our immune systems is only part of what microbes do for us. They are in charge of digesting most of our food, including fiber and complex proteins, and chopping them into more digestible forms. They also supply the essential vitamins B and K by synthesizing them from scratch, something our own metabolism cannot do. Without the vitamin K from microbes, for example, our blood would not coagulate.

            The microbiota takes about 3 – 5 years from the time we are born to become a fully established community, and during this period it’s very unstable, especially during the first few months of life. It is the early colonizers of the intestinal microbiota that have a major influence on the type of microbiome we have later in life.


            Before we’re born, the lining of our gut is full of immature immune cells, and as soon as we come into the world and bacteria start moving into their new home, these immune cells “wake up” almost magically.

            Many inflammatory diseases, such as asthma, allergies, and IBD, are characterized by an overreactive immune response.

            The good news is that, just as we can foster weight-gain microbes through a poor diet, we can promote the growth of beneficial microbes through a healthy diet.

            During pregnancy, the number of vaginal Lactobacillus increases dramatically, which is thought to occur for two important reasons. First, by keeping the vagina acidic, the presence of Lactobacillus helps discourage disease-causing microbes such as E. coli. Second Lactobacillus are great at digesting milk. By ramping up the levels of Lactobacillus in vaginal secretions, more of these bacteria will reach the baby’s gut (when born vaginally), and facilitate the digestion of the only food the baby will eat for months: her mother’s milk.  

            A study of more than seven hundred pregnant women from New York showed that children born to those who received antibiotics in their second and third trimesters had an 85 percent higher risk of childhood obesity by age seven. These findings are quite new (published in 2014) and they still need to be replicated, but if more studies show a similar trend, it suggests that childhood obesity may have roots in the very early stages of human development, and that antibiotic use during pregnancy has significantly more risk than is currently assumed in medical practice. pregnant-woman-1513183_960_720

            We are now learning that there are significant health concerns associated with C-sections, including an increased risk of chronic disorders later in life, such as asthma, allergies, obesity, autism, IBD, and celiac disease. The elevated rates of these issues associated with C-sections hover around 20 percent for most of them.

            The intestinal lumen is the inner part of the gut, and although trillions of bugs live and perform all sorts of good tasks for us in the lumen, they aren’t supposed to breach the borders of the tube. Gut: The Inside Story of Our Body’s Most Underrated Organ

            It takes about 4 – 6 months for his intestines and immune system to be ready for all the nutritious foods you want to give him. Health organizations around the world agree that human breast milk is an amazing liquid and that it’s the healthiest food for babies. Its benefits are most noticeable when babies drink it exclusively during the first 4 – 6 months and combined with solid food until age two. It turns out that oligosaccharides, which comprise about 10 percent of human milk content, are only digested by bacteria present in the baby’s large intestine.

            Diseases like obesity, type 2 diabetes, and gastrointestinal disorders all share low microbial diversity as a common feature. The so-called Western diet – high in fats, sugars, and highly refined grains – is very strongly associated with a number of human diseases, and also with a less diverse microbiota.


            When food allergies started becoming more common around the 1990s, experts agreed that delaying the introduction of these foods would reduce the likelihood of developing an allergy. “As these guidelines were implemented we’ve seen a paradoxical increase in food allergies in young children, especially with peanut allergies,” said Dr. Anna Nowak-Wegrzyn, a professor of pediatrics at the Ichan School of Medicine at Mount Sanai in New York. During the first months of life, exposure of foods to the gastrointestinal immune system encourage immune tolerance. In addition, once an allergic food is introduced, it appears to be equally important to maintain frequent, regular ingestion early on in order to maintain tolerance and truly prevent a food allergy.

            80 percent of the US’s antimicrobial usage in in livestock. It turns out that low doses of antibiotics enhance the weight gain of farm animals. Europe has stopped this practice, but unfortunately Canada and the US have not, and developing countries are just beginning to use antibiotics in livestock management.

            The statistics are truly disheartening: children spend half as much time outside as they did only twenty years ago; kids ages 8 – 18 spend a daily average of 7 hours and 38 minutes using entertainment media or screen time; and only 6 percent of 9 – 13-year-olds go outside by themselves.


            A Food and Drug Administration (FDA) committee found that antibacterial soaps provide no benefits over regular soap and water. Except for hospitals or places where additional medical hygiene is necessary, antibacterial soap doesn’t have a place in everyday use, and the same goes for antibacterial sanitizers.

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            It’s only because of vaccines that children these days have a very low risk of catching serious life-threatening infectious diseases such as smallpox, polio, diphtheria, etc.

            When children are out walking or playing in a green space, it’s a different situation from highly populated areas, as the risk of getting infected with microbes that carry human diseases decreases dramatically.


            People who grow up on farms have a much lower risk of developing asthma than anyone else in Western societies. childonfarm


I play tennis with a friend who likes to remind us that if it was easy, anyone could do it. It is true of much more than tennis. It is a challenge to keep up with all of the new and changing information and then decide what is and what is not important. Summaries are helpful and I hope that you find these summaries useful.