The "Dirt" On How To Boost Your Immune System

hands holding a plant rooted in soil

Looking to Boost Your Immune System? Don't Be Afraid to Get Dirty.

As we reflect back on our childhood days, many of us remember simpler times spent running outdoors and rolling in the grass, completely unbothered by the worry of getting a little dirty. We’d return to the house, wiping our face with our muddy fingers, and wash up for dinner. As it turns out, this outdoor playtime was its own vital probiotic boost.

In the not-so-distant future, your doctor might recommend supplementing your immune-boosting routine with spending time going back to your roots and getting a little dirty. It’s not as outlandish as it sounds.

Researchers are proving that the bacteria Mycobacterium vaccae found in soil could be vital to our health in several studies around the world. For most of history, humans and bacteria have had a symbiotic relationship; bacteria in our gut help us process our food, among many other jobs. Unfortunately, modern life—especially our cleanliness compulsion—is reducing the diversity of our gut microbiome. Getting microbes like M. vaccae back into our microbiome could have wide-ranging health benefits, from fighting depression to boosting our immune systems.

toddler wiping soiled hands on pink rag

A Little Dirt Won't Hurt.

Our obsession with cleanliness (and killing bacteria) began during the Civil War when doctors gained a better understanding of the relationship between cleanliness, dirt, and disease. The obsession accelerated with the invention of modern advertising at the end of the 19th century when the original Mad Men discovered they could make a fortune convincing consumers that being super clean meant being healthy. Their motives may not have been pure, but the public’s embrace of personal hygiene, along with public health efforts, drastically reduced death and disease. Between 1900 and 1999, US infant mortality decreased 90 percent, and maternal mortality decreased 99 percent, a drop partially attributed to better hygiene.

"All this washing has thrown our microbiome out of whack."

From an evolutionary perspective, we may have gone too far and tipped that all-important symbiotic balance. Many scientists believe that all this washing has thrown our microbiome out of whack. Because humans evolved right alongside parasites, fungi, and bacteria, our symbiotic relationships with these organisms are actually vital to our immune system’s functioning.

According to the hygiene hypothesis, children who are exposed to viruses, bacteria, and parasites at an early age have healthier immune systems and develop asthma less than other children. The prevailing theory was that children in underdeveloped countries actually had fewer allergies and illnesses, such as asthma, precisely because they did not live in sterile environments.

little girl with mask on sitting at table with books

However, the hygiene hypothesis couldn’t fully explain why high-income countries have seen a rise in diseases where the immune system attacks where it should not attack, including our own tissues (multiple sclerosis, Type 1 diabetes). Graham Rook, a University College London microbiologist,  ultimately developed the “old friends” hypothesis to explain how modern human lifestyles—indoor living, pasteurized food, and obsessive cleanliness—and medical practices, particularly the overuse of antibiotics, have upset the gut’s natural diversity.

According to Rook, because humans have less contact with the natural environment we are exposed to fewer microbial inputs in early life, therefore our immune, endocrine, and metabolic systems do not develop correctly and can malfunction. To get our immune systems back into the fighting spirit to defend against pathogens, we must reintroduce these “old friends”—microbes found in the dirt—back into our systems.

What to learn more about how your microbes would fair against diseases?


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