Image courtesy of Aki Sinkkonen.
Imagine yourself in nature. As you step through the forest, your foot is cushioned by moist, fertile soil. You look up to see light streaming through the verdant canopy above. Breathing in, the air is layered with wafts of peat moss and pine needles. As you reach out to touch the trunk of a pine tree, you feel the stress of urban life being washed away from you, and you feel replenished, rejuvenated, perhaps even healed, by immersing yourself in nature. Previously, we may have seen only psychological benefits to being in nature, but recent research at the University of Helsinki has identified tremendous physical and immunological benefits to connecting with the outdoors.
Whether you are aware of it or not, your microbiome (the set of bacteria that occupy your skin, gut and other mucosal areas of your body) engage in a silent, evolutionarily engrained conversation with the microbes in your environment. If you brush against bushes or run your hand through soil, an extremely diverse set of bacteria come into contact with your skin—giving them the opportunity to become new residents of your microbiome. Incredibly, even the ground-cover or vegetation around your home, school or place of work can significantly affect your microbiome. These resident bacteria then interact with your immune system—causing cascades of various immune cells and cytokines to be released. This extremely complex web of immunological signals can become imbalanced when your resident microbes lack diversity (a state referred to as dysbiosis) and lead to inflammatory diseases.
This link between the friendly, diverse bacteria found in nature and our overall well-being underscores a shocking truth of modernization and the advancement of sterile environments. As a result of our diligent adherence to hygiene, sterilized foods, pesticides, and use of antibiotics—in order to eradicate and separate ourselves from pathogens—we have also destroyed the bacterial landscape that helps us maintain homeostasis. We simply couldn’t live without helpful bacteria. In fact, if you were to do a genetic analysis of the DNA within your body, a measly one percent of the DNA would be yours to claim—leaving the remaining ninety-nine to the bacteria which occupy your skin, intestinal tract, eyes, nose, ears, and mouth. These bacteria help digest food and protect us from other, harmful bacteria that could wreak havoc on our body. Additionally, dysbiosis in the microbiome of our bodies has been linked to rheumatoid arthritis, inflammatory bowel disease (IBD), celiac disease, Type 1 Diabetes, metabolic syndrome, neurodegenerative disorder, and malignancy—all diseases which have become increasingly prevalent in westernized countries.
In order to quantify this recently identified relationship between foreign microbes and our overall well-being, researchers Marja Roslund and Aki Sinkkonen performed an intervention study at Finnish daycares. In their study, they compared the bacterial communities and immune systems of children attending nature-oriented, urban, and intervention daycare centers. The intervention centers were urban daycare centers that were enriched with a forest floor and sod ground covering. Over a twenty-eight-day period, children in the intervention daycares were guided through various activities including planting, crafting natural materials and playing in the nature in order to ensure sufficient exposure to natural microbiota in the soil.
Incredibly, children’s microbial and immunological profiles underwent significant changes just from interacting with soil. While children from the nature-oriented daycares had much higher microbial diversity initially, the microbial diversity of children in the intervention group increased to nearly comparable levels by the end of the twenty-eight-day period. Notably, the relative abundance of bacteria associated with IBD decreased, while the diversity of bacteria known to help maintain the lining of our intestines increased.
These shifts in bacterial communities then initiated significant downstream effects on the children’s immune systems. While we are far from understanding the complete web of interactions that comprise an immune system, there are a few key markers that point towards the overall state of one’s immunological health. For instance, they tracked the frequency of autoimmune disease preventing regulatory T cells in children. Additionally, the researchers investigated the proportion of the anti-inflammatory interleukin-10 (IL-10) to the inflammatory interleukin-17 (IL-17) as well as the amount of anti-inflammatory cytokine Transforming growth factor-Beta1 (TGF-𝛽1). In general, all three of these signaling molecules bind to different receptors on immune cells which, in turn, provokes the cells to produce either pro- or anti- inflammatory proteins.
By the end of the study, children in the intervention group presented higher IL-10 to IL-17A ratios, increased levels of TGF-𝛽1, and higher frequencies of regulatory T cells—all signs of a less pro-inflammatory immune system. Thus, it seems that just as the children in daycare centers were learning how to interact with others and navigate the world, their immune systems were receiving an education of their own. This intervention study sheds light on the crucial link between our health and our environment, providing a glimpse of a future where deliberate steps could be taken to create and curate healthy immune systems. Additionally, in a parallel study focusing on the qualitative effects of the natural intervention at daycares, researchers at the University of Helsinki found that children’s motivation to learn, activity levels, and overall well-being also increased.
While millions of dollars have been justly awarded to fund research seeking to treat inflammatory diseases that arise from microbial dysbiosis, recent results have started to point to possibly inexpensive and easy ways to prevent such diseases from occurring at all. For instance, in another recent study, researchers at the University of Helsinki designed a wide-spectrum microbial inoculation mixture that could reproduce the slow-growing and elaborate agglomeration of ancient microbes in forest soil. Engineered to leave out any naturally occurring pathogens, this inoculate could safely be integrated into our urban soils and landscapes in order to increase microbial diversity and potentially mitigate the risk of immune-mediated diseases in urban populations.
Unfortunately, there are ideological barriers to implementing such programs. “People are afraid of microbes because there are some bad microbes,” Posland said. Intuitively, the thought of bacteria conjures up ominous images of fuzzy cylindroids infested with infectious diseases. “Current legislation requires that many products do not contain microbes. Creating policy change requires collaboration between many organizations and that the decision makers understand the science and value of maintaining a healthy microbiome. It’s a slow process to change the way that things are currently done in urban planning, green infrastructure and so on, ” Sinkkonen said.
While we have made leaps and bounds in our scientific understandings of germs since the days of Louis Pasteur, trying to conquer disease by completely eradicating bacteria from our food, living environments, and bodies may no longer be the best course of action. Recent research, coupled with the rise of immunological disorders in Western populations, has proven that health is not always synonymous with sterility. It seems that we have reached a point of inflection where science and modern technology should be used to understand and reconnect us to—not separate us from—nature. Perhaps the next era of medicine and healthcare will engage a more nuanced conversation with the lifeforms that have evolved alongside us for time immemorial, allowing us to step towards a healthier world.
Bennett Hellman, Andrew. “Gut Bacteria Gene Complement Dwarfs Human Genome.” Nature News, Nature Publishing Group, 3 Mar. 2010, www.nature.com/news/2010/100303/full/news.2010.104.html.
Bien, Justyna, et al. “The Intestinal Microbiota Dysbiosis and Clostridium Difficile Infection: Is There a Relationship with Inflammatory Bowel Disease?” Therapeutic Advances in Gastroenterology, SAGE Publications, Jan. 2013, www.ncbi.nlm.nih.gov/pmc/articles/PMC3539291/. Zheng, Danping, et al. “Interaction between Microbiota and Immunity in Health and Disease.” Nature News, Nature Publishing Group, 20 May 2020, www.nature.com/articles/s41422-020-0332-7.