Microbes in our gut can have a profound impact on our health, but research is showing that those surrounding us in our environment—what’s known as the natural environmental microbiome—can have a big impact too. This suggests that we should all spend a lot more time interacting with nature, both outdoors and indoors.
I was first introduced to this emerging area of science by Professor Gretchen Daily from Stanford University. She mentioned a Finnish research project that showed how letting kindergarten-aged children play in a yard that contained “dirt” from the forest floor resulted in a significant positive impact on their gut microbiome. Seventy-nine young children took part, all living in urban environments and spending the majority of their days at different daycare centers around Finland. The only difference between them was that these daycare centers had three different types of outdoor spaces.
The first type was a fairly standard outdoor play area, comprised of concrete, gravel, and some plastic matting. The second was the type typically found in daycare environments that are already nature-orientated, with grass, soil, and planted areas for the children to play in. These two acted as a control against which to compare the third experimental space, where the concrete and gravel were covered with segments of forest floor and soil from the local coniferous forest.
The children were encouraged to play in only one of the three types of yard each day over the 28 days of the experiment (note that some kindergartens have multiple play areas). Before and after periods of play, the children’s skin and gut microbiota were measured using genetic sequencing of bacteria taken from skin swabs and stool samples, along with changes to T cells and cytokines in their blood. These cells and proteins play a critical role in preventing autoimmunity and autoimmune diseases; their levels are often used as an indication of how well the immune system is functioning.
Remarkable results emerged. The children who played in the experimental yard showed a large increase in the diversity of microbiota on their skin and in their gut in comparison to the children playing in the urban and nature-orientated areas. Importantly, these were the “good” types of microbiota—those associated with health benefits. There was also a significant increase in the children’s immunity markers, indicative of them having gained enhanced immunoregulatory pathways—which is indicative of a reduced risk of immune-mediated diseases such as inflammatory bowel disease and rheumatoid arthritis.
The importance of this study cannot be overstated. It implies that even short-term exposure to nature’s microbial diversity has the potential to radically alter the diversity of microbiota on our skin and in our gut. In addition, it suggests that the altered gut microbiota can modulate the function of our immune system.
A Healthy Microbiome Is Made, Not Born
Everyone has a distinctive community of microbes in their gut—a person’s ethnicity, the food they consume, antibiotic use, body size, and the amount they exercise all leave a clear signature on their gut microbial diversity. The role of these microbiota communities is significant. Our organs can only synthesize 11 of the 20 essential amino acids that we need, so the rest, along with 13 essential vitamins, are retrieved and synthesized by our gut microbes.
And these microbial communities don’t just help our gut extract nutrients from food. Microbes also produce some of the most important compounds for our health, including immuno-suppressants, anti-cancer, and anti-inflammatory compounds. They appear to be associated with the functioning of our immune system, central nervous system, and associated health outcomes, so much so that clear correlations have been found between particular gut microbiota—so called “sick” microbiomes—and certain illnesses. Those with a distinctive gut microbial signature include irritable bowel syndrome, inflammatory bowel disease, celiac disease, and colorectal cancer as well as nonintestinal disorders such as obesity and type 2 diabetes.
