The complex communities that reside on us... and inside us.

Hi I’m Sammy,

Your Good Farm in-house nutritionist. Here to bring you essential information on nutrition, diet and permaculture gardening - in a bite size, easy to understand, science-backed way.

The complex communities that reside on us... and inside us.

For most of human history, our ancestors lived immersed in the natural world. They walked barefoot across soil, grew and harvested food by hand, slept close to the earth and shared their homes with animals.

What we are beginning to understand is that our relationship with nature extends far beyond what we can see. Trillions of microbes live on and within us, forming complex communities throughout the gut, on the skin, in the mouth, nose and airways. Collectively known as the human microbiome, these microorganisms play important roles in digestion, immune function, metabolism and even aspects of brain health.

The health of these microbial communities is shaped not only by what we eat, but also by the world around us. The way we are born, whether we are breastfed, our use of antibiotics, the foods we eat, time spent outdoors and our interaction with healthy soils, plants and animals all help shape the diversity of microbes we carry throughout life.

Today we spend around 90 per cent of our time indoors. Our homes have become larger, our backyards smaller and our built environments increasingly dominate over natural ones. Children have fewer opportunities for unstructured outdoor play than previous generations, while many of us spend much of the day moving between houses, cars, offices and shopping centres. We sanitise our hands, disinfect our benches, vacuum every corner, wear shoes almost constantly and often see dirt as something to be avoided rather than embraced. While advances in sanitation have reduced many infectious diseases and improved public health, they have also dramatically changed our relationship with the microbial world around us.

Scientists refer to this concept as the Old Friends hypothesis. Originally proposed as the hygiene hypothesis, researchers now believe the issue is not that we live "too cleanly", but rather that we have lost regular contact with many of the diverse microbes that humans evolved alongside over hundreds of thousands of years.

Our immune system is not born knowing what should be attacked and what should be tolerated. It requires ongoing education. Early and repeated exposure to a wide range of microbes helps train immune cells to respond appropriately, reducing the likelihood of overreacting to harmless substances such as pollen, dust or certain foods.

Research from around the world continues to reinforce this idea.

One of the most compelling examples comes from farming communities. Researchers studying children raised on traditional European farms have consistently found they develop significantly fewer allergies and less asthma than children raised in nearby urban environments. The greatest protection is seen in children who have regular contact with livestock from infancy and who are exposed to the rich diversity of microbes found in barns, hay, animals and surrounding farmland. Some studies suggest that exposure during pregnancy and throughout the first year of life offers the greatest protection, highlighting just how important these early microbial encounters may be for immune development.

Similar findings have been reported in households with pets. Several large studies have found that children who grow up with dogs, particularly from infancy, tend to have lower rates of allergies, eczema and asthma than children raised without pets. Dogs continually bring soil, plant material and environmental microbes into the home, subtly enriching the diversity of the indoor microbiome.

In one Finnish study, researchers transformed ordinary urban childcare playgrounds by adding forest floor, natural soils and native plants. After just 28 days, the children playing in these biodiverse environments developed richer skin microbial communities and favourable changes in gut microbes and immune markers linked to healthier immune regulation.

The broadest perspective comes from studies of traditional hunter-gatherer communities. Compared with people living in industrialised societies, these populations consistently harbour far more diverse gut microbiomes, shaped by lifelong contact with healthy soils, plants, animals, minimally processed foods and high fibre plant foods.

One of the most encouraging aspects of this research is that many of the changes cost very little. While the health industry continues to produce an ever-growing range of products promising better health, some of the simplest ways to support our microbial world may involve doing more, not buying more: taking our shoes off and spending more time in nature.

Simple Ways to Support Our Microbial Health

Barefoot walking, also known as grounding or earthing, regularly makes its way around social media. While much of the conversation focuses on the proposed electrical connection between the body and the earth, another potential benefit is microbial exchange. For developing children especially, contact with natural surfaces may provide valuable sensory and microbial experiences. When my eldest daughter was learning to walk, I rarely put shoes on her unless we were somewhere they were needed. The soles of our feet contain thousands of nerve endings that constantly send information to the brain, helping develop balance, coordination and body awareness while also reconnecting us with the living world beneath our feet.

We can spend more time gardening without gloves, letting our hands come into contact with healthy soil. We can let children dig in the dirt, climb trees and come home with muddy bare feet. We can open the windows of our homes more often, spend weekends in the bush and welcome animals into our lives where appropriate. We can also choose fresh, seasonal and organic foods that remain closely connected to the environments in which they were grown, and reconsider the products we use around the home by reducing our reliance on harsh antibacterial cleaners and choosing gentler alternatives where appropriate. Together, these simple experiences help restore some of the everyday contact with the natural world that has become increasingly rare in modern life.

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Recommended Reading

Ed Yong. I Contain Multitudes: The Microbes Within Us and a Grander View of Life.

Justin Sonnenburg and Erica Sonnenburg. The Good Gut: Taking Control of Your Weight, Your Mood and Your Long-term Health.

Brett Finlay and Marie-Claire Arrieta. Let Them Eat Dirt: Saving Your Child from an Oversanitized World.

Martin J. Blaser. Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plagues.

David R. Montgomery and Anne Biklé. What Your Food Ate: How to Heal Our Land and Reclaim Our Health.

Robin Wall Kimmerer. Braiding Sweetgrass.

References

Blaser MJ. Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plagues. Henry Holt; 2014.

Roslund MI, Puhakka R, Grönroos M, et al. Biodiversity intervention enhances immune regulation and health-associated commensal microbiota among daycare children. Science Advances. 2020;6(42).

Rook GAW. Regulation of the immune system by biodiversity from the natural environment: An ecosystem service essential to health. Proceedings of the National Academy of Sciences. 2013;110(46):18360-18367.

Stein MM, Hrusch CL, Gozdz J, et al. Innate immunity and asthma risk in Amish and Hutterite farm children. New England Journal of Medicine. 2016;375(5):411-421.

Tun HM, Konya T, Takaro TK, et al. Exposure to household furry pets influences the gut microbiota of infants at three to four months following various birth scenarios. Microbiome. 2017;5:40.

Yatsunenko T, Rey FE, Manary MJ, et al. Human gut microbiome viewed across age and geography. Nature. 2012;486:222-227.

Sonnenburg JL, Sonnenburg ED. The Good Gut: Taking Control of Your Weight, Your Mood and Your Long-term Health. Penguin Books; 2015.

Yong E. I Contain Multitudes: The Microbes Within Us and a Grander View of Life. Bodley Head; 2016.