Forests offer so much to us simply by existing. They are the world’s greatest air purifiers. Their plants and waterscapes fascinate every sense perception, and every forest has its own unique set of aromas. They are a refuge from urban noise, with an ever-changing soundtrack of breeze, birds, and brooks.
Our stress levels and elevated blood pressures enter healthier zones from the moment we enter the forest domain to marvel at gold or verdant light filtered through foliage. The forest is part of who we are as an evolving human species, and we receive all its messages through our genes as well as our senses.
The Forest as Immune Educator
Beyond all we can see in forests, they abound in microscopic life that is intensely stimulating to our immune systems. There is unfathomable variety in the bacteria, amoebic life forms, viruses, and other microbes in forests. Most of their species are not harmful to humans. In fact, this incredible biodiversity of life may help to train our immune systems to be more resilient. For increasing numbers of people with autoimmune, allergic, or inflammatory conditions, there is also reason to appreciate forests for their potential to retrain immunity towards healthier balance.
We’ve become accustomed to thinking of viruses, fungi, mold, and bacteria as harmful things. Yet out of many thousands of species, relatively few cause severe illness. All the others remind our immune systems that we share their same circle of life.
We have microbes living on our skin and in our ears, guts, and airways. Plants, animals, insects, and invertebrates also have their own microbial associates, and this reality is just as natural and normal for us as it is for them. Interacting with visible and microscopic life is part of how our immune systems get to know our surroundings and distinguish between what is and isn’t a bodily threat.
The Science Agrees!
A recent study in Finland has helped explain how forests educate human immune systems for healthier balance. A team of researchers was inspired by the discovery that merely touching landscaping materials could improve the diversity of skin bacteria, and they decided to see if children would receive similar benefits from contact with plants.
They set up their experiment by observing young children in different daycare situations. The first group was at typical daycare centers that provided little or no green outdoor spaces for kids to play in, while the second set gave children daily visits to nearby forests. The researchers gave plant materials to a third group of daycares for kids’ outdoor play areas, like peat blocks to climb on, forest floor vegetation to play with, and sod to play upon.
The researchers checked the kids’ skin bacteria and immune cell function before and after a 28-day period of regular, direct exposure to these three types of outdoor environments, and noticed several interesting things:
• Both before and after the experiment, kids who spent regular time in forests had the greatest diversity in skin bacteria, along with the best balance in immune cell function (meaning that they showed good defense readiness without being overactive).
• Kids who played around natural plant materials (that third group) developed better skin bacteria diversity and better immune balance after 28 days.
• Kids at typical daycare centers with not much green space showed the least favorable immune balance and skin bacteria diversity before and after the experiment.
• Kids who visited forests regularly also showed more generous levels of certain beneficial species in their intestinal microbial communities. The intestines are one of the body’s most important regions for immune training, and diversity in gut bacteria is a prerequisite for best immune function, and the researchers felt that this made an important contribution to these children’s health and immunity. For more about the gut microbiome, check out this previous blog post on this very topic.
Natural Biodiversity is the Key
Spending time in forests or around outdoor plant materials exposed kids to more varieties of ‘friendly’ microbes. Even more importantly, though, “meeting and greeting” all this microbial diversity helped children develop better immune tolerance to new things. Gaining immune tolerance earlier in life is linked to lower risk for future allergies, inflammation, and autoimmune conditions — all of which are on the rise in adults as well as children, in modern times.
Even though this study focused on kids, I’d be willing to bet that the people caring for these children and guiding their outdoor activities also got stress relief and immune benefit from their nature time. Here is a link to this study for those interested in its glorious and gritty detail — which just might get you to grub around in the healthy, living soil of the naturescape nearest you!
