January 14, 2020 | David F. Coppedge

Stay Healthy; Get Dirty

Studies of two people groups confirm that exposure to nature helps prime the immune system – among other benefits.


Throughout history, most people had ample exposure to nature.

A group of people separated by political barriers showed very different degrees of health. One had more instances of allergies. The difference was in their exposure to nature. Jef Akst at The Scientist explains what researchers at the University of Helsinki and Flinders University found:

During the Second World War, the Scandinavian country ceded a large swath of territory to the Soviet Union. In the second half of the 20th century, the Finnish side became modernized, while people on the Soviet side maintained a traditional lifestyle. And by the 21st century, according to a study carried out by researchers at the University of Helsinki, the prevalence of allergies on Finland’s side of the border region known as Karelia was significantly higher than that of people living on the Russian side.

On your next vacation, consider including closeness to animals like horses.

The explanation, according to the researchers, was that the Russian families had more contact with the soil. In soil, numerous bacteria thrive. When they get on human skin and hands, the immune system learns about them and develops antibodies for them. Those who are too clean, on the other hand, are not prepared for exposure to the diverse microbes that live in dirt. Their immune systems overreact, causing allergic responses.

Exposure to soil might also prevent deadly diseases. Recall that Edward Jenner noticed that farm women tended to have natural immunity to smallpox, because they had been exposed to a weaker pathogen known as cowpox. This led to his famous experiments in vaccination.

Cleanliness has its downside. Deadly “superbugs” such as MRSA—unaffected by our strongest antibiotics—are becoming a serious threat in ultra-hygienic hospitals. It’s leading some hospitals to incorporate outdoor garden spaces for patient recovery, where patients can gain exposure to more biodiversity. Soil microbes might be the best weapons against superbugs.

The late ecologist Ilkka Hanski of the University of Helsinki along with Helsinki University Central Hospital researchers Tari Haahtela and Leena von Hertzen had recently formalized the biodiversity hypothesis, arguing that the total biodiversity—and correspondingly, microbial diversity—of people’s living environments influences human health via changes to the composition of the microbiome. A global loss of biodiversity, they reasoned, was to blame for the dysregulation of the human immune system and thus the increase in allergic and inflammatory diseases observed in developed nations around the world.

Backpacking provides all the health benefits of nature.

Controlled experiments on mice with clean bedding, mice with potting soil in the bedding, and mice reared in stables with other animals showed significant health deficits in the clean environment. Akst, who is managing editor of The Scientist, counts this new study as additional support for an old idea called the Hygiene Hypothesis:

The idea is an extension of the decades-old hygiene hypothesis, developed in the late 1980s and ’90s as researchers came to realize that living in a modernized world where bacterial exposure is limited was linked with hay fever and other disorders characterized by immune dysfunction. Later, University College London microbiologist and immunologist Graham Rook took a similar view with his “old friends” hypothesis, which posits that humans—and specifically their immune systems—have become dependent on the microbes they coevolved with for tens of thousands of years or more. “The immune system [is] a learning system,” Rook tells The Scientist. “Unless you put the data in, it can’t function correctly.

Evolution, though, knows nothing of “learning systems” and correct functioning. All the learning systems which we have observed coming into being, such as AI systems where input affects output, were intelligently designed. Since human life began in the outdoors, this cooperation between microbes and our own bodies could be a calibration method for the immune system. “This led us to think that this particular group of microbes derived from nature might be able to somehow contribute training or calibration of the immune system,” remarked one of the researchers. Perhaps some of the diseases that afflict us are our own fault, arising from lack of exposure to the natural environment that was designed to balance our systems and promote healing.

Not everything in the environment, of course, is healthy. Parasites, poisons and predators prowl about in certain environments. Harsh weather, additionally, is not a good time to be out if unprepared. Exposure to nature requires common sense, and learning what risks are imposed by particular environments. Staying indoors all the time, though, is already a known risk. Multiple studies show that. In fact, staying cooped up indoors when sick with a cold or flu may not be the best therapy. If the weather is good, nature might be the best medicine. Medical Xpress asks: “Should you exercise when you’re sick?” Not always, but in some situations it can help.

A hike in the outdoors can be close by, quick and simple. All photos by David Coppedge.

An infographic produced by The Scientist shows multiple ways that nature affects human health. Not only do soil microbes help prime the immune system, other things go on during a walk in the woods. Trees with their leaves help filter out pollutants and improve air quality for our lungs. Physical activity of walking exercises the muscles, lungs and other systems of the body; plus, if done with others, provides social benefits. Even the sounds of nature, such as bird song, have a calming effect on the mind. All the senses get involved when you spend time outdoors in nature. It reduces stress and increases one’s sense of well-being, as another article in The Scientist confirms.

The bottom line is short: Get out and walk in nature! Our Creator made the richness of life for our health and enjoyment.

See our sister site Creation Safaris for more resources about the physical, mental and spiritual benefits of exploring God’s amazing creation. These photos are all from Creation Safaris events.



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