I used to joke to my friends at work that, in the long run, the daily walk through the forest was probably of more lasting benefit to me than the hard earned pay checks.

Now I’m not so sure it was a joke. The money earned is long gone, but the good health I’ve enjoyed through the years is still with me. My medical record so far is pretty thin. I’ve never been to a hospital, touch wood.

Maybe I’ve just been lucky. But living in a beautiful forest since 1980 may have set me up for this luck.

According to a study recently published in the journal Epidemiology, nearly one in five young adults in the U.S. has high blood pressure. Researchers at the University of North Carolina at Chapel Hill also report that, while almost 20 percent of young American adults suffer from “symptomless hypertension”, only about half of those aged 24 to 32 are aware of having the condition, making the silent killer all the more deadly.

It’s not possible to link this epidemic of hypertension conclusively with any particular cause, but it seems logical that time spent in nature will help slow us down to the speed of life which we’ve been biologically programmed to live since the dawn of man.

While we may intuitively appreciate a walk in the woods, the benefits may seem somewhat intangible and undefined. I remember when my children were babies a sure way to quiet them when upset was to carry them outside under the forest canopy. The silence of the still forest had a calming effect, a chirp from a nearby bird could lure the child into quiet fascination, and the air rich with earthy smells had a soporific effect on a cranky child. Were these benefits a gift from the forest, or was my imagination working overtime?

According to Yoshifumi Miyazaki, Japan’s leading scholar on forest medicine, a walk in the forest does indeed calm a stressed baby, and much more. A walk in the woods, or ‘shinrin-yoku’, provides preventive medical effects by relieving stress and recovering the immune system diminished by stress. And for the first time, Japanese scientists have found ways to quantify the impact that forest therapy (shinrin-ryoho), can have on humans.

Miyazaki’s research studies show that ‘forest bathing’ can significantly lower levels of cortisol, a stress hormone, along with blood pressure and heart rate. Walking in the woods can boost the body’s immune system by increasing anti-cancer proteins and enhancing the activity of certain cancer-fighting cells. The research suggests that humans benefit from breathing in ‘phytoncides’, the volatile organic compounds plants emit to protect themselves from bacteria, fungi and insects. In a related study (2), researchers in a Sierra Nevada forest identified 120 airborne volatile chemicals, of which only 70 could be identified.

During 2005-2008, Miyazaki conducted experiments at 38 different forests at widely separated locations throughout Japan, ranging from the large northern island of Hokkaido to Okinawa. Stress hormone (cortisol) levels in saliva, autonomic nerve activity (sympathetic and parasympathetic) monitored by heart-rate fluctuation, blood pressure, and heart rate, were adopted as measured variables. In addition, for the first time, his team developed a method to monitor prefrontal cortex activity of the brain using near-infrared spectroscopy in the field. Measurements were taken of forest phytoncides, urban exhaust fumes, temperature and humidity, light conditions, wind velocity, and negative and positive ions.

As a result of studies involving 288 volunteers at 24 different sites, the group of volunteers looking at natural surroundings while sitting down showed the following endpoint decreases compared to the urban control group: a 13% decrease in cortisol level, an 18% decrease in sympathetic nerve activity, a 2% decrease in blood pressure, and a 6% decrease in heart rate. Parasympathetic nerve activity was enhanced by 56%, indicating a relaxed biological system.

Results compiled from several related studies (3,4,5) show a wide range of positive benefits from a walk in the woods. These benefits include:

1. decreased blood glucose levels in diabetic patients
2. decreased stress hormones
3. decreased heart rate
4. decreased blood pressure
5. general relaxation of the human body (increased parasympathetic nervous system activity)
6. possible boost to the immune system (reduced cortisol is associated with increased immune function)
7. decreased depression
8. decreased anger
9. decreased fatigue and confusion
10. increased psychological vigor

Protecting natural forests benefits human health

There is a secondary benefit to our recognition of the physical benefits derived from spending time in the forest. As we learn more about the healing power of natural forests, momentum may build to help preserve these healing environments through better forest management practices. In Japan, Miyazaki’s research findings have led to the establishment of more than 40 ‘forest therapy’ sites across Japan. The goal is to set up 100 protected natural forest reserves within the next decade.

In the US today, most people live in urban or suburban environments. But for 99.9 percent of our evolutionary history we have lived in nature, and our physiological development is still adapted to nature. Today, our fast-paced lifestyles place us in an overstimulated state which creates stress, and living in artificial environments denies us the exposure to the healing properties of nature. Getting back to nature is actually like a physiological homecoming.

Bringing ourselves and our children into nature offers significant benefits for our personal well-being, as well as needed perspective to help support and guide future forest management practices.

References:

1. 1. Science of Natural Therapy, by Yoshifumi Miyazaki , Center for Environment, Health and Field Sciences. Chiba University
2. 2. Science of The Total Environment Volume 112, Issues 2-3, March 1992, Pages 233-250
3. 3. International Journal of Biometeorology, 1998;41:125 – 7
4. 4. Environmental Health and Preventive Medicine, 2010: Volume 15, Number 1, 18 – 26
5. 5. Biology of the Neonate, 2000;78(1):70-2