By Leslie Murphy MD
Do you remember being young and exploring undiscovered places? Did you walk in the woods and feel invincible? Can you recall the feeling of relaxation that came over you when you entered that forest?
Believe it or not, there is science behind why you feel so relaxed after taking a hike in the wilderness or a stroll through the forest. A variety of research findings has discovered that walking in the forest, or “forest bathing” as it’s referred to in Japan, is responsible for positive improvements in health ranging from a better mood and sleep, to heavily reduced stress levels and even a boosted immune system that could potentially fight cancer.
In 1990, Dr. Yoshifumi Miyazaki of Chiba University performed a study in the ancient Japanese forests of Yakushima. Miyazaki found that physical activity in the form of a 40-minute walk through the forest could be connected to an improved mood and feelings of health and robustness. Furthermore, lower levels of the stress hormone cortisol were found in test subjects that took a walk in the forest, as compared to a controlled group of subjects who engaged in walks within a laboratory setting.” – (Source: Mother Earth News)
Miyazaki, a physiological anthropologist and vice director of Chiba University’s Center for Environment, Health, and Field Sciences, believes that because humans evolved in nature, it’s where they feel most comfortable even if they don’t always realize it. According to Miyazaki, since nearly all of our time has been spent in “natural environments” throughout our evolution, our bodily functions are still in tune with the outdoors, hence the “feeling of comfort” that we get when we spend time outside.
Japan currently has 48 official forest therapy trails designated for shinrin-yoku by Japan’s Forestry Agency. The Japanese government has funded about $4 million in forest-bathing research since 2004 and intends to designate a total of 100 forest therapy sites within the next ten years. As a part of the research into the benefits of forest therapy, visitors of Japan’s forest therapy parks are routinely taken to a cabin where rangers measure their blood pressure to gain valuable data that helps support the projects.
Miyazaki has taken more than 600 research subjects into the woods since 2004. He and his colleague Juyoung Lee, also of Chiba University, have found that leisurely forest walks, as opposed to walks in an urban environment, yield a 12.4 percent decrease in the stress hormone cortisol, a seven percent decrease in sympathetic nerve activity, a 1.4 percent decrease in blood pressure, and a 5.8 percent decrease in heart rate. Although a more subjective measure, study participants also report better moods and lower anxiety. As Miyazaki concludes in his 2011 paper, “This shows that stressful states can be relieved by forest therapy.” Since the research has begun, between 2.5 million and five million visitors walk the Forest Therapy trails each year.
Thanks to Miyazaki’s research, several countries interested in studying the positive health effects of nature have followed Japan’s lead. Juyoung Lee was recently hired by the South Korean government, which has poured over $140 million into a new National Forest Therapy Center. At the same time, Finland, an empire of boreal spruce and pine, has also begun funding numerous medical studies on the soothing power of forests. “Japan showed us that there could be cooperation between forestry and medical fields,” says Liisa Tyrvainen of the Finnish Forest Research Institute. “Now there is no surprise that these shifts occur when we analyze the objective data derived from physical measurements.”
Excerpts from Finland’s data collection can be found in “The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan. In the experiments documented through this paper, twelve subjects walked in and viewed either a forest or a city area. On the first day of each test, the group was halved, with six members being sent to the forest and the other six to the city. On the second day, each group was then sent to the opposing area by way of a cross-check. After calculating the data, the researchers noted that their results “show[ed] that forest environments promote lower concentrations of cortisol, lower pulse rate, lower blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than do city environments.” These positive results would later “contribute to the development of a research field dedicated to forest medicine.”
As far as preventive medicine goes, forest bathing seems to significantly mitigate the root cause of a multitude of ailments: stress. Excess stress can play a role in headaches, high blood pressure, heart problems, diabetes, skin conditions, asthma, and arthritis, among other health problems. As the results indicate, forest bathing catalyzes increased parasympathetic nervous system activity which prompts rest and helps the body conserve energy, slowing down the heart rate while increasing intestinal and gland activity. Lower cortisol concentrations are also a signal that the body’s stress-response system is being triggered less. When this system is triggered, cortisol and other stress hormones are released into the body. Overexposure to these chemicals in response to chronic stress can increase the risk of anxiety, depression, heart disease, weight gain, and memory loss.
Live in an urban environment? That’s okay! City-goers can still reap the benefits of forest bathing through a more indirect form of natural therapy. Research has indicated that attempts to mimic a forest environment can still have positive physical and psychological effects. An article entitled “Trends in research related to ‘Shinrin-yoku’ in Japan” suggests that visual stimulation in the form of natural images are perceived as more “comfortable” and “soothing” when compared to a gray screen control. Subjects who view “Shinrin-yoku images” — specifically a photograph of people taking a walk in the forest of Vincennes in Paris — have significantly decreased blood pressure and prefrontal activity. Such reduced activity in the prefrontal cortex has been associated with a decreased risk of relapsing back into depression. It is thought that this response is due to the prefrontal brain’s ability to deeply analyze sadness, which can result in unhealthy thought patterns, whereas the visual areas of the brain are associated with acceptance and non-judgement.
Other ways that city-goers can reap the effects of forest therapy include going to a natural area, such as a park, a running trail along a waterway, or a bike path through a garden. For a more encompassing experience, there is always the option of spending one weekend a month in a forest reserve or a national park. Visit a local park at least once a week. Start a garden or join a gardening club. Go for walks wherever trees,gardens, or lush greenery can be found. Find a quiet place. Venture into uncharted territory and find that special spot that can bring back the feeling of exploring the forest and being invincible again.
Make it a point to plan a forest walk this weekend. Listen to the birds, take off your shoes and walk in the dirt, and smell the flowers and the leaves. Feel the bark of trees and guess what species they are. Make a picnic and enjoy it on the forest floor. Then tell me how you enjoyed your weekend. Did you feel like you did when you were a kid? I have a feeling you will want to do it again.