The Japanese practice of “Shinrin-yoku”, meaning “taking in the forest atmosphere,” is defined as a “short, leisurely visit to a forest… similar to natural aromatherapy,” according to Li Qing, a forest bathing expert and scientist. One official website of Shinrin-yoku designates the practice as the “cornerstone of preventive health care and healing in Japanese medicine.”
Philip Barr, a physician at Duke for integrative medicine, recognizes and asserts new scientific data looking at the mental, emotional, and biophysical benefits of forest bathing and of being among trees in general. Rather poetically, he states in his article: the “healing rhythms of nature dissolve lingering issues and bring about profound peace of heart.”
Well, it could look like this:
…if you are into that. But more realistically, it could look like this:
So why is Shinrin-yoku relevant to urban forestry? Why would the benefits of forest bathing justify the need for trees in cities if the practice clearly takes place in, well, the forest?
Barr’s article in Thrive Global asked this same question. According to the Association of Nature and Forest Therapy, “forest bathing” could be as simple as “the practice of spending time in forested areas for the purpose of enhancing health, wellness, and happiness”. The key part of forest bathing is just being around trees themselves, since they produce compounds called phytoncides, which are shown to reduce stress and enhance human killer cell (NK) activity.
So what exactly is NK activity?
To break it down simply, NK cells are cells that kill tumor- or virus- infected cells by releasing anti-cancer proteins (perforin, granzymes, and granulysin). The increase in NK, caused by higher expression of these anti-cancer proteins, shows a beneficial effect on human immune systems.
Li Qing, an expert at the Nippon Medical School devotes much of his research to finding out the intricacies of how trees improve human immune health. In one of his first studies on the matter, he found that forest bathing may have beneficial effects on human immune function due to the essential oils found in trees, which enhance NK activity.
Qing’s later study in 2009 looked directly at forest bathing on immune functioning. In his study, subjects spent two to three nights in a forested area. Qing found that levels of perforin, granzyme A, and granulysin A/B (remember the anti-cancer proteins?) were significantly higher in these 2 to 3 days than those on days visited inside of a city, which did not increase NK activity at all. Not only this, but Qing also found that elevated NK levels lasted for over 30 days after the forest bathing trips. In his conclusion, Qing notes that several aspects from trees could to increases in NK activity, particularly the phytonicide compounds and capacity for trees to generate stress relief.
What have we learned? Studies show significant evidence that forest bathing has the capacity to aid stress reduction and improved mental health, and in the prevention of cancer generation and development.
This is the first post in a series on trees and public health. Stay tuned for more posts on this topic — next, about how trees help us breathe easier.