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In Japan, a forest bathing trip, called “Shinrinyoku” in Japanese, is a short, leisurely visit to a forest; it is regarded as being similar to natural aromatherapy. But which positive health effects does such a Shinrinyoku have? An intensive scientifical resarch in Japan studied the effects of forest bathing trips on human immune function. And the results are stunning. It has been proven that 'forest bathing' enhances human natural killer activity and the expression of anti-cancer proteins. So that walk in the forest is not only useful for your mental health!

Scientifical study published by the National Library of Medicine. Study executed by Q Li, K Morimoto, A Nakadai, H Inagaki, M Katsumata, T Shimizu, Y Hirata, K Hirata, H Suzuki, Y Miyazaki, T Kagawa, Y Koyama, T Ohira, N Takayama, A M Krensky and T Kawada.

In order to explore the effect of forest bathing on human immune function, the Japanese scientists investigated natural killer (NK) activity; the number of NK cells, and perforin, granzymes and granulysin-expression in peripheral blood lymphocytes (PBL) during a visit to forest fields. Twelve healthy male subjects, age 37-55 years, were selected with informed consent from three large companies in Tokyo, Japan.

Trip to the forest

The subjects experienced a three-day/two-night trip in three different forest fields. On the first day, subjects walked for two hours in the afternoon in a forest field; and on the second day, they walked for two hours in the morning and afternoon, respectively, in two different forest fields. Blood was sampled on the second and third days, and NK activity; proportions of NK, T cells, granulysin, perforin, and granzymes A/B-expressing cells in PBL were measured. Similar measurements were made before the trip on a normal working day as the control.

Almost all of the subjects (11/12) showed higher NK activity after the trip (about 50 percent increased) compared with before. There are significant differences both before and after the trip and between days 1 and 2 in NK activity. The forest bathing trip also significantly increased the numbers of NK, perforin, granulysin, and granzymes A/B-expressing cells. Taken together, these findings indicate that a forest bathing trip can increase NK activity, and that this effect at least partially mediated by increasing the number of NK cells and by the induction of intracellular anti-cancer proteins. These findings indicate that forest bathing trips increase NK activity, which was mediated by increases in the number of NK cells and the levels of intracellular anti-cancer proteins. Phytoncides released from trees and the decreased production of stress hormones may partially contribute to the increased NK activity.

Because NK cells can kill tumor cells by releasing anti-cancer proteins, such as perforin, GRN, and GrA/B, and forest bathing trips increase NK activity and the intracellular level of anti-cancer proteins, the above findings suggest that forest bathing trips may have a preventive effect on cancer generation and development.

(FVDV for Tagtik/Source: NIH/Illustration: Photo by Daniel Bernard on Unsplash)