In Japan, a popular health practice is walking through a forest, otherwise known as forest bathing, or Shinrin-yoku. Forest scents, sounds, and light, have a healing effect that has been measured scientifically.
Essential wood oils, named phytoncides, are emitted by plants and enhance the human immune system. Specific cells of the immune system, natural killer cells, increase in number in response to the phytoncides. The natural killer cells fight disease, including cancer. Phytoncides are natural preservatives and fungicides, classified as antimicrobial volatile organic compounds, and can also be used as essential oils in aromatherapy.
In 1982, the Forest Agency of Japan proposed that forest bathing trips be part of a healthy lifestyle as a national therapy for wellness and health. A new field of Forest Therapy developed, and specific forests were recognized for Forest Therapy by the Forest Therapy Executive Committee, with 31 recognized in Japan to date (Japan Times, Forest Therapy Taking Root). Japanese companies include forest therapy in employee health care benefits.
Yuko Tsunetsugu, from the Forestry and Forest Products Research Institute in Matsunosato, Tsukuba, Japan, writes eloquently about the forest’s impact upon the five senses:
Viewing a picture of people taking a walk in a beautiful forest decreases blood pressure and heart rate. The viewing also decreases prefrontal activity in the brain, the part of the brain that can get overly busy solving problems. Viewing a photo of people "forest bathing", correlates to self-described feelings of calmness and elation, compared to viewing a photo of a lovely cherry tree in full bloom. Blood pressure and heart rate lowering are also observed when people are in rooms with 45% wood content.
Scents are associated with instinct, emotion, and preference. Taking in the phytoncides of a forest by smelling them has significant physiological effects. Blood pressure decreases, prefrontal activity decreases, anxiety and depression diminish, the mind works more efficiently, and breathing slows.
Touching untreated or thinly painted wood paneling does not increase blood pressure, but when wooden paneling is thickly painted, blood pressure stays elevated.
As expected, the sound of a stream is soothing, thus blood pressure and brain activity decrease when hearing a stream running over rocks through a forest.
The literature on Shinrin-yoku mentions further benefits, including: stress reduction, lower blood sugar, better concentration, and diminished pain.
2007 Park et al. Physiological effects of Shinrin-yoku (taking in the atmosphere of the forest) using salivary cortisol and cerebral activity as indicators. J Physiol Anthropol 26(2):123-8.
2008 Li et al. A forest bathing trip increases human natural killer cell activity and expression of anti-cancer proteins in female subjects. J Biol Regul Homeostat Agents. 22(1):45-55.
2008 Li et al. Visiting a forest, but not a city, increases human natural killer cell activity and expression of anti-cancer proteins. Int J Immunopathol Pharmacol. 21(1): 117-27.
2009 Li et al. Effect of phytoncide from trees on human natural killer cell function. Int J Immunopathol Pharmacol. 22(4): 951-9.
2010 Park et al. The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan. Environ Health Preventative Med. 15(1): 18-26.
2010 Tsunetsugu et al. Trends in research related to Shinrin-yoku (taking in the forest atmosphere or forest bathing) in Japan. Environ Health Preventative Med. 15(1):27-37.
2010 Cimperman. Forest therapy. A Different Type of Doctor Blog.
~ Dr. M.