A very good excerpt first, then link to the article.
The tradition was already ages-old in Japan, but naming it went hand in hand with making recommendations for best practices: one should walk, sit, gaze and exercise among the trees; eat well-balanced meals of organic, locally sourced food; and, if available, immerse in hot springs. All five senses should be engaged, especially for certification as one of Japan’s official Forest Therapy Bases, which are well-maintained, embraced by the local community, and which are required to show, in practitioners, a decrease in physiological markers such as levels of the stress hormone cortisol after wandering in the woods.
When Akiyama recommended forest bathing all those years ago, he knew about the pioneering studies of phytoncides – basically, pungent essential oils – conducted by the Soviet scientist Boris P Tokin in the 1920s and ’30s. The oils, volatile compounds exuded by conifers and some other plants, reduce blood pressure and boost immune function, among other benefits.
In recent years, a host of other mechanisms have come to light – in fact, there are up to 21 possible pathways to improved health, according to a review paper in Frontiers in Psychology from scientists at the University of Illinois at Urbana-Champaign. Among the elements that have been identified, of particular note are bright lights and negative air ions (oxygen atoms charged with an extra electron), known to ease depression; simple views of nature, which enhance autonomic control of heart rate and blood pressure; and even the sounds of nature, which help us to recover from heightened stress.
Blood tests revealed a host of protective physiological factors released at a higher level after forest, but not urban, walks. Among those hormones and molecules, a research team at Japan’s Nippon Medical School ticks off dehydroepiandrosterone which helps to protect against heart disease, obesity and diabetes, as well as adiponectin, which helps to guard against atherosclerosis. In other research, the team found elevated levels of the immune system’s natural killer cells, known to have anti-cancer and anti-viral effects. Meanwhile, research from China found that those walking in nature had reduced blood levels of inflammatory cytokines, a risk factor for immune illness, and research from Japan’s Hokkaido University School of Medicine found that shinrin-yoku lowered blood glucose levels associated with obesity and diabetes.
‘People respond very favourably to water, whether a fountain in a healing garden or a river or shoreline’
Studies showed that just three days and two nights in a wooded place increase the immune system functions that boost feelings of wellbeing for up to seven days. The same amount of time in a built environment has no such effect. Human response includes increased awe, greater relaxation, restored attention, and boosted vitality. Health outcomes on the receiving end of the pathway are astounding: enhanced immunity, including reduced cardiovascular disease, fewer migraines, and lowered anxiety, to name but a few. According to Frances Ming Kuo , the lead author of the University of Illinois review: ‘The cumulative effect could be quite large even if many of the individual pathways contribute only a small effect.’