1015. The Therapeutic Smell of Trees

By Bonnie Tsui, theatlanticcities.com, March 2013 

Researchers have been racking up evidence that when you can’t take a break and get into nature itself, looking at photos of it relaxes our brains in a similar way. Now, scientists in Tokyo are building a case that smelling nature — the bracing scent of forest pine or cypress, for instance — lowers our blood pressure dramatically and increases anti-cancer molecules in our bloodstreams.

For the past eight years, Qing Li, an immunologist in the department of hygiene and public health at Tokyo’s Nippon Medical School, has been studying phytoncides, the essential oils and aerosols emitted by plants and trees, and their salutary effects on the human body. Studies had shown that nature visits reduce stress on the nervous system, overloaded as it is in the modern urban environment with its dense living conditions, industrial-grade fumes, and honking horns. Li’s early work showed that walks in the woods boosted natural killer immune cells that helped fight infection and cancer; eventually, he came to suspect that it was the natural scents of evergreens and other trees that did the bulk of the work.

While testing his theory — by sequestering subjects in hotel rooms, some with the benefit of cypress aromatherapy, some without; those who sniffed the phytoncides experienced significant drops in stress hormones and boosted immune cell activity — Li and others founded a Japanese organization to study forest medicine more formally. A few years later, it went global as the International Society of Nature and Forest Medicine; last year, it held its first international symposium on the research and trends on forest therapy worldwide. Following the lead of the Japanese in using phytoncide therapy and other facets of “forest bathing” to boost health are the Finns — led by Liisa Tyrväinen, the Finnish Forest Research Institute is conducting a multi-year research program on forests and human well-being — and the South Koreans, who are opening a new $140 million National Forest Therapy Center in 2014. The wisdom is old: get outside when you can; when you’re stressed, aromatherapy can help. But now the hard science is finally backing it up.