Just Being Outside Can Improve Your Psychological Health, and Maybe Your Physical Health Too
From 2004 to 2012, Japanese officials spent about $4 million dollars studying the physiological and psychological effects of forest bathing, designating 48 therapy trails based on the results. Qing Li, a professor at Nippon Medical School in Tokyo, measured the activity of human natural killer (NK) cells in the immune system before and after exposure to the woods. These cells provide rapid responses to virus-infected cells and respond to tumor formation, and are associated with immune system health and cancer prevention. In a 2009 study, Li’s subjects showed significant increases in NK cell activity in the week after a forest visit, and positive effects lasted a month following each weekend in the woods.
This is due to various essential oils, generally called phytoncides, found in wood, plants, and some fruit and vegetables, which trees emit to protect themselves from germs and insects. Forest air doesn’t just feel fresher and better—inhaling phytoncides seems to actually improve immune system function.