Researchers estimate that as many as 100 million Americans are nature deprived. There are plenty of ways to remedy this, including putting plants around your house and getting what author Wallace Nichols calls a "blue mind" by being in and around water. But a promising nature therapy is what the Japanese call shinrin-yoku. Translated as forest bathing, this practice can have a broad impact on your physical, emotional, and mental wellbeing. Here are some of the latest findings and tips for making the most of what the woods have to offer.
Tokyo seems an unlikely place to study the health impact of nature. It’s one of the largest cities on the planet, with more than 14 million inhabitants. It also has a high population density, with 6,158 people per square kilometer, versus 2,844 in Paris, 1,800 in New York, and 1,510 in London. So it’s unsurprising that the city is in many ways very urban and has a lot of concrete. However, it also boasts some amazing green space, such as the 234 tree species in the sacred forest surrounding the shrine buildings of Meiji Jingu, the 1,100 cherry trees in the Shinjuku Gyoen park, and multiple bamboo forests.
Another open space is the 49-acre forest surrounding the Institute for Nature Study. Once the estate of the Matsudaira samurai clan, it’s now an oasis for Tokyo residents looking to get away from the hustle and bustle of the city and also a leading center for investigating how doing so can positively impact human health. Japan has another 3,000 miles of woods outside its capital when the scientists there want to go further into the forest. The country has been studying the effects of shinrin-yoku for over 40 years and began a national forest bathing program in 1982 when the government decided its citizens could heal through nature exposure.
Boosting Mental Health
In 1990, Dr. Yoshifumi Miyazaki from Chiba University led a group through the forests on the island of Yakushima. He found that in just 40 minutes, they reported feeling increased energy levels and in a better mood. When he took samples, Miyazaki discovered that these subjective findings were mirrored in their physiology, as their levels of the stress hormone cortisol were lower. This result was repeated in a 2007 study he participated in. It asked students to walk through a tree-lined route for 15 minutes in the morning and sit looking at it in the evening.
Their cortisol and blood pressure were lower, pulse rate reduced, and heart rate variability (a measure of parasympathetic recovery) increased, compared to those who were in an urban area. This suggests a more balanced autonomic nervous system, which modulates between sympathetic fight or flight and parasympathetic rest and recovery.
Japan isn’t the only country studying the advantages of shinrin-yoku for mental health and emotional wellbeing. Taiwanese scientists found that a two-day forest bathing program reduced anxiety, fatigue, and tension in middle-aged women, and so was perfect for dealing with a hectic lifestyle. Polish researchersnoted that just being among trees for quarter of an hour each evening reduced negative emotions, increased positive ones, and made subjects feel reinvigorated. Multiple South Korean papers have proved that forest bathing reduces depression, stress, and anxiousness.
Improving Immunity
One of the most powerful proof points for how forest bathing improves physical health came from Dr. Quing Li, chairman of the Japanese Society for Forest Medicine. In 2005, he found that after three days in a forest, people’s immunity was significantly elevated. The number of their NK cells – the Special Forces of the immune system that attack viruses and tumors – increased by 50 percent, while NK cell activity rose by 53.2 percent. Levels of three anti-cancer proteins rose by between 28 and 39 percent.
The number of NK cells remained elevated for 30 days afterward, showing how a single forest bathing trip has a lasting positive impact. This level also remained elevated after a day trip where people walked in the forest for a lesser duration. Li discovered that it increases the amount of serum adiponectin, an anti-carcinogenic hormone. Chinese researchers discovered that forest bathing also increases the amount of B cells, which produces antibodies to combat bacteria and viruses. Perhaps these effects explain why Japanese health data suggests that the more trees people live amongst, the lower their cancer rates.
Sorting Out Sleep and Inflammation
In his book, Li reported that shinrin-yoku doesn’t just enhance immune function but also promotes better rest. Two-hour walks in the forest helped people increase their total sleep time by 69 minutes during the study and 27 minutes afterward. Additional trials demonstrated that walking in nature helped people with chronic sleep problems drift off faster, increase the duration of their slumber, and improve sleep quality. One reason might be an increase in serotonin, while it minimizes the production of neurotransmitters like adrenaline and noradrenaline that promote stress and hyperarousal.
There’s also evidence to suggest that forest bathing reduces the levels of chemicals that can cause hypertension and inflammation. For example, one study concentrating on how it lowers blood pressuresuggested that shinrin-yoku can reduce the risk of cardiovascular disease in two ways. First, it seems to limit the release of certain chemicals in the renin-angiotensin system that regulates blood pressure and fluid balance. Second, it reduces levels of markers like IL-6 that indicate when the body is stuck in a pro-inflammatory state in which disease flourishes. It can also reduce the amount of ET-1, which causes blood vessels to constrict and stimulates inflammation.
While longer forest bathing trips seem to have the greatest impact on the immune system, several studies reveal that for psychological wellbeing and stress management, consistently getting out in nature for as little as 15 minutes a day can make all the difference. Taking a regular walk through the trees in the evening or going through a park on your lunchtime stroll might also deliver many of the physical benefits, such as lowering blood pressure, increasing HRV, and taming inflammation.