06/08/2026
Research shows Forest air can increase activity of Natural Killer cells, improve immune system, reduce cortisol (stress hormones) and more..... So finding a forest and spending time there has more benefits than just quietening the noise for a while.
Find a forest 💚
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For more than 20 years, Japanese immunologist Qing Li studied what happens inside the human body when people spend time in forests.
His research found that forest air can affect more than mood. When people walk among trees, they breathe in natural compounds released by trees called phytoncides.
Trees release phytoncides to protect themselves from insects, bacteria, and fungi. When humans inhale these compounds, research suggests they may help support immune function.
Li found that time in forests can increase the activity of natural killer cells by around 50%. These immune cells help the body fight virus infected cells and cancer cells.
His work also showed that forest walks were linked with lower cortisol levels compared with city walks. Cortisol is one of the body's main stress hormones.
People who walked in forests also had lower blood pressure and lower heart rates. This points to a clear calming effect on the nervous system.
According to Li's research, about half of the benefit may come from the chemistry of forest air. The other half appears to come from the way natural settings calm the body and reduce stress.
Qing Li is a clinical professor at Nippon Medical School in Tokyo and president of the Japanese Society of Forest Medicine. The Japanese government has supported his research since 2004, and his body of work helped make forest bathing an officially prescribed clinical therapy in Japan and Korea.
This does not mean nature replaces therapy or medicine when those are needed. But it does show that being around trees can be a powerful complement to modern care.
The average person now spends more than 90% of their time indoors. That means many people live with high stress while spending less time in the natural environments the human body evolved around for thousands of generations.
