18/10/2026
For more than 20 years, Japanese immunologist Dr. Qing Li has studied how spending time in forests affects the human body. His research found that time spent among trees can increase the activity of natural killer (NK) cells, immune cells that help the body fight virus-infected and cancerous cells. Some studies reported increases of around 50% following forest bathing.
One possible explanation is phytoncides, natural compounds released by trees to protect themselves from insects and microorganisms. Research suggests that breathing in these compounds may influence immune activity.
Li also found that forest walks were associated with lower cortisol levels, blood pressure and heart rates compared with walks in urban environments, suggesting that spending time in nature can help reduce stress.
The benefits appear to come from a combination of factors, including the forest's natural chemistry and the calming effects of nature on the nervous system.
Nature is a valuable complement to a healthy lifestyle. Spending time among trees may support several biological processes involved in stress regulation and immune function.
Today, people spend much of their lives indoors, often limiting their exposure to natural environments. Making time to walk among trees may be a simple way to reconnect with nature and support overall well-being.
