In conversation with Dr. Qing Li

Written By Johanna Sorrentino

For deeper learning about the research and practice of shinrin-yoku, or forest immersion, UNature spoke with Dr. Qing Li. For the last 20 years, Dr. Li has studied the effect of forest environments on human health. Today, he is considered one of the world's leading experts in forest medicine. 

 

The scientific community has acclaimed his work, but he is also renowned for his books for the general public, translated into many languages. He is currently a clinical professor at the Department of Rehabilitation Medicine at the Nippon Medical School Hospital, and is President of the Japanese Society of Forest Medicine. 

His 2018 book, Forest Bathing, shows how forest immersion can reduce stress levels, strengthen the immune and cardiovascular systems, improve energy, and more.

Our conversation offers insight into the history and future of this important field, as well as tips for integrating forest immersion into daily life to improve health and wellness. 

 

The term shinrin-yoku was coined in 1982 by Tomohide Akiyama, the director of the Forest Agency of Japan at the time. He intended to develop a unique brand identity that would link forest visits to health and wellness-oriented ecotourism. Initially a generic term encouraging people to go into the forest, it was later adopted in the West to designate various activities. To avoid confusion with any specific practices or programs, UNature uses the term "forest immersion" to describe the general shinrin-yoku approach. 

 

UNature: What led you to take an interest in your field of research?

Dr. Li: It is a long story.

I was born in a small village in China. There were green poplar forests and a beautiful apricot forest in my village which flowered pink all through April. I love nature and forests from my childhood.

In 1984, I graduated from Shanxi Medical University in China and got my medical doctor license. In 1988, I came to Japan and studied at Kagoshima University in Japan. At that time, I visited a very beautiful forest with my friends in Yakushima—a small, round island with the mysterious, green forest. The quiet atmosphere, beautiful scenery, mild climate, special good smell, fresh air in the forests, and big Japanese cedar trees (Jomon sugi) made me very happy and relaxed. Thankful for all its bounty and beauty, I became convinced that forest immersion was absolutely essential to human health. That fascinating, inspiring visit was to have an important impact on the whole direction of my life and my future research. 

I have studied the effects of environmental chemicals, stress, and lifestyle on immune function and human health since 1988 in Kagoshima University and Nippon Medical School. I studied at Stanford University from 2001 to 2002 on the topic of anticancer protein, granulysin in human natural killer cells (immune cells). I established the method to measure granulysin in NK cells.

Because of my background, when the Forest Agency of Japan organized the project team in 2004, I was invited as a main member.

UNature: What is the driving question that your research answers?

Dr. Li: I want to know why we feel so much better when we are in forests. What is this secret power of trees that makes us so much healthier and happier? Why is it that we feel less stressed and have more energy just by walking in the forest?

Some people study forests. Some people study medicine. I study forest medicine to find out all the ways in which walking in the forest can improve our well-being. 

In fact, I had the following hypothesis before the study of forest immersion: It is well known that the immune system, including natural killer (NK) cells, plays an important role in defense against bacteria, viruses, and tumors. It is also well known that stress inhibits immune function. As a common sense, forest immersion may reduce stress.  Thus, I speculated that forest immersion may have a beneficial effect on immune function by reducing stress.

UNature: Do you have a favorite forest?

Dr. Li: My favorite forest is Akasawa Natural Recreation Forest. This is the birthplace of shinrin-yoku in Japan. Since 2006, I have been to this forest 2-3 times each year.


UNature: Since you started researching forest immersion in 2004, how has the practice and study evolved?

Dr. Li: We have found the following benefits of forest immersion since 2004:

  1. It boosts immune function, increases anti-cancer proteins, and has a preventive effect on cancers.

  2. It reduces stress hormones and helps with stress management.

  3. It suppresses the sympathetic or “fight or flight” system, enhances the parasympathetic or “rest and recover” system, and shows relaxing effects.

  4. It improves sleep quality and shows a preventive effect on sleep disorders or insomnia.

  5. It reduces negative emotions, increases positive feelings, and shows a preventive effect on depression.

  6. It reduces blood pressure and heart rate and shows a preventive effect on hypertension and heart diseases.

  7. It may apply to rehabilitation medicine.

  8. Nature immersion in city parks has benefits on human health.

  9. It has a preventive effect on lifestyle related diseases.

  10. It shows a preventive effect on COVID-19 by reducing stress and boosting immune function.

UNature: What did you see in this research that inspired you to establish Forest Medicine as a new preventive medicine?

Dr. Li: Imagine a new medical science that could let you know how to be more active, more relaxed, healthier, and happier with reduced stress and reduced risk of lifestyle-related diseases. This new medical science is Forest Medicine. Forest Medicine studies the effects of forest environments on human health and is a new interdisciplinary science, belonging to the categories of environmental and preventive medicine.

In fact, stress and immune function are two keywords that inspired me to establish Forest Medicine as a new preventive medicine because stress can induce many chronic diseases such as: 

  • cancers 

  • hypertension 

  • depression 

  • cardiovascular diseases 

  • stroke 

  • gastric ulcer 

  • obesity 

  • alcoholism 

  • panic disorder 

  • eating disorder 

  • You name it.

On the other hand, forest immersion can reduce stress and stress hormones such as adrenaline, noradrenaline, and cortisol.

Therefore, it may have preventive effects on the above chronic diseases by reducing stress and stress hormones. Forest immersion boosts human immune systems by increasing human NK activity, the number of NK cells, and anti-cancer proteins. It suggests that forest immersion may have preventive effects on cancers. It is very important in preventive medicine.


UNature: What should the average person living in an urban environment know about Forest Medicine in terms of its potential impact on their lives?

Dr. Li: Forest immersion affects the five senses (sight, hearing, taste, smell and touch). The average person living in an urban environment can practice forest immersion in city parks on a weekly basis. My studies have shown that walking in city parks can reduce negative emotions such as anxiety, depression, anger, fatigue, confusion and improve your positive feelings, such as vigor. Walking in city parks also can reduce stress and stress hormones.

People in the city also can use aroma inside their homes to enjoy the sense of smell of the forest on a daily basis.

You also can put some plants inside your homes or offices to enjoy the sense of sight of the forest on a daily basis.

You also can watch videos (YouTube) taken from forest landscapes to enjoy the senses of sight and hearing on a daily basis. 

You can try to go to the forest on vacations.

UNature: What does your research teach us about natural killer (NK) cells and Forest Medicine’s role in disease prevention?

Dr. Li: Natural killer (NK) cells play an important role in defense against bacteria, viruses, and tumors. Three-day/two-night forest immersion significantly increased human NK activity, numbers of NK cells and percentages of perforin, granzymes A/B(GrA/B), and granulysin (GRN)-positive cells in both males and females. Moreover, the increased NK activity, number of NK cells, and percentages of GRN-, perforin-, and GrA/B-positive cells lasted more than 7 days and even for 30 days in both males and females. It means that forest immersion has a preventive effect on cancers. It is very important in preventive medicine.

 

The Nature Connectivity courses offered by UNature go into depth on the benefits of forest immersion on human NK cell activity. Learn more.

 

UNature: You were one of the first scientists to show that inhalation of phytoncides increases the number and activity of NK cells. How did the scientific community react to this discovery? Is there a difference between the Western and Asian reception? 

Dr. Li: In fact, the effect of forest immersion is a total effect of five senses. However, the sense of smell makes the biggest effect, which are called phytoncides or essential oils from trees. I have found that phytoncides boost immune function, reduce stress hormones, and show benefits on human health, through the following two studies:

From a feeling to a science is the keyword to answer your question. Because I have published my results in the above scientific journals the scientific community gave a positive reaction to this discovery. 

In 2011, my research on Forest Medicine received an award from Nippon Medical School, Japan’s oldest private medical school established in 1876. In 2022, my research on Forest Medicine received the Japanese Society for Hygiene Award, which is the biggest preventive medicine society in Japan. These awards provide evidence that Forest Medicine has been recognized by Japanese medical universities and the medical community as a new preventive medicine in Japan. 

Both the Western and Asian people believe the scientific evidence of phytoncides; therefore, there is no difference between the Western and Asian reception.

 

For more transdisciplinary research on the impact of our contact with nature, visit the research section of the UNature website.

 

UNature: Your research has shown that forest immersion can reduce depression, anxiety, anger, fatigue, and confusion, and increase positive mood states. What is it about nature that helps us feel relaxed and calm?

Dr. Li: In fact, the effect of forest immersion is a total effect of five senses. 

  1. Sense of sight: forest landscape, green color, yellow color and red color

  2. Sense of smell: special good smell, fragrance from trees

  3. Sense of hearing: forest sounds, bird song

  4. Sense of touch: touching trees, put your whole body in the forest atmosphere

  5. Sense of taste: eating foods and fruits from forests, taste the fresh air in forests

 

A 2022 study conducted by UNature in partnership with McGill University (Montreal, Canada) found that immersive, sensory activities in a forest boost positive mood states and decrease negative mood states. Read the study.

 

UNature: Does your research suggest any indication of the frequency or duration of forest immersion for continued health and wellness?

Dr. Li: The relaxing effects of forest immersion begin to appear 20 minutes after you begin, and reach their maximum effect after two hours.

The longer you bathe in the forest, the greater the effect will be. To achieve the immune-boosting effect, at least two hours of forest immersion is necessary. One day (6 hours) can have an immune-boosting effect that lasts for one week.

Three days and two nights of forest immersion can have an immune-boosting effect that lasts for four weeks. The results are explained in this study:

Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins.

Therefore, if you can take a 2-night/3-day forest immersion, once a month will be recommended. If you only can take one-day forest immersion, once a week will be recommended.

 

UNature’s Nature (Re)Connection programs offer forest immersion experiences led by a certified guide that will allow you to benefit from nature’s impact on your physical, psychological, and cognitive health. Learn more.

 

UNature: What role does your research play in helping to re-establish the bridge between humans and the natural world?

Dr. Li: We modern people are disconnected with nature! Forest immersion is like a bridge. By opening our senses, it bridges the gap between us and the natural world. My research provided the scientific evidence in helping to re-establish the bridge between humans and the natural world.

 

Together with the World Society on Forests and Parks for Public Health, UNature has the privilege of co-organizing the 2025 World Conference on Forests for Public Health to take place in Luxembourg. The aim of the conference is to bridge the gap between scientific research and practice. 

 

UNature: Where do you think this field of research should focus next?

Dr. Li: Forest medicine should be developed into a new preventive medicine and new clinical medicine for some lifestyle-related diseases such as hypertension, heart diseases, depression, sleep disorders, and some cancers. Forest medicine also should be applied to rehabilitation medicine.  However, this requires more evidence. Therefore, I think this field of research should focus on the preventive effects of forest immersion on lifestyle-related diseases (chronic diseases).


UNature: What advice would you give organizations like ours?

Dr. Li: First of all, the benefits of forest immersion should be promoted by organizations like UNature who are working to bring nature reconnection programs to a wider group of people. 

Please start a campaign to let more people know about the effects and benefits of forest immersion.

Let’s go to the forest to get health and happiness!

Johanna Sorrentino
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