“Forest bathing activates our defensive cells”

Dr. Qing Li is an immunologist and a world leading expert on shinrin yoku, forest bathing or forest medicine. He has written the power of the forest (Roca Editorial), which invites us to connect with nature through the five senses.

Its objective is to rediscover nature to people who live trapped by the artificiality of urban life, so that they can take advantage of its benefits and recover their health.

Qing Li, the doctor who prescribes forest baths to his patients

Originally Chinese and living in Japan, Qing Li is Secretary General of the International Society for Nature and Forest Medicine and Professor at Tokyo Medical University.

–When did you start to be interested in forest medicine?
–In 1988 I visited the island of Yakoshima, which has a wonderful forest. It is a small island, south of Japan. I went with a group of friends and we spent the night outdoors, in tents. I remembered a lot about things as a child, when I played in the forest with the animals, which connected me with the feeling that there is something in nature that affects us positively.

At the time of that excursion I had just graduated in medicine. I was starting my career as a doctor, researching the harmful effects of pollution on our health, and the results were alarming. Later, in 2002, at a time when there was a special concern from the government to improve health problems caused by pollution and stress, I received a grant and started research on forest medicine.

–What happens in my body when I come into contact with the forest?
–When we enter the forest we calm down through the five senses. Using our eyes, we contemplate the wonderful landscape: the green color of the trees, the shine of their crowns, their flowers, of different shades, the butterflies and insects… Through our ears we hear the singing of the birds or the sound of the wind .

Through our nose we breathe the pure air and the aromas of the forest, rich in phytoncides, volatile substances that are enormously positive for our health, and with our hands we touch the trees, the moss, the ferns, the green grass… and with our feet, the cold water of the river, feeling more vital.

All this activity calms us down, relaxes us and relieves stress.

Are the effects biochemical?
–A forest bath of between 2 and 4 hours for two days can increase the activity of our white blood cells by 40% during the next 30 days. In addition to having a higher oxygen concentration, forest air is full of phytoncides, volatile compounds that protect trees from bacteria, insects, and fungi.

A forest bath of 2 to 4 hours for two days can increase the activity of our white blood cells by 40% in the following 30 days.

How do these substances work?
–Some of the most important are alpha-pinene, beta-pinene and d-limonene. Phytoncides increase the number and activity of defensive human cells natural killer and potentiate the activity of anticancer proteins. In addition, stress hormone levels are reduced, sleep hours are increased, and markers of anxiety, anger, fatigue, and confusion are reduced.

Other research has shown that forest bathing significantly lowers blood pressure and heart rate.

In your book you refer to the Mycobacterium vaccaea bacterium found in soil that stimulates the immune system.
–This is a study by Dr. Mary O’Brien, an oncologist at the Royal Marsden Hospital in London. Dr. O’Brien was conducting an experiment to see if an injection of M.vaccae boosted the immune system of lung cancer patients. He found that this bacterium works as an antidepressant, improving the emotional quality of life of patients, making them feel more animated, with a higher energy level, with better cognitive functioning…

In a subsequent experiment with mice, it was found that the neurons that are activated by the injection of M.vaccae they are those associated with the immune system, which suggests that there is a very close connection between this system and our emotions. In other words, these microbes that are found in the soil, and that we breathe in when walking through the forest, stimulate our immune system, which makes us feel better.

–So, do forest bathing affect our mental health?
–They promote clarity of ideas and creativity and make us more kind and generous. A study from the University of Michigan found that people gained 20% more memory and attention after taking a walk among the trees. The same did not happen when they walked through the city.

–What are the most suitable rituals to get the most out of the forest bath?
–First you have to make a plan before going to the forest so as not to get too tired, because if you are tired, the forest bath will not be very effective. You have to walk slowly, see how far you can go, take a course that you can take on. I recommend doing 2.5 km every two hours or, if you do 4 hours a day, you can cover 5 km, resting from time to time, drinking water, sitting down…

It is very important to use all five senses. Be present, take a deep breath, listen to the sounds…

–What depends on whether a forest is more or less curative?
–A forest will be more curative the more leafy it is and the older the trees, because the more phytoncides they will exhale. Another important element is that the weather is good, since with the heat the trees emit more natural volatile compounds. Noon is the ideal time, because it is when the tree provides more oxygen.

The more leafy the forest and the older the trees, the more phytoncides you will exhale.

An ideal schedule would be to walk from 10 a.m. to 12 p.m., then have a one-hour picnic and follow the route for another two hours, from 2 p.m. to 4 p.m. In Japan this would be the cut off time because afterward we could meet a bear and be in danger.

–Does it matter if the forest is wet or dry?
–After the rain, the conditions are very favorable, since the water wets the leaves and increases the aroma of the trees. Other aspects to consider are that the forest is in a place as far away as possible from sources of pollution or noise and that, even if it is leafy, it is bright.

–You explain in your book how in 1982 a national health program was created to practice forest bathing and how the Akazawa forest was the first designated for forest bathing. shinrin yoku. Why was this initiative taken?
–At that time there was a phenomenon that was a wave of stress due to technology. The perfectionist spirit of the Japanese led them to work unreasonable overtime to finish the job and this led to an increase in deaths from overwork, which in Japan is known as karoshi.

The Japanese government decided to reduce overtime and launched the shinrin yoku, because he thought that contact with nature would restore health to people. These two actions were very effective.

–Apart from being places of health, you define forests as natural sanctuaries.
–Buddhism and Shintoism, the two great religions of Japan, are closely linked to forests. It is not uncommon to find people praying or meditating in the forest, as these large green spaces are thought to constitute the realm of the divine, but since 2003 forests have been shown to have beneficial effects on our health scientifically. So, what was previously considered only from tradition today can also be understood from science.

Since 2003, forests have been shown to have beneficial effects on our health scientifically.

–A study has shown that d-limonene is more effective than antidepressants. Do you recommend putting diffusers at home with essential oils to manage stress?
–The best thing is to go to the forest, without a doubt, because there we can walk, relax and use all five senses, but smell also has potential. Essential oils can help us a lot, especially in urban environments, but the best thing is to have direct contact with nature.

What are your favorite forests?
–My favorite forest base is Akazawa. It is a Japanese cypress forest, very aromatic and with a very good quality environment. I also like the Tianmenshan National Forest Park in China, where Avatar was filmed, and in Finland the world’s first theme forest dedicated to wellness caught my eye, near the Ikaalinen Spa: there are signs along the slopes to draw attention to the walker to observe the environment, relax and get in a good mood.