The man who transformed a quiet walk through the woods into a scientifically proven prescription for better health never imagined he would one day inspire a global movement.
Today, millions of people across the world know the practice as Shinrin-yoku, or forest bathing. At the center of this movement stands Dr. Qing Li, the physician-scientist who coined the term Forest Medicine and devoted decades to proving that forests can heal the human body as effectively as they soothe the mind. Dr. Li (MD, PhD is an immunologist, working as clinical professor at the Department of Rehabilitation Medicine, Nippon Medical School Hospital in Tokyo.
His research has shown that spending time among trees can strengthen the immune system, lower stress hormones, improve sleep, reduce blood pressure, ease anxiety and depression, and even enhance the body’s natural anti-cancer defenses. What was once considered little more than a pleasant feeling has evolved into an evidence-based field of preventive medicine.
Yet, the story of the man who changed how the world sees forests begins far from research laboratories—in a small Chinese village surrounded by trees.
Where it all began
For Dr. Li, the healing power of forests was never an abstract scientific question. It was a childhood memory.
“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 enjoyed them very much. I have loved nature and forests since my childhood.”
Those early encounters with nature quietly shaped his future. After graduating from Shanxi Medical University in China in 1984 and obtaining his medical license, Li moved to Japan in 1988 to pursue advanced studies at Kagoshima University. It was there that a single trip to Yakushima changed the trajectory of his life.
He visited Yakushima, a mystical island blanketed with ancient cedar forests, including the legendary Jomon Sugi, a cedar believed to be thousands of years old.
“The quiet atmosphere, beautiful scenery, mild climate, special good smell, and fresh, clean air in forests and the big Japanese cedar trees made me very happy and relaxed,” he says. “I became convinced that forest bathing was essential to human health.”
That visit became, in his words, “the whole direction of my life and my future research.”
From environmental medicine to Forest Medicine
Dr. Li did not begin his career studying forests. His expertise lay in environmental medicine.
“I have studied the effects of environmental chemicals, stress, and lifestyle on immune function and human health since 1988,” he says. “I am interested in the effect of all environmental factors on human health. I am also interested in the effect of forest environments on human health.”
His scientific journey took another significant turn when he spent 2001 and 2002 at Stanford University studying granulysin, an anti-cancer protein found in natural killer (NK) cells—immune cells that destroy virus-infected and cancerous cells.
“The method I established to measure granulysin,” he explains, “made a great contribution to my forest bathing research later.”
By then, he was asking questions that few scientists had considered seriously.
“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?”
Paying attention, Japan’s Forest Agency launched a national research project on forest bathing in 2004 and invited Dr. Li as one of its principal researchers.
That invitation marked the birth of a new scientific discipline.
“Some people study forests. Some people study medicine,” he says. “I study Forest Medicine to find out all the ways in which walking in the forest can improve our well-being.”
Turning intuition into evidence
Before his research began, forest bathing was largely regarded as a cultural practice and a pleasant escape from the pressures of urban life. Dr. Li wanted scientific proof.
He began with a simple hypothesis.
“It is well known that the immune system, including natural killer cells, plays an important role in defense against bacteria, viruses, and tumors,” he explains.
“It is also well known that stress inhibits immune function. Forest bathing may reduce stress. Thus, I speculated that forest bathing may have beneficial effects on immune function by reducing stress.”
To test that theory, his team conducted studies involving volunteers who spent several days in forest environments.
Researchers collected blood and urine samples before and after each trip. They monitored blood pressure, heart rate, and stress hormones, while participants also completed psychological assessments.
The findings surprised even the researchers.
“Forest bathing boosts immune function by increasing NK cell activity and intracellular anti-cancer proteins such as granulysin, perforin, and granzymes,” Dr. Li says.
Equally significant was what happened to stress.
“Forest bathing reduces stress hormones such as adrenaline, noradrenaline, and cortisol.”
His research also found improvements in sleep quality, reductions in blood pressure and heart rate, protective effects against hypertension and heart disease, lower risk of depression, benefits for people with chronic obstructive pulmonary disease (COPD), and even potential applications in rehabilitation medicine.
Perhaps most importantly, Dr. Li had demonstrated something medicine had rarely considered—that nature itself could function as preventive healthcare.
The science behind feeling better
For Dr. Li, one phrase captures the evolution of his life’s work.
“From feeling to science.”
“Before 2004, forest bathing was just a feeling. Now, forest bathing has become a new science.”
The underlying mechanism, he believes, revolves around one powerful factor: “Stress is a keyword to understand the science of Shinrin-yoku.”
Modern medicine has long established the destructive effects of chronic stress. “It can induce many diseases,” he explains. “Cancers, hypertension, depression, cardiovascular diseases, stroke, gastric ulcer, obesity, alcoholism, panic disorder, eating disorders—you name it.”
Forests work in the opposite direction.
“Shinrin-yoku can reduce stress.”
When stress hormones decline, the body’s immune system functions more effectively, inflammation decreases, blood pressure falls, and mental well-being improves. It is a measurable physiological change.
As his research gained international recognition, so did the movement itself.
He is the author of Forest Medicine and Forest Bathing: How Trees Can Help You Find Health and Happiness. The latter became a US bestseller and has been translated into more than 26 languages.
A prescription written by nature
One of the questions Dr. Qing Li is asked most often is deceptively simple: How much time in nature is enough?
His answer isn’t based on intuition or anecdotal wisdom. It comes from years of clinical research.
“We have found that a two-night, three-day forest bathing trip could boost the immune system, and this effect can last for a month,” he says. “Therefore, this is what we recommend.”
“We have also found that a one-day forest bathing trip could boost immune function, and this effect can stay for a week. So even one-day urban park forest bathing once a week is recommended,” Dr Li advises.
The benefits begin sooner than most people expect.
“The anti-anxiety, antidepressant, and relaxation effects begin to appear 15 to 20 minutes after forest bathing and reach a peak at around two hours. Even short periods of around 15 to 20 minutes can have a meaningful impact on reducing negative emotions.”
In an age where wellness often comes wrapped in expensive gadgets, supplements, and memberships, Dr. Li’s prescription is refreshingly simple: step outside, slow down, and let the forest do the work.
Not all forests smell the same—and that matters
What exactly makes forests so therapeutic? The answer lies partly in something we cannot even see.
Trees constantly release natural aromatic compounds known as phytoncides—volatile organic substances that help plants protect themselves from insects, fungi, and disease-causing microorganisms.
Humans inhale these compounds while walking through forests, and Dr. Li’s research suggests they are partly responsible for many of forest bathing’s remarkable health benefits.
“Coniferous forests produce higher levels of phytoncides, which play a crucial role in the benefits of forest bathing,” he explains.
Towering cedars, cypress, and pine trees are therefore particularly rich environments for forest bathing. But that does not mean only Japan’s forests possess healing powers.
“In general, the benefits of forest bathing are proportional to tree size, tree density, and the total area of the forest,” Dr. Li says. “Larger trees, higher density, and expansive forest areas yield greater benefits. Provided these conditions are met, I believe that forests around the world—not just those in Japan—can offer the same therapeutic effects.”
According to Dr. Li, science is universal. The therapeutic effects belong to forests—not to one nation.
What city-dwellers can do to derive the same benefits?
For billions of people living in crowded cities, escaping into dense forests every month is unrealistic.
Does that mean they miss out?
Not at all, says Dr. Li. “Forest bathing in city parks can reduce negative emotions such as anxiety, depression, confusion, anger, and fatigue and improve positive feelings such as vigor and friendliness.
“Forest bathing of six hours in big city parks with lots of big trees can reduce stress hormones such as adrenaline.”
A new chapter in preventive medicine
More than 20 years after beginning his first forest bathing experiments, Dr. Li believes the field is entering an exciting new phase.
“The most notable research finding is the efficacy of forest bathing in alleviating depressive symptoms in patients with mild depression. This highlights the potential of Forest Medicine as a treatment for depression.”
His team has also demonstrated improvements in inflammatory markers, oxygen saturation, and symptoms among individuals at risk of developing chronic obstructive pulmonary disease (COPD).
Earlier this year, his research explored how inhaling the aroma of Japanese cypress influences swallowing by altering activity in specific regions of the brain.
“I am currently investigating the effects of inhaling Japanese cypress (hinoki) essential oil on swallowing function, as well as the underlying mechanisms,” he says.
Such discoveries point towards a future where forests may become recognized not merely as recreational spaces but as healthcare resources.
“Forest bathing as a non-pharmacological intervention may represent a new strategy for the prevention and treatment of lifestyle-related diseases such as hypertension, depression, sleep disorders, and some cancers,” he says. “Forest bathing may even be incorporated into rehabilitation medicine.”
A global movement rooted in ancient wisdom
When Japan officially introduced Shinrin-yoku in the early 1980s, few imagined it would become an international phenomenon.
Today, Forest Medicine conferences attract researchers from around the world. Nature therapy programs have emerged across Europe, North America, and Asia, while governments and healthcare professionals are beginning to recognise forests as valuable public health resources.
“Forest bathing has gained international attention in recent years,” Dr. Li says.
After spending a lifetime studying forests, publishing groundbreaking research and helping establish an entirely new branch of preventive medicine, Dr. Li has reached a conclusion that is as personal as it is scientific.
“Forest bathing has given me good health. I am 64 years old now. My blood pressure, blood lipids, and blood sugar are all normal. I don’t take any medication because of forest bathing.”
But perhaps the greatest gift has been less tangible.
“Forest bathing has made me happier, healthier, and more famous in the world.”
The boy who wandered beneath blooming apricot trees in a small Chinese village has gone on to inspire millions of people to rediscover something humanity once instinctively knew—that nature is not simply scenery. It is sustenance.
The healing power of trees is not folklore. It is biology.
Dr Qing Li’s official website: https://www.im-wald-sein.com/en/prof-dr-qing-li-wald-medizin-forest-therapy-shinrin-yoku-website-deutsch
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