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The Science—and Magic—of Forest Bathing

Nature’s the ultimate stress-buster, says…Science. It’s simple math: You look at a tree, you feel better. No one knows this as well as Dr. Qing Li, a researcher from Japan who focuses on something called forest medicine. Li’s work confirms what intuition and common sense have long told us: Being around trees is healthy. But it’s more than just that: Li has found that spending time in nature is not just good for those of us who are feeling overwhelmed, anxious, or fatigued (i.e., everyone). It can actually have positive effects on sleep, energy levels, immune function, and cardiovascular and metabolic health. That research is well-known in Japan, and the idea of “forest bathing”—spending time in nature with purpose and attention—is well-practiced. But the idea of walking into the woods instead of the pharmacy hasn’t exactly caught on in the US and other Western societies.

Now comes the spotlight moment that forest bathing deserves. Li, who serves as the chairman of the Japanese Society for Forest Medicine, just wrote his first book, Forest Bathing: How Trees Can Help You Find Health and Happiness. And he let us in on how to bring the practice into everyday life—even for those of us who don’t live anywhere near a forest.

A Q&A with Qing Li, M.D.

What is forest bathing? How is it different than hiking or taking a walk?

In Japanese, it’s shinrin-yoku: “shinrin” means “forest,” and “yoku” means “bath.” So “shinrin-yoku” means “bathing in the forest” or “taking in the forest through our senses.” There is no water involved, and you don’t have to hike or even go on a nature walk. Forest bathing is simply being around trees, in nature, connecting with it through our senses of sight, hearing, taste, smell, and touch. Forest bathing is a bridge. By opening our senses, it bridges the gap between us and the natural world.

Studies have found that forest bathing has a bounty of health benefits. It can strengthen your immune and cardiovascular systems, lift your energy and mood, and even help you sleep more, lose weight, and live longer.

Why has forest bathing become so popular and important in Japan?

Japanese culture, philosophy, and religion are rooted in the forests that blanket Japan. Not to mention all manner of everyday things are carved out of the forests, from houses and shrines to walking sticks and spoons. Two thirds of the country is covered in forest. It is one of the world’s greenest countries, with a huge diversity of trees. If you fly over Japan, you will be amazed to see how green it is: 3,000 miles of forest, from Hokkaido in the north to Okinawa in the south.

Forest bathing, as a formal practice, was first established and given its name in 1982 by Tomohide Akiyama. He was the director general of the Ministry of Agriculture, Forestry and Fisheries of Japan, and he thought that the people of Japan were in need of healing through nature. The idea was also part of a campaign to protect the forests: If people were encouraged to visit forests for their health, they would be more likely to want to protect and look after them. The Japanese government invested a lot of money in forest bathing with the goals of protecting the forests, promoting human health, and preventing lifestyle-related diseases.

How do you study forest bathing and measure its effects?

Some people study forests. Some people study medicine. I study forest medicine—to understand the ways in which being in the forest can improve our well-being. I want to know why we feel so much better when we are in nature. What is the secret power of trees to make us so much healthier and happier? Why is it that we feel less stressed and have more energy just by being in nature?

For much of my career, I have studied the effects of environmental chemicals, stress, and lifestyle on immune function. Since it is well-known that stress inhibits immune function, I speculated that forest bathing may have a beneficial effect on immune function by reducing stress. And I tested this hypothesis by conducting many experiments: I looked at the effects of walking in forests and of phytoncides—the scents that trees give off—on immune cells, stress hormones, blood pressure, and heart rate. I compared the mortality rates from cancer between people who live in areas with high versus low forest coverage. And I compared the effects on mood and mental state (anxiety, depression, anger, fatigue, and confusion) of walking in forests versus walking on treeless city streets.

“I want to know why we feel so much better when we are in nature. What is the secret power of trees to make us so much healthier and happier?”

How does forest bathing ease stress? What are some of the other benefits?

Forest bathing eases stress by reducing stress hormones—cortisol, adrenaline, and noradrenaline. Through my research, I have found that it can also:

reduce blood pressure and heart rate

increase the activity of natural killer cells—immune cells that play an important role in defense against bacteria, viruses, and tumors

increase the activity of the parasympathetic nervous system (which helps the body rest and recover) and reduce the activity of the sympathetic nervous system (which is responsible for the fight-or-flight response), producing psychologically calming effects

increase the level of the hormone adiponectin (lower blood adiponectin levels are associated with several metabolic disorders, including obesity, type 2 diabetes, cardiovascular disease, and metabolic syndrome)

reduce symptoms of anxiety, depression, anger, fatigue, and confusion and help prevent depression

improve sleep

increase energy, creativity, concentration, and memory

How do these benefits manifest? Why does forest bathing have such wide-reaching effects?

The benefits derive from the total effect of the forest environment—taking in the quiet atmosphere, beautiful scenery, refreshing scent, and clean air through all five senses. Pay special attention to:

Sight: the colors of nature, especially the green, yellow, and red of leaves

Smell: the fragrance emitted by trees

Hearing: nature sounds and bird song

Touch: engaging with the forest with your whole body

Taste: the flavor of foods—especially fruits—from the forest

What has the greatest effect, however, are the scents (phytoncides) given off by trees. Phytoncides are the natural oils within a plant, and they’re part of a tree’s defense system against bacteria, insects, and fungi. Phytoncides have been shown to help lift depression and anxiety and decrease the level of stress hormones. And in my research, I discovered that they also boost natural killer cell activity and the production of anti-cancer proteins.

“Phytoncides are the natural oils within a plant, and they’re part of a tree’s defense system against bacteria, insects, and fungi.”

In one in vitro experiment, I incubated the human natural killer (NK) cells with phytoncides for five to seven days, then measured several markers of immune function. I found that phytoncide exposure increased NK cell activity, including an increase in intracellular anticancer proteins, such as perforin, granulysin, and granzymes, indicating that these scents may have beneficial effects on human immune function.

In a following in vivo experiment, I investigated how essential oils from trees affect human immune function. Observing biological responses in healthy male subjects over three nights indoors, we vaporized stem oil from hinoki cypress overnight, analyzed urine samples each morning, and took blood samples on the final day. Phytoncide exposure significantly increased NK cell activity, NK cell count, and the total measure of anticancer proteins, such as perforin, granulysin, and granzyme A/B. It also decreased urine concentrations of stress hormones, such as adrenaline and noradrenaline, and significantly reduced symptoms of anxiety, depression, anger, fatigue, and confusion. Based on these findings, we think the phytoncides in forest air may contribute to increased NK activity during forest bathing.

Walking in the forest can help us to clear our minds and feel at peace by encouraging us to step away from our stresses and devices. There is real science behind these mood shifts, and there’s a chemical basis for the calming feeling we get from being among the trees.

What’s the best way to start forest bathing?

There are many different activities you can do in the forest that will help you to relax and connect with nature. It doesn’t matter how physically fit—or unfit—you are. To practice forest bathing, you can:

walk slowly in the forest

do Tai Chi, yoga, or deep breathing

find a place you like and just sit, read, or enjoy the scenery

take off your shoes and walk barefoot

have a picnic

By trying different activities, you will learn what suits you and how to best make use of the relaxing influence of the forest.

Here are some additional tips:

Make a plan based on your physical abilities to avoid tiring yourself out.

If you have an entire day, stay in the forest for about four hours and walk about three miles. If you have just half a day, stay in the forest for about two hours and walk about one and a half miles.

Stop to rest whenever you feel tired. And drink whenever you feel thirsty.

If possible, bathe in a hot spring after spending time in a forest. It has been reported that hot spring baths also enhance immune function and reduce stress and blood pressure. Furthermore, a synergistic effect is expected between the forest bath and the hot spring bath.

Let your goals determine how much time to spend in the forest. If you want to boost your immunity, a three-day, two-night trip is recommended. But if you just want to relax and relieve stress and you have access to a forested park near your home, try a day trip. (I recommend taking day trips once a week, or three-day trips once a month.)

Note: Forest bathing is a preventive measure. If you come down with an illness, see a doctor.

What if we don’t have access to a park or forest?

I recommend engaging with nature in some way every day. If you have trees or a park nearby, you can simply open your window. Researchers at the University of Melbourne found that as little as forty seconds of looking out of the window at a natural scene helps us focus and stay alert. If you don’t have a window, pictures of nature and green vegetation will help. So have a picture of nature as a screensaver on your computer or as the lock screen on your phone. And when you take a break, just sit back and enjoy them.

“If you have trees or a park nearby, you can simply open your window.”

You can also grow plants in your home or office. They not only make it look like a forest but also help us breathe by increasing oxygen. Plants are natural air purifiers, and they act like sponges, soaking up the toxic chemicals found in paints, fabric, cigarettes, and cleaning products.

You can use essential oils (phytoncides) from trees to connect to nature through the sense of smell. Hinoki oil is a personal favorite of mine. But all the conifer essential oils (like Japanese cedar, pine, or hiba) can remind you of the peace and quiet of the forest and bring you some of the powerful effects of a forest bath without your even having to go outside. You can use a diffuser for essential oils or fill your home with candles or a bowl of cedarwood shavings.

You can take off your shoes to connect with nature by touch or listen to YouTube recordings of birdsong and other sounds of nature. All these things will help you to connect with nature—even if you’re stuck indoors—and reap the many benefits of shinrin-yoku.

Wellness