Cancer and Canopy: The Healing Power of Forest Bathing

Many of humankind’s earliest stories involve sacred trees and forests. There are stories of sacred figs in India (including the Buddha’s Bodhi tree), healing palo santo (“holy stick”) trees in South America, and mystical baobabs across Africa. The ancient Germanic tribes and Celts cultivated sacred oak groves, and in Norse cosmology the center of the universe is a giant tree, Yggdrasil. In other words, forests have always been sacred sites.

[read: “Dendrolatry and the Spiritual Meaning of Trees.”]

It’s not hard to see why trees became bound up with spirituality. They grow, but parts of them die every year, only to revive themselves when the conditions are right. They’re often seen as symbols of immortality.

In the form of forests, their power over us is even stronger. For starters, we couldn’t live without them because we wouldn’t be able to breathe our planet’s air. But there’s something more subtle than that going on, and researchers are curious just what role forests play in everything from human happiness to cancer treatment.

From Shinrin-Yoku to “Park Prescriptions”

You probably know the Japanese practice of Shinrin-yoku by its English name: “forest bathing.” It was developed in the 1980s as a form of nature therapy. While the term was coined by Tomohide Akiyama, the head of the Japanese Ministry of Agriculture, Forestry, and Fisheries at the time, it is Japanese researcher Dr. Qing Li who has turned it from a therapeutic suggestion (and one that was actually designed to save Japan’s forests) into a field of research on human health.

[Read: “The Healing Magic of Forest Bathing.”]

Dr. Li is a physician and immunologist at Nippon Medical School Hospital in Tokyo and the foremost expert on forest medicine, including its effects on cancer.

His studies primarily address the many ways in which being in the forest (not actively hiking or jogging, but simply spending time there with awareness) decreases stress levels. And since we know stress can have negative, even catastrophic effects on the body, it makes sense that there would be other physiological effects.

Dr. Li’s research (and the studies of those who have followed in his footsteps) have found that forest bathing can:

• Lower blood pressure
• Slow the heart rate and increase heart-rate variability
• Speed up digestion
• Lower the stress hormones cortisol and adrenaline
• Suppress the sympathetic nervous system’s “fight-or-flight” response
• Enhance the parasympathetic nervous system’s recovery mode
• Increase sleep time (which can reduce the risk of cardiac issues, diabetes, stroke, and kidney disease)
• Improve vigor and reduce feelings of fatigue

What’s interesting is that, while we know walking can have beneficial effects on health, doing so in a forest is even better. In fact, the health benefits are simply not the same if you walk in a city environment.

Using Forests to Fight Cancer

It goes without saying that treating cancer or its symptoms is far more complex than sitting under a tree. However, the evidence for forest bathing’s positive effects on cancer patients makes it worthy of attention.

There are three interrelated effects of forest bathing to keep in mind when it comes to cancer: its effect on immune function, its role in promoting NK cell activity, and the benefits of phytoncides.

1. Forest Bathing and Immunity

Multiple studies have shown that forest bathing has a beneficial effect on the body’s immune response. This is important because one of the main questions that cancer researchers have long had is how the body’s immune response fails to recognize and destroy cancer cells.

The ability of cancer cells to proliferate in the body is also dependent on our body’s inflammation response; chronic inflammation can encourage tumor growth. However, forest bathing has been shown, time and time again, to have an anti-inflammatory effect.

2. Forest Bathing’s Effect on NK Cells

NK (“natural killer”) cells have a very complex way of operating within the body. But at their most basic, we can think of them as having the ability to help kill tumor cells. What’s most interesting is research that found on days when people forest bathed, there was more NK cell activity in their bodies. And this increased NK cell activity lasted up to 30 days after their trip to the forest.

3. Forest Bathing and Phytoncides

If you’re wondering what it is about a forest that can activate NK cells, the answer is phytoncides, the volatile organic compounds emitted by trees. Researchers believe that these natural compounds have anti-oxidative, anti-inflammatory, and anti-microbial properties and that they increase the number of NK cells and other anti-cancer proteins in the body. In this sense, we might say that phytoncides have chemotherapeutic properties, though more studies are needed to explore the exact mechanisms at play.

How to Take a Forest Bath

The key to forest bathing is to use all five senses to fully take in nature. But that means you have to leave your phone behind. If you can Instagram it, it’s probably not a forest bath.

The good news is that the benefits of forest bathing can be seen in as few as two hours amongst the trees, so there’s no need to pitch a tent. You can go by yourself or with a group as long as you use the time to be present in your own body and in your surroundings.

Here are some basic elements of forest bathing to help you get the most out of your time in nature:

• Choose a safe spot that allows you to walk around without needing your phone or camera.
• Let your body guide you through the trees.
• Listen to the sounds, see the different colors and textures, smell and taste the fresh air, and feel the ground beneath your feet.
• Touch the tree trunks, soil, or leaves; poke a finger in ravine beds or flowing water.
• Connect with your mind by paying attention to your breath and how your body feels in this environment.

Forest bathing doesn’t require any special skills, just a commitment to the endeavor.

[Read: “Forest Bathing in My Own Backyard.”]

Americans spend less than 8 percent of their time outdoors—and even less of that among trees—and yet there’s mounting evidence that it can do wonders for our health.

Granted, there are plenty of responsibilities that stop us from taking time for ourselves and few opportunities to “get away from it all” out in the forest. But there’s no arguing that at the end of the day, the benefits outweigh anything that might hold us back.

See the forest and the trees in this guided meditation: “The Forest Grove.”