Did you know that the discovery of aspirin can be traced back to a compound found in willow bark – salacin – which has been used for thousands of years to relieve pain? (1) Have you heard about the bark of the cinchona tree, which contains the same form of quinine that is used to treat malaria? (2)
It’s no secret that many trees have beneficial – sometimes even medicinal – properties, but what if the forests themselves are actually therapeutic, too? That’s the idea behind the practice of forest bathing, and research indicates that it’s true.
What is forest bathing?
In Japanese, shinrin means forest and yoku means bath, so shinkrin-yoku is the practice of bathing in the forest atmosphere. In essence, it describes the Japanese practice of letting nature wash over all five senses: smell, touch, sound, sight and even taste.
If that sounds a little “woo” to you, you’re not alone. When I first heard that shinrin-yoku is associated with profound health benefits, I was skeptical. Sure, taking a walk in the woods could probably improve sleep, lower blood pressure and more, but I figured it probably had to to more with the exercise than the trees.
It turns out, though, that taking a walk in a forest has unique biological impacts that are not found when the same exercise is performed in other environments, probably due to unique biological compounds such as photoncides and the “happy microbe,” Mycobacterium vaccae. (3)
We’ll dive into the details in just a moment, but as always that none of these statements have been evaluated by the FDA, this article is not medical advice, and it is not meant to diagnose or treat any condition. Now that we’ve got that out of the way, let’s dive in.
What’s so special about forests?
According to the Environmental Protection Agency, the average American spends 90% of their time indoors. (4) Not only is it possible to go long periods without really noticing the changing of seasons, bird songs, and the sweet scent of blossoms in the air, it’s a pretty typical experience for many.
Sure, we have apps that play us video and soundscapes from forests, streams, or beaches, but we spend much less time in those places than at any other point in history. And while I am a huge fan of those apps (I have one that plays on my T.V. often), not all of the beneficial components of nature are available to us via a screen.
While there are many more mechanisms what we’re still exploring, here are two things you’ll find in forests that profoundly impact well-being.
If you’ve ever inhaled the warm, woodsy scent of cedar or the fresh, clean scent of pine, you’ve experienced the natural aromatherapy of phytoncides. This distinctive category of woodland-based essential oils are released by trees and plants as part of their defence system.
According to Dr. Qing Li, a physician, professor at Nippon Medical School in Tokyo, and president of the Japanese Society of Forest Medicine:
Trees release phytoncides to protect them from bacteria, insects and fungi. Phyton is Green for ‘plant,’ and cide is ‘to kill.’ Phytoncides are also part of the communication pathway between trees: the way trees talk to each other. The concentration of phytoncides in the air depends on the temperature and other changes that take place throughout the year. The warmer it is, the more phytoncides there are in the are.” (3)
In this study, inhaling tree-derived phytoncides reduced stress hormone levels in both men and women and increased natural killer (NK) cell activity (a vital part of our immune system).
Other research suggests that a particular phytoncide – d-limonene- may have mood lifting effects. (6)
Fortunately, while getting outside is still important, we can bring some of the benefits of forest bathing indoors by diffusing essential oils that are rich in phytoncides, particularly d-limonene (lemony), alpha-pinene (pine-scented), beta-pinene (fresh herb scented) and camphene (deep, woodsy scent).
Evergreens like cedars, pine trees, and spruces are the largest producers of phytoncides, so look for essential oils such as:
- Black spruce
- Balsam fir
- Douglas fir
- Fir needle
- Ho wood
- Atlas cedarwood
- Himalayan cedarwood
- Scots pine
- Buddha wood
There is also a substance in soil that we breathe in when we walk in the forest and which makes us feel happier. This is a common and harmless bacteria, Mycobacterium vaccae.
The benefits of Mycobacterium vaccae were discovered almost by accident by Dr. Mary O’Brien, and oncologist at the Royal Marsden Hospital, London. Dr. O’Brien was conducting an experiment to see if injecting patients with lung cancer with M. vaccae would boost their immune systems and help them fight disease. Her experiment found no proof that it did, but she did make an unexpected recovery: an injection of the bacteria ‘significantly improved patient quality of life.’ Her patients reported feeling more positive and having higher energy levels and better cognitive functioning.” – Forest Bathing: How Trees Can Help You Find Health and Happiness by Dr. Qing Li (3)
Dr. Li goes on to explain that a few years later, researchers at Bristol University made a fascinating discovery. When they injected M. vaccae into mice, “they found that the mice behaved as though they were on antidepressants. This was very interesting in itself, but the scientists also discovered something else. The neurons that were activated were those associated with the immune system, which suggested that there is a close connection between the immune system and our emotions.” (3)
Further research has found that it seems to activate a pathway related to serotonin, which alongside oxytocin is considered one the body’s “happy hormones.”
Now, I am not saying that bacteria found in soil should be considered a treatment for any diagnosis, but these studies do suggest that M. vaccae may lift mood in certain circumstances. More research is needed to determine exactly what those circumstances are and aren’t. And as Dr Li writes, “Forest-bathing is a preventative measure against disease; if you come down with an illness, I recommend that you see a doctor.”
Several human studies are underway to examine the role M. vaccae may play in mental health, so hopefully we’ll have more actionable data soon. For now, I think of my porch container garden as a place to grow veggies and get regular exposure to healthy soil.
9 Benefits of Forest Bathing
According to Dr. Li, “The good news is that even a small amount of time in nature can have an impact on our health. A two-hour forest bath will help you unplug from technology and slow down. It will bring you into the present moment and de-stress and relax you.” (3)
Here are some of the benefits his research has confirmed:
- Reduced blood pressure
- Lower stress levels
- Improved cardiovascular and respiratory health
- Lower blood sugar levels
- Improved concentration and memory
- Mood lift
- Improved energy
- Better sleep
- Better immune function due to an increase in natural killer (NK) cells
Let’s take a closer look at some of those:
Benefits of Forest Bathing for Longer Sleep
Studies show that getting good quality sleep makes us smarter, happier, more productive, more creative, keeps us looking younger, helps our immune system function properly, and plays a vital role in balancing hormones. (3) (6) (7) (8) (9) (10) (11)
On the other hand, “Sleep deficiency is linked to numerous health problems, including increased risk of heart disease, kidney disease, high blood pressure, diabetes and stroke.” (3)
In one of Dr. Li’s studies, a group of men walked in a forest for about 1.5 miles – which is about the same distance they usually traveled – either in in the morning or afternoon. Before the trip, the men slept an average of 383 minutes per night. After forest bathing the average sleep time increased to 452 minutes, and even on the day after practicing shinrin-yoku it was still elevated (410 minutes).
Dr. Li concluded that forest bathing improves sleep even when the amount of daily physical activity stays about the same as usual. He also found that afternoon walks had a more profound effect than morning walks.
Mood Lifting Benefits of Forest Bathing
In one study, participants were asked to assess their emotional state before and after forest bathing. After two hours, they reported a reduction in:
. . . and an increase in vigor, which is defined as “healthy physical or mental energy.” (12)
According to Dr. Lli, spending time in nature can also boost creativity and problem solving ability by 50%. (3)
Forest Bathing & Immune Function
One of the ways we test the health of the immune system is by looking at the activity of our natural killer (NK) cells. Natural killer cells are a type of white blood cell and are so called because they can attack and kill unwanted cells, for example, those infected with a virus, or tumor cells.” (3)
In one study conducted by Dr. Li, individuals who forest bathed for two nights and three days experienced a 53.2% increase in natural killer cell activity. Curious about how long it would last, he continued to measure levels after the trip and found that the effect lasted up to thirty days. (3)
Cardiovascular & Respiratory Health
When an exotic invasive beetle from eastern Russia (the emerald ash borer) found its way to U.S. shores and began wiping out over 100 million ash trees, the hardest hit areas experienced a decline in cardiovascular and respiratory health.
According to the United States Department of Agriculture Forest Service, “the spread of the emerald ash borer across 15 states—first recorded in 2002—was associated with an additional 15,000 deaths from cardiovascular disease and an additional 6,000 deaths from lower respiratory disease.” (13)
On the flipside, trees seem to have a beneficial impact not just in forests, but in neighborhood environments, too.
A group of Canadian, American and Australian researchers studying tree density and health in Toronto found that having ten trees on a city block can make residents feel as good as being given a $10,000 pay raise or being seven years younger.” (3)
How To Practice Forest Bathing (Shinrin-Yoku)
While there isn’t one “right” way to practice forest bathing, here are some tips for getting the most out of your sessions:
- Find your walking trail, park, waterfall, etc. Discover The Forest is a site that can help you find ones nearby based on your zip code. Ideally, your forest bathing atmosphere will have wide paths, be free of the sounds of traffic, and about 3 miles long. Nearby restrooms are a plus.
- Leave your phone behind or put it in airplane mode to reduce distraction. If I’m with my family, I usually bring my phone so that I can take a photo for our T.V. slideshow (a Mother’s Day gift to me) if I want to. Research suggests that taking photos for the purpose of sharing them on social media can diminish the joy of our experiences, but I haven’t found that to be true for me since my goal is simply to document personal memories.
- Take water and snacks. Forest bathing helps shift our nervous system from sympathetic (fight or flight) mode to parasympathetic (rest and digest) mode. Personally, when my body flips into a restful state I often find that stress was distracting me from how hungry or thirsty I was, and in order to enjoy forest bathing I need to eat something.
- Try some of the activities outline below (walking, yoga, sitting under a tree) and plan to stay for awhile. Two hours is ideal, but Dr. Li says you’ll begin to notice the effects after twenty minutes.
Choose one (or more) of these activities that are most enjoyable to you:
- Stroll through the forest
- Listen to the sound of the wind in the trees, birdsong, leaves rustling, a nearby stream
- Taking in the natural aromatherapy surrounding you
- Run your hands over the rough bark of a tree.
- Pick a few evergreen needles, squeeze them in your hand, and inhale their fresh scent (phytoncides)
- Watch dappled light dance on the forest floor
- Wade into a stream
- Stretch or do yoga
- Find a comfy spot to sit and take in your surroundings
- Take of your shoes to get the benefits of earthing
Tip for Forest Bathing With Kids
My kids are 0% interested in the fact that forest bathing reduces stress levels, elevates mood and increases natural killer cell activity.
But . . . they really like treasure hunts. Since the goal of forest bathing is to let nature wash over all five senses – smell, touch, sound, sight and taste – I sometimes create a treasure hunt for them that engages each one. It’s a lot of fun and I sometimes hunt a little, too. :)
Here’s a list to start with in case you want to try it:
⭐ Something prickly
🌱 3 kinds of leaves
⭐ Something that smells good
🌻 Something yellow
🌰 A seed
⭐ Something smooth
🍁 Something crunchy
⭐ Something rough
🌿 Something you think of as a treasure
⭐ An interesting rock
It doesn’t take a long time, and we all leave feeling more relaxed.
Have you ever tried forest bathing? Did you enjoy it?
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1. Michael J. R. Desborough and David M. Keeling (2017) The aspirin story – from willow to wonder drug
2. Achan, Jane et. al. (2011) Quinine, an old anti-malarial drug in a modern world: role in the treatment of malaria
3. Li, Qing (2018) Forest Bathing: How Trees Can Help You Find Health and Happiness
5. Komori, T et. al. (1995) Effects of citrus fragrance on immune function and depressive states
6. Scientific American (2008) Sleep On It: How Snoozing Makes You Smarter
7. PBS (2012) Can Sleep Make You Smarter?
8. BBC (2013) How Sleep Makes Your Mind More Creative
9. American Psychological Association (2014) Sleep Deprivation: More Sleep Would Make Most Americans Happier, Healthier and Safer.
10. Stump, Scott (2013) “Nap Rooms” Encourage Sleeping On The Job To Boost Productivity
11. Harris, Shelby (2013) Sleep and Longevity: 5 Ways Sleep Keeps You Young
12. Dictionary.com. Vigor
13. United States Department of Agriculture Forest Service (2014) Exploring Connections Between Trees and Human Health