What science is saying about the benefits of reconnecting with nature for boosting your immune system and improving mental health.
What is 'Forest Bathing'?
The term 'Forest Bathing' has been more recently popularized by Wellness Guru's across North America, but it is not a new one. The term comes from the Japanese tradition known as "Shinrin-yoku". This does not imply physically bathing in a forest creek, rather it refers to the act of engaging with Nature by walking around in a forest and opening your senses to the biodiversity all around you. It is a form of forest therapy that can benefit those of all ages to improve health and wellbeing and help your mind cope with the overstimulation of fast-paced urban living.
In addition to the meditative benefits of engaging with Nature and using your senses to connect with your environment, there appear to be evident changes to our physiology, and scientists are starting to explore how being in biodiversity can have long-lasting impacts on our immune system and mental health. Here's How.
Reduces Stress and improves Mental Health
For anyone who has spent a significant amount of time in Nature, they know that there is nothing like a hike in the woods to quiet the ruminating mind. A Japanese study looked at the effects of engaging with nature on Stress, Depression, Anxiety and overall wellbeing. They observed that the more stressed out an individual was, the greater impact that 'Shinrin-yoku' had on mitigating and decreasing their stress response (1). It appears that time in Nature helps to decrease cortisol levels, a hormone over-secreted by the Adrenal glands in response to ongoing stress or sympathetic stimulation (2,3). If cortisol is too high, it can over-time interfere with the circadian rhythm and affect one's sleep and mood.
In addition to measuring salivary cortisol, heart rate variability monitoring showed an increase in parasympathetic activity amongst forest-bathers compared to their urban counterparts. Parasympathetic activity refers to the part of our autonomic nervous system that is responsible for relaxing our body and helping us digest, something that is compromised in those suffering from chronic stress and anxiety. For those with Depression, subjective psychological tests showed an increase in positive thoughts and a decrease in the expression of negative thoughts and emotions after spending time in nature compared to those in an urban setting (3).
Effects on Boosting the Immune System
When we enter the forest, a number of different compounds are released by the trees, fungi, and herbs all around. As we inhale the fresh forest air, we are inhaling a cocktail of chemical terpenes that have been shown to increase immune cell activity, and decrease inflammation. "Even though terpenes come from trees, mushrooms, and herbs that are communicating with one another, our immune system can also decode them. Like other plants, we respond to terpenes by strengthening our body's defenses."- Clemens G. Arvay, MSc.
There are a few different mechanisms that can be explored to understand the effects that forest bathing has on boosting the immune system. One of the most studied are the effects of a class of compounds released by coniferous trees (evergreens) into the air of the forest. These compounds are known as 'Phytoncides' and have a direct effect on Natural Killer (NK) cells, one of our first lines of defense against unwanted invaders(4,5). NK lymphocytes are responsible for destroying cells infected by viruses and cancer. Being in the forest was shown to increase NK cells in humans significantly. The boost in these cells was measured to last for up to 7 days post forest exposure(4).
Additional Health Benefits
Some additional health benefits observed and warranting further exploration/research include:
Decrease in diastolic Blood Pressure (potentially linked to parasympathetic activation)
Increased microbial diversity potentially leading to improved skin, digestion, mood, oral and genitourinary health
Improvement in ADHD
Pain relief/reduction (potentially linked to the anti-inflammatory properties of terpenes)
Increased Energy
Forest Bathing Tips and Tricks
1. The concentration of terpenes in the forest air vary depending on the season, location and weather. Levels are highest in the summer and lowest in the winter. They begin to rise in April and May and are optimal in June and August. Levels also increase after rainfall or Fog. The terpene content is highest in the forest's center, so try to avoid staying on the outside- Don't be afraid to get right in there and explore!
2. Incorporate a forest Meditation and engage all of your senses.
Sit on a log or somewhere comfortable and begin by closing your eyes.
Start by using your sense of smell. Notice all the different scents around you. The scents of the forest are heightened after rainfall, when the highest content of essential oils are in the air.
Next shift your focus to your physical sensation. Feel the breeze between the trees, the temperature, the sunlight that manages to penetrate through the canopy. Feel free to remove your footwear and feel the dirt between your toes and the ground beneath your feet.
Once you have connected to the physical world around you, begin to focus on your sense of sound. Listen to the breeze rustling through the leaves, the birds singing, the buzzing of the bees and the babbling brook off in the distance.
After sufficiently connecting to the noises all around you, open your eyes and finish by using your sense of vision. Pay attention to the colours and textures of the forest. Zoom in to the microenvironment and focus on the individual species of plants, insects, fungi, mosses, lichens, etc. Notice the variations in the bark of the trees, the colours of the leaves, and the patterns of the branches. Finish by zooming out and engaging your eyes to the landscape all around you.
3. Wear protective footwear and long light pants if you are going off the trail! If hiking in the forests of South-Western Ontario, you may want to be cautious of running into Poison Ivy, Poison Oak, Poison hemlock, Giant Hogweed, and Stinging Nettle to name the most common. Wearing hiking boots and long pants is an excellent way to avoid exposure when your sense of curiosity takes over.
Happy exploring and engaging with the forest!
References
1. Morita, E., Fukuda, S., Nagano, J., Hamajima, N., Yamamoto, H., Iwai, Y. & Shirakawa, T. (2007). Psychological effects of forest environments on healthy adults: Shinrin-yoku (forest-air bathing, walking) as a possible method of stress reduction. Public health, 121(1), 54-63.
2. Park, B. J., Tsunetsugu, Y., Kasetani, T., Hirano, H., Kagawa, T., Sato, M., & Miyazaki, Y. (2007). Physiological effects of shinrin-yoku (taking in the atmosphere of the forest)—using salivary cortisol and cerebral activity as indicators—. Journal of Physiological Anthropology, 26(2), 123-128.
3. Lee, J., Park, B. J., Tsunetsugu, Y., Ohira, T., Kagawa, T., & Miyazaki, Y. (2011). Effect of forest bathing on physiological and psychological responses in young Japanese male subjects. Public health, 125(2), 93-100.
4. Tsao, T. M., Tsai, M. J., Hwang, J. S., Cheng, W. F., Wu, C. F., Chou, C. C., & Su, T. C. (2018). Health effects of a forest environment on natural killer cells in humans: an observational pilot study. Oncotarget, 9(23), 16501.
5. https://www.mindbodygreen.com/articles/the-science-of-forest-bathing
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