I am very fortunate to live in an area where the climate seldom restricts me from outdoor activities. While the summer temperature in Houston can be sweltering and humid, I never have to face a freezing winter and imagine an icicle forming on my nose. My other great fortune in terms of locale is that I live next to a forest. No, I do not live next to the Sequoia National Park in California. This refuge, though, still has enough trees, hiking trails, and wildlife for me to enjoy the benefits. It has also taught me a lot about myself.
My expedition into this nearby forest began five months ago when I experienced a moment of desperation to get away from my house. I was spending too much time studying and stewing. I also have a teenage son, and some “fresh air” does us both a world of good. Whether with him or alone, venturing into the forest was first solely a novel experience and an explorative endeavor. Then, something extraordinary and unexpected happened to me. I began to feel better!
Learning from a Japanese Outdoor Practice
The more time I spent outdoors, the more I started planning my daily schedule so that I would not miss an opportunity to walk in my forest and deep-breathe its fresh air. I next embarked on some research into the health benefits of forests (and spending time in nature), which resulted in my learning about “forest bathing.” Shinrin-yoku (which means “forest bathing”) was originated in Japan in the 1980s when the government actually encouraged its urban-dwellers to immerse themselves in nature to reduce stress and improve overall health.
Notably, forest bathing is not a heart-pumping, sweat-producing, vigorous hike in the woods. Instead, it is a much slower-paced walk focused on the individual’s experience of nature itself. I decided to continue my research into forest bathing because – as a science-oriented nerd – I needed published scientific evidence as described below to support the claims of forest bathing as beneficial for overall health and well-being.
One of the first such research articles that I found presented findings of a 2009 Japanese study demonstrating that a three-day camping trip both increased natural killer cells by 50% and increased immune function. Inhaling specific tree-derived compounds – called phytoncides – reduced concentrations of stress hormones in men and women; it also enhanced the activity of white-blood cells considered natural killer cells.1 Proteins which we have identified as being anti-cancer (perforin, granulysin, and granzyme) are expressed more after engaging in forest bathing.2
In addition, this Japanese practice has been found to reduces blood glucose levels (even in patients diagnosed with diabetes). The study subjects described in another research journal were diabetics who performed a forest-bathe walk every eight months over a six-year period. Even though the research subjects’ forest-bathing time occurred only periodically, these patients’ blood glucose levels still showed significant improvement.3
Physiological Benefits of Forest Bathing
In 2011, a published article described a study that compared the effects of forest-walking to walking in the city. In that study, both activities required the same amount of physical effort, but medical researchers found that the forest environment led to larger reductions in blood pressure and certain stress hormones.4
On average, the forest walkers (ranging from 36-77 years old) experienced a reduction in their systolic blood pressure from 141 mmHg to 134 mmHg after four hours of walking in the forest. That is really something to consider if you are someone living with high blood pressure or perhaps the information can be weaved into a conversation with our hypertensive patients.
An additional factor may explain this decline in blood pressure, although it was not described in this study. Trees release compounds into the forest air that some scientific researchers believe may be healthful for humans and other mammals. Some of the compounds produce distinctive scents (such as the scent of cedar).
Furthermore, adiponectin is a hormone that is secreted by fat cells; it contributes to the regulation of our fat metabolism, glucose levels, and calorie utilization speed. There is evidence showing that forest bathing increases adiponectin serum levels in the blood.5,6
We know that high blood pressure affects all body systems, and avoiding (or controlling) hypertension and keeping stress levels low are beneficial. Results of numerous research studies show that physiological – as well as mental and psychological – benefits to health can be gained by nature-based walking!
Any activity that perhaps relieves stress promotes my interest on an intellectual level. Such was the case with the practice of “earthing,” which involves walking barefoot on soil, grass, sand, or any naturally found surface. One study of earthing suggested that a health benefit is derived from the relationship that is formed between our bodies and the Earth’s electrons.6,7 Others suggested this connection to the natural environment can increase antioxidants, reduce inflammation, and improve sleep quality.8.9
The physiological processes in the gut are widely recognized as affecting the central nervous system and brain – which thereby neurologically impacts mood. Besides its well-recognized mental and psychological benefits, there is increasing evidence that spending time in nature can positively affect both the function of the gut (through reducing stress) and brain. Medical research has provided strong evidence that physical movement has a positive effect on the intestinal system (including the colon). Likewise, strong evidence exists that physical movement has a positive effect on our mental health and well-being.
Does Gardening Improve Health?
Gardening has been revealed through studies to provide benefits not only in reducing emotional stress but in reducing the risk of cognitive decline (i.e., as occurs in dementia).10,11 In this way, gardening can be a health-boosting “two for one!” Of course, gardening enables you to move your body and stay flexible. However, the following is something else to consider when you decide whether to plant a garden in your yard. From a physiological standpoint, exposure to the bacteria in soil has been shown to be good for the gut. Like our bodies, dirt has a microbiome (and one common soil bacteria is Mycobacterium vaccae). Exposure to the bacteria in a soil specifically is shown to be good for mental health and even a treatment for depression.
Researchers have already found clear evidence that childhood exposure to outdoor microbes is linked to a more robust immune system.12 Immersing your hands in a garden’s soil can thereby boost your health over your whole lifespan!
The Dental Connection
Those of us working in the dental field can often experience an incredibly stressful workday. After all, so many people fear visiting a dental office! Therefore, utilizing healthful ways to alleviate stress can benefit both our patients and us. Of course, I realize my luck in living so close to a trail-filled, forested environment. I recognize that not everyone lives near a setting in which to commune with nature. However, my point is to encourage you to make a commitment to spending more time in nature.
Do you live or work near a park? Then, try to allot some time each week for a short walk (or bike ride) in it. The following are three more ideas for increasing your time spent in the natural world. Eat outdoors when the opportunity arises (as sunlight provides the best source of Vitamin D). After you arrive home each day from work, notice how the air feels on your skin, and the sky looks overhead. Surround yourself with greenery, as indoor plants can add more “nature” in your home or work environment (and boost your mood).
Then, share your appreciation of the natural world with your kids by taking them to a botanical garden or on a forest bath. Ever since I learned to appreciate the benefits of experiencing a quiet time in my forest, my daily morning ritual (inclusive of taking my dogs outdoors and drinking my morning coffee) has included taking a breath of fresh air to remind me of nature and its bounties. Being outside has helped me in many more ways than I can count.
Happy forest bathing and earthing!
Note: See the incredible website of the International Society of Nature and Forest Medicine at www.infom.org for further information about the benefits of forests to our health.
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- Li, Q., Kobayashi, M., Wakayama, Y., Inagaki, H., Katsumata, M., Hirata, Y., Miyazaki, Y. Effect of Phytoncide from Trees on Human Natural Killer Cell Function. International Journal of Immunopathology and Pharmacology. 2009; 22(4): 951–959. Retrieved from https://doi.org/10.1177/039463200902200410.
- Li Q. Effect of Forest Bathing Trips on Human Immune Function. Environmental Health and Preventive Medicine. 2010; 15(1): 9–17. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2793341/.
- Ohtsuka, Y., Yabunaka, N., and Takayama, S. (1998). Shinrin-yoku (forest-air bathing and walking) effectively decreases blood glucose levels in diabetic patients. International Journal of Biometeorology41(3): 125–127. (https://doi.org/10.1007/s004840050064).
- Li, Q., Otsuka, T., Kobayashi, M. et al.(2011). Acute effects of walking in forest environments on cardiovascular and metabolic parameters. European Journal of Applied Physiology111(11): 2845–2853. (https://doi.org/10.1007/s00421-011-1918-z).
- Ideno, Y., Hayashi, K., Abe, Y. et al. (2017). Blood pressure-lowering effect of Shinrin-yoku (Forest bathing): A systematic review and meta-analysis. BMC Complementary and Alternative Medicine 17(1): 409. (https://doi.org/10.1186/s12906-017-1912-z).
- Li Q, Kobayashi M, Kumeda S, et al. Effects of Forest Bathing on Cardiovascular and Metabolic Parameters in Middle-Aged Males. Evid Based Complement Alternat Med. 2016;2016:2587381. doi:10.1155/2016/2587381 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4963577/.
- Chevalier, G., Sinatra, S.T., Oschman, J.L., and Delany, R.M. (2013). Earthing (grounding) the human body reduces blood viscosity-a major factor in cardiovascular disease. Journal of Alternative and Complementary Medicine 19(2): 102–110. (https://doi.org/10.1089/acm.2011.0820)
- Oschman, J.L., Chevalier, G., and Brown, R. (2015). The effects of grounding (earthing) on inflammation, the immune response, wound healing, and prevention and treatment of chronic inflammatory and autoimmune diseases. Journal of Inflammation Research 8:83–96. (https://doi.org/10.2147/JIR.S69656).
- Sokal, K., and Sokal, P. (2011). Earthing the human body influences physiologic processes. Journal of Alternative and Complementary Medicine 17(4): 301–308 (https://doi.org/10.1089/acm.2010.0687).
- Whear, R., Coon, J.T., Bethel, A. et al. (2014). What Is the impact of using outdoor spaces such as gardens on the physical and mental well-being of those with dementia? A systematic review of quantitative and qualitative evidence Journal of the American Medical Directors Association 15(10): 697–705 (https://www.ncbi.nlm.nih.gov/pubmed/25037168)
- Van Den Berg, A.E., and Custers, M.H. (2011). Gardening promotes neuroendocrine and affective restoration from stress. Journal of Health Psychology, 16(1), 3–11. (https://www.ncbi.nlm.nih.gov/pubmed/20522508)/.
- Olszak, T., An, D., Zeissig, S. et al. (2012). Microbial exposure during early life has persistent effects on natural killer T cell function. Science 336(6080): 489–49. (https://science.sciencemag.org/content/336/6080/489)