"In every walk with nature one receives far more than he seeks." —John Muir
I have always enjoyed spending time in forests. If I’m feeling stuck, anxious, or down about something, a walk amongst the trees gives me fresh insight, calms my mind, or lifts my spirits. In the 1980s, shinrin-yoku, meaning “forest bathing” or “taking in the forest atmosphere,” was developed in Japan and has become an important part of Japanese preventive healthcare and healing. Since then, scientific research has established its many health benefits and shinrin-yoku, also known as forest therapy, is spreading across the world. Shinrin-yoku is the practice of slowly walking through a forest and observing your surroundings. Practitioners might only walk a quarter of a mile in two hours. Here is a summary of some of the research that has established the many health benefits of shinrin-yoku and forest therapy. After reading this blog post, you may find yourself reaching for your shoes to spend time in a nearby forest.
After spending time in a forest environment, study participants reported significantly lower feelings of anxiety, tension, depression, hostility, fatigue, and confusion while feeling more comfortable, relaxed, and at ease than before their outing.1, 3, 6, 8, 10, 11 These results were reported for those returning from a two-night excursion as well as those spending only 15 minutes in a forest! Their moods were also compared to study participants who spent the same amount of time walking in an urban environment. Even though their negative and positive feelings were comparable prior to their outings, those who spent time in the forest had significant improvement over those who spent time in urban areas. One study even showed higher rates of anxiety in participants after spending time in an urban environment.1 If you’re having a bad day and nothing seems to be going right, it might be worth heading to a nearby park or forest to spend just 15 minutes amongst the trees.
In addition to psychological benefits, the effects of shinrin-yoku show up in physical measurements as well. The heart rates of study participants who spent time in a forest environment were lower than they were before their outing and significantly lower than those of participants who spent time in an urban environment.1, 3, 8, 10 Also, after a two-night trip to an evergreen forest, participants had significantly lower amounts of indicators associated with high blood pressure than those who spend time in an urban environment, even when there was no measured difference before the trips.1, 6 Additionally, measurements of heart rate variability (a measurement of variability between heart beats that indicates stress or balance in the nervous system) improved in participants who spent time in a forest environment and were significantly better than those who spent time in an urban environment.1, 10 Decreased heart rate, healthier blood pressure, and more balanced heart rate variability all indicate that spending time in forests reduces the stress response and balances the nervous system.
Measuring cortisol levels is another way to examine the impact of shinrin-yoku on the stress response. Cortisol is a hormone released by your body in response to stress that reduces immune response in order to focus energy to overcome the threat. Typically, cortisol levels return to normal once the threat has passed and your body returns to normal functioning. However, when we feel like we’re constantly under attack from day-to-day stressors, like meeting deadlines and paying bills, our cortisol levels can remain elevated, increasing our risks for anxiety, depression, digestive problems, headaches, heart disease, sleep problems, weight gain, and cognitive impairment.7 Several research studies took blood samples before and after visits to forest and urban environments in order to measure cortisol levels. After spending time in a forest, study participants had significantly reduced cortisol levels than before their trip and levels were much lower for those who spent time in a forest as compared to an urban environment.2, 3, 6, 8
Studies also found immune function improved with time spent in a forest. Researchers measured immune function by looking at natural killer (NK) cell activity and numbers as well as other indicators of immune system function. NK cells are a type of white blood cell that are a vital part of our immune system. They are our frontline defense against tumors and infections. When our immune system response is repressed due to a heightened stress response, NK cell activity and numbers are reduced. Researchers found that along with reduced stress hormone levels, trips to a forest significantly improved activity and numbers of NK cells and other immune function indicators.2, 4, 5 Improved immune function was maintained even when measured a week after a two-hour forest trip2 and a full month after a weekend trip.4
Taking a walk through a forest supports immune function in multiple ways. Researchers measured concentrations of phytoncides in both forest and city air and found that there were significant levels in the forest but not in the city. Phytoncides are aromatic compounds released by trees and other plants to protect themselves against harmful germs and insects.9 They are antibacterial and immune supportive. These compounds contribute to the aroma of the forest and are present in many essential oils derived from evergreen trees that are used in aromatherapy. Inhalation of phytoncides and decreased stress hormones from walking in a forest may both contribute to increased NK cell activity and numbers, improving immune function.5
Spending regular time in nature is a beneficial addition to your self-care routine. Excursions to forests reduce feelings of stress, improve mood and vibrancy, balance the nervous system, calm the stress response, and support immune system health. These benefits will spill over into your daily life to offer more enjoyable days, improved focus, better sleep, being more present in relationships, and feeling better physically, mentally, and emotionally. A walk in the forest takes you away from the demands of modern life and allows you to connect with nature and perhaps feeling more at home on this Earth. So, what are you waiting for? Lace up your shoes, breathe in the fresh air, and take a walk amongst the trees.
- Lee, Juyoung et al. “Influence of Forest Therapy on Cardiovascular Relaxation in Young Adults.” Evidence-Based Complimentary and Alternative Medicine, vol. 2014, 10 Feb. 2014. PubMed, doi:10.1155/2014/834360.
- Li, Qing et al. “A day trip to a forest park increases human natural killer activity and the expression of anti-cancer proteins in male subjects.” Journal of Biological Regulators and Homeostatic Agents, vol. 24, no. 2, April-June 2010, 157-165. PubMed, https://www.ncbi.nlm.nih.gov/pubmed/20487629.
- Li, Qing et al. “Effects of Forest Bathing on Cardiovascular and Metabolic Parameters in Middle-Aged Males.” Evidence-Based Complimentary and Alternative Medicine, vol. 2016, July 2016. PubMed, doi: 10.1155/2016/2587381
- Li, Qing et al. “Forest Bathing Enhances Human Natural Killer Activity and Expression of Anti-Cancer Proteins.” International Journal of Immunopathology and Pharmacology, vol. 20, no. 2, 1 Apr. 2007, (S2) 3-8. SageJournals, http://journals.sagepub.com/doi/pdf/10.1177/03946320070200S202.
- Li, Qing et al. “Visiting a Forest, But Not a City, Increases Human Natural Killer Activity and Expression of Anti-Cancer Proteins.” International Journal of Immunopathology and Pharmacology, vol. 21, no.1, 2008, 117-127. SagePublications, http:// journals.sagepub.com/doi/pdf/10.1177/039463200802100113.
- Mao, GX et al. “Effects of short-term forest bathing on human health in a broad-leaved evergreen forest in Zhejiang Province, China.” Biomedical and Environmental Sciences, vol. 25, no. 3, June 2012, 317-324. PubMed, doi: 10.3967/0895-3988.2012.03.010.
- Mayo Clinic Staff. “Chronic stress puts your health at risk.” 21 Apr. 2016. https://www.mayoclinic.org/healthy-lifestyle/stress-management/in-depth/stress/art-20046037. Accessed 2 Feb. 2018.
- Ochiai, H et al. “Physiological and Psychological Effects of a Forest Therapy Program on Middle-Aged Females.” International Journal of Environmental Research and Public Health, vol. 12, no. 12, Dec. 2015, 15222-32. PubMed, doi: 10.3390/ijerph121214984.
- “Phytoncide.” Medical definition. Merriam-Webster.com. Merriam-Webster Dictionaries. n.d. Web. 30 Jan. 2018.
- Song, C et al. “Effect of Forest Walking on Autonomic Nervous System Activity in Middle-Aged Hypertensive Individuals: A Pilot Study.” International Journal of Environmental Research and Public Health, vol. 12, no. 3, Mar. 2015, 2687-699. PubMed, doi: 10.3390/ijerph120302687
- Takayama, N et al. “Emotional, Restorative and Vitalizing Effects of Forest and Urban Environments at Four Sites in Japan.” International Journal of Environmental Research and Public Health, vol. 11, no. 7, Jul. 2014, 7207-7230. PubMed, doi: 10.3390/ijerph110707207.