The forest represents a unique natural environment with its different ecosystems of plants, animals, fungi, insect and riparian zone. Outdoor enthusiasts take the forest for granted when they pass through on their way to the mountain top and many are unaware that the forest has a lot to offer in terms of health benefits.
There is a growing body of evidence which suggests that spending time in a natural environment can benefit our health and well-being.3 Spending time does not have to involve physical activity but just relaxing and observing the surrounding natural environment.
The Value of Urban Parks
Most people live in cities and this urban environment has been associated with improved living conditions and increased life expectancy however urbanization and artificial environments also brings increased pollution, noisy traffic and a reduction in natural open spaces which can impact a person’s health and quality of life.4,5 Anecdotal evidence links psychological stress to city environment with its greater crime, noise and pollution compared to those not living in urban areas6 and urbanization has been associated with an increase in mental disorders.7
Many urban parks help bring nature close to home with its generous green environment of trees. A field experiment in Japan has shown that a 15 minute walk in an urban park resulted in a greater sense of well being along with beneficial physiological and psychological effects.8 Green spaces in cities represents not only beautiful landscapes but areas to escape, relax and to improve our health.
There is a growing amount of studies done in Japan about Shinrin-yoku; also known as Forest Medicine or Forest Bathing. Shinrin-yoku involves spending time in the natural (forest) environment whether just relaxing (sitting) or walking. There has been increased importance in controlling stress and promoting relaxation among those living in modern-day society and “Shinrin-yoku” is considered to be one of the most accessible ways to get in touch with nature and to lower excessive stress to manageable levels.
Various studies have shown physiological benefits, while in a forest environment, such as reduced blood pressure, positive effects on the nervous system related to stress reduction and increased calm.9 The psychological benefits range from reduced chronic stress, reduction in hostility and depression.10
In one particular study, one group of people were exposed to the forest environment (for 15 minutes) where they sat in chairs viewing the landscape and also walked around while another group visited the urban environment after which both groups switched experimental conditions.9 Compared to an urban environment, being exposed to nature resulted in reductions in blood pressure, stress, and pulse rate.
Forest bathing can also boost weakened immune function. When male subjects walked for 2 hours in the morning and afternoon in a forest park, their immune system responded by increasing the number and activity of natural killer cells (NKC) and anti-cancer proteins11 and this response lasted for one week after the conclusion of the experiment. NKC are specialized cells of our immune system which represents a front line defense system that controls the spread of certain tumors, and limits the spread of bacteria and viruses.12
The positive effects of the natural environment on our health is believed to be due to inhalation of plant chemicals (phytochemicals) mostly produced by trees of which terpenes represents the major essential oils that confers various health benefits.13 These aromatic volatile wood essential oils have been termed phytoncides and they have been shown to increase both NKC14 and proteins inside our body which help combat tumors15 whereas city living has no influence on these biological functions.16
Oak, cedar, pine trees and many plants produce phytoncides which play an important role in plant immunity and help protect them from bacteria, virus and fungus.
The Waterfall Effect
Waterfalls are a natural part of the forest environment and come in all shapes and sizes and its flow rate varies with the season, environmental conditions and topography. The volume of water, its speed and height create different patterns. Whatever its characteristics, waterfalls represents an integral part of the landscape that defines beauty and evokes positive mood and health effects.
There are countless times, I’ve stood close to waterfalls and got wet by the spray emitted from the falling water and the greater the volume of water and turbulence at the base of the falls, the greater the floating mist which spreads outwards. Tiny, negatively charged ions which floats in the air are produced when the turbulence of the falling water and its impact on surfaces at the base of the falls causes bubbling and splashing that disrupts the water surface.17
Although the concentration of negatively charged ions are higher close to the waterfall, rather than away from it, the levels do fluctuate according to the volume of water flowing, the height of the waterfall, surrounding topography and air humidity.
There has been a rash of experiments and conclusion drawn about the benefits of negatively charged ions on reducing psychological stress, anxiety and depression but a review of those studies and other studies has not shown any consistent positive effects although there appears to be some suggestion that it might improve depressive symptoms.18
A recent study has shown significant improvements in subjective stress perception upon exposure to ionized water aerosols19 but where the waterfall effect of negatively charged ions has shown the most benefit is on the immune system; specifically the immunoglobulin IgA found in abundance in saliva and represents our first line of defense from invading pathogens via the mouth.20 Negatively charged ions also interact with forest phytoncides, such as ɑ-pinene and beta-pinene which function to strengthen our immunity and reduce physiological stress.21 Since negative ions can remain suspended in the air and drift far away, a current study revealed that the beneficial effect on our health can occur even at a distant site from a waterfall.19
- Spend time in an urban park, especially those which support trees and other vegetation to make you feel more at home with nature.
- Spend time away from the city and head off on a trail which winds its way through the forest.
- Visit forested areas where waterfalls are a natural part of the environment.
- Meditate and practice deep breathing to relieve stress and inhale therapeutic phytoncides.
Ron (solo75) has enjoyed the outdoors for the past 42 years; most of those years are solo trips where he likes to observe nature and take photographs.
- Bauman AE. Updating the evidence that physical activity is good for health: an epidemiological review 2000-2003. J Sci Med Sport. 2004;7:6–19. doi: 10.1016/S1440-2440(04)80273-1.
- Blair SN, Kohl HW, Gordon NF, Paffenbarger RS Jr., How much physical activity is good for health? Annu Rev Public Health. 1992;13:99-126.
- Bowler DE, Buyung-Ali LM, Knight TM, Pullin AS. A systematic review of evidence for the added benefits to health of exposure to natural environments. BMC Public Health. 2010;10:456. doi:10.1186/1471-2458-10-456.
- Vlahov D, Freudenberg N, Proietti F, et al. Urban as a Determinant of Health. Journal of Urban Health : Bulletin of the New York Academy of Medicine. 2007;84(Suppl 1):16-26. doi:10.1007/s11524-007-9169-3.
- Sanghamitra Bandyopadhyay and Elliott Green, Urbanization and Mortality Decline, Queen Mary, University of London and London School of Economics, November 25, 2013.
- Alison Abbott, Stress and the city: Urban decay, Nature 490,162–164 (11 October 2012) doi:10.1038/490162a.
- Srivastava K. Urbanization and mental health. Industrial Psychiatry Journal. 2009;18(2):75-76. doi:10.4103/0972-6748.64028.
- Chorong Song, Harumi Ikei, Miho Igarashi, Michiko Takagaki and Yoshifumi Miyazaki, Physiological and Psychological Effects of a Walk in Urban Parks in Fall, Int. J. Environ. Res. Public Health 2015, 12, 14216-14228; doi:10.3390/ijerph121114216.
- Park BJ, Tsunetsugu Y, Kasetani T, Kagawa T, Miyazaki Y. The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan. Environmental Health and Preventive Medicine. 2010;15(1):18-26. doi:10.1007/s12199-009-0086-9.
- Morita E, Fukuda S, Nagano J, Hamajima N, Yamamoto H, Iwai Y, Nakashima T, Ohira H, Shirakawa T. Psychological effects of forest environments on healthy adults: Shinrin-yoku (forest-air bathing, walking) as a possible method of stress reduction. Public Health. 2007 Jan;121(1):54-63. Epub 2006 Oct 20.
- Li Q, Kobayashi M, Inagaki H, Hirata Y, Li YJ, Hirata K, Shimizu T, Suzuki H, Katsumata M, Wakayama Y, Kawada T, Ohira T, Matsui N, Kagawa T. A day trip to a forest park increases human natural killer activity and the expression of anti-cancer proteins in male subjects. J Biol Regul Homeost Agents. 2010 Apr-Jun;24(2):157-65.
- Arundhati Mandal, Chandra Viswanathan, Natural killer cells: In health and disease, Hematology/Oncology and Stem Cell Therapy Volume 8, Issue 2, June 2015, Pages 47–55.
- Cho KS, Lim Y, Lee K, Lee J, Lee JH, Lee I-S. Terpenes from Forests and Human Health. Toxicological Research. 2017;33(2):97-106. doi:10.5487/TR.2017.33.2.097.
- Qing Li, Effect of forest bathing trips on human immune function, Environ Health Prev Med (2010) 15:9–17.
- Rauf Bhat, Carsten Watzl, Serial Killing of Tumor Cells by Human Natural Killer Cells – Enhancement by Therapeutic Antibodies, PLOS One March 28, 2007 https://doi.org/10.1371/ journal.pone.0000326.
- Li Q, Morimoto K, Kobayashi M, Inagaki H, Katsumata M, Hirata Y, Hirata K, Suzuki H, Li YJ, Wakayama Y, Kawada T, Park BJ, Ohira T, Matsui N, Kagawa T, Miyazaki Y, Krensky AM, Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins, Int J Immunopathol Pharmacol. 2008 Jan-Mar;21(1):117-27.
- Kolar, M. Gaisberger, P. Madl, W. Hofmann, M. Ritter, and A. Hart, Characterization of ions at Alpine waterfalls, Atmos. Chem. Phys., 12, 3687–3697, 2012.
- Vanessa Perez, Dominik D Alexander and William H Bailey, Air ions and mood outcomes: a review and meta-analysis, BMC Psychiatry201313:29 DOI: 10.1186/1471-244X-13-29.
- Grafetstätter C, Gaisberger M, Prossegger J, et al. Does waterfall aerosol influence mucosal immunity and chronic stress? A randomized controlled clinical trial. Journal of Physiological Anthropology. 2017;36:10. doi:10.1186/s40101-016-0117-3
- Abdollah Jafarzadeh; Mostafa Sadeghi; Gholamreza Asadi Karam; Reza Vazirinejad, Salivary IgA and IgE levels in healthy subjects: relation to age and gender, Braz. oral res. vol.24 no.1 São Paulo Jan./Mar. 2010.
- Kawakami K, Kawamoto M, Nomura M, Otani H, Nabika T, Gonda T., Effects of phytoncides on blood pressure under restraint stress in SHRSP. Clin Exp Pharmacol Physiol. 2004 Dec;31 Suppl 2:S27-8.