A New Day for Trees
Jacob Schor ND, FABNO
This February’s full moon will mark the New Year for Trees. In Biblical times knowing the age of a tree was important. Fruit from a tree less than three years of age was considered inedible. Once the tree was older than three tithes were taken. A New Year for Trees was set to approximate when the earliest blooming tress in Israel would wake from winter dormancy and begin their new fruit bearing cycle.
On the Jewish calendar this day is observed on the 15th day of the month of Shevat or Tu B’Shevat. This year Tu B’Shevat begins at sunset, February 7th.
The significance of Tu B’Shvat has shifted over the centuries. During the Middle Ages, Tu B’shvat became something of an esoteric holiday. In the mid 1500s, Rabbi Yitzchak Luria of Safed and his disciples celebrated the day with a ritualized meal in which the fruits of Israel were assigned symbolic meanings to represent concepts from the Kabbalah. Eating the ten specified fruits in ritualized order while reciting the appropriate blessings, at least in their thinking, would bring human beings and the world, closer to spiritual perfection.
In recent years the theme of the holiday has shifted to reflect conservation and ecological themes. This dates back to 1890 when Rabbi Zeev Yavetz, celebrated the day by having his students plant trees in the agricultural colony of Zichron Yaakov. In 1908 the Jewish Teachers Union and later the Jewish National Fund copied this and turned the holiday into an annual effort to reforest Israel. In the early 1900s, the Jewish National Fund devoted the day to planting eucalyptus trees in the Hula Valley to stop malaria. This turned into a practice of annual tree planting and continues; this year on Tu’Bshvat over a million Israelis will take part in tree-planting.
The New Year of tress is observed in part by eating a meal that contains dried fruits and nuts, in particular the seven ‘fruits’ that are praised in the Torah: grapes, figs, pomegranates, olives, dates, wheat and barley. Rabbi Luria’s esoteric celebration has converted into a holiday that awakens ecological awareness and it has become common to sit for a ‘seder.’ There are books, Haggadah, available that are used to lead the celebrants through the meal, in much the same way Passover is celebrated. For example: http://tubshvat.hazon.org/hazons-tu-bshvat-seder-and-sourcebook/
Dried fruit and almonds traditionally eaten on Tu Bishvat
Regular readers of my newsletters will recognize that this is the moment when I suddenly shift gears and delve into the scientific literature and try to make it relevant to whatever seemingly irrelevant topic I’ve been writing about.
Thus you might expect me to review the health benefits of figs, dates, pomegranates, etc.
Instead, I want to write about trees.
For the moment, let’s ignore the fact that we need trees to supply us with fruit and nuts, tomaintain our climate, our wildlife habitats, as the prime material we use to build our homes, make paper and wipe our bottoms. Instead let me limit this discussion to what effect being around trees does for our health.
The idea that “green space” is fundamental to mental well being has become a popular research subject in recent years, so much so that a recent Dutch paper employed the term, “Vitamin G” for green space implying that it is essential for our health and sanity. What is it about green space that is healthful? A seemingly plausible explanation was that the more accessible green spaces were, the more people would exercise and that increased exercise leads to better health. A 2008 study disproved this hypothesis. Green space did not correlate with time spent exercising.
Something about green space does change the way people perceive their lives. The further people live from open green spaces, the more lonely they perceive themselves to be and the fewer social contacts they have. The closer one lives to a green space, the less impact the stressful events in people’s lives seem to have on them. Though not proven as well as we might wish, there is a growing hypothesis that people need some minimum daily requirement of green space exposure to maintain a state of mental health.
This brings us to recent research on a traditional Japanese practice called Shinrin-yoku or ‘forest bathing’ or ‘taking in the forest atmosphere.’ The practice entails just what it sounds like, walking quietly through a forest. That such a practice would leave someone feeling better seems intuitively correct but the degree it does is surprising. We first noticed papers on forest bathing in 2007 when three separate publications published human trials. 2007 Nin March 2007 Tsunetsugu et al reported that college students who either sat for 15 admiring a forest view or walked for a similar period of time both felt better and also had lower blood pressure, heart rate and cortisol levels compared to doing similar activities in an urban setting.
In the same month Park et al reported data on a similar experiment, but in addition to shuttling participants back and forth from city to forest, activity in the prefrontal cortex of their brain was measured. The forest not only lowered cortisol but prefrontal cortex activity as well.
These small experiments were followed by the October publication of a much larger trial in which Morita et al took 98 participants into the forest and watched their responses. Forest exposure was associated with significantly decreased scores for hostility and depression on personality testing and increased ‘liveliness.’ The higher the initial stress level in the individual, the more pronounced the benefit of forest exposure.
The next significant publication appears to be Park et al in January 2010. They tested to see if different forested area produced similar results. In each series of the experiment, 12 subjects (280 participants in total) walked in and viewed a forest or city area. “On the first day, six subjects were sent to a forest area, and the others to a city area. On the second day, each group was sent to the other area as a cross-check.... The results show that forest environments promote lower concentrations of cortisol, lower pulse rate, lower blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than do city environments.”
In a review paper published in 2010 Tsunetsugu et al raise the question of whether it is the wood odor, the sound or running water, the scenary or the total ‘forest experience’ that triggers the benefit.
Four papers on forest bathing were published in 2011, one in February and three in September.
The February paper, this one by Lee et al differed only in duration from prior trials. Rather than half or one day exposure, participants spent 3 days in a forest environment. Similar physiologic improvements were documented suggestive of lower stress.
Of the three September papers, two reconfirm earlier findings. One looked for a correlation between frequent forest walking and blood pressure but did not find a statistically significant lower pressure associated with greater forest exposure.
Unfortunately none of these papers have yet explained the source of the benefit. Is it the sounds of the forest, the frequency of light filtered by leaves, the various chemicals that trees emit into the air, or that lack of urban discordance? One can hypothesize that it could be any one or combination of factors such as these. Will an indoor fountain that mimics the sound of a forest brook have the same impact? Will abundant houseplants act as a trigger to relaxation? These questions remain unanswered. Suffice to say we humans feel better in the midst of trees.
One is acutely aware of this in Denver. We live in a place where trees do not grow naturally. Old photographs of our neighborhood of our library, elementary school and homes when they were first built, show them standing alone in the middle of an empty prairie. The trees that line our streets and shade our yards are there only because people have planted, watered and cared for them over the century.
If we want to have trees in our lives, we need to actively plant and care for them.
Even with the value we put on trees locally, globally, 4,500 acres of forest disappear per hour. The world is losing about 18 million acres of forest per year. People in Sub-Saharan Africa are burning wood for fuel at a rate that is 30 to 200% faster than it can grow back. Trees store carbon and destroying them hastens the carbon release that causes climate change.
Here in Denver we have a lovely organization called Denver Digs trees that distributes free trees to residents for planting. I take pleasure in the lovely tree that my neighbor Bill and I planted a decade ago, supplied by this group.
The group supplies free trees for planting twice a year, Spring and Fall.
If you resonate with those bumper stickers that say “Think globally Act locally” then this program is for you.
If you are the sort who wants to also act globally then Green World is the website for you. As the name implies, this group works to plant trees on a global scale. Their goals are lofty but their plan is simple. Donations are used to plant trees in parts of the world where they will do the most good. Their website is worth reading.
Trees enrich our lives. On this New Year of Trees, I hope that you will take a moment to appreciate trees and consider making an effort to leave the world with a few more trees.
BMC Public Health. 2006 Jun 7;6:149.
Vitamin G: effects of green space on health, well-being, and social safety.
Groenewegen PP, van den Berg AE, de Vries S, Verheij RA.
NIVEL--Netherlands Institute for Health Services Research, POBox 1568 NL-3500 BN Utrecht, The Netherlands. email@example.com
Looking out on and being in the green elements of the landscape around us seem to affect health, well-being and feelings of social safety. This article discusses the design of a research program on the effects of green space in the living environment on health, well-being and social safety.
The program consists of three projects at three different scales: at a macro scale using data on the Netherlands as a whole, at an intermediate scale looking into the specific effect of green space in the urban environment, and at micro scale investigating the effects of allotment gardens. The projects are observational studies, combining existing data on land use and health interview survey data, and collecting new data through questionnaires and interviews. Multilevel analysis and GIS techniques will be used to analyze the data.
Previous (experimental) research in environmental psychology has shown that a natural environment has a positive effect on well-being through restoration of stress and attentional fatigue. Descriptive epidemiological research has shown a positive relationship between the amount of green space in the living environment and physical and mental health and longevity. The program has three aims. First, to document the relationship between the amount and type of green space in people's living environment and their health, well-being, and feelings of safety. Second, to investigate the mechanisms behind this relationship. Mechanisms relate to exposure (leading to stress reduction and attention restoration), healthy behavior and social integration, and selection. Third, to translate the results into policy on the crossroads of spatial planning, public health, and safety. Strong points of our program are: we study several interrelated dependent variables, in different ordinary settings (as opposed to experimental or extreme settings), focusing on different target groups, using appropriate multilevel methods.
[PubMed - indexed for MEDLINE]
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BMC Public Health. 2008 Jun 10;8:206.
Physical activity as a possible mechanism behind the relationship between green space and health: a multilevel analysis.
Maas J, Verheij RA, Spreeuwenberg P, Groenewegen PP.
NIVEL (Netherlands Institute for Health Services Research), PO Box 1568, 3500 BN, Utrecht, The Netherlands. firstname.lastname@example.org
The aim of this study was to investigate whether physical activity (in general, and more specifically, walking and cycling during leisure time and for commuting purposes, sports and gardening) is an underlying mechanism in the relationship between the amount of green space in people's direct living environment and self-perceived health. To study this, we first investigated whether the amount of green space in the living environment is related to the level of physical activity. When an association between green space and physical activity was found, we analysed whether this could explain the relationship between green space and health.
The study includes 4.899 Dutch people who were interviewed about physical activity, self-perceived health and demographic and socioeconomic background. The amount of green space within a one-kilometre and a three-kilometre radius around the postal code coordinates was calculated for each individual. Multivariate multilevel analyses and multilevel logistic regression analyses were performed at two levels and with controls for socio-demographic characteristics and urbanicity.
No relationship was found between the amount of green space in the living environment and whether or not people meet the Dutch public health recommendations for physical activity, sports and walking for commuting purposes. People with more green space in their living environment walked and cycled less often and fewer minutes during leisure time; people with more green space garden more often and spend more time on gardening. Furthermore, if people cycle for commuting purposes they spend more time on this if they live in a greener living environment. Whether or not people garden, the time spent on gardening and time spent on cycling for commuting purposes did not explain the relationship between green space and health.
Our study indicates that the amount of green space in the living environment is scarcely related to the level of physical activity. Furthermore, the amount of physical activity undertaken in greener living environments does not explain the relationship between green space and health.
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Health Place. 2009 Jun;15(2):586-95. Epub 2008 Oct 15.
Social contacts as a possible mechanism behind the relation between green space and health.
Maas J, van Dillen SM, Verheij RA, Groenewegen PP.
NIVEL (Netherlands Institute for Health Services Research), P.O. Box 1568, 3500 BN Utrecht, The Netherlands. email@example.com
This study explored whether social contacts are an underlying mechanism behind the relationship between green space and health. We measured social contacts and health in 10,089 residents of the Netherlands and calculated the percentage of green within 1 and a 3km radius around the postal code coordinates for each individual's address. After adjustment for socio-economic and demographic characteristics, less green space in people's living environment coincided with feelings of loneliness and with perceived shortage of social support. Loneliness and perceived shortage of social support partly mediated the relation between green space and health.
Soc Sci Med. 2010 Apr;70(8):1203-10. Epub 2010 Feb 12.
Green space as a buffer between stressful life events and health.
van den Berg AE, Maas J, Verheij RA, Groenewegen PP.
Wageningen University and Research Centre, PO Box 47, Wageningen, The Netherlands. firstname.lastname@example.org
This study investigates whether the presence of green space can attenuate negative health impacts of stressful life events. Individual-level data on health and socio-demographic characteristics were drawn from a representative two-stage sample of 4529 Dutch respondents to the second Dutch National Survey of General Practice (DNSGP-2), conducted in 2000-2002. Health measures included: (1) the number of health complaints in the last 14 days; (2) perceived mental health (measured by the GHQ-12); and (3) a single item measure of perceived general health ranging from 'excellent' to 'poor'. Percentages of green space in a 1-km and 3-km radius around the home were derived from the 2001 National Land cover Classification database (LGN4). Data were analysed using multilevel regression analysis, with GP practices as the group-level units. All analyses were controlled for age, gender, income, education level, and level of urbanity. The results show that the relationships of stressful life events with number of health complaints and perceived general health were significantly moderated by amount of green space in a 3-km radius. Respondents with a high amount of green space in a 3-km radius were less affected by experiencing a stressful life event than respondents with a low amount of green space in this radius. The same pattern was observed for perceived mental health, although it was marginally significant. The moderating effects of green space were found only for green space within 3 km, and not for green space within 1 km of residents' homes, presumably because the 3-km indicator is more affected by the presence of larger areas of green space, that are supposed to sustain deeper forms of restoration. These results support the notion that green space can provide a buffer against the negative health impact of stressful life events.
Copyright 2010 Elsevier Ltd. All rights reserved.
Med Hypotheses. 2011 Jun;76(6):877-80. Epub 2011 Mar 22.
Does biodiversity improve mental health in urban settings?
Dean J, van Dooren K, Weinstein P.
School of Population Health, University of Queensland, Australia. email@example.com
Globally, the human and economic burdens of mental illness are increasing. As the prevalence and costs associated with mental illness rise, we are progressively more aware that environmental issues such as climate change and biodiversity loss impact on human health.
This paper hypothesises that increased biodiversity in urban environments is associated with improved mental health and wellbeing. It proposes the ecological mechanism through which the association may exist, and explores the extant literature to determine the extent of empirical evidence to support our hypothesis.
While there is a substantial literature investigating the impact of 'green space' and contact with nature on mental health, we identified only one original research paper that directly investigated the link between biodiversity and mental health. This suggests that the extant evidence considers only 'one part of the story', providing an evidence base which is inadequate to inform policy on biodiversity conservation and public health.
Our hypothesised relationship between environmental change and mental health proposes conservation and restoration of biodiversity in urban environments as a form of intervention for improving human health. It also highlights the need for a better evidence base to demonstrate the synergistic benefits of increased biodiversity and mental health to decision makers. Well-designed quantitative epidemiological research is needed to establish the strength of any such causal relationship.
Copyright © 2011 Elsevier Ltd. All rights reserved.
J Physiol Anthropol. 2007 Mar;26(2):135-42.
Physiological effects of Shinrin-yoku (taking in the atmosphere of the forest) in an old-growth broadleaf forest in Yamagata Prefecture, Japan.
Tsunetsugu Y, Park BJ, Ishii H, Hirano H, Kagawa T, Miyazaki Y.
Forestry and Forest Products Research Institute, Ibaraki, Japan. firstname.lastname@example.org
The physiological effects of "Shinrin-yoku" (taking in the atmosphere of the forest) were examined by investigating blood pressure, pulse rate, heart rate variability (HRV), salivary cortisol concentration, and immunoglobulin A concentration in saliva. Subjective feelings of being "comfortable", "calm", and "refreshed" were also assessed by questionnaire. The subjects were 12 male university students aged from 21 to 23 (mean+/-SD: 22.0+/-1.0). The physiological measurements were conducted six times, i.e., in the morning and evening before meals at the place of accommodation, before and after the subjects walked a predetermined course in the forest and city areas for 15 minutes, and before and after they sat still on a chair watching the scenery in the respective areas for 15 minutes. The findings were as follows. In the forest area compared to the city area, 1) blood pressure and pulse rate were significantly lower, and 2) the power of the HF component of the HRV tended to be higher and LF/(LF+HF) tended to be lower. Also, 3) salivary cortisol concentration was significantly lower in the forest area. These physiological responses suggest that sympathetic nervous activity was suppressed and parasympathetic nervous activity was enhanced in the forest area, and that "Shinrin-yoku" reduced stress levels. In the subjective evaluation, 4) "comfortable", "calm", and "refreshed" feelings were significantly higher in the forest area. The present study has, by conducting physiological investigations with subjective evaluations as supporting evidence, demonstrated the relaxing and stress-relieving effects of "Shinrin-yoku".
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J Physiol Anthropol. 2007 Mar;26(2):123-8.
Physiological effects of Shinrin-yoku (taking in the atmosphere of the forest)--using salivary cortisol and cerebral activity as indicators.
Park BJ, Tsunetsugu Y, Kasetani T, Hirano H, Kagawa T, Sato M, Miyazaki Y.
Forestry and Forest Products Research Institute, Ibaraki, Japan. email@example.com
The purpose of this study is to examine the physiological effects of Shinrin-yoku (taking in the atmosphere of the forest). The subjects were 12 male students (22.8+/-1.4 yr). On the first day of the experiments, one group of 6 subjects was sent to a forest area, and the other group of 6 subjects was sent to a city area. On the second day, each group was sent to the opposite area for a cross check. In the forenoon, the subjects were asked to walk around their given area for 20 minutes. In the afternoon, they were asked to sit on chairs and watch the landscapes of their given area for 20 minutes. Cerebral activity in the prefrontal area and salivary cortisol were measured as physiological indices in the morning at the place of accommodation, before and after walking in the forest or city areas during the forenoon, and before and after watching the landscapes in the afternoon in the forest and city areas, and in the evening at the place of accommodation. The results indicated that cerebral activity in the prefrontal area of the forest area group was significantly lower than that of the group in the city area after walking; the concentration of salivary cortisol in the forest area group was significantly lower than that of the group in the city area before and after watching each landscape. The results of the physiological measurements show that Shinrin-yoku can effectively relax both people's body and spirit.
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Public Health. 2007 Jan;121(1):54-63. Epub 2006 Oct 20.
Psychological effects of forest environments on healthy adults: Shinrin-yoku (forest-air bathing, walking) as a possible method of stress reduction.
Morita E, Fukuda S, Nagano J, Hamajima N, Yamamoto H, Iwai Y, Nakashima T, Ohira H, Shirakawa T.
Department of Health Promotion and Human Behaviour, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501, Japan. firstname.lastname@example.org
Shinrin-yoku (walking and/or staying in forests in order to promote health) is a major form of relaxation in Japan; however, its effects have yet to be completely clarified. The aims of this study were: (1) to evaluate the psychological effects of shinrin-yoku in a large number of participants; and (2) to identify the factors related to these effects.
Four hundred and ninety-eight healthy volunteers took part in the study. Surveys were conducted twice in a forest on the same day (forest day) and twice on a control day. Outcome measures were evaluated using the Multiple Mood Scale-Short Form (hostility, depression, boredom, friendliness, wellbeing and liveliness) and the State-Trait Anxiety Inventory A-State Scale. Statistical analyses were conducted using analysis of variance and multiple regression analyses.
Hostility (P<0.001) and depression (P<0.001) scores decreased significantly, and liveliness (P=0.001) scores increased significantly on the forest day compared with the control day. The main effect of environment was also observed with all outcomes except for hostility, and the forest environment was advantageous. Stress levels were shown to be related to the magnitude of the shinrin-yoku effect; the higher the stress level, the greater the effect.
This study revealed that forest environments are advantageous with respect to acute emotions, especially among those experiencing chronic stress. Accordingly, shinrin-yoku may be employed as a stress reduction method, and forest environments can be viewed as therapeutic landscapes. Therefore, customary shinrin-yoku may help to decrease the risk of psychosocial stress-related diseases, and evaluation of the long-term effects of shinrin-yoku is warranted.
[PubMed - indexed for MEDLINE]
Environ Health Prev Med. 2010 Jan;15(1):18-26.
The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan.
Park BJ, Tsunetsugu Y, Kasetani T, Kagawa T, Miyazaki Y.
Center for Environment, Health and Field Sciences, Chiba University, Kashiwa-no-ha 6-2-1, Kashiwa, Chiba, 277-0882, Japan, email@example.com.
This paper reviews previous research on the physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing), and presents new results from field experiments conducted in 24 forests across Japan. The term Shinrin-yoku was coined by the Japanese Ministry of Agriculture, Forestry, and Fisheries in 1982, and can be defined as making contact with and taking in the atmosphere of the forest. In order to clarify the physiological effects of Shinrin-yoku, we conducted field experiments in 24 forests across Japan. In each experiment, 12 subjects (280 total; ages 21.7 +/- 1.5 year) walked in and viewed a forest or city area. On the first day, six subjects were sent to a forest area, and the others to a city area. On the second day, each group was sent to the other area as a cross-check. Salivary cortisol, blood pressure, pulse rate, and heart rate variability were used as indices. These indices were measured in the morning at the accommodation facility before breakfast and also both before and after the walking (for 16 +/- 5 min) and viewing (for 14 +/- 2 min). The R-R interval was also measured during the walking and viewing periods. The results show that forest environments promote lower concentrations of cortisol, lower pulse rate, lower blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than do city environments. These results will contribute to the development of a research field dedicated to forest medicine, which may be used as a strategy for preventive medicine.
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Environ Health Prev Med. 2010 Jan;15(1):27-37.
Trends in research related to "Shinrin-yoku" (taking in the forest atmosphere or forest bathing) in Japan.
Tsunetsugu Y, Park BJ, Miyazaki Y.
Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan, firstname.lastname@example.org.
"Shinrin-yoku", which can be defined as "taking in the forest atmosphere or forest bathing", has been receiving increasing attention in Japan in recent years for its capacity to provide relaxation and reduce stress. Since 2004, the authors of this paper have been involved in an investigation designed to ascertain the physiological effects of "Shinrin-yoku" within the framework of the "Therapeutic Effects of Forests" project. We have conducted physiological experiments, both in actual forests and in the laboratory, to elucidate the physiological effects on individuals of exposure to the total environment of forests or to only certain elements of this environment, such as the odor of wood, the sound of running stream water, and the scenery of the forest. We have obtained physiological measurements of central nervous activity, autonomic nervous activity, and biomarkers reflecting stress response that can be applied in this line of approach. Using these measurements, we have summarized the separate elements of forests in terms of the five senses. We have also reviewed a selection of field studies and introduced a number of results from ongoing projects as well as those from early studies. Future perspectives are also discussed.
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Public Health. 2011 Feb;125(2):93-100. Epub 2011 Feb 1.
Effect of forest bathing on physiological and psychological responses in young Japanese male subjects.
Lee J, Park BJ, Tsunetsugu Y, Ohira T, Kagawa T, Miyazaki Y.
Centre for Environment, Health and Field Sciences, Chiba University, 6-2-1 Kashiwanoha, Kashiwa City, Chiba Prefecture 277-0882, Japan. email@example.com
To provide scientific evidence supporting the efficacy of forest bathing as a natural therapy by investigating its physiological benefits using biological indicators in outdoor settings.
Within-group comparisons were used to examine psychological and physiological responses to exposure to real forest and urban environments.
Young Japanese male adults participated in a 3-day, 2-night field experiment. Physiological responses as well as self-reported psychological responses to forest and urban environmental stimuli were measured in real settings. The results of each indicator were compared against each environmental stimulus.
Heart rate variability analysis indicated that the forest environment significantly increased parasympathetic nervous activity and significantly suppressed sympathetic activity of participants compared with the urban environment. Salivary cortisol level and pulse rate decreased markedly in the forest setting compared with the urban setting. In psychological tests, forest bathing significantly increased scores of positive feelings and significantly decreased scores of negative feelings after stimuli compared with the urban stimuli.
Physiological data from this field experiment provide important scientific evidence on the health benefits of forest bathing. The results support the concept that forest bathing has positive effects on physical and mental health, indicating that it can be effective for health promotion. Despite the small sample size in this study, a very clear tendency towards positive physiological and psychological outcomes in forests was observed.
Copyright © 2010 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
Nihon Eiseigaku Zasshi. 2011 Sep;66(4):663-9.
[Physiological benefits of forest environment: based on field research at 4 sites].
[Article in Japanese]
Lee J, Park BJ, Tsunetsugu Y, Kagawa T, Miyazaki Y.
Center for Environment, Health and Field Sciences, Chiba University, Japan.
To provide scientific evidence of the health benefits of forest therapy in terms of physiological indices. Design: Within-group comparison made by conducting field experiments. Participants: Forty-eight young male adults.
Field experiments were conducted at four local sites in Japan. At each site, 12 adults participated in a three-day experiment. To compare physiological reactions between two environmental stimuli, experiments were conducted in forest and urban environments. The participants were randomly assigned to visit either the forest or an urban setting and were instructed to view the landscape in a seated position. The physiological reactions of each participant were recorded before, during, and after viewing the stimuli, and the differences in physiological indices were compared between the two groups.
Physiological data revealed that participants demonstrated significantly different reactions in the forest and urban environments. Analysis of heart rate revealed that participants showed a significantly higher ln(HF) and a lower ln(LF/HF) in the forest environment than in the urban environment. Systolic and diastolic blood pressures, pulse rate, and salivary cortisol concentration significantly decreased in the forest environment compared with the urban environment. Subjective evaluation data were generally in accordance with physiological reactions, showing significantly higher scores for "comfortable, natural, soothed, and refreshed feelings" in the forest environment than in the urban environment.
This study provided very clear scientific evidence of the physiological effects of forest therapy. Our data indicate that forest therapy can decrease stress and facilitate physiological relaxation.
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Nihon Eiseigaku Zasshi. 2011 Sep;66(4):670-6.
[Psychological relaxation effect of forest therapy: results of field experiments in 19 forests in Japan involving 228 participants].
[Article in Japanese]
Tsunetsugu Y, Park BJ, Lee J, Kagawa T, Miyazaki Y.
Department of Wood Engineering, Chiba University, Chiba, Japan.
In the present study, we aimed to clarify the psychological effects of shinrin-yoku (taking in the atmosphere of the forest) by conducting field experiments.
The experiments were conducted in 19 forested and urban areas in Japan during the 2007-2010 period. Twelve male students participated at each of the 19 areas (a total of 228 persons). Subjective ratings of "comfortable-uncomfortable", "soothing-stimulating", and "natural-artificial" feelings were conducted after each of the participants had viewed the scenery for 15 min in the forested and urban areas. A postviewing questionnaire on "stressed-refreshed" feelings was also administered and the Profile of Mood State (POMS) questionnaire was employed to assess six aspects of mood before and after viewing the sceneries.
The forest environments were perceived as significantly more "comfortable", "soothing", and "natural" than the urban environments after viewing the sceneries. The score for "refreshed feeling" was also significantly higher in the forested areas. The score for the "vigor" subscale of POMS was significantly higher after viewing the scenery in the forested areas, whereas the scores for negative feelings such as "tension-anxiety", "depression-dejection", "anger-hostility", "fatigue", and "confusion" significantly decreased.
Collectively, these results suggest that the forest environments have significant beneficial and relaxing effects on human's moods compared with the urban environments.
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Environ Health Prev Med. 2011 Sep;16(5):299-306. doi: 10.1007/s12199-010-0197-3. Epub 2011 Jan 6.
No association between the frequency of forest walking and blood pressure levels or the prevalence of hypertension in a cross-sectional study of a Japanese population.
Morita E, Naito M, Hishida A, Wakai K, Mori A, Asai Y, Okada R, Kawai S, Hamajima N.
Department of Preventive Medicine, Nagoya University Graduate School of Medicine, Tsurumai-cho, Showa-ku, Nagoya, Japan. firstname.lastname@example.org
To study the non-temporary effects of successive walks in forested areas (shinrin-yoku) on hypertension prevalence and blood pressure levels.
Data for the analysis were derived from the baseline survey of the Japan Multi-Institutional Collaborative Cohort (J-MICC) study in the Shizuoka area. Eligible participants were individuals aged 35-69 years who attended a health check-up center during 2006 and 2007. Of the 5,040 individuals who participated in the J-MICC study, Shizuoka, 4,666 were included in this analysis [3,174 men and 1,492 women; age (mean ± standard deviation) 52.1 ± 8.7 years]. The frequency of forest walking was estimated by a self-administrated questionnaire. Hypertension was defined as a systolic blood pressure ≥ 140 mmHg, a diastolic blood pressure ≥ 90 mmHg or, based on information provided in the questionnaire, the use of medication for hypertension.
After adjusting for age, body mass index (BMI), smoking status, alcohol consumption, and habitual exercise, the odds ratios of hypertension associated with forest walking once a week or more frequently, relative to less than once a month were 0.98 in men [95% confidence interval (CI) 0.68-1.42] and 1.48 (95% CI 0.80-2.71) in women. There was no significant trend between adjusted blood pressure levels and the frequency of forest walking.
The results of our cross-sectional study in a Japanese population show no association between either blood pressure levels or the prevalence of hypertension and the frequency of forest walking.