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What is forest medicine?

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Abstract

Imagine a new medical science that could let you know how to be more active, more relaxed and healthier with reduced stress and reduced risk of lifestyle-related disease and cancer by visiting forests. This new medical science is called forest medicine. Forest medicine encompasses the effects of forest environments on human health and is a new interdisciplinary science, belonging to the categories of alternative medicine, environmental medicine and preventive medicine. This book presents up-to-date findings in forest medicine to show the beneficial effects of forest environments on human health.

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... In Japan, a forest bathing is a short leisurely visit to a forest, called "Shinrin-yoku" in Japanese, which is similar in effect to natural aromatherapy, for the purpose of relaxation. "Shinrin" means forest and "yoku" means bathing in Japanese [1,2]. Since forests occupy 67% of the land in Japan, forest bathing is easily accessible. ...
... Since forests occupy 67% of the land in Japan, forest bathing is easily accessible. Forest bathing as a recognized relaxation and/or stress management activity and a method of preventing diseases and promoting health is becoming a focus of public attention in Japan [2]. ...
... We previously found that forest bathing enhances human natural killer (NK) activity by increasing the number of NK cells and intracellular levels of anticancer proteins such as perforin, granulysin, and granzymes in both male and female subjects [1][2][3][4][5]. The increased NK activity was shown to last for more than 30 days after a trip [3,4]. ...
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In the present study, we investigated the effects of a forest bathing on cardiovascular and metabolic parameters. Nineteen middle-aged male subjects were selected after they provided informed consent. These subjects took day trips to a forest park in Agematsu, Nagano Prefecture, and to an urban area of Nagano Prefecture as control in August 2015. On both trips, they walked 2.6 km for 80 min each in the morning and afternoon on Saturdays. Blood and urine were sampled before and after each trip. Cardiovascular and metabolic parameters were measured. Blood pressure and pulse rate were measured during the trips. The Japanese version of the profile of mood states (POMS) test was conducted before, during, and after the trips. Ambient temperature and humidity were monitored during the trips. The forest bathing program significantly reduced pulse rate and significantly increased the score for vigor and decreased the scores for depression, fatigue, anxiety, and confusion. Urinary adrenaline after forest bathing showed a tendency toward decrease. Urinary dopamine after forest bathing was significantly lower than that after urban area walking, suggesting the relaxing effect of the forest bathing. Serum adiponectin after the forest bathing was significantly greater than that after urban area walking.
... Forest therapy or "forest bathing" refers to visiting a forest or engaging in various therapeutic activities in a forest environment to improve one's health and wellbeing [1,2]. Societies have been urbanizing rapidly and more people reside in an urban environment with limited access to nature; therefore, diverse efforts including political and landscaping efforts have been made to make nature more accessible [3]. ...
... Societies have been urbanizing rapidly and more people reside in an urban environment with limited access to nature; therefore, diverse efforts including political and landscaping efforts have been made to make nature more accessible [3]. With an increasing awareness of health benefits of forest therapy, it has been implemented on diverse population [1]. Particularly, the psychological benefits of forest therapy have received special attention as people residing in urban environments have been reported to be at an increased risk of prolonged exposure to stressful situations and mental health problems [4][5][6]. ...
... The specific aims of this study were to: (1) provide a broad overview and synthesize the evidence on the usefulness of forest therapy to improve the level of depressive symptoms in adults; and (2) assess the methodological rigor and scientific evidence quality of existing research studies to guide future studies evaluating the effects of forest therapy on adults' experiencing depressive symptoms. In the present review, forest therapy was defined as visiting a forest or engaging in various therapeutic activities in a forest environment to improve one's health and wellbeing [1,2]. ...
Article
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This study systematically reviewed forest therapy programs designed to decrease the level of depression among adults and assessed the methodological rigor and scientific evidence quality of existing research studies to guide future studies. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The authors independently screened full-text articles from various databases using the following criteria: (1) intervention studies assessing the effects of forest therapy on depressive symptoms in adults aged 18 years and older; (2) studies including at least one control group or condition; (3) peer-reviewed studies; and (4) been published either in English or Korean before July 2016. The Scottish Intercollegiate Guideline Network measurement tool was used to assess the risk of bias in each trial. In the final sample, 28 articles (English: 13, Korean: 15) were included in the systematic review. We concluded that forest therapy is an emerging and effective intervention for decreasing adults’ depression levels. However, the included studies lacked methodological rigor. Future studies assessing the long-term effect of forest therapy on depression using rigorous study designs are needed.
... Forest therapy or "forest bathing" refers to visiting a forest or engaging in various therapeutic activities in a forest environment to improve one's health and wellbeing [1,2]. Societies have been urbanizing rapidly and more people reside in an urban environment with limited access to nature; therefore, diverse efforts including political and landscaping efforts have been made to make nature more accessible [3]. ...
... Societies have been urbanizing rapidly and more people reside in an urban environment with limited access to nature; therefore, diverse efforts including political and landscaping efforts have been made to make nature more accessible [3]. With an increasing awareness of health benefits of forest therapy, it has been implemented on diverse population [1]. Particularly, the psychological benefits of forest therapy have received special attention as people residing in urban environments have been reported to be at an increased risk of prolonged exposure to stressful situations and mental health problems [4][5][6]. ...
... The specific aims of this study were to: (1) provide a broad overview and synthesize the evidence on the usefulness of forest therapy to improve the level of depressive symptoms in adults; and (2) assess the methodological rigor and scientific evidence quality of existing research studies to guide future studies evaluating the effects of forest therapy on adults' experiencing depressive symptoms. In the present review, forest therapy was defined as visiting a forest or engaging in various therapeutic activities in a forest environment to improve one's health and wellbeing [1,2]. ...
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The purpose of this study was to systematically review forest therapy programs designed to decrease the level of depression among adults and subsequently identify the gaps in the literature. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The authors independently screened full-text articles from various databases using the following criteria: 1) intervention studies assessing the effects of forest therapy on depression in adults aged 18 years and over; 2) studies including at least one control group or condition; 3) been peer-reviewed; and 4) been published either in English or Korean before July 2016. The Scottish Intercollegiate Guideline Network (SIGN) measurement tool was used to assess the risk of bias in each trial. In the final sample, a total of 28 articles (English: 13, Korean: 15) were included in the present systematic review. This review concluded that forest therapy is one of the emerging and effective interventions for decreasing the level of depression in adults. However, the studies included in this review lacked methodological rigor. Future studies assessing the long-term effect of forest therapy on depression using rigorous study designs are needed.
... Terms like healing forest and forest medicine [7] are associated with forests in China, Japan, and Korea. In countries that consider a forest environment as a means of healing, there is a growing social demand to promote health and well-being by utilizing forests as a therapeutic space [8][9][10]. ...
... forest that restores the balance and harmony of the human body and provides comfort and restfulness [5,6]. Terms like healing forest and forest medicine [7] are associated with forests in China, Japan, and Korea. In countries that consider a forest environment as a means of healing, there is a growing social demand to promote health and well-being by utilizing forests as a therapeutic space [8][9][10]. ...
Article
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We aimed to understand the correlation between the microclimate environment within a forest and NVOC (Natural volatile organic compounds) concentration and the concentration of NVOC more efficiently through the prediction model method. In this study, 380 samples were collected and analyzed to examine the characteristics of NVOC emitted from a birch forest. NVOC were analyzed in May and July 2019, and measurements were performed at three different locations. Using a pump and stainless-steel tube filled with Tenax-TA, 9 L of NVOC was collected at a speed of 150 mL/h. The analysis of NVOC composition in the forest showed that it comprised α-pinene 27% and camphor 10%. Evaluation of the correlation between the NVOC concentration and the microclimate in the forests showed that the concentration increased markedly with the increase in temperature and humidity, and the concentration decreased with the increase in wind velocity. Nineteen substances in total including α-pinene and β-pinene were detected at high concentrations during the sunset. The results of the study site analysis presented a significant regression model with a R2 as high as 60.1%, confirming that the regression model of the concentration prediction of NVOC in birch forest has significant explanatory power.
... Forest therapy (or forest bathing) is defined as visiting forests to conduct treatment activities to improve one's health in a forest environment; it is known to increase immunity and improve health by utilizing various elements of nature, such as fragrance and landscape [4,5]. ...
Article
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Forest therapy involves visiting forests or conducting forest-based treatment activities to improve one’s health. Studies have investigated the health benefits of forests, but consensus has not been reached. This study comprised a systematic review and meta-analysis to determine how forest therapy affects the physiological and psychological health of adults. The Cumulative Index to Nursing and Allied Health Literature, Embase, and Medline databases were searched on 31 August 2021. Systematic review and meta-analysis, risk evaluation, GRADE evaluation, and advertisement effect evaluation were performed for each article. The effect size was calculated by dividing blood pressure as a physiological indicator and depression as a psychological indicator. Of the 16,980 retrieved studies, 17 were selected based on the inclusion criteria. Of these, eight studies were included in the meta-analysis. The effect size of forest therapy on improving systolic and diastolic blood pressure was not significant; however, it significantly reduced depression. While the results have limited generalizability due to the inclusion of few studies, the effects of forest therapy on reducing depression have been confirmed. Since the application of forest therapy was heterogeneous in these studies, a moderator effect analysis or subgroup analysis in meta-analysis should be performed in the future.
... 33 Pamatojoties uz daudziem meža vides iedarbības pētījumiem, Japānā ir izveidots pat īpašs mežu medicīnas virziens, kas paredz regulārus mežu apvidu apmeklējumus un ārstniecības iestāžu ierīkošanu mežos un dārzos. 34 Latviešu tautas tradīcijā dabas un meža labvēlīgais spēks izsenis ticis sajusts un godāts. ...
Article
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Wholeness means uniformity and completeness, as well as health in a broader sense. Wholeness is understood as totality that consists of physical and mental health, as well as attitude towards life and emotional balance. In Latvian folklore and tradition, health has been highlighted as a special value, which could be inherited, given by God and selfmaintained, following the advice provided by the tradition. The author examines the key values portrayed in Latvian folklore, which have been related to the wholeness, healthy lifestyle and health maintenance or preventive measures.
... Current research findings also underline the additional health benefits from outdoor recreation activities in natural environments (e.g. Li, 2012;Pietilä, 2014;Von Lindern, 2014). Recreation and health benefits jointly result from the recreational environment provided by different ecosystems, inter alia forests, meadows, or a vista, together with multiple inputs such as human, social, and built capital, including conventional goods and services, e.g. ...
Conference Paper
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In this study we define the spatial allocation for the value of recreation ecosystem services in Finland. The Finnish national recreation inventory, a representative survey data of Finnish recreationists and their recreation visits (last close-to-home visit and overnight nature trip), allows us to estimate the annual number of recreation trips to various area types: 1) areas used based on everyman’s right, 2) state-owned recreation and nature conservation areas and 3) leisure homes and their surroundings. To obtain the values of recreation visits to each area type in different parts of Finland, we use aggregate travel cost method. GIS is used to map the regional visits as well as their values. Results emphasize the relative importance of close-to-home recreation compared to overnight nature trips in total number of visits and values. The spatial allocation of close-to-home values followed population density as the type of ecosystems had minor role. Majority of the close-to-home recreation benefits were obtained from the areas that are used based on everyman’s rights. The approach offered an example how to utilize the national recreation data, available also in some other European countries, to define and map the value of recreational ecosystem services.
... Diseases caused by stress and physical inactivity are currently one of the main reasons of illness in the developed world [76][77][78]. At the same time, many scientific studies have shown that interactions with nature can provide a positive influence on mental and physical health and self-awareness [77,[79][80][81]. Moreover, multiple studies have indicated that activities undertaken in forests reduce stress [82][83][84] and the amount of the stress hormone cortisol [85]. ...
Article
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There are many ethnobotanical studies on the use of wild plants and mushrooms for food and medicinal treatment in Europe. However, there is a lack of comparative ethnobotanical research on the role of non-wood forest products (NWFPs) as wild food and medicine in local livelihoods in countries with different socio-economic conditions. The aim of this study was to compare the present use of wild food and medicine in three places representing different stages of socio-economic development in Europe. Specifically we explore which plant and fungi species people use for food and medicine in three selected rural regions of Sweden, Ukraine and the Russian Federation. We studied the current use of NWFPs for food and medicine in three rural areas that represent a gradient in economic development (as indicated by the World Bank), i.e., Småland high plain (south Sweden), Roztochya (western Ukraine), and Kortkeros (Komi Republic in North West Russia). All areas were characterised by (a) predominating rural residency, (b) high forest coverage, and (c) free access to NWFPs. A total of 205 in-depth semi-structured interviews were conducted with local residents in the three study areas. The collected NWFPs data included (1) the species that are used; (2) the amount harvested, (3) uses and practices (4) changes over time, (5) sources of knowledge regarding the use of NWFPs as wild food and medicine and (6) traditional recipes. In Sweden 11 species of wild plant and fungi species were used as food, and no plant species were used for medicinal purposes. In Ukraine the present use of NWFPs included 26 wild foods and 60 medicinal species, while in Russia 36 food and 44 medicinal species were reported. In the economically less developed rural areas of Ukraine and Russia, the use of NWFPs continues to be an important part of livelihoods, both as a source of income and for domestic use as food and medicine. In Sweden the collection of wild food has become mainly a recreational activity and the use of medicinal plants is no longer prevalent among our respondents. This leads us to suggest that the consumption of wild food and medicine is influenced by the socio-economic situation in a country.
... Current research findings also underline the additional health benefits from outdoor recreation activities in natural environments (e.g. Li, 2012;Pietilä, 2014;Von Lindern, 2014). Recreation and health benefits jointly result from the recreational environment provided by different ecosystems, inter alia forests, meadows, or a vista, together with multiple inputs such as human, social, and built capital, including conventional goods and services, e.g. ...
... An alternative health promotion approach is forest therapy. It is a complementary and alternative treatment method, with the forest environment to be the foundation and the preventive medicine to be the core (Li, 2013;Zhang et al., 2020;Stier-Jarmer et al., 2021). Improving physical and mental health and preventing disease is the end goal of forest therapy by carrying out a set of activities in a specific forest environment to make people consciously use all five senses, such as forest retreats, forest walks, and others (Lee et al., 2017;Zhang et al., 2020;Antonelli et al., 2021;Stier-Jarmer et al., 2021). ...
Article
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Exposure to forest environments promotes human health. The number of relevant studies in this area has increased rapidly. However, an overall review of relevant analyses from the perspectives of bibliometrics and visualization is lacking. A scientometric analysis of 2,545 publications from 2007 to 2021 via the Web of Science database was conducted to identify the knowledge structure and frontiers objectively. The publications were subsequently analyzed in terms of the distribution of journals and countries, citation bursts, major subject areas, and evolutionary stages. The findings showed that the knowledge foundation of forest therapy was multidisciplinary with most published in the fields of environmental sciences and ecology but lacking input from social disciplines. The research hotspots evolved from the early focus on individual benefits obtained from nature to increasing attention on human well-being at the social-ecological scale. More rigorous experiments with strict randomized controlled trials and blinding are needed to accommodate the trend of forest therapy toward non-pharmacological treatments. According to Shneider’s four-stage theory, forest therapy research is in the third stage of the scientific research process. More future studies utilizing novel technologies and decision-making frameworks to solve practical issues are needed for introducing health into policies and promoting human well-being.
... The methods applied in forest therapy and prevention programs vary considerably. A key component is the perception of the forest environment with all five senses ("fivesense experience", including vision, smell, hearing, touch, and taste), which can be combined with meditation and walking or hiking in the forest, as well as various recreational activities and cognitive behavioural therapy [10]. In Germany, forest therapy and forest bathing have been successfully combined with classical naturopathic elements, such as water immersion (e.g., Kneipp therapy) and climatotherapy (climatic terrain cure, heliotherapy, fresh-air rest cure) to enhance the health benefits of forest therapy programs [11]. ...
Article
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Background: The aim of this systematic review of systematic reviews was to identify, summarise, and synthesise the available evidence of systematic reviews (SRs) and meta-analyses (MAs) on the preventative and therapeutic psychological and physical effects of forest-based interventions. Methods: Both bibliographic databases and grey literature sources were searched for SRs and MAs published until May 2020. Eight databases were searched for relevant articles: MEDLINE, Embase, Web of Science, Cochrane Library, PsycInfo, CiNii, EBSCO, and Scopus. Grey literature was sourced from Google Scholar and other web-based search tools. SRs and MAs that included randomised controlled (RCT), non-randomised controlled (NRCT), and non-controlled trials (NCT) on health-related effects of forest-based interventions were eligible if they had searched at least two databases. The methodological quality of eligible reviews was assessed by AMSTAR-2. Results: We evaluated 11 systematic reviews covering 131 different primary intervention studies, mostly from Asian countries, three of which included supplementary meta-analyses. The quality assessment resulted in moderate confidence in the results of two reviews, low confidence in six, and critically low confidence in three. The results of the eight moderate and low-rated reviews indicated that forest-based interventions are beneficial to the cardiovascular system, immune system, and mental health (in the areas of stress, depression, anxiety, and negative emotions). Evidence for the effectiveness of forest-based interventions on metabolic parameters in adults, the severity of atopic dermatitis in children and adolescents, and social skills and sociality in healthy primary school children was weak. Discussion/Conclusions: Evidence suggests beneficial therapeutic effects of forest-based interventions on hypertension, stress, and mental-health disorders, such as depression and anxiety. Changes in immunological and inflammatory parameters after forest therapy should be verified in bio-geographically native forests. In the future, more attention should be paid to careful planning, implementation, and reporting of primary studies and to systematic reviews on the effects of forest-based interventions.
... Forests are recognized as one of the core health resources because they provide excellent ecological environments and rich scenic views that create a safer and more relaxing environment than other types of vegetation [26]. At present, most scientific research mainly focusses on the difference in the effect of the urban-forest dichotomy, and results proved the good performance of forests in relation to health benefits [27]. ...
Article
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Short-term exposure to a forest environment is beneficial to human physiological and psychological health. However, there is little known about the relationship between the restorative perception of environment and physiological and psychological restoration achieved by experiencing the forest environment. This study evaluated the relationship between the restorative perception of different types of forests and human physiological and psychological effects. A sample of 30 young adult students from Beijing Forestry University was exposed to coniferous, deciduous, and mixed forests as well as an urban site. Restorative perception of the environment was measured using the PRS questionnaire. Restorative effects were measured using physiological indicators (blood pressure and heart rate) and three psychological questionnaires (Restorative Outcome Scale; Subjective Vitality Scale; Warwick–Edinburgh Mental Well-being Scale). The results demonstrated the following: (1) There were significant differences in the perceived restorative power of the three types of forests, with the highest level in the mixed forest, followed by the coniferous forest and the deciduous forest. (2) All types of forests were beneficial to physiological and psychological restoration. The mixed forest had the greatest effect in lowering blood pressure and heart rate as well as increasing vitality, while the coniferous forest had the strongest increases in psychological restoration and positive mental health. (3) The level of perceived restorative power of environment was positively related to the physiological and psychological restoration. These findings provide practical evidence for forest therapy that can maximize the restorative potential of forests.
... There is quite a variety of methods applied to forest therapy. The critical element of forest therapy is recognition in the forest environment, including the five senses, which can be combined with meditation, forest walking, various recreational activities, and cognitive behavioral therapy [26]. ...
Article
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This systematic review and meta-analysis aimed to summarize the effects of forest therapy on depression and anxiety using data obtained from randomized controlled trials (RCTs) and quasi-experimental studies. We searched SCOPUS, PubMed, MEDLINE(EBSCO), Web of science, Embase, Korean Studies Information Service System, Research Information Sharing Service, and DBpia to identify relevant studies published from January 1990 to December 2020 and identified 20 relevant studies for the synthesis. The methodological quality of eligible primary studies was assessed by ROB 2.0 and ROBINS-I. Most primary studies were conducted in the Republic of Korea except for one study in Poland. Overall, forest therapy significantly improved depression (Hedges’s g = 1.133; 95% confidence interval (CI): −1.491 to −0.775) and anxiety (Hedges’s g = 1.715; 95% CI: −2.519 to −0.912). The quality assessment resulted in five RCTs that raised potential concerns in three and high risk in two. Fifteen quasi-experimental studies raised high for nine quasi-experimental studies and moderate for six studies. In conclusion, forest therapy is preventive management and non-pharmacologic treatment to improve depression and anxiety. However, the included studies lacked methodological rigor and required more comprehensive geographic application. Future research needs to determine optimal forest characteristics and systematic activities that can maximize the improvement of depression and anxiety.
Article
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The present study aimed to evaluate the effects of physical activities on human health in forests in countryside and rural areas. The test experiment was conducted in a countryside forest, whereas the controlled experiment was conducted in an urban area where the study participants resided. A total of 22 participants (aged 20.9 ± 1.3 years) were evaluated in this study. Heart rate variability and salivary cortisol level were used as indices of physiological conditions, and semantic differential method, profile of mood states (POMS), and state-trait anxiety inventory (STAI) were used to evaluate the participants’ emotional states. The participants were asked to walk around forest and urban areas for 15 min. The results were as follows. As compared to the urban area, in the forest area, 1) the power of the high-frequency (HF) component of the heart rate variability (HRV) was significantly higher; 2) low-frequency (LF)/(LF+HF) was significantly lower; 3) salivary cortisol level was significantly lower; 4) the participants felt more comfortable, natural, relaxed, and less anxious and showed higher levels of positive emotions and lower levels of negative emotions. Consequently, walking in the forest area induces relaxing short-term physiological and psychological effects on young people living in urban areas.
Article
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Many studies have proved that having nature experiences in forests is conducive to human physiological and psychological health. However, currently there is little research focusing on the effects of forest characteristics and the experiential characteristics of nature experiences on changes in health. In the study, three types of forest (mixed forest; deciduous forest; coniferous forest) and an urban site were used to measure the effects of these environments on participants’ physiological and psychological restoration after nature experience activities (sitting and walking activities). The study participants were 30 young adult students from Beijing Forestry University. Restorative effects were measured by physiological indicators (blood pressure and heart rate) and four psychological questionnaires (Profile of Mood States (POMS); Restorative Outcome Scale (ROS); Subjective Vitality Scale (SVS); Warwick-Edinburgh Mental Well-being Scale (WEMWBS)). Results demonstrated that all types of forest were beneficial to lower blood pressure and heart rate as well as to reduce negative feelings while boosting positive emotions. The mixed forest was more effective in lowering blood pressure and heart rate as well as increasing vitality. The levels of restoration and positive mental health increased significantly, while all subscales of the POMS (with the exception of vigor) decreased greatly in the coniferous forest. Relative to the sitting activity, obvious decreases in blood pressure and negative emotions were observed, while significant increases in restoration, vitality and positive mental health were observed after the walking activity. In conclusion, the impact on subjects’ health restoration varied with different forest characteristics, and the experiential characteristics of exposure may be helpful for creating supportive interventions and lifting the benefits of forest therapy as people interact with the forest.
Article
Humans have enjoyed forest environments for ages because of the quiet atmosphere, beautiful scenery, mild climate, special good smell, and fresh, clean air. In Japan, since 2004, a serial studies have been conducted to investigate the effect of forest bathing trips on human health. A new science called Forest Medicine was established in 2012. The Forest Medicine is a new interdisciplinary science, belonging to the categories of alternative medicine, environmental medicine and preventive medicine, which encompasses the effects of forest environments on human health. It has been reported that forests have the following beneficial effects on human health. 1 Forest bathing can increase human natural killer (NK) activity and the number of NK cells and the intracellular levels of anti-cancer proteins suggesting the preventive effect on cancers. 2 Forest bathing can reduce blood pressure, heart rate, stress hormones such as urinary adrenaline and noradrenaline and salivary cortisol. 3 Forest bathing can increase the activity of parasympathetic nerve and reduce the activity of sympathetic nerve. 4 Forest bathing also can increase the levels of serum adiponectin and dehydroepiandrosterone sulfate. 5 Forest bathing also can reduce the scores for anxiety, depression, anger, fatigue and confusion and increased the score for vigor in the POMS test showing psychological effect. 6. Forest bathing also can reduce blood glucose levels in diabetic patients. 7 These findings suggest that forest bathing may have preventive effects on life-style related disease.
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Children living in foster care group homes are more likely to have physical, mental, and social health problems due to parental abuse, neglect, and family breakdown. The purpose of the current study was to develop and apply the urban forest-based health promotion program on children living in group homes in Korea to investigate its effects on perceived health, psychological health, and connectedness to nature. Eight children (mean age = 12.13 [SD = 1.25] years) from three group homes participated in the study. The intervention was conducted individually for each group home once per week for 8 weeks. Quantitative and qualitative data were collected and analyzed. Participants showed significant improvement in restoration. Six themes were identified that reflect participants' experience and the effectiveness of the urban forest-based health promotion program. This program may be considered a possible intervention to promote children's psychosocial health and connectedness to nature. Continuous efforts are needed to further examine the program's effectiveness. [Journal of Psychosocial Nursing and Mental Health Services, xx(x), xx-xx.].
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In Japan, a forest bathing trip, called "Shinrinyoku" in Japanese, is a short, leisurely visit to a forest; it is regarded as being similar to natural aromatherapy. This review focuses on the effects of forest bathing trips on human immune function. Beginning in 2005, adult Japanese individuals, both male and female, participated in a series of studies aimed at investigating the effect of forest bathing trips on human immune function. The subjects experienced a 3-day/2-night trip to forest areas, and blood and urine were sampled on days 2 (the first sampling during each trip) and 3 (the second sampling during each trip), and on days 7 and 30 after the trips. Natural killer (NK) activity, the numbers of NK, granulysin-, perforin-, and granzymes A/B-expressing lymphocytes in the blood, and the concentration of urinary adrenaline were measured. The same measurements were made before the trips on a normal working day as a control. The mean values of NK activity and the numbers of NK, granulysin-, perforin-, and granzymes A/B-expressing cells on forest bathing days were significantly higher than those on the control days, whereas the mean values of the concentration of urinary adrenaline on forest bathing days were significantly lower than that on the control days in both male and female subjects. The increased NK activity lasted for more than 30 days after the trip, suggesting that a forest bathing trip once a month would enable individuals to maintain a higher level of NK activity. In contrast, a visit to the city as a tourist did not increase NK activity, the numbers of NK cells, or the level of intracellular granulysin, perforin, and granzymes A/B. These findings indicate that forest bathing trips resulted in an increase in NK activity, which was mediated by increases in the number of NK cells and the levels of intracellular granulysin, perforin, and granzymes A/B.
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Metabolic syndrome is diagnosed according to several criteria. Of these, some require glucose intolerance and others require obesity for the diagnosis. We investigated the relationship between metabolic risk factor clustering and cardiovascular disease (CVD) mortality stratified by high blood glucose or obesity. We followed 7,219 Japanese men and women without a history of CVD for 9.6 years. We defined high blood pressure, high blood glucose, high triglycerides, low HDL cholesterol, and obesity as metabolic factors. The multivariate adjusted hazard ratio (HR) for CVD mortality according to the number of clustering metabolic factors was calculated using the Cox proportional hazards model. During follow-up, 173 participants died of CVD. The numbers of metabolic risk factors and CVD mortality were positively correlated (P(trend) = 0.07). The HR was obviously higher among participants with than among those without high blood glucose and clustering of > or =2 other metabolic risk factors (HR 3.67 [95% CI 1.49-9.03]). However, the risk increase was only modest in participants without high blood glucose even if they had > or =2 other metabolic risk factors (1.99 [0.93-4.28]). Conversely, metabolic risk factor clustering was related to CVD mortality irrespective of obesity. Our findings suggest that glucose tolerance plays an important role in CVD mortality. Because the prevalence of nonobese participants with several metabolic risk factors was quite high and their CVD risk was high, excluding them from the diagnosis of metabolic syndrome because of the absence of obesity might overlook their risk.
Article
We previously reported that 2-night/3-day trips to forest parks enhanced human NK activity, the number of NK cells, and intracellular anti-cancer proteins in lymphocytes, and that this increased NK activity lasted for more than 7 days after the trip in both male and female subjects. In the present study, we investigated the effect of a day trip to a forest park on human NK activity in male subjects. Twelve healthy male subjects, aged 35-53 years, were selected after giving informed consent. The subjects experienced a day trip to a forest park in the suburbs of Tokyo. They walked for two hours in the morning and afternoon, respectively, in the forest park on Sunday. Blood and urine were sampled in the morning of the following day and 7 days after the trip, and the NK activity, numbers of NK and T cells, and granulysin, perforin, and granzyme A/B-expressing lymphocytes, the concentration of cortisol in blood samples, and the concentration of adrenaline in urine were measured. Similar measurements were made before the trip on a weekend day as the control. Phytoncide concentrations in the forest were measured. The day trip to the forest park significantly increased NK activity and the numbers of CD16(+) and CD56(+) NK cells, perforin, granulysin, and granzyme A/B-expressing NK cells and significantly decreased CD4(+) T cells, the concentrations of cortisol in the blood and adrenaline in urine. The increased NK activity lasted for 7 days after the trip. Phytoncides, such as isoprene, alpha-pinene, and beta-pinene, were detected in the forest air. These findings indicate that the day trip to the forest park also increased the NK activity, number of NK cells, and levels of intracellular anti-cancer proteins, and that this effect lasted for at least 7 days after the trip. Phytoncides released from trees and decreased stress hormone levels may partially contribute to the increased NK activity.
Article
We previously reported that the forest environment enhanced human natural killer (NK) cell activity, the number of NK cells, and intracellular anti-cancer proteins in lymphocytes, and that the increased NK activity lasted for more than 7 days after trips to forests both in male and female subjects. To explore the factors in the forest environment that activated human NK cells, in the present study we investigate the effect of essential oils from trees on human immune function in twelve healthy male subjects, age 37-60 years, who stayed at an urban hotel for 3 nights from 7.00 p.m. to 8.00 a.m. Aromatic volatile substances (phytoncides) were produced by vaporizing Chamaecyparis obtusa (hinoki cypress) stem oil with a humidifier in the hotel room during the night stay. Blood samples were taken on the last day and urine samples were analysed every day during the stay. NK activity, the percentages of NK and T cells, and granulysin, perforin, granzyme A/B-expressing lymphocytes in blood, and the concentrations of adrenaline and noradrenaline in urine were measured. Similar control measurements were made before the stay on a normal working day. The concentrations of phytoncides in the hotel room air were measured. Phytoncide exposure significantly increased NK activity and the percentages of NK, perforin, granulysin, and granzyme A/B-expressing cells, and significantly decreased the percentage of T cells, and the concentrations of adrenaline and noradrenaline in urine. Phytoncides, such as alpha-pinene and beta-pinene, were detected in the hotel room air. These findings indicate that phytoncide exposure and decreased stress hormone levels may partially contribute to increased NK activity.
Article
To explore the effect of forest bathing on the human immune system, we investigated the effect of phytoncides (wood essential oils) on natural killer (NK) activity and the expression of perforin, granzyme A and granulysin in human NK cells. We used NK-92MI cell, an interleukin-2 independent human NK cell line derived from the NK-92 cell, in the present study. NK-92MI cells express the CD56 surface marker, perforin, granzyme A, and granulysin by flow cytometry and are highly cytotoxic to K562 cells in chromium release assay. Phytoncides significantly increase cytolytic activity of NK-92MI cells in a dose-dependent manner and significantly increase the expression of perforin, granzyme A, and granulysin in the NK-92MI cells. Phytoncides also partially, but significantly, restore the decreased human NK activity and the decreased perforin, granzyme A, and granulysin expression in NK-92MI cells induced by dimethyl 2,2-dichlorovinyl phosphate (DDVP), an organophosphorus pesticide. Pretreatment with phytoncides partially prevents DDVP-induced inhibition of NK activity. Taken together, these data indicate that phytoncides significantly enhance human NK activity and this effect is at least partially mediated by induction of intracellular perforin, granzyme A, and granulysin.