nebligen Wald
nebligen Wald

The science behind
What does research say?

Image by Satyawan Narinedhat

Science

Exposure to nature and green environments is increasingly recognized as an important resource for stress recovery and general health (1, 2). The forest and its health-promoting effects have recently attracted growing attention in the international scientific world.

Just recently a study with more than 19,000 participants proved that spending at least 120 minutes a week in nature is associated with good health and well-being (3).

More studies, especially from Asia, have reported that exposure to the forest environment promotes recovery and relaxation and has positive effects on both body and mind. Here you will find a brief overview of the current state of knowledge in the field of forest therapy, which is far from complete. 

 

Cardiovascular System

A significant number of scientific studies have reported that spending time in a forest leads to a significant reduction in blood pressure and thus reduces the risk of cardiovascular disease (4). This effect was observed in both younger and older study participants (5-6)
The reduction in blood pressure was most pronounced in people with moderate hypertension, which shows that these people in particular benefit from forestbased interventions (7).

 

In another study, positive effects of the forest were observed in patients with chronic heart failure.
After spending time in the forest, inflammatory mediators and oxidative stress decreased (8).
In addition, it was reported that spending time in the forest has the potential to delay the development of atherosclerosis (9).

 

Immune system

Whether the forest has a positive effect on our immune system and thus contributes to preventing or fighting common diseases is an interesting question. Various scientific studies have describe that so-called phytoncides (terpenes), which are secreted from trees and plants, strengthen the immune defense. In particular, the studies of Prof. Li, a Japanese pioneer in the field of forest therapy, deserve special mention.

Within different studies, he was able to show that spending time in the forest leads to a significant increase in natural killer (NK) cells in the of blood of female and male study participants. NK cells are important players in the innate immune system that recognize and kill both virus-infected and tumor cells. Furthermore, he showed that after spending time in the forest, NK cell activity was increased while the concentration of stress hormones significantly decreased (10-13).

Similar observations were made in a study by Im et al. It was reported that the subjective stress load and the values of various inflammatory mediators were significantly reduced after a two-hour stay in the forest compared to a stay of the same length in the city (14).

Taken together, it is suggested that spending time in the forest can boost the body's immune system.

Image by Satyawan Narinedhat

Literature:

[1]        Stier-Jarmer M, Throner V, Kirschneck M, Immich G, Frisch D, Schuh A. The Psychological and Physical Effects of Forests on Human Health: A Systematic Review of Systematic Reviews and Meta-Analyses. Int J Environ Res Public Health. 2021 Feb 11;18(4):1770

[2]        Schuh, A.; Immich, G. Waldtherapie—Das Potential des Waldes für Ihre Gesundheit; Springer-Verlag: Berlin/Heidelberg, Germany, 2019.

[3]        White MP, Alcock I, Grellier J, Wheeler BW, Hartig T, Warber SL, Bone A, Depledge MH, Fleming LE. Spending at least 120 minutes a week in nature is associated with good health and wellbeing. Sci Rep. 2019 Jun 13;9(1):7730.

[4]        Ideno Y, Hayashi K, Abe Y, Ueda K, Iso H, Noda M, Lee JS, Suzuki S. Blood pressure-lowering effect of Shinrin-yoku (Forest bathing): A systematic review and meta-analysis. BMC Complement. Altern. Med. 2017, 17, 409.

[5]        Hassan A, Tao J, Li G, Jiang M, Aii L, Zhihui J, Zongfang L, Qibing C. Effects of Walking in Bamboo Forest and City Environments on Brainwave Activity in Young Adults. Evid Based Complement Alternat Med. 2018 Feb 11;2018:9653857.

[6]           Mao GX, Cao YB, Lan XG, He ZH, Chen ZM, Wang YZ, Hu XL, Lv YD, Wang GF, Yan J. Therapeutic effect of forest bathing on human hypertension in the elderly. J Cardiol. 2012;60:495–502

[7]        Ohe Y, Ikei H, Song C, Miyazaki Y. Evaluating the relaxation effects of emerging forest-therapy tourism: A multidisciplinary approach. Tour Manag. 2017. 62: 322-334

[8]        Mao GX, Cao YB, Yang Y, Chen ZM, Dong JH, Chen SS, Wu Q, Lyu XL, Jia BB, Yan J, Wang GF. Additive Benefits of Twice Forest Bathing Trips in Elderly Patients with Chronic Heart Failure. Biomed Environ Sci. 2018 Feb;31(2):159-162

[9]        Lee JY, Lee DC. Cardiac and pulmonary benefits of forest walking versus city walking in elderly women: A randomised, controlled, open-label trial. Eur J Integr Med. 2014. 6:5-11

[10]         Li Q, Morimoto K, Nakadai A, Inagaki H, Katsumata M, Shimizu T, Hirata Y, Hirata K, Suzuki H, Miyazaki Y, Kagawa T, Koyama Y, Ohira T, Takayama N, Krensky AM, Kawada T. Forest bathing enhances human natural killer activity and expression of anti-cancer proteins. Int J Immunopathol Pharmacol. 2007 Apr-Jun;20(2 Suppl 2):3-8.

[11]        Li Q, Morimoto K, Kobayashi M, Inagaki H, Katsumata M, Hirata Y, Hirata K, Shimizu T, Li YJ, Wakayama Y, Kawada T, Ohira T, Takayama N, Kagawa T, Miyazaki Y. A forest bathing trip increases human natural killer activity and expression of anti-cancer proteins in female subjects. J Biol Regul Homeost Agents. 2008 Jan-Mar;22(1):45-55.

[12]        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.

[13]      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.

[14]      Im SG, Choi H, Jeon YH, Song MK, Kim W, Woo JM. Comparison of Effect of Two-Hour Exposure to Forest and Urban Environments on Cytokine, Anti-Oxidant, and Stress Levels in Young Adults. Int J Environ Res Public Health. 2016 Jun 23;13(7):625.