Comparison of Effect of Two-Hour Exposure to Forest and Urban Environments on Cytokine, Anti-Oxidant, and Stress Levels in Young Adults

Abstract

The purpose of this study was to investigate the effect of two-hour exposure to a forest environment on cytokine, anti-oxidant and stress levels among university students and to compare the results to those measured in urban environments. Forty-one subjects were recruited. For our crossover design, subjects were divided into two groups based on similar demographic characteristics. Group A remained in the urban environment and was asked to perform regular breathing for 2 h. Blood samples were collected and the serum levels of cytokines including interleukin-6 (IL-6), IL-8, tumor necrosis factor-α (TNF-α), and glutathione peroxidase (GPx) were examined. Subjects were moved to a small town in a rural area for an equal amount of time to exclude carryover effects, and then remained for another 2 h in a forest environment. The second set of blood samples was collected to assess the effect of exposure to the forest environment. Using the same method, Group B was first exposed to the forest environment, followed by exposure to the urban environment. Blood samples collected after the subjects were exposed to the forest environment showed significantly lower levels of IL-8 and TNF-α compared to those in samples collected after urban environment exposure (10.76 vs. 9.21, t = 4.559, p < 0.001, and 0.97 vs. 0.87, t = 4.130, p < 0.001). The GPx concentration increased significantly after exposure to the forest environment (LnGPx = 5.09 vs. LnGPx = 5.21, t = −2.039, p < 0.05).

Neuroprotective Effects of Limonene (+) against Aβ42-Induced Neurotoxicity in a <i>Drosophila</i> Model of Alzheimer’s Disease

“…5) Forest bathing is also suggested to have therapeutic effects for neurodegenerative diseases, by decreasing both heart rate and blood pressure and increasing parasympathetic nerve activity in affected individuals. 11) Furthermore, exposure to the forest environment significantly reduces interleukin-6 and elevates the level of glutathione peroxidase, 12) which are involved in the defense against pathogens and the reduction of oxidative stress, respectively. 13,14) In addition, forest bathing has been proven to decrease malondialdehyde levels, which is a sign of oxidative stress.…”

How Should Forests Be Characterized in Regard to Human Health? Evidence from Existing Literature

“…Terpenes that relevantly affect cellular and animal systems have shown anti-inflammatory, anti-tumorigenic or neuroprotective activities [13]. Only five of the studies in our review measured terpene levels in forest air, identifying mainly alpha-and beta-pinene, tricyclene, camphene, limonene, camphor, alpha-phellandrene, carene and isoprene [21][22][23][24][25]. Lee et al (2018) significantly associated alpha-phellandrene with an acute insulin reaction, consistent with another in vivo study where alpha-phellandrene increased immune responses [84].…”

“…The specific forest variables identified were: tree density (five articles), diameter at breast height (two articles), biodiversity level (one article), species dominance (one article), tree height (one article), BVOCs concentrations (five articles), air quality (four articles) and pollutant concentrations (one article). The main BVOCs identified by the five studies that reported concentrations were alpha-and beta-pinene, tricyclene, camphene, limonene, camphor, alpha-phellandrene, carene and isoprene [21][22][23][24][25]. Table 1.…”

Much More Than a Pleasant Scent: A Review on Essential Oils Supporting the Immune System

“…In a work conducted by Im and colleagues among university students, serum IL-8 and TNFα levels were significantly decreased after a two-hour exposure to a forest environment compared to those after exposure to an urban environment suggesting a reduction in inflammation [79]. Mao and co-workers [80] demonstrated a significant reduction of the level of IL-6 in the sera of elderly patients with essential hypertension after a seven-day forest bathing trip with two, 1.5 h walks daily, compared to its baseline level.…”