Abstract
Various formats of forest bathing have been receiving increasing attention owing to their perspectives in health promotion and the treatment of chronic lifestyle diseases. The majority of field studies are still being conducted in the Far Eastern region, and they often make psychological assessments mainly in the green season. In our pretest–posttest field experiment, twelve healthy, working-age volunteers participated in a 2-h leisurely forest walking program, first in the green season (May) and then in the winter season (January), in the Mecsek Hills, next to Pécs, Hungary. Systolic blood pressure decreased after the trips both in late spring and in the winter. Based on changes in the expressions of CD69, an early activation marker, NKG2D, a major recognition receptor, perforin, granzyme B, and TIM-3, an inhibitory immune checkpoint molecule, on CD8+ cytotoxic T, NK, NKdim, NKbright, and NKT cells, we detected the stimulation of NKbright cells and activation of all examined immune cell subsets in the green season. In the winter, a slight activating and an interesting balancing effect regarding TIM-3 could be observed considering our finding that basal (pretest) TIM-3 expression by NK cells was significantly lower in the winter. Our work expands the knowledge on and potentials of forest medicine.
Highlights
Li and colleagues found in a series of studies that the natural killer (NK) cell number and activity and the percentages of perforin, granulysin, and granzyme A/B-expressing cells among peripheral blood lymphocytes significantly increased after a forest bathing trip compared to before the trip in healthy male [2] as well as healthy female subjects [3]
Systolic blood pressure was found to become significantly lower owing to the forest trip in late spring as well as in winter (Figure 3)
Values of routine clinical laboratory parameters, including total white blood cell count, granulocyte, lymphocyte, and monocyte counts, red blood cell count, hemoglobin concentration, platelet count, serum sodium and potassium concentrations, serum levels of aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), urea, creatinine, and C-reactive protein, and fasting plasma glucose, measured before the trip did not differ from the values registered after the trip, either in May or in January
Summary
The effects of the forest environment on human health and well-being have become a growing field of research interest in the last decade due to its overall beneficial impact. Field experiments were initialized in Japan investigating the effects of a forest bathing trip (“Shinrin-yoku”), which is traditionally a three-day/two-night trip to forest areas involving short, leisurely walks within the forest [1]. A similar city trip to places without forests did not lead to such immunological changes [4]. A forest bathing trip decreased the adrenaline concentration in urine [3,4], while a city trip did not [4]
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