Effect of forest bathing trips on human immune function - PubMed (original) (raw)

Effect of forest bathing trips on human immune function

Qing Li. Environ Health Prev Med. 2010 Jan.

Abstract

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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Figures

Fig. 1

Fig. 1

Effect of a forest bathing trip on natural killer (NK) activity (a) and the number of NK cells (b). Columns: Before values obtained before the trip, Day 1 values obtained after the first day of the trip, Day 2 values obtained after the second day of the trip. Data are presented as the mean ± standard deviation (SD) (n = 12). *P < 0.05, **P < 0.01, significantly different from before the trip, #P < 0.05 significantly different from day 1 by paired t test. Cited from Li et al. [2]

Fig. 2

Fig. 2

Effect of a forest bathing trip on the number of granulysin-, perforin-, and granzymes A/B-expressing cells in peripheral blood lymphocytes (PBLs). Data are presented as the mean ± SD (n = 12). *P < 0.05, **P < 0.01, significantly different from before the trip, #P < 0.05 significantly different from day 1 by the paired t test. Cited from Li et al. [2]

Fig. 3

Fig. 3

Effect of a forest bathing trip (a, n = 12) and a city tourist visit (b, n = 11) on NK activity. Data are presented as the mean ± SE. *P < 0.05, **P < 0.01, significantly different from before the trip by paired t test. Cited from Li et al. [3]

Fig. 4

Fig. 4

Effect of a forest bathing trip (a, n = 12) and a city tourist visit (b, n = 11) on granulysin- (GRN), perforin-, and granzymes (Gr) A/B-expressing cells in PBLs. Data are presented as the mean ± SE. *P < 0.05, **P < 0.01, significantly different from before the trip by paired t test. Cited from Li et al. [3]

Fig. 5

Fig. 5

Effect of a forest bathing trip on NK activity in female subjects. Data are presented as the mean ± SE (n = 13). *P < 0.05, **P < 0.01, significantly different from before the trip by the paired t test. Cited from Li et al. [4]

Fig. 6

Fig. 6

Effect of a forest bathing trip on the percentage of NK cells. Data are presented as the mean ± SE (n = 13). **P < 0.01, significantly different from before the trip by the paired t test. Cited from Li et al. [4]

Fig. 7

Fig. 7

Effect of a forest bathing trip on the levels of GRN-, perforin-, and GrA/B-expressing cells in PBLs. Data are presented as the mean ± SE (n = 13). *P < 0.05, **P < 0.01, significantly different from before the trip by paired t test. Cited from Li et al. [4]

Fig. 8

Fig. 8

Effect of the forest bathing trip on the percentage of T cells. Data are presented as the mean ± SE (n = 13). *P < 0.05, **P < 0.01, significantly different from before the trip by paired t test. Cited from Li et al. [4]

Fig. 9

Fig. 9

Effect of a forest bathing trip on adrenaline and noradrenaline concentrations in urine. a Effect of a forest bathing trip on urinary adrenaline concentration in male subjects (n = 12), b effect of a city trip on urinary adrenaline concentration in male subjects (n = 11), c effect of a forest bathing trip on urinary adrenaline concentration in female subjects (n = 13), d effect of a forest bathing trip on urinary noradrenaline concentration in female subjects (n = 13). Data are presented as the mean ± SE. *P < 0.05, **P < 0.01, significantly different from before the trip by paired t test. Cited from Li et al. [3] and [4]

Fig. 10

Fig. 10

Mechanism of forest bathing-induced induction in NK activity. AIF Apoptosis-inducing factor, Cyto-c cytochrome c

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