Effects of a Forest Walk on Urinary Dityrosine and Hexanoyl-Lysine in Young People: A Pilot Study.

Ai Yamada,Tokushi Horike,Yoshiko Sato,Da-Hong Wang,Masamitsu Miyanaga

doi:10.3390/ijerph17144990

Abstract

A few studies indicate exposure to forests may alleviate oxidative stress in the body. However, more evidence is needed to support this potentiality. The purpose of the current study aimed at examining whether there is any difference in urinary levels of oxidatively modified proteins or lipids—dityrosine (DT) and hexanoyl-lysine (HEL), respectively, after a forest or urban walk. The study was performed on 29 university students who took part in forest walks (Shinjo Village) in Okayama Prefecture of Japan and on 42 university students who took part in urban walks in the downtown area of Okayama City. Urine samples before and after the walks were analyzed for DT and HEL excretion. Air phytoncides during the walks were also measured. We found a decreased tendency in urinary DT and HEL (p < 0.05) in most participants after the forest walks, but not after the urban walks. We further found the total levels of air phytoncides in the forest field were 1.50 times higher compared with those in the urban field. This study suggests the possibility that regular immersion in a forest environment might contribute toward weakening of the oxidative modifications of proteins or lipids in the body.

Highlights

In the fields of preventive medicine and public health, much attention has been given in recent years to the effects of forest bathing
This study suggests the possibility that regular immersion in a forest environment might contribute toward weakening of the oxidative modifications of proteins or lipids in the body
It is known that oxidative stress is caused by a generation of excess reactive oxygen species (ROS) that exceed the capacity of antioxidant defense systems in the body to remove them

Summary

Introduction

In the fields of preventive medicine and public health, much attention has been given in recent years to the effects of forest bathing The forest environment here refers to a large area of land covered mainly by trees), such as increases in human natural killer (NK) activity and anti-cancer protein expression, decreases in blood pressure among hypertensive patients, and mental stress reduction [1,2,3,4,5]. It is known that oxidative stress is caused by a generation of excess reactive oxygen species (ROS) that exceed the capacity of antioxidant defense systems in the body to remove them. Wang et al recently reported that urinary hydrogen peroxide (H2 O2 )

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