The therapeutic benefits
of forest bathing may be difficult to fully explain with only phytoncides, but most likely, the green scenery, soothing
sounds of streams and waterfalls, and natural aromas of wood, plants and
flowers in these complex ecosystems all play a part. Forest therapy is a
good example of how our own health is dependent on the health of our natural
A recent review of field experiments across Japan compared physical markers of
stress in natural environments to those in city settings. 280 adults spent time
in forest and urban areas on alternate days. Compared to city environments,
forest settings were associated with lower levels of cortisol, slower heart
rates, lower blood pressure, greater activity of parasympathetic nerves that
promote relaxation, and reduced activity of sympathetic nerves associated with
“fight or flight” reactions to stress.
Another study of forest bathing measured fluctuations in salivary amylase, an
indicator of changes in sympathetic nervous activity, and also concluded that
forests were associated with less environmental stress.
Researchers have studied the psychological effects of forest bathing as well.
Almost 500 Japanese adults were surveyed on days they spent time in a forest
and also in their normal environment. Statistical analyzes revealed that,
compared to their normal environments, inside a forest the participants
reported significantly less depression and hostility, and felt significantly
more lively. And the greater the level of stress individuals experienced, the
greater the positive effects of forest bathing. Researchers concluded that
forests are “therapeutic landscapes” and that forest bathing may decrease the
risk of stress-related diseases.
Lower Blood Sugar
Forest therapy may also help control blood sugar. A Japanese study followed 87
adults diagnosed with type-two diabetes for six years. During this time,
participants walked in a forest for 3 or 6 kilometers (1.9 or 3.7 miles),
depending on their physical ability, on nine different occasions. At the end of
the study, researchers found that the forest walkers had lower blood glucose
(synonymous with blood sugar), improved insulin sensitivity, and decreased
levels of hemoglobin A1c, an indicator of how well blood glucose has been
controlled over the past 3 months.
This wasn’t a controlled study and, in general, any form of exercise practiced
regularly can help improve blood sugar regulation in people with diabetes. But
given the frequency of the walks (only nine times in six years) and the fact
that blood sugar levels were significantly decreased but not significantly
different between those who walked the long distance and those who walked the
short distance, researchers concluded that factors other than exercise also
contributed to the positive long-term results, including changes in hormonal
secretion and nervous system function associated with blood sugar metabolism.
Research in the United States has investigated the effects of outdoor green
spaces on symptoms of attention-deficit/ hyperactivity disorder (ADHD) in
children. In a randomized controlled study, doctors specializing in
environmental psychology at the University of Illinois studied 17 children
diagnosed with ADHD who were exposed to three different environments.
After 20-minute walks in a city park, children experienced substantially
improved concentration compared to 20-minute walks in downtown and residential
settings. Researchers concluded that the positive results were comparable to
the effects of Ritalin.
Researchers at Johns Hopkins University School of Medicine studied the effects
of nature scenery and sounds on pain perception. The randomized controlled
clinical trial included 120 adults undergoing bone marrow aspiration and biopsy
performed with only local anesthetic, a painful procedure, in one of three
One group experienced nature scenery and sounds during the biopsy, the second
group city scenery and sounds, and the third group a standard medical setting.
Overall, the procedure was poorly tolerated, but researchers concluded that
viewing a nature scene and listening to nature sounds is a safe and inexpensive
way to reduce pain during bone marrow biopsy.
Studies in Japan have examined markers of immunity in both men and women after
three-day trips to the forest. Healthy volunteers participated in three
two-hour sessions of walking in a forest. Before, during and after the
experiences researchers measured the number and activity of natural killer
cells, immune cells that destroy cancerous cells in the body; anti-cancer proteins
including perforin, granulysin and granzymes A/B; and levels of stress hormones
adrenaline and noradrenaline. They also measured levels of phytonicides in the
forest air. (Phytonicides are essential oils released by trees and plants to
defend against insects, animals and decomposition.)
Compared to control measurements taken on normal working days, forest walking
significantly decreased levels of stress hormones, increased anti-cancer
proteins, and increased the number and activity of natural killer cells. 30
days after the experience, natural killer cells were still more active,
suggesting that monthly forest walks could be an important lifestyle factor in
the prevention of cancer as well as helpful adjunctive therapy for people
diagnosed with cancer.
Researchers believed that the wood essential oils were at least partially
responsible for the positive effects of forest air. Separate studies have
further investigated phytonicides in laboratory settings and confirmed that
they can increase anti-cancer proteins and enhance natural killer cell