For stressed-out workers, this may someday be a doctor’s prescription: Walk around in the woods.

Scientists in Japan have been learning a lot in recent years about the relaxing effects of forests and trees on mental and physical health. Based on their findings, some local governments are promoting “forest therapy.”

Experience shows that the scents of trees, the sounds of brooks and the feel of sunshine through forest leaves can have a calming effect, and the conventional wisdom is right, said Yoshifumi Miyazaki, director of the Center for Environment Health and Field Sciences at Chiba University.

Japan’s leading scholar on forest medicine has been conducting physiological experiments to examine whether forests can make people feel at ease.

One study he conducted on 260 people at 24 sites in 2005 and 2006 found that the average concentration of salivary cortisol, a stress hormone, in people who gazed on forest scenery for 20 minutes was 13.4 percent lower than that of people in urban settings, Miyazaki said.

This means that forests can lower stress and make people feel at ease, he said, noting that findings in other physiological experiments, including fluctuations in heart beats and blood pressure, support this conclusion.

“Humans had lived in nature for 5 million years. We were made to fit a natural environment. So we feel stress in an urban area,” Miyazaki said. “When we are exposed to nature, our bodies go back to how they should be.”

Taking a walk in a forest, or “forest bathing” as it is sometimes called, can strengthen the immune system, according to Li Qing, a senior assistant professor of forest medicine at Nippon Medical School in Tokyo.

Li conducted experiments to see whether spending time in a forest increases the activity of people’s natural killer (NK) cells, a component of the immune system that fights cancer.

In one, 12 men took a two-night trip to a forest in Nagano Prefecture in 2006, during which they went on three leisurely strolls and stayed in a hotel in the woods. Thirteen female nurses made a similar trip to another forest in the prefecture in 2007.

NK activity was boosted in the subjects in both groups, and the increase was observed as long as 30 days later, Li said.

“When NK activity increases, immune strength is enhanced, which boosts resistance against stress,” Li said, adding that forest therapy for immune-compromised patients may be developed within a few years.

Li said the increase in NK activity can be attributed partly to inhaling air containing phytoncide, or essential wood oils given off by plants.

Miyazaki of Chiba University said forests gratify the five senses by providing the sounds of birds, cool air, green leaves, the touch of trees, wild plants and grasses.

“The atmosphere of forests makes people calm,” he said.

Based on studies on the effects of forests, the public and private sectors are now promoting forest therapy.

The Forest Therapy Executive Committee, a group of researchers, other intellectuals and the government-affiliated National Land Afforestation Promotion Organization, started officially recognizing certain forests by granting the designations of Forest Therapy Base and Forest Therapy Road in 2006. The titles are given to forests that have been found by researchers through scientific evidence to have relaxing effects.

Officials from the Forest Agency and the Health, Labor and Welfare Ministry participate in the group as observers.

A forest therapy base comprises a forest and walking paths typically managed by local governments.

So far, 31 bases and four roads nationwide have gained such recognition.

Visitors to some of the therapy bases and roads have the option of taking part in various health programs, including medical checkups, breathing and aromatherapy classes, and guided walks with experts on forests and health care.

At the Akazawa Natural Recreation Forest in Agematsu, Nagano Prefecture, which was recognized as a forest therapy base in 2006, visitors can get free medical checkups among Japanese cypress trees on Thursdays. The forest is known as the Japanese birthplace of the concept of forest bathing in 1982.

Some companies have come to use forest therapy for their employees’ health care.

The Shinano Municipal Government in Nagano Prefecture, which manages the Iyashi no Mori (Healing Forests) forest therapy base, has contracts with four companies, a town official said.

Visitors to the forest therapy base can take part in various programs, including dietary management, hydrotherapy and aromatherapy.

The formal designations have drawn more people to such towns.

The Oguni Municipal Government in Yamagata Prefecture said 1,280 people visited the Nukumidaira beech forest there in fiscal 2007, including some 100 people who took part in forest walking tours with “matagi” traditional hunters.

“Before we got the recognition (in 2006), there were not so many visitors to the woods. Now we can see some people in the forest even on weekdays,” said Juro Watanabe, a town official in charge of forest therapy.

Recognition as a forest therapy base can be a big help, said Shigetaka Harashima, manager of the forest therapy project for the Okutama Municipal Government in Tokyo.

The town received official recognition in April 2008 and is now cooperating with experts to draw up therapy programs that will be available next year.

Chiba University’s Miyazaki said he hopes the number of forest therapy bases and roads will reach 100 nationwide over the next decade so people will have plenty of choices when they look for different types of forests.

“Some people like broadleaf forests and others prefer forests of conifer trees like hinoki cypress that give off a strong aroma,” Miyazaki said. “I hope people try to find a forest that suits their tastes and visit them from time to time.”

For more information about Forest Therapy Bases and Roads, visit forest-therapy.jp/