It’s widely assumed that escaping the noise and stress of the city to spend some time in nature is good for us. In recent years scientists have been putting this assumption to the test, and evidence is mounting of the positive effects of contact with nature on our physical, emotional and mental wellbeing.

Some of the most interesting evidence of the health benefits of nature is coming out of Japan, and revolves around the popular practice of ‘Shinrinyoku’ or ‘forest bathing’. The practice was introduced in 1982 in a prescient move by the Forest Agency of Japan to encourage a healthy lifestyle and decrease stress levels. Forest bathing has now become a recognised relaxation and stress management activity in Japan – but studies conducted in the last few years shows forest bathing is also increasing a component of the immune system that fights cancer.

Forest bathing experiments
Qing Li is a senior assistant professor at Nippon Medical School in Tokyo who is studying forest medicine. He is currently the president of the Japanese Society of Forest Medicine, which was established in 2007. Dr Li has conducted a number of experiments to test the effects of forest bathing on our moods, stress levels and immune system.

In one study the Profile of Mood States (POMS) test was used to show that forest bathing trips significantly increased the score of vigour in subjects, and decreased the scores for anxiety, depression and anger – leading to the recommendation that habitual forest bathing may help to decrease the risk of psychosocial stress-related diseases.

Other studies on immune function looked into whether forest bathing increases the activity of people’s natural killer (NK) cells, a component of the immune system that fights cancer. In two studies, small groups of men and women respectively were assessed before and after a two-night/three-day forest bathing trip. During the trips the subjects went on three forest walks and stayed in a hotel in the forest. Blood tests were taken before and after the trip, revealing a significant boost in NK activity in the subjects in both groups. The increase was observed as long as 30 days after the trip. Follow-up studies showed a significant increase in NK activity was also achieved after a day-trip to a forest, with the increase observed for seven days after the trip.

Dr Li attributes the increase in NK activity partly to breathing in air containing phytoncide (wood essential oils) like α-pinene and limonene, which are antimicrobial volatile organic compounds emitted from trees to protect them from rotting and insects.

Anyone can forest bathe

Japan has many conditions that favour the practice of forest bathing: Forests occupy 67 per cent of the land in Japan and are easily accessible; Japanese tree species including Japanese cypress, Japanese cedar, Japanese beech and Japanese oak are all proven to be effective in raising NK activity; and the Japanese government now officially recognises certain forests by granting the designations of Forest Therapy Base and Forest Therapy Road. However, Dr Li says forest bathing is possible anywhere in the world where there is a patch of decent forest (generally defined as land with a tree canopy cover of more than 10 per cent and area of more than 0.5 ha).

He says while forest bathing it’s not important to do heavy physical exercise, but rather one should ‘enjoy the forest through the five senses: the murmuring of a stream, bird’s singing, green colour, fragrance of the forest, eat some foods from the forest and just touch the trees’.

Dr Li’s tips for forest bathing are:

• Make a plan based on your daily physical activity and do not get tired during the forest bathing.
• If you take whole day forest bathing, it is better to stay in forest for about 4 hours and walk about 5 kilometres. If you take a half day forest bathing, it is better to stay in forest for about 2 hours and walk about 2.5 kilometres.
• If you feel tired, you can take a rest anywhere and anytime you like.
• If you feel thirsty, you can drink water/tea anywhere and anytime you like.
• Please find a place in the forest you like. Then, you can sit for a while and read or enjoy the beautiful scenery.
• If it is possible, it is better to take a hot spring bath (a spa) after the forest bathing.
• You can select the forest bathing course based on your purpose.
• If you want to boost your immunity (natural killer activity), a three-day/two-night forest bathing trip would be recommended.
• If you just want to relax for reducing your stress, a day trip to a forest park near to your home would be recommended.
• Forest bathing is just a preventive measure for diseases; therefore, if you come down with an illness, I would recommend you to see a doctor – not visit a forest.

Future research
For those of us lacking the time or resources to forest bathe, Dr Li says a two-hour walk in a city park with a good density of trees can significantly boost the score for vigour and decrease symptoms of anxiety and depression. He has not yet investigated whether walking in a city park can enhance human immunity, but is planning to do so shortly. Dr Li is also researching the effect of forest bathing on cardiovascular and metabolic parameters and says he’s planning to develop forest bathing to be a preventive measure for some diseases such as depression, hypertension and cancers.