Why forests make us healthier

“Shinrin Yoku” is the Japanese name for "bathing in the forest air”: spending time consciously in a forest and absorbing the experience to the full to achieve maximum relaxation. The method has been used In Japan ever since the 1980s for stress management and as a preventive healthcare therapy. What is more: “forest medicine” has even been taught at Japanese universities since 2012 – and it is researched with the involvement of immunologists, cardiologists and neurobiologists.

Numerous studies demonstrate the health-promoting effects of a prolonged period of time spent in a forest. These include:

• Stress relief due to reduced cortisol levels
• Lowering of the blood pressure
• These two factors also reduce the risk of cardiovascular disease
• Strengthening the immune system due to an increase in killer cells in the blood

But how does this work?

The effect of forest bathing on our well-being is complex and comprises a wide range of different elements that involve all sensory levels.

It really is the case that even the sight of meadows, trees and forest has a beneficial effect: in 1984, for example, the Swedish doctor Roger Ulrich found that patients recovered more quickly after an operation if they had a view of the greenery through the window of their hospital room. Meanwhile an American study showed that patients who had a view of nature could not only be discharged more quickly, they also needed fewer painkillers. According to a Japanese study, the mere sight of a forest causes a drop in blood pressure, a slowing down of the pulse rate, and a decrease in the concentration of the stress hormone cortisol.

Relaxation through listening: just one minute of hearing forest sounds can result in a decrease in both our stress and anxiety levels. It is not only the increased tranquillity of a forest: the natural soundscape such as the rustling of leaves, the chirping of birds and the babbling of a brook activate our relaxation system – the parasympathetic nervous system. This is important for our regeneration, metabolism and self-healing. Unfortunately, it gets used far too little in the modern, hectic way of life frequently to be found in urban settings.

Instead, we activate the prefrontal cortex excessively in our day-to-day lives: this is the part of the brain we use when we need to concentrate or follow something. But in order to remain healthy and balanced, it is important for our brain activity to repeatedly shift to other areas that are perceived as calm. Studies from Japan show that the forest environment lowers the blood flow in the prefrontal cortex – and our brain can relax. According to studies, regular visits to the forest can also be effective against depression and burn-out.

And finally, natural sounds stimulate our “default mode network”: this is a network of brain areas that are also active when we daydream and ultimately arouse our alertness. By contrast, it is barely possible to produce this effect by means of artificially created sounds. In other words, our thought processes are able to reorganise thanks to natural sounds.

It is particularly fascinating to look at what we breathe in when we’re in a forest. Forest air not only contains a high concentration of oxygen, but also 90 % fewer dust particles than city air. The scent of pine needles also helps activate our relaxation system. And the higher level of humidity in the forest helps moisten the respiratory tract, making it less susceptible to bacteria and viruses.

But one particularly remarkable effect of forest bathing comes from the plant messenger substances that we absorb in the forest through the air we breathe: the so-called terpenes. Plants produce these active substances to protect themselves from pests and pathogens and also release them into the air via needles and leaves – they can actually communicate with each other in this way.

When we inhale these substances, they activate our immune system by increasing the production of killer cells. These white blood cells are an important part of our defence system as they recognise and kill cells infected by viruses as well as cancer cells.

Terpenes not only cause our bodies to produce more killer cells, they also make these cells more active: according to a Japanese study, the number of killer cells in our blood increases by 40 % after one day in the forest, and the effect lasts for seven days. Terpenes have since been incorporated in cancer research.

They are also said to increase the production of certain messenger substances in our brain that can regulate blood pressure as well as blood sugar and cortisol levels. The latter acts to prevent depression and cardiovascular disease, and it also strengthens the immune system.

And finally, they ensure increased production of the hormone DHEA: this “fountain of youth” hormone slows down our cell metabolism as well as protecting our nerve cells, heart and blood vessels.

That all sounds quite positive, doesn’t it? And the good thing is – you get all this free of charge from a relaxing day in the forest.

Here are some tips if you want to tap into the healing properties of forest bathing yourself:

• Go into the forest with a sense of mindfulness. What counts is not your muscular effort but your perception of the surroundings, which should be conscious as possible. This works more effectively if you walk at a leisurely pace and take breaks as you please.
• Combine your walk in the forest with relaxation exercises. These can be quite simple if you like: take five minutes to consciously breathe in and out through your nose and inhale the air as calmly and as deeply as possible. Or use your favourite meditation technique. Or else simply read a relaxing book. It is important for you to calm your thoughts down and focus your attention on one specific thing.
• Consciously absorb the natural setting with all your senses: sit in a nice spot for a moment with your eyes closed. Then start to be particularly aware of your sense of touch. What are the contact points between your body and the environment? What textures and temperatures do you perceive? Then pay attention to your sense of smell. What can you smell? Can you tell individual fragrances apart? Then home in on all the sounds you can hear, both near and far. Finally, open your eyes and look around slowly and consciously. What colours do you perceive? Which elements of the environment do you see? What are the shapes of the plants?
• Take plenty of time. Even though even a very brief forest bath of 30 minutes can lower the stress hormone level in your blood, the longer the better. For the purpose of stress management, anything from a few hours at a time to an entire day is recommended. If you even want to increase the killer cells in your blood and activate your immune system, take a two to three-day forest bath each month.
• Increase the relaxing effect by leaving your smartphone muted in your backpack, or else simply leave it at home.

Would you also like to go on unique, relaxing excursions relating to the theme of trees and forests in Switzerland? We have compiled a collection of the eight most fascinating destinations for you: https://www.mobility.ch/en/magazine/lifestyle/tree-rich-excursions.