Table of ContentsEvolutionarily, humans have always lived outdoors in nature. Therefore, our biological ‘normal state’ is to be surrounded by natural stimuli. Our body is thus best attuned to life in a natural environment. Only with the onset of urbanization did we begin to live in a highly altered and partly artificial environment, which could be partly responsible for a multitude of chronic functional disorders and stress perceptions in modern humans.A simple way to escape the stress of the city and everyday life is offered by the so-called Shinrin-yoku. Loosely translated from Japanese, it means “taking in the forest atmosphere with all senses” or, in short, forest bathing. This is counted among nature or ecotherapies and is gaining increasing popularity in our Western world. Science is also extensively studying the physiological effects of being surrounded by nature. Forest bathing can strengthen the immune system against viral or bacterial infections, prevent cancer, relieve stress, and promote relaxation. Our organism has been accustomed to the bacteria, viruses, fungi, and plant substances found there for millions of years. They are therefore old friends to us and thus promote immune tolerance within us.
What makes forest air so special?
Forest air is a highly potent cocktail of bioactive healing substances called phytoncides, a collective term for a group of antibiotic-acting substances from plants.A significant group of these healing substances in forest air are terpenes. They are found, for example, in essential oils. Over 40,000 of these secondary plant compounds can be distinguished. These have a variety of different functions. For example, they serve as protection for trees during strong sunlight, visible as a blue haze over the forest. They also act as attractants for insects and animals. They are also used by plants to warn other plants of pests. Plants can then form terpenes as poison to kill pests or repel them with an unpleasant taste. They also serve the communication of trees, fungi, and herbs. Terpenes strengthen the immune system and are anti-carcinogenic. Terpenes strengthen the immune system directly as well as through the effect on the hormone system by reducing stress hormones. Most terpenes are found in the forest in summer, and fewest in winter. Terpenes are particularly intense in the forest during rain or fog. We find them in the highest concentration especially near the ground, where we usually spend our time. Coniferous trees, in particular, release terpenes. Deciduous trees, especially beech, oak, birch, and hazelnut trees, also do.
Influence on the Immune System
A walk in the forest has been proven to strengthen the immune system. A single day in the forest increases natural killer cells by almost 40 percent, and by more than 50 percent on the second day. Furthermore, these cells are also fitter. The increase in activity of these cells is detectable for the next seven days after a day in the forest. If you stay in the forest for three days, the number of killer cells increases for the following 30 days. In addition, forest air has a positive effect on oxidative stress in our body. This is triggered by free radicals, which are particularly reactive. In one study, lipid peroxidation was reduced in subjects who had spent time in the forest. Lipid peroxidation refers to the chemical process in which these free radicals begin to oxidize and thus destroy the body’s own fats. Forest bathing can therefore prevent the development of a chain reaction that can lead to damage to cell membranes. This study also found a reduction in inflammatory cytokines.
Improvement of Pain
In addition to the metabolic changes from forest bathing, nature sounds and images alone can influence pain perception. A study in the USA found that merely listening to nature sounds and viewing a natural scene could alleviate pain during a bone biopsy, in contrast to city sounds and no sounds.
Metabolic Adaptations such as Reduction of Blood Sugar and Triglycerides
Shinrin-yoku (Japanese term for forest bathing) can also have a positive effect on metabolism. Studies have shown that a forest walk can reduce triglycerides. Triglycerides are fats stored in adipose tissue as an energy reserve. In some people, triglyceride levels are elevated, e.g., in the presence of a lipid metabolism disorder. In such cases, forest bathing can be a supportive measure for normalizing metabolism. Another effect of forest bathing on metabolism is an increase in the tissue hormone adiponectin, which has a positive influence on fat and sugar metabolism. Furthermore, low adiponectin levels are associated with diseases such as type 2 diabetes and coronary heart disease, as it affects insulin secretion. In addition, the body produces more anti-carcinogenic proteins.
Relaxation and Stress Reduction through Forest Bathing
A stay in the forest also acts as a highly potent psychotropic drug without side effects, as it relaxes and relieves stress. The forest affects our autonomic nervous system, relieving stress through psychological influences as well as through terpenes. For example, it has been shown that stress hormones like cortisol and adrenaline are sustainably reduced.In men, adrenaline decreases by almost 30 percent after one day in the forest compared to the baseline, and by 35 percent on the following day. In women, the values even decreased by 50 percent on the first day and by 75 percent on the second day. Researchers also found that a stay in the forest led to a reduction in feelings of anxiety, aggression, and exhaustion.Deep dark forests are not as relaxing as a savanna-like bright environment with tall trees and clearings that we can survey. The latter supports our need for protection and security and promotes our relaxation. But not only the forest relaxes us; many natural elements calm us: flowers and shrubs (even indoors), blooming landscapes, meadows and clearings with scattered trees, gardens with fruit trees and vegetable patches, soils covered with mushrooms, birds, as well as calm flowing or still waters and the sea. Scientist Qing Li, author of the book ‘Forest Medicine’ published in 2012, recommends spending two to three days a month and about four hours daily in the forest for a sustained increase in anti-cancer effects and natural killer cells.But you don’t have to do that much. Just try to take an extended forest walk once a week and, whenever possible, spend time in nature, for example during breaks or while exercising. If you are lucky enough to have a garden or a park nearby, use them as often as possible.
Effects on Mood
A 2019 review extensively examined the psychological effects of forest bathing. Various emotional states were categorized, including depressive mood, tension, anxiety, fatigue, and anger. Without exception, an improvement was observed in every category after forest bathing. This can therefore help to release negative emotions to create space for positive feelings!
Improved Concentration
Green environments benefit physical and mental health and improve attention span. New studies on young adults, for example, have shown that short stays in nature improve memory and attention performance. Even just looking at nature images helps. Similar results have also been achieved in studies with older people. An improvement in attention also seems to occur through listening to nature sounds. Already in the 90s, Stephen Kaplan established the “Attention Restoration Theory,” which states that a natural environment presents less cognitive load than an urban one, thus allowing concentration to be better maintained. Therefore, whenever possible, move your work into nature – or at least your work breaks – and use green nature images for your next wallpapering project.
Beneficial Effects on Children
Spending time in nature also promotes concentration and attention in children, e.g., in Attention Deficit Syndrome (ADS). Children in a forest kindergarten are less often sick, have less overweight, and their concentration and gross motor skills are better developed. Green extends life and improves birth weight.The results of a 2015 review by James and colleagues are truly impressive. Their research indicates that green spaces protect against negative effects on mental health, cardiovascular diseases, and mortality. During pregnancy, a green environment also positively affects birth weight. Green encourages movement and normalizes body weight. In fact, the more time you spend in green spaces, the more you move and the more ideal your body weight. Another study from 2017 reached a similar conclusion: increased green spaces in residential areas are associated with a lower risk of dying from several common causes of death.
Reduction of Mortality due to Air Pollution
Similarly, mortality rates due to air pollution, such as fine particulate matter exposure, are reduced with more green environments. I sincerely wish that urban developers would read these studies and that gray high-rise landscapes would soon be a thing of the past.
Fig. according to James et al 2015 Here, the factors are shown how a green environment can influence health.
Heart Health
Blood pressure also decreases when people spend time in a forest environment, according to a systematic review by Ideno and colleagues from 2017, which examined over 20 studies with 732 subjects. Not only the systolic value decreases, but also the diastolic value, which is otherwise much more difficult to influence. This has also been confirmed in further studies.In addition to the positive influence of forest bathing on blood pressure, it also helps patients with chronic heart failure. A study proved that a four-day stay in the forest significantly improved the parameters associated with this disease. Thus, forest bathing can promote the functional state of our heart.
Sleep
And, the more contact you have with nature, the better you can sleep, and this also works for older people. So, throw your sleeping pills in the trash and enjoy a few romantic nights in nature. So, are there any reasons not to spend some time in nature today?
