Science has demonstrated that the ecology of the forest assists the human body in boosting immune response. Specifically, the molecular interactions between certain tree species and human bodies triggers the production of Natural Killer (NK) cells in humans. NK cells are a type of white blood cell that attack virally infected cells and tumor growths. The tree maintains its’ own health by showering the area with antimicrobial organic compounds known as phytoncides.
When a human sits beneath a tree, these phytoncides are absorbed by the body and trigger the production of immune-boosting NK cells.
This describes the astounding mechanism by which forest therapy boosts immune response and, in fact, triggers a physiological reaction that acts as a natural preventative medicine.
Turning to the question of why humans in society develop cancer and chronic illness while it remains almost unheard of in indigenous cultures requires us to look even deeper. The argument for phytoncide-triggered NK cell production is, all by itself, a compelling one; however, there is another interesting perspective to consider. Several prominent doctors and scientists have argued that chronic stress deteriorates immune function to the point that the body no longer can fight off such diseases. We know that almost all humans carry some cancerous cells; the difference between those who get cancer and those who don’t is about the cells metastasizing, or the point at which cancer cells begin to multiply uncontrollably and invade other regions of the body. Studies of cancer patients have revealed that there is a strong correlation between these cells metastasizing and chronic stress. Combined with environmental factors that come with civilization like radiation and toxins in our food, air and water, chronic stress may be the single most debilitating factor in cases of serious illness.
Sometimes people scoff at the idea of sitting under a tree, as if such relaxation is a waste of time. They do not understand that chronic stress essentially poisons the body. Stress, as a biological function, was and still is essential for our survival. However, the body is not meant to experience the biochemical state of stress at all times. Stressful events are physiologically taxing on the body. Like a rubber band stretched too tight, eventually the body’s immune response will collapse under the pressure. This is in part because of the physiological effects of cortisol, a hormone that is released when you perceive a threat. Cortisol, while biologically useful in truly stressful situations, dampens immune function and, in excess, can cause intestinal bleeding and ulcers as well as bone thinning and osteoporosis. While we need cortisol on one level, overdosing on it can truly be fatal.
And herein lies the problem of ‘diseases of civilization.’ Unless you are living with an indigenous tribe in the forest, it is statistically probable that you are living with chronic stress, even if you are not subjectively aware of it. Gabor Mate writes,
“The fight-or-flight alarm reaction exists today for the same purpose evolution originally assigned to it: to enable us to survive. What has happened is that we have lost touch with the gut feelings designed to be our warning system. The body mounts a stress response, but the mind is unaware of the threat. We keep ourselves in physiologically stressful situations, with only a dim awareness of distress or no awareness at all. As Seyle pointed out, the salient stressors in the lives of most human beings today- at least in the industrialized world- are emotional. The higher level of economic development, it seems, the more anesthetized we have become to our emotional realities. We no longer sense what is in our bodies and cannot therefore act in self-preserving ways. The physiology of stress eats away at our bodies not because it has outlived its usefulness but because we may no longer have the competence to recognize its signals.”
The good news is that science has confirmed what Buddhism has long advocated: the mind (and brain) can be changed through practice. Forest therapy is one practice that has specifically been proven to support stress reduction by training our brains and bodies to relax.
Even breaking the pattern of chronic stress by taking a Shinrin Yoku walk once a week can have positive impact on long-term health.
We tend to think that healing has to be arduous, difficult, painful work. Who knew that sitting peacefully under a tree might just be the secret to health and longevity?