Forests and Well-Being – Notes from “The Nature Fix”

Florence Williams’ book, The Nature Fix (Norton, 2017) summarizes some of what we know about how time in nature affects our well-being. It’s a “popular” book, but that’s not to say it is short on substance. Among the endorsements inside the cover is one from famed biologist Edward O. Wilson, whose work includes the biophilia hypothesis which says that evolution has “wired” us to be drawn to nature and all its plants and animals.

Williams is a journalist, and what she writes in this book is woven into a series of interviews, walks, and back country expeditions with experts in the field. It’s the story of her active, “hands-on” research on the subject, and so it is an engaging read. It also lays out some of the evidence and a few of the theories about how nature might decrease our stress hormones, lower our blood pressure, and have other benefits to our well-being. My notes here are part of my effort to understand this better; it seems intuitive to me that being in nature has benefits to our bodies and souls, but I want to look at the science behind it. So here are a few notes from the first section of her book.

In Japan, forest therapy (sometimes referred to as “Forest Bathing”) or “Shinrin yoku” is quite popular. It is based on Shinto and Buddhist practice and seeks to let nature into your body through all five senses. It is also linked to E.O. Wilson’s idea of biophilia, that we have an innate emotional affiliation with other living organisms. In forest therapy, people spend time in forests and become immersed in the sights, sounds, smells, and other experiences there. 

If this sounds a little sketchy, consider the results found by Yoshifumi Miyazaki, a physical anthropologist in Tokyo. He found that leisurely forest walks decreased cortisol, compared to urban walks. (Cortisol is a stress hormone, and with chronic stress cortisol creates problems, from dysregulated blood sugar to heart problems, depression and anxiety, memory and concentration problems, and so on.) Forest walkers had decreased sympathetic nerve activity, lower blood pressure and heart rate. (The constant stimulation and demands of life trigger activity from the sympathetic nervous system, resulting in “fight or flight” reactions. On the other hand, relaxation and feeling at ease are associated with a system that works in opposition to it, the parasympathetic nervous system.) When the walkers completed questionnaires, the nature group report better mood and less anxiety. 

More evidence comes from psychologist Roger Ulrich, who connected subjects to EEG and showed them slides, either of nature or of urban scenes. Those who watched nature slides had greater alpha rhythm, which is associated with relaxation and release of pleasurable endorphins. He also exposed subjects to a stressful activity, and then had them watch 10 minutes of either (a) nature scenes, or (b) urban scenes. Within five minutes, the sympathetic activity of the nature scene group returned to baseline, while the other group only partly recovered. 

Qing Li, an immunologist at the Nippon Medical School in Tokyo, looked at the impact of mood states and stress on the immune system. Li was interested in NK cells, a kind of white blood cell that sends self-destruct messages to tumor cells or virus-infected cells. Stress can decrease the number of these beneficial NK cells. Li took a group into the forest for three days that included hiking in the woods for a couple of hours daily. They had a 40% increase in NK cells. Li wondered if this was due to aromatic volatile substances coming from trees, and so Li had thirteen people spend three nights in a hotel where a humidifier could vaporize oil from hinoki cypress trees (or, for a control group, just water vapor). The cypress oil resulted in a 20% increase in NK cells, compared to controls.

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