By Gillian Bethel
The scientific evidence is in! Human beings need contact with nature for optimal physical and psychological health.
Researcher Ming Kuo of the University of Illinois puts it this way: “Time spent in and around tree-lined streets, gardens, parks, and forested and agricultural lands is consistently linked to objective, long-term health outcomes. The less green a person’s surroundings, the higher their risk of morbidity and mortality [disease and death]—even when controlling for socioeconomic status and other possible confounding variables.”
She continues, “The range of specific positive health outcomes tied to nature is startling! For each of the following, available evidence points to a favorable impact: depression and anxiety disorder, diabetes mellitus, attention-deficit/hyperactivity disorder (ADHD), various infectious diseases, cancer, healing from surgery, obesity, birth outcomes, cardiovascular disease, musculoskeletal complaints, migraines, respiratory disease, and others. Finally, neighborhood greenness has been consistently tied to life expectancy and all-cause mortality.”¹
Perhaps these “green benefits” explain why many of us found ourselves longing to spend time in natural green spaces during the COVID-19 lockdown. Some countries even have special terms for this kind of therapy. The Germans enjoy “forest solitude” and the Japanese “forest bathing”! These two activities have become so popular in the past year that it’s hard to find quiet woodland to be alone in!
But not everyone is looking for forests. In England, record numbers of people headed to the beach as soon as the lockdown was lifted. To many people, it just feels good to get out in nature—leafy backyards and parks work too!
So how does nature affect us mentally and physically? Studies suggest many answers, but two that stand out are stress reduction and improved immune function. These two are actually linked to each other because stress reduction raises immunity. But we’ll look at them separately.
Mental restoration in nature seems to depend on a synergy of benefits. Here are just a few: the air in forested and mountainous areas and near moving water contains high concentrations of negative ions, which reduce depression and increase feelings of well-being; peaceful sounds of nature, even played through headphones, can also bring about relaxation; sunlight increases the brain’s release of serotonin, the “happy hormone”; and of course, outdoor exercise, such as walking, relieves mental and physical tension and boosts endorphins—nature’s tranquilizers.²
Then there’s the “awe effect.” A study in 2020 showed that older adults who took weekly 15-minute “awe walks” in a natural setting for eight weeks reported increased positive emotions and less distress in their daily lives.³
Studies have found that even window views and images of nature can reduce sympathetic nervous activity (the stress response) and increase parasympathetic activity (the relaxation response).⁴ “Being there” is even more effective.
Science apart, we’ve all felt the peaceful effect of being in our favorite natural environments for a while. We seem to be designed for being soothed by the natural world, as long as it’s nonthreatening!
How is being in nature helpful for immunity? Again, it’s multifactorial. In fact, Ming Kuo suggests that almost all the benefits of nature play into improved immunity, either directly or indirectly.
But specifically, according to Kuo, many plants give off phytoncides—antimicrobial organic compounds which reduce blood pressure, alter autonomic nerve activity, and boost immune functioning, among other effects. Natural environments also contain mycobacterium vaccae, a microorganism that also appears to boost immune functioning.⁵
Pro-inflammatory cytokines are a component of our immune system that can be either beneficial or harmful to us. When overactive, they are thought to be involved in a number of chronic diseases, including diabetes, cardiovascular disease, and depression. They, too, respond to nature. Kuo reports that “extended time in a forest decreased inflammatory cytokines implicated in chronic disease by roughly one-half.”⁶
Natural killer (NK) cells in our immune system are notable for their ability to prevent and even destroy malignant tumors as well as attack viruses and other invaders. A Japanese study showed the marked effect that a three-day “forest bathing” trip had on them. Kuo relates that “two 2-hour forest walks on consecutive days increased the number and activity of anti-cancer natural killer cells by 50 and 56%, respectively, and activity remained significantly boosted even a month after returning to urban life—23% higher than before the walks.”⁷
Notice that the participants in this study took long walks in the forest. Exercise—even in a gym—is well known for enhancing NK cell numbers and activity, but certainly walking in nature would be much more beneficial. And overnight stays are not necessarily required to reap benefits. A day trip to a natural park with one walk produced a similar effect.8
The takeaway from all the evidence is clear: being out in nature can make a big difference in our mental and physical health. Even without much activity, time spent in nature can be very healing and preventive.
And if we can’t get outside, just the sights and sounds of nature can be beneficial, too.
The best part of all these “natural wonders” is that we don’t need to understand the chemistry to get the blessings! We can just enjoy the experience and the effects. Are you ready to try? C’mon, let’s go!
Ming Kuo, “How Might Contact with Nature Promote Human Health?” Frontiers in Psychology, frontiersin.org, Aug 25, 2015.
Individual references can be found in Kuo’s article.
Nicholas Weiler, “‘Awe Walks’ Boost Emotional Well-Being” University of California San Francisco, ucsf.edu, Sept 21, 2020.
Quing Li et al., “A Day Trip to a Forest Park Increases Human Natural Killer Activity and the Expression of Anti-Cancer Proteins,” J Biol Regul Homeost Agents, 24(2), 2010, pp. 157–65.
Gillian Bethel, PhD, taught stress management at lifestyle centers for ten years and is the author of the book From Stress to Joy.