The Physiological Benefits of Spending Time in Nature

Our instincts have told us and experts confirmed it: spending time in nature is essential to your health. 

Imagine, for a second, what life would have been like 300,000 years ago when anatomically modern humans first walked the earth. Or even 500 years ago, before modern civilization, when we lived in the natural environment and our resources came from around us. 

In stark contrast, more than 55 percent of the world’s population lives in urban areas today. In North America, 82 percent live in urban areas as of 2018. And, by various estimates, the average American spends between 80 and 99 percent of the time indoors.

“From the perspective of physiological anthropology, human beings have lived in the natural environment for most of the 5 million years of their existence,” a study on the physiological effects of forest bathing reports. “Therefore, their physiological functions are most suited to natural settings.”

Our health is intricately tied to Nature’s. So, what are we missing out on by not living in the forest as we have for millions of years? Or, at the very least, visiting it regularly? How has our health been affected by removing ourselves from the environment that we evolved in? 

While there is still much to be studied on the subject of human health and nature, we do know a walk in the woods can positively impact many normal physiological functions. And the long-term holistic health implications can be profound.

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Lowers Stress, Improves Creativity and Boosts the Immune System

Research in the field of Shinrin-yoku, or forest bathing as it is commonly referred to today, has demonstrated that this simple and accessible activity can lower stress levels and aid in the recovery of the human immune system. It can also improve attention span and creativity levels.

A study of the physiological effects of Shinrin-yoku–taking in the forest atmosphere or forest bathing–across 24 forests in Japan revealed forest environments promote lower concentrations of cortisol, lower pulse rate, lower blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than city environments. Just 15 minutes of forest bathing can effectively relax the human body. And after spending three days in the forest, the prefrontal cortex relaxes.

Forest surroundings can help the immune system recover. Lower cortisol levels are linked with higher natural killer cell (NK) activity. So, as one walks through the forest and their cortisol levels decrease, the NK white blood cells can help reject tumors and virally infected cells. NK cell activity and numbers increase by around 50 percent. Even 30 days after forest bathing study participants showed a 33 percent increase in NK cell activity.

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Improve Cognitive Function and Mood

Our brains are hardwired to observe nature because our survival depended on it for the vast majority of our existence as a species. In today’s constructed environment, we are missing out on many of the benefits of being in nature including a brain boost and a chance to relax the mind.

Humans have two types of attention: involuntary attention and directed attention. Involuntary attention is grabbed by whatever is most immediate to our survival, such as a car honking or sirens. Directed attention is what we use to override our instinctual involuntary attention. It allows us to determine whether a car horn is signaling immediate danger to us, or if it is directed somewhere else. 

Our involuntary attention is constantly being grabbed by noises and sights. These require directed attention to overcome the stimuli, making urban environments more stressful to the body. In contrast, natural environments contain inherently fascinating stimuli, such as sunsets and non-threatening animals like birds. They modestly invoke involuntary attention, allowing directed-attention mechanisms a chance to replenish. Essentially, you’re giving your brain a much-needed break.

A study at the University of Michigan tested the effect of a walk’s scenery on cognitive function. The results showed that participants’ performance on the cognitive test improved by almost 20 percent after walking in nature. By comparison, the subjects that walked in an urban environment did not reliably improve on the test. That comes as no surprise, though, as research has indicated that urban living may adversely affect psychological functioning and increase psychopathology

In order to function properly, the brain requires 20 percent of the body’s oxygen supply despite comprising only two percent of the body. Yet, in classrooms and boardrooms where there is poor ventilation, often a result of the need to reduce a building’s energy consumption, concentrations of carbon dioxide can go up to several thousand parts per million (ppm). Outdoor concentrations are typically at around 380 ppm. In a 2012 study, researchers found that CO2 could be an indoor pollutant that oftentimes goes ignored, negatively impacting human decision-making performance and concentration.

Getting outside can help improve self-esteem and mood, and increase memory span. A 2007 study by the University of Essex found that 90 percent of a study cohort suffering from depression felt a higher level of self-esteem after a walk through a country park. And almost three-quarters felt less depressed. 

Contact with nature can give us a sense of connectedness, a feeling of awe, and can trigger positive emotional reactions because it was important for our survival. A 2012 study aimed to explore whether walking in nature may be beneficial for individuals with major depressive disorder. Participants exhibited significant increases in memory span after the nature walk compared to the urban walk. They also showed increases in mood.

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Reset Your Circadian Rhythm

Humans’ physiology and daily rhythms evolved in the natural light-dark cycle, allowing functions to occur at optimal times of the day. But, in today’s age of electrical lighting and technology, our natural circadian rhythm has been delayed. And it’s causing weight gain and sleepiness in the population. Luckily, a good camping trip can reset your circadian rhythm.

A 2013 study published in Current Biology demonstrated that sleeping in sync with the natural light-dark cycle helps to reset the circadian clock. Researchers compared the circadian rhythm of participants living in a typical city environment for a week compared to sleeping in the Colorado wilderness without artificial lights. No phones or flashlights were permitted, only the light from a campfire.

After a week sleeping under the stars, participants’ circadian clock had synchronized to solar time. Melatonin onset naturally occurred on average near sunset and offset occurred before wake time just after sunrise. However, in the typical electrical lighting environments that we live in today, melatonin offset is occurring two hours after habitual wake time. This makes it hard to wake up and feel rested when it should have occurred 50 minutes before you wake up.

“Natural selection favored the human circadian clock system to promote energy intake and metabolism, physical activity, and cognition during the light portion of the day and to promote sleep and related functions during darkness at night,” according to the study authors.

Insufficient sleep can also contribute to weight gain and obesity. A study on social jetlag and obesity found that “improving the correspondence between biological and social clocks will contribute to the management of obesity.” Late nights and early mornings can lead to us scrounging for snacks, increasing body mass index (BMI).

So, grab your sleeping bag and take a snooze (or five) under the stars. Your body, mind, and energy levels will thank you later.

This article is for informational purposes only, even if and regardless of whether it features the advice of physicians and medical practitioners. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice.

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