Updated June 08, 2015.

It might seem a bit funny that something as, well, natural as being outside has been tackled by scientists, aiming to prove which factors affect our health and longevity. But it’s true.

Back in 1984, acclaimed Harvard biologist Edward O. Wilson explored the concept that humans are programmed through evolution to be attracted to nature, and that it plays a significant role in our survival, in his book Biophilia.

Since then, scientists treating disorders ranging from dementia to obesity have studied whether being outside, in greater proximity to plants and other living things, has a positive effect.

Concerns about increased urbanization have given this area of research a new urgency. For example, three-quarters of the European population live in urban environments, while in North America, it’s more than 80%. Just having access to green spaces has been shown to keep residents healthier: a 2005 survey of eight European cities showed that people who live in areas with the most greenery are three times more apt to be active, and 40% less likely to be obese. Since even small amounts of regular exercise can improve longevity, any factors that promote activity may have a life-extending benefit.

In fact, some studies do suggest that being outside, interacting with nature, is associated with reduced mortality.

So what’s happening to our bodies when we’re outdoors? This is a challenging question for scientists, since it’s not practical to say, take 10,000 people, keep half of them inside for five years, and compare them with their outdoor counterparts at the end of the study period.

Further complicating this area of research is the fact that there are so many ways of interacting with natural elements, from walking among plants or tending to a garden, to participating in wilderness programs, each of which may have a different effect on the brain or body.

In their 2011 review, published in The Scandinavian Journal of Public Health, environmental psychologists Matilda Annerstedt and Peter Wahrborg summarize 38 different studies examining how nature affects our state of health. Though they point out that much of the research is observational and qualitative –- that is, hard data about the exact effect on the mind and body is sparse -- there is growing evidence that exposure to nature is beneficial to our health.

Nature as a health promoter: Studies conducted in the UK, the United States, Australia, the Netherlands, New Zealand and Japan suggest that being in nature can:

• Reduce stress
• Reduce mental fatigue
• Improve mental focus and attention
• Lower blood pressure
• Lower levels of obesity

The stress-reduction effect is suggested as the main health benefit of being in nature, because of stress’s role in the development of many ailments, from depression and anxiety disorders to cardiovascular disease.

Why does it work for our health? Though the exact mechanism is still a mystery, a 2009 paper published in the International Journal of Environmental Research and Public Health suggests that nature offers the following advantages:

• It’s associated with higher levels of physical activity
• It often correlates with socializing, which improves health
• It offers relief from daily routines and demands

In addition, there may be some yet-undetermined effect on our brains when we spend time outside. There is some evidence for this, in a 2011 review published in Environmental Science and Technology. Comparing the effects of exercising indoors with doing the same activity outside, the research found that exercising outdoors was associated with less anxiety, anger, and fatigue –- and more energy and satisfaction.

Read the entire article on exercising outdoors

Being outside also provides exposure to the sun, allowing our skin to synthesize vitamin D, which has been linked to a lower incidence of heart disease and even certain cancers.

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Though none of this nature-is-good-for-you research will come as a surprise to anyone who feels more relaxed or focused after a walk along the ocean, a winter hike, or gardening, future investigation will determine how exactly being in nature affects the brain and body, and whether there’s an optimum ‘dose’ of time spent outdoors.

<sub>Sources:

Bjørn Grinde and Grete Grindal Patil. Biophilia: Does Visual Contact with Nature Impact on Health and Well-Being? Int J Environ Res Public Health. 2009 September; 6(9): 2332–2343.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2760412/

Elizabeth Richardson, Jamie Pearce, Richard Mitchell, Peter Day, and Simon Kingham. “The association between green space and cause-specific mortality in urban New Zealand: an ecological analysis of green space utility. “ BMC Public Health. 2010; 10: 240.

Matilda Annerstedt and Peter Wahrborg. “Nature-Assisted Therapy: Systematic Review of Controlled and Observational Studies.” Scandinavian Journal of Public Health, 2011; 39: 371–388

Takano T, Nakamura K, Watanabe M. Urban residential environments and senior citizens’ longevity in megacity areas: the importance of walkable green spaces. J. Epidem. Com. Health. 2002;56:913–918.

The World Factbook: Urbanization. US Central Intelligence Agency Public Information Sheet. Accessed May 21, 2012.
https://www.cia.gov/library/publications/the-world-factbook/fields/2212.html</sub>