What Green Can Do for Public Health

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Public health issues that we currently grapple with such as diabetes, cardiovascular disease, cancer and other diseases require billions of dollars for treatment. Some of these issues are a result of an environment degraded by humans causing polluted air, exposure to heavy metals, and climate change.

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Olympic National Park, Washington (USA) Photo by Mark Ellison

Recent research has also found that contact with the natural environment in a broader sense can also enhance health. Some of the health problems that we are experiencing may have roots in our disconnection from nature, a setting from which humans have evolved over the past five million years. Nature has been replaced with modern environments offering exposure to an array of artificial stimulation with little health benefit.

A growing body of research is revealing the benefits of time in nature that can have significant public health implications. A study by Yoshinori Oshtsuka from the College of Education at Hokkaido University in Japan found that time in nature is beneficial for reducing blood glucose levels for those with type II diabetes. Time spent walking in a forest resulted in a much larger reduction of glucose levels in comparison to similar amounts of time spent walking outdoors in an urban setting, using a treadmill or underwater exercise. In the study glucose levels were reduced 39% (71 mg/dl ) from time spent in nature, by far the largest impact of any of the exercise regimes. The author hypothesizes that the phytoncides (chemicals) emitted by trees are presumed to be the factor impacting the greater reduction in glucose levels.

Studies have also linked time in nature with increases in natural killer cells (NK) that help to strengthen immunity and aid in fighting off the development of tumors such as cancer. The phytoncides found in a forest setting help to increase NK cell activity. Research has found that a three day/ two night forest trip can increase NK cell activity for up to a month.

In many urban areas the health disparity between rich and poor residents is often stark. Research by Rich Mitchell, Ph.D., Professor of Health and Environment at the Institute for Health and Wellbeing at the University of Glasgow has identified a link between the presence of green space and population health. Mitchell found that urban communities with the most amount of green space had the least disparity in health between rich and poor. Communities with little nature had greater disparities in health, with poorer residents having a cardiovascular disease mortality rate more than twice that of the wealthiest.

Communities that value natural settings and make them available to all socioeconomic groups will reap the benefits of a healthier population. It should be a public health right to have access to high quality nearby nature regardless of socioeconomic status. An investment in preserving natural areas can pay huge dividends with a healthier population, which can also help build a more vibrant economy. Achieving this goal will require collaboration between public health, environmental health, parks & recreation, education, healthcare professionals and others. Working together a “green” public health movement can gain traction.

The Physiological Effects of Shinrin-yoku

Park, B., Tsunetsuga, Y., Kasetani, T., Kagawa, T., & Miyazaki, Y. (2010). The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan. Environmental Health Preventive Medicine, 15(1), 18-26.

Abstract: The results of studies performed on the physiological effects of Shinrin-yoku show that forest environments could lower concentrations of cortisol, lower pulse rate, lower blood pressure, increase parasympathetic nerve activity, and lower sympathetic nerve activity compared with city settings. The results of the physiological measurements suggest that Shinrin-yoku can aid in effectively relaxing the human body, and the psychological effects of forest areas have been correlated with the various physical environmental factors of forest. The studies of Shinrin-yoku provide valuable insights into the relationship between forests and human health.

Access the entire manuscript at www.ncbi.nlm.nih.gov/pmc/articles/PMC2793346/?tool=pubmed

Comments by Mark Ellison:

The health promoting and stress reducing benefits of Shinrin Yoku that have been found through scientific research in Japan offer many possibilities for improved public health  in other countries, including the United States. Research on this topic has been occurring for several years in Japan, but not as extensively elsewhere. More emphasis needs to be placed globally on research exploring how nature impacts physical and mental health, as well as on the development of programs that help people connect to nature.   This can have a tremendous impact on public health and have positive financial implications for individuals, governments and organizations as a result of having healthier, more effective employees, and lower healthcare costs.