Nature exposure has long been correlated to improved mental wellbeing and physical health, able to reduce blood pressure, heart rate, muscle tension, and the production of stress hormones. A growing body of evidence implicates that greater exposure to or contact with natural environments can greatly benefit populations in high-income, largely urbanized societies, while merely living in a greener neighborhood has the potential to better health outcomes. Living in greener areas has been correlated to decreased risks of cardiovascular disease, obesity, diabetes, and mental distress, as well as increased longevity and improved self-reported health.

While the health benefits of nature exposure are well-documented and well-known, thus far the amount of time required to attain them remains unknown.  Researchers from the University of Exeter aim to change that by quantifying the exposure-response relationship in a recently published analysis.

Quantifying Nature Exposure for Health Benefits

Using data from the Monitor of Engagement with the Natural Environment survey (MENE), researchers analyzed a cohort of 20,000 adults in England to clarify the relationship between nature exposure and self-reported health and well-being. As the world’s largest study collecting data on individual weekly contact with the natural environment, the MENE survey presents valuable trend data for how people interact with nature.

Published this June in Scientific Reports, the NIHR-funded study revealed that spending two hours in natural environments a week is necessary to promote health benefits. Individuals who spent a minimum of 120 minutes in nature per week were significantly more likely to report good health and higher mental well-being than both those who spent no time in nature and those who averaged less than 120 minutes.

No benefits were found for people who visited natural settings for under two hours during the week, implicating that 120 minutes may be the threshold for attaining health benefits. The findings were broadly applicable, persisting across gender, age, socio-economic status, and ethnicity – the threshold also applied to individuals with long-term illnesses or disabilities. Moreover, it was proven realistic and easily reachable as the average participant spent 94 minutes in a natural environment weekly.

The dosage of exposure was proven inconsequential; there was no difference between individuals who achieved 120 minutes in a single visit and those who spread the time out across several intervals.

Lead study author Dr. Mathew White comments on the results: “It’s well known that getting outdoors in nature can be good for people’s health and well-being but until now we’ve not been able to say how much is enough. The majority of nature visits in this research took place within just two miles of home so even visiting local urban green spaces seems to be a good thing. Two hours a week is hopefully a realistic target for many people, especially given that it can be spread over an entire week to get the benefit.”

The initial findings from a forthcoming E.U. project suggest that the 2-hour minimum is not only applicable to the English, but also to the rest of the European population and potentially even wider demographics.

Study Limitations

Dr. White and colleagues acknowledge several limitations hindering immediate action upon the study’s findings. The observational, cross-sectional nature of the data gathered allows for the possibility that the association between nature exposure and improved well-being is at least in part due to healthier, happier people spending more time outdoors. Furthermore, the results reveal little about the quality of exposure needed – the plant and/or animal species richness of the environment – and whether it has any correlation to increased health benefits.

Although Dr. White’s findings provide significant insight into the value of nature exposure and for the first time, quantify the amount of time required outdoors, there is not yet enough clinical data upon which to base specific guidelines. Further longitudinal studies similar to those used in the development of physical activity guidelines are needed as well as nature-based intervention studies to better understand causality. Similar studies are also necessary to determine the sufficient amount of time of sustained weekly nature exposure at threshold levels for the achievement of physical and mental health benefits.

While these forthcoming studies will be an essential step toward the development of future nature exposure guidelines for public use, current findings offer support to healthcare professionals making lifestyle recommendations to patients. Looking ahead, the quantification of the exposure-response relationship may contribute to policy changes, providing much needed clinical evidence for the basis of national and/or global guidelines to promote population health outcomes.