It’s a fact: spending time in nature is beneficial to both our physical and psychological health. But is there a minimum threshold for obtaining a significant positive effect? This was the question raised by a team of researchers from the University of Exeter (England). Through their very large-scale study, they were able to determine the “minimum weekly dose of nature” we should all be taking.

Many studies report improvement in health and well-being when we spend time in natural environments (forests, parks, beaches, etc.). Although evidence varies (in quantity and quality) depending on the research, living in “greener” urban areas is regularly associated with a lower risk of cardiovascular disease, asthma, and depression. Some studies (see White M. et al., 2013) also indicate better cognitive development in children that live near green areas. Most often, research on the impact of these green spaces on health accounts for factors like green space size and distance from homes. Another alternative and complementary approach involves studying human exposure to nature and measuring the time actually spent in a natural environment. This is the orientation taken by the research team led by Mathew P. White of the European Center for Environment and Human Health (University of Exeter).

19,806 people were selected from a survey carried out in England on engagement with the natural environment. The scientists examined associations between contact with nature during the past 7 days and self-reported health and well-being. The scientists calculated recreational contact with nature or time spent in a natural environment during the past week by multiplying the number of recreational visits declared per week by the length of a randomly chosen visit during the past week. Seven categories were defined for duration: 0 minutes (11,668 people); 1 to 59 minutes (n = 355); 60 to 119 minutes (n = 1,113); 120 to 179 minutes (n = 1,290); 180-239 minutes (n = 1,014), 240-299 minutes (n = 882); ?300 minutes (n = 3,484). Possible responses for self-reported health status were: “very bad,” “bad,” “fair,” “good,” and “very good.”

The results indicated that people who spent between 1 and 119 minutes in nature during the last week did not report better health or well-being than those who spent no time in a green space. However, from 120 minutes, these levels were systematically higher than those participants who had no exposure. The authors suggest that this weekly two-hour contact with nature could represent a minimum threshold for receiving significant benefits to our health and well-being. Moreover, the study reports that this “threshold” is valid for both men and women of all ages, belonging to different professional and ethnic groups, living in both rich and poor areas, and even among those suffering from a long-term illness or disability. Finally, whether it’s a single visit or several shorter immersions, how these 120 minutes are obtained seems to be of little importance.

In conclusion, although this research has significant limitations, including how these 2 hours per week are used (walking, jogging, relaxing on a bench…?), it has the merit of highlighting the importance of directly measuring contact with nature, rather than only measuring residential proximity to nature as an indirect indicator of exposure. According to the authors, these results offer a: “starting point for discussions around providing simple, evidence-based recommendations about the amount of time spent in natural settings that could result in meaningful promotion of health and wellbeing.”