How much "green exercise" produces the greatest improvement in mood and sense of personal well-being? A new study in the American Chemical Society's semi-monthly journal Environmental Science & Technology has a surprising answer.
The answer is likely to please people in a society with much to do but little time to do it: Just five minutes of exercise in a park, working in a backyard garden, on a nature trail, or other green space will benefit mental health.
Jules Pretty and Jo Barton explain in the study that green exercise is physical activity in the presence of nature. Abundant scientific evidence shows that activity in natural areas decreases the risk of mental illness and improves the sense of well-being. Until now, however, nobody knew how much time people had to spend in green spaces to get those and other benefits.
"For the first time in the scientific literature, we have been able to show dose-response relationships for the positive effects of nature on human mental health," Pretty said.
From an analysis of 1,252 people (of different ages, genders and mental health status) drawn from ten existing studies in the United Kingdom, the authors were able to show that activity in the presence of nature led to mental and physical health improvements.
They analyzed activities such as walking, gardening, cycling, fishing, boating, horse-riding and farming. The greatest health changes occurred in the young and the mentally-ill, although people of all ages and social groups benefited. All natural environments were beneficial including parks in urban settings. Green areas with water added something extra. A blue and green environment seems even better for health, Pretty noted.
From a health policy perspective, the largest positive effect on self-esteem came from a five-minute dose.
"We know from the literature that short-term mental health improvements are protective of long-term health benefits," Pretty said. "So we believe that there would be a large potential benefit to individuals, society and to the costs of the health service if all groups of people were to self-medicate more with green exercise," added Barton.
A challenge for policy makers is that policy recommendations on physical activity are easily stated but rarely adopted widely as public policy, Pretty noted, adding that the economic benefits could be substantial.
Policy frameworks that suggest active living point to the need for changes to physical, social and natural environments, and are more likely to be effective if physical activity becomes an inevitable part of life rather than a matter of daily choice.