Imagine a supplement that claimed to reduce heart disease, diabetes and premature death. People would be lining up for miles to buy it. Yet that's exactly what time spent in nature can do for people, an analysis of over 140 studies found. Maybe it's time your doctor prescribed a trip to the park.

Most people know that taking a timeout in nature is good for both body and soul. But it's the breadth of what this analysis found that makes it so noteworthy.

The researchers reported that people spending time in or living close to natural green spaces had a lower risk of type 2 diabetes, cardiovascular disease, premature death and preterm birth. They also had reduced diastolic blood pressure, heart rate and stress; and they slept longer and better.

Aiming to be as broad as possible, the analysis reviewed 143 studies involving over 290 million people. It studied how the health of people with little access to green spaces compared to those with the highest exposure.

Greenspace was defined broadly, anything from trees on a city street to pristine wilderness. Virtually all of the study articles (96 percent) were published in the last 10 years, illustrating the growth of interest in how greenspace affects health. The studies came from 20 different countries, with half from Europe.

People spending time in or living close to natural green spaces had a lower risk of type 2 diabetes, cardiovascular disease, reduced diastolic blood pressure, heart rate and stress. They also slept longer and better.

Spending time in or living close to natural green spaces was associated with diverse and significant health benefits. Even the sight of greenery had benefits. In that study, hospital patients who had their gallbladder removed needed fewer potent painkillers after surgery when their hospital room looked out on greenery compared to patients whose room faced a brick wall.

There are some caveats to the findings. On some topics, such as diabetes, results varied greatly from study to study, though the average came up as beneficial. And the analysis did include some studies that the authors characterize as poor quality. They decided not to exclude any studies that they had assigned a low quality score to, aiming instead for breadth of the analysis. And of course in any analysis of over 140 different studies, there is always the problem of how to compare apples to oranges, though protocols for doing so do exist.

Despite these few cautions, lead author, Caoimhe Twohig-Bennett, of the Norwich Medical School, sees a definite practical message: “We hope that this research will inspire people to get outside more and feel the health benefits for themselves. Hopefully our results will encourage policymakers and town planners to invest in the creation, regeneration, and maintenance of parks and greenspaces, particularly in urban residential areas and deprived communities that could benefit the most.”

The analysis appears in Environmental Studies.