A two-hour “dose” of nature a week significantly boosts health and wellbeing, research suggests, even if you simply sit and enjoy the peace.

The physical and mental health benefits of time spent in parks, woods or the beach are well known, but the new research is the first major study into how long is needed to produce the effect. If confirmed by future research, two hours in nature could join five a day of fruit and veg and 150 minutes of exercise a week as official health advice.

The finding is based on interviews with 20,000 people in England about their activity in the previous week. Of those who spent little or no time in nature, a quarter reported poor health and almost half said they were not satisfied with their life, a standard measure of wellbeing. In contrast, just one-seventh of those who spent at least two hours in nature said their health was poor, while a third were not satisfied with their life.

“What really amazed us was this was true for just about every group we could think of,” said Dr Mathew White, at the University of Exeter Medical School, who led the study. The benefits of a two-hour dose were the same for both young and old, wealthy and poor, and urban and rural people, he said.

It also applied to those with long-term illnesses and disabilities, White said. “So getting out in nature seemed to be good for just about everybody. It doesn’t have to be physical exercise – it could be just sitting on a bench.”

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The researchers were also surprised that it did not matter whether the two hours in nature were taken in one go or in a series of shorter visits, or whether people went to an urban park, woodlands or the beach.

Prof Helen Stokes-Lampard, the chair of the Royal College of General Practitioners, said: “It’s fascinating to see this link between exposure to nature and better health and wellbeing. This research makes a strong case for people to get out and about in more natural environments.

“More widely, patients often benefit from non-medical interventions such as an exercise class, learning a skill or joining a community group – often referred to as ‘social prescribing’. However, with the pressures currently facing primary care, many GP practices [can’t] spend the necessary time with a patient to link them with the most appropriate activity.”

The research, published in the journal Scientific Reports, used data from a Natural England survey, the world’s largest study collecting data on people’s weekly contact with the natural world. It did not include time people spent in their gardens, as this was not measured. But White said half of people saw their gardens as representing more of a chore than a pleasure in any case. The data showed that two hours was the threshold for positive impacts: spending much more than that in natural environments did not appear to have any additional benefits.

“I am continually surprised by the size of the effect,” White said. The boost to health was the same as previous studies have shown come from taking recommended levels of exercise, or living in well-off neighbourhoods compared with poorer areas.

The study did not attempt to find out why being in nature was so beneficial, but White suggested a sense of tranquillity could be the key: “Most people are under multiple pressures at any given time. So you go away in a natural setting, it is quiet, it is relaxing and it gives you time to start to process things.

“We are also increasingly finding that the richness in biodiversity of a setting seems to be important. We have tracked 4,500 people’s visits from the same survey and what you find is they get more stress reduction if the location was an area of outstanding natural beauty, a site of special scientific interest or that kind of thing.”

The researchers took a series of factors into account in reaching their conclusions, including the greenness of a person’s neighbourhood, levels of air pollution, and whether they were married, had children or had dogs.

They could not completely take account of whether the health boost was down to taking more exercise. But the researchers wrote: “Research into shinrin-yoku – Japanese “forest bathing” – for instance, suggested that various psychophysiological benefits can be gained from merely sitting passively in natural versus urban settings.”