A healthy diet should include 10 portions of fruit and vegetables a day, doubling the five-a-day official advice, say British health experts.

The research, which involved a 12-year study, also found that vegetables were four times healthier than fruit.

The study, by University College London, found that eating large quantities of fruit and vegetables significantly lowered the risk of premature death. People who ate at least seven portions of fruit and vegetables each day were 42%less likely to die from any cause over the course of the study.

Prof Simon Capewell, of the department of public health at the University of Liverpool, said the advice should be 10 portions a day. “Humans are designed to be omnivorous: a handful of nuts, seeds, fruit and the occasional antelope. We’re not meant to be eating junk food.”

Researchers examined the eating habits of 65,000 people in England between 2001 and 2013.

They found that seven helpings a day of fruit or vegetables could reduce a person’s overall risk of premature death by 42% when compared with people who ate just one whole portion.

People who ate between five and seven portions a day had a 36% reduced risk of death, those who ate three to five portions had a 29% decreased risk and those who ate one to three helpings had a 14% reduced risk.

Those with the highest intakes were also 25% less likely to die from cancer and 31% less likely to die from heart disease.

To implement a seven-a-day message would be really challenging for many in society and would require governmental support

“We need to urgently examine seriously the proposal to increase recommended intake to seven a day,” said Naveed Sattar, professor of metabolic medicine at the University of Glasgow. “To implement a seven-a-day message would be really challenging for many in society and would require governmental support such as subsidising the cost of fruitand vegetables, perhaps by taxing sugar-rich foods.”

The study also found that vegetables were far more beneficial than fruit. Each portion of vegetables lowered the risk of death by 16 per cent. However, each piece of fruit only lowered the chance of death by 4 per cent.

The authors said the findings lent support to the Australian government’s advice of “two plus five” a day, which encourages people to eat two helpings of fruit and five of vegetables. Dr Alison Tedstone, the group’s director of diet and obesity, said: “Our focus remains on increasing overall consumption of fruit and vegetables to meet current recommendations.”

The study was published in the Journal of Epidemiology and Community Health.