The diet regime is already known to have a powerful protective effect against a number of diseases, including diabetes and cancer.
Experts hailed the new findings, presented at the world's biggest heart conference in Rome, Italy, as "extraordinary", showing that the diet was "more powerful than any drug".
High consumption of vegetables had the greatest impact on survival, followed by oily fish intake, amount of fruit eaten and consumption of mono-unsaturated fat, found in olive oil.
Professor Giovanni de Gaetano, head of the Department of Epidemiology and Prevention at the IRCCS Neuromed Institute in Italy, said: "We found that among those with a higher adherence to the Mediterranean diet, death from any cause was reduced by 37 per cent in comparison to those who poorly adhered to this dietary regime.
"The Mediterranean diet is widely recognised as one of the healthier nutrition habits in the world.
"In fact, many scientific studies have shown that a traditional Mediterranean lifestyle is associated with a lower risk of various chronic diseases and, more importantly, of death from any cause.
"But so far research has focused on the general population, which is mainly composed of healthy people. What happens to people who have already suffered from cardiovascular disease? Is the Mediterranean diet optimal for them too?"
He said the research suggested exactly this, with the Med diet showing a "powerful" effect, cutting deaths from all causes.
Doctors should "consider diet before drugs" and the state should subsidise fruit and vegetables to encourage Britons towards healthier diets, he said.
"The National Health Service pays for drugs, but it doesn't pay for vegetables," he said.
"The state should consider contributing towards those foods that make up the Mediterranean diet."