Feb. 25, 2013 at 9:25 AM ET
A Mediterranean diet rich in fruits, vegetables, olive oil and a little wine can cut the risk of heart attacks and strokes by 30 percent, researchers reported on Monday in a study that shows the real-life benefits of a diet long encouraged by doctors.
The results were so startling that the study was cut short after less than five years, and the results rushed to publication in the New England Journal of Medicine.
“A Mediterranean diet supplemented with extra-virgin olive oil or nuts reduced the incidence of major cardiovascular events,” the researchers, led by Dr. Ramon Estruch of the Carlos III Health Institute in Barcelona, wrote.
The study was done in Spain, where people already supposedly eat the Mediterranean diet -- which is characterized by lots of salad, fruit, vegetables, nuts, a little fish, a little lean meat, a small amount of cheese and olive oil. Wine is also served at meals. But the 7,400 volunteers in the trial got extra counseling, and either a weekly supply of extra-virgin olive oil or mixed nuts.
Many studies have shown that people who eat a Mediterranean diet are less likely to die of heart disease. This one was powerful because it randomly assigned people to eat such a diet as part of their normal lives over several years.
The 7,400 patients aged 55 to 80 were all high risk of heart disease because of diabetes, a family history of heart disease, high blood pressure, unhealthy cholesterol levels or they were overweight or smokers.
They were randomly assigned to one of three groups: a Mediterranean diet with extra-virgin olive oil added; the same diet but with mixed nuts; or just a standard diet with advice to cut fat. They were given either a liter of olive oil per week (for the olive oil group), 30 grams of walnuts, hazelnuts and almonds (for the nut group), or little non-food presents for the control group.
They all got individual and group counseling.
After nearly five years, 58 people who simply followed a low-fat diet had strokes, but just 32 people did if they ate a Mediterranean diet with nuts, and 49 who followed the Mediterranean diet with extra olive oil. The Mediterranean diet also cut the risk of heart attack.
Thirty people died from heart disease in the control group, compared to 31 who ate the Mediterranean diet with nuts and 26 who at the Mediterranean diet with olive oil.
But the people who ate a Mediterranean diet were less likely to die overall in the five years, compared to those in the control group. Overall, the Mediterranean diets cut the risk of heart disease death, heart attacks and strokes by 30 percent, the researchers calculated.
"This is another piece of evidence for the benefits of diets containing 'good' fats such as those in olive oil and nuts," said nutrition expert Marion Nestle of New York University.
"I wonder whether they plan to continue the trial for a longer time—I didn’t see any comment on that—because a few more years might give greater clarity," Nestle added in an e-mail.
There are lots of reasons why a Mediterranean-style diet might reduce heart disease. Researchers had noticed that people in Northern Europe, who eat butter and lard more than olive oil, were more likely to die of heart disease than their Southern European neighbors, even if they were just as overweight and exercised the same amount. A study of the diet’s benefits published back in the 1960s showed the diet cut the rate of strokes and heart attacks, probably because it lowered cholesterol levels.
Olive oil and nuts contain monounsaturated fats, which are better for artery health than the saturated fats found in butter, meat and lard. The diet is also high in fiber and vitamins such as A, C and E, as well as minerals. Walnuts and fish are rich in omega-3 fatty acids, which have been shown to benefit heart health. And reducing meat has been shown to cut the risk of both heart disease and cancer.