Mediterranean diet can ward off heart disease: study

A Mediterranean diet high in olive oil, nuts, fish and fresh fruits and vegetables may help prevent heart disease and strokes, according to a new large study from Spain.

Past research suggested people who eat a Mediterranean-like diet have healthier hearts, but those studies couldn't rule out that other health or lifestyle differences had made the difference.

For the new trial, researchers randomly assigned study volunteers at risk of heart disease to a Mediterranean or standard low-fat diet for five years, allowing the team to single out the effect of diet, in particular.

"This is good news, because we know how to prevent the main cause of deaths - that is cardiovascular disease - with a good diet," said Dr. Miguel Angel Martinez-Gonzalez, who worked on the study at the Universidad de Navarra in Pamplona.

He and colleagues from across Spain assigned almost 7,500 older adults with diabetes or other heart risks to one of three groups.

Two groups were instructed to eat a Mediterranean diet - one supplemented with extra-virgin olive oil and the other with nuts, both donated for the study - with help from personalized advice and group meetings. The third study group ate a "control" diet, which emphasized low-fat dairy products, grains and fruits and vegetables.

Over the next five years, 288 study participants had a heart attack or stroke or died of any type of cardiovascular disease.

As with many clinical trials, the observed rates of cardiovascular events were lower than anticipated, with reduced statistical power to separately assess components of the primary end point. However, favorable trends were seen for both stroke and myocardial infarction. We acknowledge that, even though participants in the control group received advice to reduce fat intake, changes in total fat were small and the largest differences at the end of the trial were in the distribution of fat subtypes. The interventions were intended to improve the overall dietary pattern, but the major between-group differences involved the supplemental items. Thus, extra-virgin olive oil and nuts were probably responsible for most of the observed benefits of the Mediterranean diets. Differences were also observed for fish and legumes but not for other food groups. The small between-group differences in the diets during the trial are probably due to the facts that for most trial participants the baseline diet was similar to the trial Mediterranean diet and that the control group was given recommendations for a healthy diet, suggesting a potentially greater benefit of the Mediterranean diet as compared with Western diets.

In conclusion, in this primary prevention trial, we observed that an energy-unrestricted Mediterranean diet, supplemented with extra-virgin olive oil or nuts, resulted in a substantial reduction in the risk of major cardiovascular events among high-risk persons. The results support the benefits of the Mediterranean diet for the primary prevention of cardiovascular disease.