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Mediterranean Diet Gains New Attention in Clinical Study

A Spanish team gave participants olive oil and nuts and found dramatically lower risk of heart disease

Jacob Gaffney
Posted: February 28, 2013

A new study of the Mediterranean diet is generating a large amount of buzz. The research echoes numerous studies in the past decade that found that a traditional diet common in countries like Italy and Spain, heavy in olive oil, nuts, fish—and often red wine—can lower risks of heart disease. Most previous studies were surveys of populations. The new research appears to be the first major clinical trial in which people's meals were supplemented to mimic a Mediterranean diet, and the results showed clear benefits.

Time and time again, observational medical research has noted greater heart and brain health in those who follow the Mediterranean diet, characterized by a high intake of olive oil, fish, fruit, grains and vegetables. Red meat and high-fat dairy products are consumed rarely. For those who choose to drink, the beverage is often red wine in moderation.

The new study, published online Feb. 25 by the New England Journal of Medicine, concluded that when the diets of an elderly Spanish population were supplemented with extra olive oil and nuts, cardiovascular and neurological benefits increased. The researchers, who work in several medical clinics across Spain, began this project, known by the acronym PREDIMED, in 2003 to look for ways to reduce the growing health burden of cardiovascular disease.

The 9,000 participants were chosen based on having at least two risk factors for heart disease or stoke, for example, if they smoked, suffered from type-2 diabetes, high cholesterol, hypertension or were obese.

The authors noted that previous research ranks the Mediterranean diet as the most likely dietary model to provide protection against coronary heart disease. But could it help those already at risk? "Small clinical trials have uncovered plausible biologic mechanisms to explain the salutary effects of this food pattern," they wrote. The scientists hypothesized that having the subjects follow a souped-up Mediterranean diet could show even more protection.

In order to test this theory, one-third of the subjects were provided food to supplement their Mediterranean diets, including Spanish extra-virgin olive oil, almonds, hazelnuts and California walnuts. Another third of the subjects followed an un-supplemented Mediterranean diet. The final third were assigned a low-fat diet, received less dietary guidance and served as the control group.

After nearly five years of followup visits, the scientists noted causes of death and compared the results across dietary patterns. In nearly every category of death, followers of either Mediterranean diet were at a lower risk when compared to the control group.

In the categories of strokes and heart attacks, followers of the supplemented version enjoyed even greater levels of protection. Stroke risk, already a 33 percent lower risk in the un-supplemented Mediterranean diet group, dropped to a whopping 46 percent lower risk for the group given more nuts and olive oil. This also happened with risk of heart attack, to a lesser degree.

"A causal role of the Mediterranean diet in cardiovascular prevention has high biologic plausibility," the authors wrote. "The results of our trial might explain, in part, the lower cardiovascular mortality in Mediterranean countries than in northern European countries or the United States."

The scientists do caution that their results remain limited in scope. "Because all the study participants lived in a Mediterranean country and were at high cardiovascular risk; whether the results can be generalized to persons at lower risk or to other settings requires further research," they wrote.

The study did not focus on wine, but refers to red wine as a "salient component" of the diet.

Evidence of the benefits of a Mediterranean diet has been chronicled for more than a decade by Wine Spectator. Antonia Trichopoulou, a professor at the University of Athens Medical School, who collaborates with the World Health Organization, studied the diets of tens of thousands of Europeans and found similar results in a 2003 study. "Wine is an integral part of the Mediterranean diet, provided that consumption is moderate and during meals," she said.

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