The rate of myocardial infarctions (MIs), strokes, and heart disease–related deaths in persons at high risk for cardiovascular disease (CVD) may be reduced by about 30% in those who consume a Mediterranean diet, according to the first major clinical trial to use rigorous end points to measure the effects of the diet on CV risks.
“We have demonstrated the protective effects of a Mediterranean diet with the highest scientific evidence level,” lead author Ramon Estruch, MD, a professor of medicine at the University of Barcelona, told ConsultantLive. “It is a randomized intervention trial, which included a high number of participants (nearly 7500) and a long follow-up (a mean of nearly 5 years), and the final variables analyzed were hard end points, such as acute myocardial infarction, stroke, and cardiovascular death.”
Dr Estruch and colleagues reported their results online February 25, 2013, in the New England Journal of Medicine.
The randomized trial tested the efficacy of 2 Mediterranean diets, one supplemented with extra-virgin olive oil and the other with nuts, compared with a control diet in which patients were given advice on eating a low-fat diet. At study entry, the patients had no CVD and had either type 2 diabetes mellitus or at least 3 of the major CV risk factors. The main aim was to evaluate the effects of a Mediterranean intervention on a composite of acute MI, stroke, and CV death.
“Our main conclusion is that a Mediterranean diet reduces the risk of cardiovascular events by 30%. The trial was stopped early since the statistical differences between the effects of the Mediterranean diet versus those of the low-fat diet were lower than 0.02,” says Dr Estruch. “At this moment, the protective effects on stroke were higher than the other secondary end points, but we believe that if the trial was not stopped, the effects on myocardial infarction or cardiovascular death would reach statistical significance.”
So what diet should primary care physicians recommend to their patients to prevent CVD?
“We recommend that subjects at high cardiovascular risk should eat a traditional Mediterranean diet,” says Dr Estruch. “A low-fat diet is not the best diet for protection against cardiovascular disease, even in obese patients. According to our results, a traditional Mediterranean diet will be more helpful.”
But some experts question the study’s results. Dean Ornish, MD, president, Preventive Medicine Research Institute, and a proponent of a very low-fat diet for heart disease prevention, suggested that the low-fat, control group’s diet was not very low in fat. “In the ‘low-fat’ group, total fat consumption decreased insignificantly, from 39% to 37%. This doesn’t even come close to the American Heart Association guidelines of a low-fat diet (less than 30% fat) or ours for reversing heart disease (less than 10% fat),” wrote Dr Ornish in a Huffington Post commentary. “The authors should have concluded that the Mediterranean diet reduced cardiovascular risk when compared to whatever diet they were eating before, not when compared to a low-fat diet, since patients in the control group (‘low-fat diet’) were not consuming a low-fat diet.”
Dr Estruch replies: “In respect to a very, very low fat diet (less than 10% fat content), only a few people, such as vegans, are able to follow it for a long time. In our study, many more people in the control low-fat diet group dropped out from the trial than in the Mediterranean diet arms.”