Reduced incidence of major cardiovascular events for at-risk patients adherent to Mediterranean diet

1. High risk cardiovascular patients adherent to a Mediterranean diet supplemented with nuts or extra virgin olive oil had a lower incidence of major cardiovascular events compared to patients advised to follow a reduced fat diet at a median follow-up of 4.8 years.

2. Stroke incidence was lower in patients on a Mediterranean diet compared to the patients following a reduced fat diet.

Evidence Rating Level: 1 (Excellent)     

Study Rundown: Observational studies have shown that people adherent to the Mediterranean diet often have low cardiovascular risk. While there are biologic mechanisms which support health benefits of adherence to the diet, high quality randomized studies evaluating this diet are lacking. The PREDIMED (Prevención con Dieta Mediterránea) trial sought to evaluate the Mediterranean diet supplemented with either nuts or olive oil. Original trial results published in 2013 were shown to have flawed analysis, and this reevaluation of trial results is reported. The primary outcome, occurrence of a major cardiovascular event, was significantly less frequent in the groups assigned to the Mediterranean diet with either nuts or olive oil compared to the reduced fat control group.

This analysis importantly accounts for patients who were previously thought to be randomized to a trial group but were in fact not randomized. Study strengths include its randomized, prospective design and evaluation of a diet with different nutritional supplementations. Limitations include a lack of outcomes evaluation once patients are no longer provided with nutritional support as part of the study.

Click to read the study, published in NEJM

Relevant Reading: A comprehensive meta-analysis on evidence of Mediterranean diet and cardiovascular disease: Are individual components equal?

In-Depth [randomized controlled trial]: This randomized controlled trial enrolled 7447 patients between 2003 and 2009. Patients aged 55 to 80 at high risk for cardiovascular disease but without any history of major cardiovascular events were eligible. Three trial groups included Mediterranean diet groups supplemented with either nuts (n = 2454) or extra virgin olive oil (n = 2543) and a control group (n = 2450) which was advised to reduce fat intake. All patients received dietary counseling. Patients were evaluated for adherence to the diet, and patients assigned to the nuts or olive oil groups received these items as part of the study. The primary outcome was incidence of major cardiovascular events including myocardial infarction, stroke, and death from cardiovascular disease. Secondary endpoints included individual incidence of stroke, myocardial infarction, and death.

Median follow-up time was 4.8 years. Patients in the Mediterranean diet groups had significant increases in fish and legume consumption compared to the control group. In an intention-to-treat analysis the primary composite cardiovascular event outcome occurred in 3.8% of the olive oil group, 3.4% of the nuts group, and 4.4% of the control group (hazard ratio [HR], 0.70 and 0.70; 95% confidence interval [CI], 0.53 to 0.92 and 0.53 to 0.94; for the olive oil and nuts groups compared to the control group, respectively). Patients on either Mediterranean diet were significantly less likely to experience a stroke than the control group, though there was no significant difference observed for outcomes of myocardial infarction, all cause death, or death from cardiovascular cause.

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