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Prevention of CVD With Supplemented Mediterranean Diet
Study Questions:
What is the relative merit for cardiovascular disease (CVD) prevention of the Mediterranean diet with nutrient supplements compared to a low fat diet?
Methods:
In a multicenter trial in Spain, 7,447 participants (55-80 years of age, 57% women) who were at high CVD risk, but with no CVD at enrollment, were assigned to one of three diets: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control diet (advice to reduce dietary fat). Participants received quarterly educational sessions and, depending on group assignment, free provision of extra-virgin olive oil, mixed nuts, or small nonfood gifts. High risk was defined as either type 2 diabetes mellitus or at least three of the following: smoking, hypertension, elevated low-density lipoprotein cholesterol levels, low high-density lipoprotein cholesterol levels, overweight or obesity, or a family history of premature coronary heart disease. The primary endpoint was a major CV event (myocardial infarction, stroke, or death from CV causes). After a median follow-up of 4.8 years, the trial was stopped on the basis of a prespecified interim analysis. In 2013, the authors reported the results for the primary endpoint in the same journal (New England Journal of Medicine). The previously published report was withdrawn, and revised effect-estimates were based on analyses that do not rely exclusively on the assumption that all the participants were randomly assigned.
Results:
A primary endpoint event occurred in 288 participants; there were 96 events in the groups assigned to a Mediterranean diet with extra-virgin olive oil (3.8%), 83 in the groups assigned to a Mediterranean diet with nuts (3.4%), and 109 in the control group (4.4%). In the intention-to-treat analysis including all the participants and adjusting for baseline characteristics and propensity scores, the hazard ratio was 0.69 (95% confidence interval [CI], 0.53-.91) for a Mediterranean diet with extra-virgin olive oil and 0.72 (95% CI, 0.54-0.95) for a Mediterranean diet with nuts, as compared with the control diet. Results were similar after the omission of 1,588 participants whose study group assignments were known or suspected to have departed from the protocol.
Conclusions:
In this study involving persons at high CV risk, the incidence of major CV events was lower among those assigned to a Mediterranean diet supplemented with extra-virgin olive oil or nuts than among those assigned to a reduced-fat diet.
Perspective:
The authors are to be congratulated for the re-analysis of this very important study, which many will be happy to quote. Observational studies have supported the value of the Mediterranean diet as well as olive oil and nut supplements. This randomized study is particularly strong in that it was conducted in a high-risk cohort and powered adequately in a population that often follows the Mediterranean diet, which is already high in nuts and olive oil.
Keywords: Cholesterol, HDL, Cholesterol, LDL, Coronary Disease, Diabetes Mellitus, Type 2, Diet, Fat-Restricted, Diet, Mediterranean, Dietary Fats, Hypertension, Myocardial Infarction, Nuts, Obesity, Overweight, Primary Prevention, Smoking, Stroke
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