The Mediterranean diet is effective in the primary prevention of cardiovascular disease (CVD), but there is little evidence of its efficacy in the secondary prevention of CVD. A large-scale, long-term randomized clinical trial compared the efficacy of the Mediterranean diet with that of a low-fat diet in secondary CVD prevention.

Men and women 20 to 75 years of age with established coronary heart disease were eligible for the study, which was conducted in a single center. The 1,002 patients included in the study (82.5% men; average age, 59.5 years) were randomly assigned to the Mediterranean diet, comprising 35% or more calories as fat, or the low-fat, high complex carbohydrates diet, comprising less than 30% of calories as fat. During seven years of follow-up, patients in each group received comprehensive, tailored, and continuous dietary support.

The primary outcome-a composite of major cardiovascular events, including myocardial infarction, revascularization, ischemic stroke, peripheral artery disease, and cardiovascular death-occurred in 87 patients (17.3%) in the Mediterranean diet group and 111 patients (22.2%) in the low-fat diet group. In all models, the Mediterranean diet was superior to the low-fat diet, with hazard ratios for the primary end point ranging from 0.719 to 0.753. The differences were more evident in men than women, with the primary outcome occurring in 16.2% of men in the Mediterranean diet group compared with 22.8% in the low-fat diet group. There were no statistical differences between the groups for women.

The authors note that the study was conducted in a controlled environment with continuous support, so the results may not apply to other settings. Furthermore, the study included only patients who had established coronary heart disease and was conducted in Spain, a country where the Mediterranean diet is highly accepted.