Whether a Mediterranean-style diet reduces cardiovascular events and mortality more than a low-fat diet is uncertain. The objectives of this study were to actively compare low-fat and Mediterranean-style diets after first myocardial infarction (MI) in a randomized, controlled clinical trial and to compare dietary intervention per se with usual care in a case-control analysis. First MI survivors were randomized to a low-fat (n = 50) or Mediterranean-style (n = 51) diet. The 2 diets were low in saturated fat (<7% kcal) and cholesterol (<200 mg/day); the Mediterranean-style diet was distinguished by greater omega-3 fat intake (>0.75% kcal). Participants received individual dietary counseling sessions, 2 within the first month and again at 3, 6, 12, 18, and 24 months, along with 6 group sessions. Combined dietary intervention groups (cases, n = 101) were compared with a usual-care group (controls, n = 101) matched for age, gender, MI type and treatment, and status of diabetes mellitus and hypertension. Primary-outcome-free survival (a composite of all-cause and cardiac deaths, MI, hospital admissions for heart failure, unstable angina pectoris, or stroke) did not differ between low-fat (42 of 50) and Mediterranean-style (43 of 51) diet groups over a median follow-up period of 46 months (range 18 to 72; log-rank p <0.81). Patients receiving dietary intervention had better primary-outcome-free survival (85 of 101) than usual-care controls (61 of 101) (log-rank p <0.001), with unadjusted and adjusted odds ratios of 0.33 (95% confidence interval 0.18 to 0.60, p <0.001) and 0.28 (95% confidence interval 0.13 to 0.63, p = 0.002), respectively. In conclusion, active intervention with either a low-fat or a Mediterranean-style diet similarly and significantly benefits overall and cardiovascular-event-free survival after MI.

Editor's Comments. These 2 studies appear similar with respect to the research question that each poses. Is the Mediterranean diet beneficial for reducing mortality from heart disease and all-cause mortality? Most professionals would respond in the affirmative. In fact, the Mediterranean diet has been shown to be associated with lower cardiovascular mortality in both apparently healthy populations and in patients with heart disease. Mitrou et al found that the Mediterranean diet was associated with lower mortality (all-cause, CVD, and cancer) in men and women. This study is purported to be the first with an American cohort. Tuttle et al studied a group of people after first MI and assessed Mediterranean versus low fat diet. The sample size is rather small. Nonetheless they demonstrated that both low fat and Mediterranean diets reduced mortality in post-MI patients. One logical conclusion would be that the Mediterranean diet and low fat diets are equally beneficial, but these data may not entirely bear this out. One of the reasons that I selected these studies is to show the difference between epidemiological and experimental research. The Epidemiological cohort in Mitrou et al of over 214,000 men and 166,000 women is impressive in sample size and increases the power of the data. It should be emphasized that Mitrou et al did not use a sample of people with heart disease. Though the study by Tuttle et al included people with heart disease, it did not look exclusively at the Mediterranean diet. Closer inspection of the data from Tuttle et al confirms that the actual difference between the 2 groups with respect to nutrient intake was minimal. Tuttle et al verified the nutritional content of each diet over the course of the 2 years. The only significant difference in intake was in omega-3 fat, thus there were no differences in nutrients such as saturated or polyunsaturated fat, or fiber. The appropriate question, therefore, is what characterizes one diet as "Mediterranean" and the other as "low fat," if the only difference is omega-3 intake. Clearly, a "Mediterranean" diet is different from a "low fat" diet, but not only in omega-3 intake. The conclusions from Tuttle et al, therefore, may be questionable. More importantly, if the practitioner simply reads the abstract (and not the complete article), the conclusion would be that we could simply coach patients toward a low fat diet and get the same results. This conclusion is not accurate given the data presented in the Tuttle et al article or given the conclusions from a large data set on Mediterranean diet.

-JLR