Active dietary intervention, not diet type, improves outcomes

March 25, 2007

The first trial to compare a Mediterranean-style diet with the American Heart Association (AHA) Step-2 diet plan indicates that active dietary intervention improves cardiovascular (CV) outcomes in high-risk patients. Katherine Tuttle, MD, reported results of the randomized trial during the American College of Cardiology's 56th annual scientific session. Dietary intervention decreased CV events by two-thirds.

The first trial to compare a Mediterranean-style diet with the American Heart Association (AHA) Step-2 diet plan indicates that active dietary intervention improves cardiovascular (CV) outcomes in high-risk patients. Katherine Tuttle, MD, reported results of the randomized trial during the American College of Cardiology's 56th annual scientific session. Dietary intervention decreased CV events by two-thirds.

"While previous trials have shown that a Mediterranean diet improves cardiovascular risk the trial designs have not included an active comparator arm. Control groups received advice rather than active dietary intervention," said Dr. Tuttle, medical and scientific director, Providence Medical Research Center, Spokane, Wash.

In this 2-year study, 90 patients were randomized to follow the Mediterranean or AHA diet within 6 weeks after having a first myocardial infarction (MI). Both groups received active dietary intervention of equal intensity including two individual counseling sessions with a dietician in the first month with additional sessions at months 3, 6, 12, 18, and 24. Patients following both diets also attended at least six group counseling sessions over the 2-year period and attended classes offered monthly. Participants prepared their own food.

The Mediterranean and AHA diet plans were similar in cholesterol and saturated fat intake, but the Mediterranean diet was higher in total fat due to increases in monounsaturated fat and omega-3 fatty acid intake, which was mostly from fish-based sources. Both groups increased consumption of whole grains and fresh vegetables.

The trial also included a comparator group who received "usual care" consisting of standard dietary advice while hospitalized for a first MI with no additional dietary intervention. The comparator group was matched for sex, age, MI type, diabetes, and hypertension with the dietary intervention groups.

The primary outcome was survival free of death, recurrent MI, unstable angina, stroke, or hospitalization for chronic heart failure. "We found no difference between the AHA and Mediterranean-style dietary intervention groups. However, both dietary intervention groups fared much better than those having usual care," Dr. Tuttle said.

At a mean follow-up of 46 months, the odds ratio of having a primary outcome event was 0.33 in those receiving dietary intervention. There were eight events in each diet group for a total of 16 among patients receiving dietary intervention, compared with 40 events among the usual care comparator patients.

HDL cholesterol increased and triglycerides decreased similarly in both dietary intervention groups but there was no significant decrease in LDL cholesterol, Dr. Tuttle said. The only significant difference in nutrient intake was in the Mediterranean diet group where the average intake of omega-3 fatty acids increased to the goals set by the study.

"While event-free survival did not differ between the AHA and Mediterranean groups despite greater omega-3 intake, dietary intervention was associated with improved outcomes compared to usual care," Dr. Tuttle said.