Quick study: How the Mediterranean diet may help to prevent heart disease

THE QUESTION: Does the Mediterranean diet have an anti-inflammatory effect that may explain its protective role against cardiovascular disease?

THE HISTORY: The Mediterranean diet is defined as a general eating pattern high in "good fats" (from such sources as olive oil, avocado, nuts and seeds) and low in quantities of "bad fat" (from red meat, certain dairy products and commercially processed foods). Adherence to this dietary pattern has been associated with lower mortality and lower incidence of cardiovascular disease and cancer among elderly Europeans. But the mechanisms behind these associations have yet to be determined.

Recent evidence supports the idea that inflammation is a common pathway for atherosclerosis and cardiovascular disease risk factors. While several studies have investigated the effects of single dietary nutrients in reducing inflammation and reversing atherosclerosis, little attention has been given to the effect of overall dietary patterns.

THIS STUDY investigated the effect of the overall Mediterranean dietary pattern on plasma levels of C-reactive protein, an inflammatory marker of cardiovascular health, in the healthy cohort of the Atherosclerotic Disease, Vascular Function and Genetic Epidemiology Study, which included 326 women and 585 men, ages 60-70, between January 2002 and December 2003.

Researchers measured the participants' adherence to the diet. A score was generated for each subject based on intake of particular foods. A high sensitivity detection method was used to assess the plasma levels of C-reactive protein, or CRP.

THE RESULTS: A higher adherence to the Mediterranean diet was associated with lower levels of CRP. This observation suggests an anti-inflammatory effect that may support the diet's protective role against cardiovascular disease.

WHO MAY BE AFFECTED: Cardiovascular disease is the No. 1 killer in the United States and Europe. Among risk factors that can be changed or modified, diet seems to play an important role.

WHY IT MATTERS: Previous studies have suggested that the lower prevalence of cardiovascular disease in southern Europe can partly be explained by adherence to the Mediterranean diet, but these studies have been conducted only on European subjects who already had a healthy diet. Furthermore, these studies did not look at the mechanistic pathways that can explain this protection.

This new study had an ethnically diverse population with what is referred to as a "Westernized diet." Also, instead of just studying whether participants had heart disease, researchers looked at a pathway that leads to the disease—inflammation.

CAVEATS: Further studies are needed to elucidate the mechanisms of the positive effects of the Mediterranean diet. Clinical studies on dietary patterns should include a more diverse population with diets that are more realistic in the United States.

STANFORD CONNECTION: The Atherosclerotic Disease Vascular Function and Genetic Epidemiology Study is a joint collaboration between Stanford University and the Kaiser Permanente Division of Research. Stanford authors include first author Alexandre Kiazand, PhD, and co-authors Joan Fair, PhD, Stephen Fortmann, MD, PhD, and Mohammed Mahbouba.

FIND THIS STUDY: It was published in the Feb. 28 online issue of the American Heart Association's journal Circulation. The study was based on a poster that was presented at the annual Conference on Cardiovascular Disease Epidemiology and Prevention on March 2-5 in Arizona. —Tracie White