Mediterranean Diet May Be Effective in Reducing Prevalence of Metabolic Syndrome

Mediterranean Diet and Metabolic Syndrome

In another study in this issue of JAMA, Katherine Esposito, M.D., of the Second University of Naples, Italy, and colleagues demonstrated that a Mediterranean style diet had beneficial effects on endothelial (a layer of flat cells lining the closed internal spaces of the body, including the blood vessels) function and in reducing vascular inflammatory markers in patients with the metabolic syndrome.

According to background information in the article, the metabolic syndrome consists of several factors that increase the risk of cardiovascular disease and type 2 diabetes. Recent estimates indicate that the metabolic syndrome is highly prevalent in the United States, with an estimated 24 percent of the adult population affected. Its clinical identification is based on measures of abdominal obesity, atherogenic dyslipidemia (the formation of high levels of lipid deposits in the arteries), elevated blood pressure, and glucose intolerance. The metabolic syndrome has been identified as a target for dietary therapies to reduce risk of cardiovascular disease; however, the role of diet as contributing to the metabolic syndrome is poorly understood.

The randomized trial was conducted from June 2001 to January 2004 at a university hospital in Italy among 180 patients (99 men and 81 women) with the metabolic syndrome. Patients in the intervention group (n=90) were instructed to follow a Mediterranean-style diet and received detailed advice about how to increase daily consumption of whole grains, fruits, vegetables, nuts, and olive oil; patients in the control group (n=90) followed a prudent diet (carbohydrates, 50 percent-60 percent; proteins, 15 percent-20 percent; total fat, less than 30 percent).

The researchers found that after 2 years, patients in the Mediterranean diet intervention group had significant decreases in body weight, blood pressure, levels of glucose, insulin, total cholesterol, and triglycerides and a significant increase in levels of high-density lipoprotein cholesterol, all of which were greater than those recorded in the control group. Serum concentrations of interleukins 6 (IL-6), 7 (IL-7), and 18 (IL-18) and high-sensitivity C-reactive protein (hs-CRP) were significantly reduced in patients in the intervention group compared with those in the control group. Endothelial function score improved in the intervention group but remained stable in the control group.

Forty patients consuming the intervention diet still had features of the metabolic syndrome, compared with 78 patients consuming the control diet. Participants who followed the intervention diet showed a reduction in the number of the components of the syndrome such that the overall prevalence of the metabolic syndrome was reduced by approximately one half.

"The results of this study represent the first demonstration, to our knowledge, that a Mediterranean-style diet rich in whole grains, fruits, vegetables, legumes, walnuts, and olive oil might be effective in reducing both the prevalence of the metabolic syndrome and its associated cardiovascular risk," the authors conclude. (JAMA. 2004;292:1440-1446)