The Mediterranean-Style Diet and Metabolic Syndrome

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Esposito K, Marfella R, Ciotola M, et al.: Effect of a Mediterranean-style diet on endothelial dysfunction and markers of vascular inflammation in the metabolic syndrome. JAMA 292:1440-1446, 2004.

What is the problem, and what is known about it so far?

Metabolic syndrome is a group of risk factors (like obesity, high blood pressure, and other things) that increases the chance of getting heart disease and type 2 diabetes. How a person's diet affects this syndrome isn't known, but the American Heart Association and studies by other researchers have reported that following a Mediterranean-style diet helps people avoid heart disease. A Mediterranean diet is high in whole grains, fruits, vegetables, peas and beans, walnuts, and olive oil.

Researchers wanted to find out if a Mediterranean-style diet would help lower the chance of people getting metabolic syndrome.

Who was studied?

A total of 180 men and women were studied for 2 years.

How was the study done?

Participants in the study were put in one of two groups. One group, called the intervention group, was given detailed advice at monthly meetings on how to reduce the amount of calories they ate. They also were given diaries to keep track of what they ate. The researchers recommended that the intervention group's daily calories should consist of 50-60% carbohydrates, 15-20% proteins, and less than 30% fat (with less than 10% saturated fat). Each person in the intervention group was given advice and had monthly counseling with a nutritionist for the first year. In the second year, each person had a private session every other month.

The second group, called the control group, was given general instructions about healthy food choices, but no specific or personalized information. For two years this group met every other month with researchers.

Both the intervention group and the control group were given general guidelines on how to increase their physical activity by at least 30 minutes each day.

What did the researchers find?

After 2 years, the intervention group showed a major decrease in body weight, blood pressure, and levels of glucose, insulin, total cholesterol, and triglycerides (fat in the blood). This group also showed a large increase in high-density lipoprotein (the "good" cholesterol) levels. This meant that more than half of the intervention group no longer had metabolic syndrome and reduced their chances of getting type 2 diabetes and heart disease.

The control group showed no major improvements in body weight, blood pressure, or the other factors. As a result, 78 of the 90 patients in the control group still had metabolic syndrome and increased risk of getting heart disease and type 2 diabetes.

What were the limitations of the study?

It is difficult to tell if any one part of the Mediterranean diet helped people, or if the benefits were because of a combination of all the items in the diet.

What are the implications of the study?

This study suggests that when people follow a diet high in whole grains, fruits, vegetables, legumes, walnuts, and olive oil, they might lower their chances of getting metabolic syndrome, heart disease and type 2 diabetes. If they already have metabolic syndrome, following a Mediterranean-style diet might help them treat themselves.