December 5, 2011

Study affirms ‘Mediterranean diet’ improves heart health

Olive oil and nuts boost insulin action, reduce heart disease risks

A team of Johns Hopkins researchers has uncovered further evidence of the benefits of a balanced diet that replaces white bread and pasta carbohydrates with unsaturated fat from avocados, olive oil and nuts—foods typical of the so-called “Mediterranean diet.”

In a report prepared for the American Heart Association’s scientific sessions held this month in Orlando, Fla., the Johns Hopkins investigators say that swapping out certain foods can improve heart health in those at risk for cardiovascular disease, even if the dietary changes aren’t coupled with weight loss.

“The introduction of the right kind of fat into a healthy diet is another tool to reduce the risk of future heart disease,” said Meghana Gadgil, a postdoctoral fellow in the Division of General Internal Medicine at the Johns Hopkins University School of Medicine, who presented the research.

Gadgil and her colleagues analyzed data from the OmniHeart Trial, which studied the cardiovascular effects of three different balanced diets on 164 people with mild hypertension but no diabetes. The researchers compared the body’s ability to regulate blood sugar and maintain healthy insulin levels while on a carbohydrate-rich diet, a protein-rich diet and a diet rich in unsaturated fats. People whose bodies fail to effectively use insulin usually develop type 2 diabetes, which is a major risk factor for heart disease.

The researchers found that a generally balanced diet higher in unsaturated fats such as those in avocados, olive oil and nuts improves insulin use significantly more than a diet high in carbohydrates, particularly such refined ones as white bread and pasta. The preferred diet is very similar to the Mediterranean diet, inspired by the foods of southern Italy and Greece and emphasizing healthy fats, fruits and vegetables.

Participants in the study were fed each of the three diets for six weeks in a row, with two to four weeks off in between. Blood samples were collected after fasting periods in weeks four and six of each diet and used to monitor insulin and glucose levels. The study was designed to keep participants at their starting weights. “A lot of studies have looked at how the body becomes better at using insulin when you lose weight,” Gadgil said. “We kept the weight stable so we could isolate the effects of the macronutrients. What we found is that you can begin to see a beneficial impact on heart health even before weight loss.”

Other Johns Hopkins researchers in–volved in the study are Cheryl Anderson, Lawrence J. Appel and Edgar R. Miller III.