olive oil

Have scientists finally discovered the secret to the Mediterranean diet’s health-promoting powers? Maybe. (Spoiler alert: It’s the not the red wine. Alas.)

It’s the olive oil. Olive oil may lower the risk of heart disease at least in part because it helps maintain healthy blood flow and clear debris from arteries, according to a new study published in the journal Circulation.

 The oil helps “good” cholesterol do its job, according to researchers.

“A Mediterranean diet rich in virgin olive oil improves the function of high-density lipoproteins, HDL, popularly known as ‘good’ cholesterol,” lead study author Dr. Alvaro Hernáez of the Hospital del Mar Medical Research Institute in Barcelona told the Huffington Post

For the new study, the researchers examined data from 296 older adults (average 66 years old) at risk for cardiovascular disease who were randomly assigned to one of three diets: a Mediterranean diet supplemented with one liter per week (about four tablespoons daily) of extra virgin olive oil, a Mediterranean diet supplemented with 30 grams (1 oz.) of nuts a day, or a low-fat diet. They followed their assigned diets for one year.

The blood tests and lab work showed better HDL functioning in the group who ate the Mediterranean diet with extra olive oil.

How does the olive oil help? “Our hypothesis is that these dietary antioxidants may bind to HDL particles and protect them against different kinds of attacks,” Hernáez said. “As HDLs are more protected, they can perform their biological functions more efficiently and, therefore, they are able to remove cholesterol from arteries or contribute to the relaxation of blood vessels for longer.”

Olive oil may not be the only reason the Mediterranean diet is so helpful, Dr. Daniel Rader of the University of Pennsylvania in Philadelphia writes in an editorial that accompanies the Circulation article. Even though the exact reasons behind the diet’s benefits remain elusive, following it still makes sense for heart health. In one study, the diet cut the risk of heart disease in half for a group of adults followed over 10 years, compared to a similar group of people who did not follow the diet.