A major 5-year-old study done in Spain showed dramatic evidence.
The results were just published in the New England Journal of Medicine.
In the study, volunteers split people into three groups.
One ate a Mediterranean diet with extra olive oil, another ate a Mediterranean diet with extra nuts and a third group ate a regular low fat diet.
After 5 years, both groups eating Mediterranean style had a 30-percent lower risk for heart problems, especially heart attacks and strokes.
The study included men and women who didn't have heart disease but were at high risk for it.
But what goes into the Mediterranean diet? Action News went to Estia restaurant at Broad and Locust in Center City to find out.
Oscar Chavez, the head chef, invited us into his kitchen to show us the basics.
It includes lots of fresh fish, grilled and lightly dressed with lemon juice and extra virgin olive oil.
It also includes lots of fresh vegetables.
"Chickory, spinach, zucchini, eggplant, carrots," Chavez said.
The veggies can be lightly grilled, orr mixed in a salad, again using olive oil.
People in the study ate about a 1/4 cup of olive oil a day.
It may sound like a lot but Estia manager Jeff Hudson doesn't think so.
"Because we are using olive oil every step of the process- the marinade, preparing the food, as well as dress and finish the food," Hudson said.
The Mediterreanean diet also includes fresh fruit and nuts. Nothing is processed.
"Everything comes fresh," Hudson said.
Compared to other eating plans, it doesn't have a lot of dairy or red meat.
As for grains and starch, "It's a small side. It's not the main component of the dish. The main component is the protein and vegetables," Hudson said.
The Mediterranean diet also tastes good.
In the study, only 7-percent of people on these diets dropped out within two years, compared to 14-percent who dropped out of the low-fat groups.
Doctors think the diet works because it helps lower bad cholesterol, and it may also help control blood sugar.