Pour on the olive oil, preferably over fish and vegetables: One of the longest and most scientific tests of a Mediterranean diet suggests this style of eating can cut the chance of suffering heart-related problems, especially strokes, in older people at high risk of them.

The study lasted five years and involved about 7,500 people in Spain. Those who ate Mediterranean-style with lots of olive oil or nuts had a 30 percent lower risk of major cardiovascular problems compared to those who were told to follow a low-fat diet but who in reality, didn't cut fat very much. Mediterranean meant lots of fruit, fish, chicken, beans, tomato sauce, salads, and wine and little baked goods and pastries.

Mediterranean diets have long been touted as heart-healthy, but that's based on observational studies that can't prove the point. The new research is much stronger because people were assigned diets to follow for a long time and carefully monitored. Doctors even did lab tests to verify that the Mediterranean diet folks were consuming more olive oil or nuts as recommended.

Most of these people were taking medicines for high cholesterol and blood pressure, and researchers did not alter those proven treatments, said one study leader, Dr. Ramon Estruch of Hospital Clinic in Barcelona.

But as a first step to prevent heart problems, "we think diet is better than a drug" because it has few if any side effects, Estruch said. "Diet works."

Results were published online Monday by the New England Journal of Medicine and were discussed at a nutrition conference in Loma Linda, Calif.

People in the study were not given rigid menus or calorie goals because weight loss was not the aim. That could be why they found the "diets" easy to stick with