The diet features lots of fruit, vegetables, nuts and olive oil; moderate amounts of fish and poultry; but little dairy, red or processed meat or sweets; as well as moderate amounts of wine with meals.

Researchers focused on changing the foods people ate, not cutting calories

Those following a Mediterranean diet were told to consume more "healthy fats"

Healthy fats, such as Omega-3 fatty acids, can be found in salmon, flax seeds and walnuts

Following a Mediterranean diet lowered the risk of stroke by 33% to 46%, without counting calories, a new study shows.

Mediterranean diets feature lots of fruit, vegetables, nuts and olive oil; moderate amounts of fish and poultry; but little dairy, red or processed meat or sweets; as well as moderate amounts of wine with meals.

The Spanish researchers who led the study focused on particular types of food, rather than cutting calories. The 7,447 study participants were allowed to consume as many calories as they wished, and were given no instructions about exercise.

Researchers randomly assigned people to follow one of three diets: a Mediterranean diet supplemented with olive oil; a Mediterranean diet supplemented with nuts; or a low-fat diet, including bread, potatoes and pasta, according to a study published in today's New England Journal of Medicine.

Researchers followed participants, ages 55 to 80 years old, for nearly five years. Everyone in the trial had a high risk for heart disease — due to diabetes, smoking or other issues — but no cardiovascular problems at the time the study began.

Compared to those told to eat a low-fat diet, those on an olive-oil rich Mediterranean diet had a 33% lower stroke risk, while those eating a Mediterranean diet with extra nuts had a 46% lower risk of stroke.

Researchers stopped the study early when they noticed a clear advantage to the Mediterranean diet, which also appeared more popular with participants. Fewer people following the Mediterranean diet dropped out of the study.

In most diet studies, those told to reduce fat "have a very hard time maintaining such a diet," says Walter Willett, chair of the department of nutrition at the Harvard School of Public Health. "One of the advantages of the Mediterranean diet is that most people find it is easy to stay with for the long run, because it offers great variety, satiety and enjoyment."

Some of the benefits of the Mediterranean diet may come from "healthy fats," such as the Omega-3 fatty acids found in salmon and walnuts. Unlike saturated fats from fried foods, such as doughnuts or bacon, Omega-3 fatty acids appear to protect the heart, Willett says.

"Fat in the diet continues to be demonized, even though the evidence is clear that some types of fat improve blood cholesterol," Willett says. "This study adds further proof that diets high in healthy fats can be superior to a low-fat diet."

Yet critics say that no one in the Spanish study managed to reduce dietary fat.

Those in the low-fat group made relatively minor changes, reducing their fat consumption from 39% of daily calories to 37%, notes Dean Ornish, president of the non-profit Preventive Medicine Research Institute and clinical professor at the University of California, San Francisco.

The American Heart Association advocates a diet with less than 30% of calories coming from fat. Ornish urges people to get fewer than 10% of their calories from fat, due to studies suggesting an ultra low-fat diet can reverse heart disease, when combined with exercise and other lifestyle changes.

"The authors should have concluded that the Mediterranean diet reduced cardiovascular risk when compared to whatever diet they were eating before, not when compared to a low-fat diet," Ornish says.

Ornish notes that researchers also overstated their findings.

In their paper, researchers say that people following a Mediterranean diet reduced their risk of "major cardiovascular events," a term that includes heart attacks, stroke or heart disease-related death, by 30%.

That's about the same size benefit provided by cholesterol-lowering drugs, says cardiologist Suzanne Steinbaum, author of Dr. Suzanne Steinbaum's Heart Book."

But Ornish notes that the biggest decline was in the risk of stroke. When broken out individually, the declines in heart attacks and deaths could have been due to chance, the study says.

Experts agree that people should try to maintain a healthy weight and exercise more to reduce their risk of heart disease, diabetes and cancer.

But authors of the new paper note that, given that most people have trouble losing weight, following a Mediterranean diet could be an important way for some people to reduce their risk.

The study was funded by the Spanish government, although olive oil and nuts were donated by manufacturers. Researchers involved have also done work for drug companies and groups promoting alcohol, nuts and other products.