The largest study to date on the "Mediterranean diet" confirms that it can drastically reduce incidence of cardiovascular disease among those at risk - far more effective than a simple low-fat diet.

Up to 30 percent of heart attacks, strokes, and deaths were reduced among people at high risk, according to the results published this morning in the New England Journal of Medicine.

The typical Mediterranean diet is heavy in olive oil, fruit, vegetables, nuts, beans, and grains, with moderate intake of fish and poultry, low consumption of dairy, red meats, and sweets, and some red wine consumed with meals.

The diet involves no caloric restriction, since olive oil and nuts are calorie-dense and high in fats.

Previous studies showcased the general benefits of the Mediterranean diet, but this study was the first major clinical trial to measure the Mediterranean diet's effect on heart risks. Inconclusive evidence like the low rates of heart disease in the Mediterranean region suggested possible health benefits of the diet, but that could have been attributed to other lifestyle factors.

"Now along comes this group and does a gigantic study in Spain that says you can eat a nicely balanced diet with fruits and vegetables and olive oil and lower heart disease by 30 percent," said Dt. Steven E. Nissen of the department of cardiovascular medicine at the Cleveland Clinic Foundation. "And you can actually enjoy life."

The NY Times reported that the study's results were so dramatically clear that the researchers ended it early after only five years, because there was no need to continue.

While planning their trial, researchers conducted a systematic review of other studies, which concluded that the Mediterranean diet is the most likely dietary model to protect against coronary heart disease and other cardiovascular conditions.

The study designed a randomized trial that tested the effects of a Mediterranean diet (one group was supplemented with extra-virgin olive oil and another with nuts) against those of a control low-fat diet on primary cardiovascular prevention.

The subjects were 7,447 people in Spain over who were overweight, smoked, or had risk factors for heart disease like diabetes, but did not have any cardiovascular disease when they enrolled.

The participants in the Mediterranean diet groups were counseled on how to follow the diet and supplied with either extra virgin olive oil, or a combination of walnuts, almonds, and hazelnuts each week to supplement their meals throughout the day.

The low-fat control group was counseled on how to follow a low-fat diet.

Ultimately, the Mediterranean diet group showed high compliance with the diet, with most participants sticking to it throughout the five-year period. The low-fat control group, however, had trouble lowering their fat intake, leading the researchers to reconsider them as representing a typical modern diet that included regular consumption of red meat and commercial baked goods.

Dr. Ramon Estruch of the University of Barcelona, who led the study, did not expect to find such a dramatic effect so soon. "This is actually really surprising to us," he said.

While the study shows a clear heart health benefit for those at risk of heart disease, more research is needed to show clear benefits for people at low risk.

Some experts have stated their skepticism of the study's conclusions. Dr. Dean Ornish, who favors a low-fat vegan diet, pointed out in the Huffington Post that since the control group did not actually follow a strict low-fat diet, the study does not show clear benefits of a Mediterranean diet over a low-fat diet.

Dr. Ornish suggest that a diet heavy in fruits, vegetables, whole grains, fish, and legumes, but low in total fats, sugar, white flour, and processed foods is the best way to prevent heart disease.

Still, at the very least the study shows that a Mediterranean diet is far healthier than a typical American diet containing red meat and processed foods.

To plan a heart-healthy Mediterranean diet, follow these guidelines:

  • at least three servings a day of fruits
  • at least two servings a day of vegetables
  • four tablespoons a day of extra virgin olive oil
  • an ounce a day (a quarter cup) of nuts like almonds, walnuts, and hazelnuts
  • three servings a week of legumes (beans, peas lentils)
  • three servings a week of fish
  • if you drink, have seven glasses of wine a week with meals

Avoid eating the following:

  • Dairy products
  • Processed meats and red meat
  • Commercially made cookies, cakes, and pastries

Get started with some tasty Mediterranean recipes at Eatingwell.com.