The Mediterranean diet has long been considered a healthy diet, so it may be difficult for some to understand why the study that came out last week in the New England Journal of Medicine is considered so important. The diet is a nutritional paradox. It is high in fat, and yet the people around the Mediterranean — in Turkey, Italy, France, Spain, and Greece — enjoy a much lower rate of cardiovascular disease than other parts of the world.

The new study is noteworthy because its findings were so conclusive as to the benefits of the Mediterranean diet that the study had to be halted early because it would have been unethical to ask those in the control group who were not on the diet to continue. Researchers found that even people who were already at risk for heart attacks, strokes, and heart disease reduced their risk of disease by 30 percent if they ate the Mediterranean way.

Mediterranean cooking uses a good deal of olive oil, a monounsaturated fat, and is also very high in fiber and antioxidants from fruits, vegetables, legumes, and nuts. People in the region eat very little red meat, so their intake of saturated fat is low. Milk consumption is limited, except for cheese and yogurt.

The study, by a team of Spanish researchers, is the first to measure the effect of the Mediterranean diet on cardiovascular disease in the everyday lives of older people. The large, scientifically rigorous, clinical trial followed 7447 men and women ranging in age from 55 to 80 years.

A Subject Pool of At-Risk Oldsters

All the participants were considered to be at high risk for cardiovascular problems because of a variety of factors including smoking and being overweight. Most were already taking drugs for blood pressure, diabetes, or high cholesterol to lower their risk of heart disease and had family histories that included cardiovascular disease or diabetes, high blood pressure, or high cholesterol, though none of them had been diagnosed with heart disease.

Men and women were randomly assigned to one of three groups. One group followed a Mediterranean diet with an emphasis on olive oil. They were told to use at least four tablespoons of extra-virgin olive oil each week. A second group was instructed on a Mediterranean diet that focused on nuts. This group was given a combination of walnuts, almonds, and hazelnuts and told to eat about an ounce - or ¼ cup - every day. The third group was assigned to follow a low-fat diet.

Both Mediterranean diet groups ate at least two servings of vegetables and three servings of fruit each day. They were asked to eat fish, seafood, and legumes at least three times a week. Their diet excluded red meat and processed foods and sweets. Those who normally drank wine were encouraged to drink at least seven glasses a week with their meals. The participants were asked to eat poultry, eggs, cheese, and yogurt in moderation. The researchers checked certain biomarkers in the blood and urine as a way of measuring compliance with the diet.

Low Fat Is Hard to Do

About halfway through the study, the researchers decided to add more intensive counseling and support for the low-fat group because they were having trouble getting subjects to stay on it. The Mediterranean diet groups followed it over the course of the nearly five-year study with little trouble. In the end, those on the low-fat diet did not lower their fat intake very much. In fact, the diets of the low-fat group ended up looking more like the typical American diet with more red meat, sodas, and commercially-made cookies, cakes and pastries being consumed.

The Mediterranean diet is not difficult to follow. It allows a wide variety of food choices and even a daily glass of wine. It does not require that all fats be eliminated from the diet.

Regardless of whether the diet focused more on olive oil or nuts, the researchers found that the Mediterranean diet resulted in a 30 percent greater reduction in heart disease compared to those who were assigned to the low-fat diet. The biggest difference between those eating the Mediterranean diets and those on the low-fat diet was a reduced risk of stroke. Specifically, the group who ate nuts had a 46 percent lower risk of stroke and the group who consumed olive oil had a 33 percent decreased risk of stroke.

It is unlikely that it was just the nuts or olive oil that contributed to the positive effect of the Mediterranean diet. More probably, it was the sum total of the all the included healthful foods and the fact that the diet is easy to follow. It allows a wide variety of food choices and even a daily glass of wine. It does not require that all fats be avoided. In fact, this study seems to offer evidence for the idea that eating plenty of good fats is better than going low-fat for preventing cardiovascular events, though that interpretation is being debated.

The study was published in the New England Journal of Medicine.