The study, by Dr. Ramon Estruch, a professor of medicine at the University of Barcelona, and his colleagues, was long in the planning. The investigators traveled the world, seeking advice on how best to answer the question of whether a diet alone could make a big difference in heart disease risk. They visited the Harvard School of Public Health several times to consult Dr. Frank M. Sacks, a professor of cardiovascular disease prevention there.

In the end, they decided to randomly assign subjects at high risk of heart disease to three groups. One would be given a low-fat diet and counseled on how to follow it. The other two groups would be counseled to follow a Mediterranean diet. At first the Mediterranean dieters got more intense support. They met regularly with dietitians while members of the low-fat group just got an initial visit to train them in how to adhere to the diet, followed by a leaflet each year on the diet. Then the researchers decided to add more intensive counseling for them, too, but they still had difficulty staying with the diet.

Image

One group assigned to a Mediterranean diet was given extra-virgin olive oil each week and was instructed to use at least 4 four tablespoons a day. The other group got a combination of walnuts, almonds and hazelnuts and was instructed to eat about an ounce of the mix each day. An ounce of walnuts, for example, is about a quarter cup — a generous handful. The mainstays of the diet consisted of at least three servings a day of fruits and at least two servings of vegetables. Participants were to eat fish at least three times a week and legumes, which include beans, peas and lentils, at least three times a week. They were to eat white meat instead of red, and, for those accustomed to drinking, to have at least seven glasses of wine a week with meals.

They were encouraged to avoid commercially made cookies, cakes and pastries and to limit their consumption of dairy products and processed meats.

To assess compliance with the Mediterranean diet, researchers measured levels of a marker in urine of olive oil consumption — hydroxytyrosol — and a blood marker of nut consumption — alpha-linolenic acid.

The participants stayed with the Mediterranean diet, the investigators reported. But those assigned to a low-fat diet did not lower their fat intake very much. So the study wound up comparing the usual modern diet, with its regular consumption of red meat, sodas and commercial baked goods, with a diet that shunned all that.