The “Mediterranean diet,” featuring vegetables, fruits, fish, nuts and olive oil but almost no red meat or sweets, slightly reduces the risk of cardiovascular disease. Most of the effect was seen in a reduction in strokes.

That is the conclusion of a five-year diet experiment conducted in Spain, the results of which were revealed Monday at a meeting in California.

While the benefit was small, this route to better health was without risk or side effects – and included wine.

The experiment compared three different diets in people at higher-than-normal cardiovascular risk. All of the diets were significantly different from what most Americans eat.

For example, virtually everyone in the Spanish study used olive oil as their main culinary fat, ate less than one serving of red meat a day and had at least one meatless day a week. Two-thirds ate fish three times a week. Almost everyone had less than one soft drink a day, and nearly three-quarters had fewer than two baked sweets a week.

How such a diet might affect health in the United States is uncertain. It is possible the benefits might be even greater.

The benefit of the Mediterranean diet was first recognized more than 50 years ago by Ancel Keys, a physiologist at the University of Minnesota who compared rates of heart disease in seven countries with different diets.

In the new study, about 7,500 people, most in their 60s, were randomly assigned either one of two Mediterranean diets or a control diet.

People on the Mediterranean diets were advised to emphasize olive oil, nuts, fresh fruits and vegetables, fatty fish, poultry instead of red meat, a sauce called “sofrito” (made by simmering herbs, garlic, tomatoes and oil together), and red wine with dinner if they drank alcohol.

People assigned to the control diet got slightly different advice. Lean fish, pasta and bread were recommended, and olive oil, nuts and sofrito were discouraged.

The researchers looked at numerous health outcomes, the main one being a combination of heart attack or stroke or cardiovascular death. In the two Mediterranean diets there was about a 30 percent reduction in such events compared with the control diet.

The most dramatic decline was in the rate of stroke in the Mediterranean diet groups. The rates of heart attack and death were slightly lower too, but significantly so in statistical terms.

The Mediterranean diet proved beneficial even though the people on the control diet cut their calories over the five-year experiment.