The Mediterranean diet has long been touted as healthy. Now a study released Monday of the effects of a diet rich in olive oil, nuts, vegetables, fruits and fish confirms that.
The study, published in the New England Journal of Medicine, showed that the diet can reduce the risk of stroke and other cardiovascular diseases by 30 percent.
Such a diet may seem like common sense, but researchers say the findings are significant because of the study's size and scientific rigor. It followed more than 7,400 people at risk of heart disease for nearly five years and measured the effects of the Mediterranean diet against a group that was assigned a low-fat diet.
"This study backs up what we thought we knew with science, and the results were pretty dramatic," said Dr. Rita Redberg, a UCSF cardiologist specializing in heart disease in women. "If this were a pill, people would be clamoring for it."
Redberg, who was not involved with the study, said one of the diet's main benefits is that it's not only heart-healthy, but it also promotes a way of eating that people can follow for a lifetime rather than just a few months. "This is a diet that's pretty doable, particularly for people living in Northern California, where we certainly have access to plenty of fruits and vegetables and grains," she said.
The study, which was conducted in Spain, involved people between 55 and 80 who did not have heart disease but were at risk of developing cardiovascular problems because of various factors, such as being overweight, smoking, having a family history of the disease, or having high blood pressure or high cholesterol.
Participants were assigned to one of three groups. People in two of the groups were required to follow a Mediterranean diet - in other words, meals rich in vegetables, fruit, fish and legumes. Those in the Mediterranean diet groups were instructed to add at least 4 tablespoons a day of extra-virgin olive oil to their daily diet. Those in the other group supplemented their meals with a combined ounce of walnuts, almonds and hazelnuts each day.
Participants in the control group, which was being compared against the groups eating the Mediterranean diet, were encouraged to lower their fat intake by eating lean meats and low-fat dairy products. Midway through the study, its authors said, they intervened to offer more specific guidance about what the participants should eat and how to prepare their foods.
The results were so clear that the study was ended early. The two groups assigned to the Mediterranean diet had fairly similar results, with 3.4 percent of the group that ate extra nuts suffering major cardiovascular problems, compared with 3.8 percent in the olive-oil group.
Meanwhile, 4.4 percent of participants in the control group had major cardiovascular problems. Reduced stroke risk, rather than lower heart attack risk, accounted for most of the difference between the Mediterranean groups and the low-fat group.
While the findings were heralded by many in the health care community, not everyone was impressed.
Dr. Dean Ornish, UCSF professor and president of the nonprofit Preventive Medicine Research Institute in Sausalito, criticized the study, contending that the control group was not monitored carefully enough and wasn't assigned a truly low-fat diet.
"A Mediterranean diet is a healthier diet than what most people are eating," Ornish said. "The problem is they claim (the study) was comparing it to a low-fat diet, and it wasn't."
Ornish said the American Heart Association recommends a diet with fewer than 30 percent of calories coming from fat, but the control group's levels edged closer to 40 percent. Ornish, who promotes his own heart-healthy diet, urges people trying to reverse the effects of heart disease to cut that figure to as low as 10 percent.
Easy to follow
Dr. Cesar Molina, co-founder of the South Asian Heart Center at El Camino Hospital in Mountain View, said the study promotes a diet that people can easily follow.
"You just have two fists of cooked vegetables per day; one fist - or the size of a tennis ball - serving of fruit each day," he said. He advised people to make olive oil their primary choice of dietary oil and have about 12 nuts daily - preferably walnuts, because they are a source of the healthful omega-3 fatty acid.
The study noted that some authors had financial ties to food, wine and other industry groups, and foods were supplied by olive oil and nut producers in Spain, as well as the California Walnut Commission.
Dennis Balint, chief executive officer of the California Walnut Commission, said walnut growers represented by his group provided a daily half-ounce of walnuts to the group that supplemented the Mediterranean diet with nuts.
Balint said he was surprised by the magnitude of the study's results, but not that the diet with nuts proved healthful. "Every nut has its strong suit. Our strong suit is the fact that walnuts have plant-based omega-3," he said.