The findings, published Jan. 22 in of Journal of the American Medical Association, come from what's thought to be the first clinical trial to test whether Mediterranean-style eating can ward off cardiovascular disease in people at increased risk.
Last year, researchers reported the main finding from the study: Older adults who adopted a Mediterranean diet -- rich in olive oil, nuts, fruits and vegetables, whole grains and fish -- cut their risk of suffering a heart attack or stroke by about 30 percent over five years.
Now the new findings suggest the benefit extends to peripheral artery disease as well, said researcher Dr. Miguel Martinez-Gonzalez, a professor at the University of Navarra in Pamplona, Spain.
Estimated to affect 8 million people in the United States alone, peripheral artery disease arises when artery-clogging "plaques" restrict blood flow in the legs. People often go for years without any symptoms, Martinez-Gonzalez noted, but as the condition progresses, it can cause painful cramps during walking -- what doctors call "claudication."
In this study, older adults who maintained a Mediterranean diet were one-half to two-thirds less likely to develop painful peripheral artery disease, compared to those who tried to follow a low-fat regimen.
Martinez-Gonzalez said the findings give "robust support" to the notion that Mediterranean-style eating helps keep the arteries healthy.
The diet differs in key ways from the modern-day "Western" style of eating -- which typically features a lot of sugar- and salt-added processed foods and saturated fat from red meat and butter. The Mediterranean diet includes few of those foods, and while it's fairly high in fat, the fat is mainly the heart-healthy, unsaturated sort from olive oil, nuts and fish.
Experts have long known that people who stick to a Mediterranean diet have a lower risk of heart attack and death from heart disease. But it hadn't been clear whether the diet, itself, deserved the credit.
To rigorously test that idea, Martinez-Gonzalez and his colleagues recruited nearly 7,500 adults aged 55 to 80 who were at increased risk of developing clogged arteries -- because they had either diabetes or multiple other risk factors, like obesity or smoking.
The researchers randomly assigned the men and women into three groups. One group was told to follow a low-fat diet, while the other two received counseling from a dietitian on Mediterranean-style eating. Along with the advice, one group was given a weekly supply of extra-virgin olive oil and was told to use at least four tablespoons a day. The other group received a regular supply of mixed nuts (walnuts, almonds and hazelnuts), and was told to toss back an ounce each day.
Over five years, 89 participants developed painful peripheral artery disease. But it turned out that the odds varied by diet.
In the low-fat group, people developed peripheral artery disease at a rate of almost 0.5 percent per year. That rate was halved in the Mediterranean group that ate mixed nuts, and was lower still in the olive-oil group -- at just 0.15 percent.
There are caveats, according to Martinez-Gonzalez's team -- one being the fairly small number of peripheral artery disease cases in the study. And one of the researchers is a consultant to the International Nut Council, an industry group.
But an expert not involved in the study agreed that it adds to the list of reasons to adopt a Mediterranean diet.
The original trial showed that, whether you favor nuts or olive oil, the diet can curb the risk of heart attack and stroke, said Dr. Suzanne Steinbaum, director of the Women and Heart Disease program at Lenox Hill Hospital, in New York City.
"Now we can recommend the Mediterranean diet as a preventive strategy for all disease of the cardiovascular system, including heart attacks, strokes and peripheral artery disease," Steinbaum said.
The American Heart Association has more about Mediterranean diets.