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Mediterranean diet may reduce risk for PAD
Adherence to a Mediterranean diet supplemented with extra-virgin olive oil or nuts was associated with a lower risk for peripheral arterial disease, according to new findings from the PREDIMED study.
The PREDIMED investigators had previously reported a link between the Mediterranean diet and reduction in MI and stroke.
Miguel Ruiz-Canela, PhD, of the University of Navarra in Pamplona, Spain, and colleagues studied the association of Mediterranean diets and the occurrence of symptomatic PAD using the randomized PREDIMED trial, which was conducted from October 2003 to December 2010. The researchers assessed men aged 55 to 80 years and women aged 60 to 80 years (n=7,477; mean age, 67 years; 58% women) without PAD or CVD who had diabetes or at least three CV risk factors.
The participants were randomly assigned to one of three groups: a Mediterranean diet supplemented with extra-virgin olive oil; a Mediterranean diet supplemented with nuts; or counseling on a low-fat diet (control group).
The researchers’ endpoint of interest was a confirmed diagnosis of PAD, defined as at least one of the following: ankle-brachial index <0.9 at rest, clinical diagnosis of arterial occlusive disease based on imaging tests, revascularization or amputation.
During a median follow-up of 4.8 years, the researchers observed 89 confirmed new cases of clinical PAD (olive oil group, 18; nuts group, 26; control group, 45), according to their findings published in a research letter to JAMA.
After adjustment for classic atherosclerotic risk factors, both Mediterranean diets were associated with lower risk for PAD compared with controls (olive oil HR=0.34; 95% CI, 0.2-0.58; nuts HR=0.5; 95% CI, 0.3-0.81). Further adjustment for other factors did not change the results, the researchers found.
The number needed to treat to prevent one case of PAD per year was 336 (95% CI, 269-566) for the olive oil group and 448 (95% CI, 316-1,536) for the nuts group.
According to the researchers, this study is the first randomized primary prevention trial to suggest an association between a dietary intervention and PAD. However, the results must be considered an exploratory analysis because PAD was not a prespecified endpoint in the PREDIMED trial protocol.
“Replication by another randomized controlled trial with PAD as a prespecified endpoint is needed before causal conclusions can be drawn,” Ruiz-Canela and colleagues wrote. “We cannot ascertain whether the observed association is due to a reduced incidence of asymptomatic PAD (true primary prevention) or to a reduced conversion from this early stage of PAD to symptomatic and clinically meaningful PAD.”
Disclosure: One researcher reports financial ties with the International Nut Council.
Perspective
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These findings add to the knowledge base the endpoint of PAD as a condition that can be improved by lifestyle changes. There have been previous publications on typical major adverse CV events — MI, death, strokes and associated endpoints — and I think it’s reasonable to presume that other manifestations of atherosclerotic vascular disease might be benefited by diet.
The findings are consistent with what the PREDIMED investigators have published about the Mediterranean diet, but not all studies of the Mediterranean diet show the dramatic benefits that PREDIMED has shown. I think that the Mediterranean diet is a good recommendation for people with many different manifestations of atherosclerotic disease, whether PAD or CHD or anything else, but I wouldn’t say that it’s the only diet.
There are some things about PREDIMED that are important to recognize for an American audience. One is that it was conducted in Spain, which is culturally more adapted to not only a Mediterranean-style diet, but a Mediterranean-style lifestyle. When we did our study here, an important finding was the adaptability of not only the diet, but the lifestyle to people who live in America. It may be a bit challenging. The preferences of food are different here. People in America might not be able to follow a Mediterranean diet the same as those in Spain. We don’t have all the foods available to us.
When we did our study of people for secondary prevention of CVD, we randomly assigned them to a low-fat diet or a Mediterranean diet, but also had a control group of people who didn’t receive any special dietary intervention. Both of our study diets — the American adaptation of the Mediterranean diet and the traditional low-fat diet as recommended by the American Heart Association — improved outcomes similarly. I think the Mediterranean diet is a good choice, but I also think that for some populations, such as Americans, a low-fat diet with equal adherence and attention to the diet is also a good choice. The most important thing is that there is some intervention toward a healthier diet. In PREDIMED, there is the low-fat vs. the Mediterranean diet, but no control group that didn’t receive a dietary intervention. We don’t know that the low-fat diet didn’t benefit patients. In Spain, a Mediterranean diet seems to provide greater benefit than a low-fat diet, but maybe in Spain, many people aren’t as adherent to the low-fat diet as Americans.
While this study presents an important finding, I don’t think we can make a blanket statement that the Mediterranean diet is superior to other heart-healthy diets or that it will be adaptable to all types of people in all parts of the world. Other studies suggest that there are choices. That’s important for patients because not everybody wants to follow a Mediterranean diet. This is a good diet, however, and we have evidence that it’s helpful for peripheral vascular disease as well as for CVD, but if you don’t follow that diet and instead choose to follow a low-fat diet, for example, that’s a good choice too. What we’re really interested in is total risk reduction.