Mediterranean Diet Protects Against Vascular Death, but Not Stroke, Across Ethnic Groups

October 15, 2009 (Baltimore, Maryland) (UPDATED October 19, 2009) — A new study shows that adherence to the Mediterranean Diet (MeDi) protects against vascular death across ethnic groups but does not appear to affect the risk for ischemic stroke or nonvascular death.

A longitudinal analysis of the multiethnic population from the NOrthern MAnhattan Study (NOMAS) showed protection against vascular death varying from about 25% to about 40%, depending on how well people adhered to the diet, researchers led by Clinton Wright, MD, MSc, from the University of Miami Miller School of Medicine, Florida, report.

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Dr. Clinton Wright describes the focus of the study.

The results showed no relationship between MeDi adherence and ischemic stroke or nonvascular death, he noted, "but we did find quite a robust association between MeDi and vascular death."

The findings were presented here at the American Neurological Association 134th Annual Meeting.

Mediterranean Diet

The MeDi is so named because research has found that persons living around the Mediterranean Sea have lower rates of vascular disease, cancer, and other diseases. Less work had been done on the MeDi in US populations, the researchers note, and even less among multiethnic groups.

"In our study, because we are focused on stroke and vascular outcome as well as cognition, we wanted to start by looking at the relationship between the adherence to the [MeDi] and ischemic stroke, vascular death, and nonvascular death to quantify that," Dr. Wright told Medscape Neurology.

Dr. Clinton Wright

Dr. Wright's group has studied food frequencies and particular nutrients in NOMAS and had several advantages in assessing MeDi adherence. The multiethnic population features a mix of 55% Hispanic, 21% white, and 24% black participants, who live in the same region, minimizing the environmental differences. At baseline, the 3298 NOMAS participants were all at least 40 years old, had never had a stroke, had lived in Manhattan for at least 3 months, and had a home with a telephone. They self-indicate racial and ethnic background.

During 8.6 years of follow-up, 150 ischemic strokes and 284 vascular deaths occurred in this NOMAS population.

Study results showed the more persistently people adhere to the diet, the more they are protected against vascular death; protection was most pronounced for those with a MeDi score of 6 or above.

Risk for Vascular Death Associated With MeDi Adherence

Furthermore, the fruits, vegetables, nuts, healthy oils, seafood, and low-salt diet of the MeDi worked without drinking the red wine so often mentioned in connection with it.

Normally, alcohol would have been included in the diet adherence score, explained Dr. Wright, but the researchers knew from earlier studies that modest alcohol consumption reduced the risk for stroke. They were concerned that if both diet and alcohol were included, it would not be possible to separate the effects. The model created later that included moderate alcohol consumption did not show significant change from the nonalcohol model in terms of protection provided by the MeDi.

In addition, the researchers controlled for age, race/ethnicity, education, moderate to heavy physical activity, cigarette smoking, and body mass index. The levels of protection and of statistical significance remain about the same, with greater adherence to the diet producing more significant protection.

Dr. Wright also looked to see whether the length of time people had lived in the United States would make a difference. "Many of the people in our sample are from the Dominican Republic. I was hypothesizing that you might adhere less to a MeDi if [you lived in] the States for a long time; you might start becoming more American in your diet. But the interesting thing is we didn't see that so much," he said.

"I don't know if that's because the northern Manhattan neighborhood is sort of an enclave, and people maintain a lot of their diet and habits they brought with them. I have to study that further. [In further research,] I'm looking a little bit more on MeDi adherence and where they lived, their Zip codes," he added.

There is more work to be done. Dr. Wright explained that the study will continue to accumulate strokes in the current population samples, and researchers will look into the individual causes of vascular death to tease out the important factors.

"We have almost 1300 people who came in from this study and got brain magnetic resonance imaging scans, and we measured the prevalence of subclinical white matter lesions and subclinical infarcts, and so I'm looking at the relationship of adherence to MeDi and subclinical damage in the brain," he added. "It looks promising."

Other Factors At Work?

Asked for comment on these findings by Medscape Neurology, Gregory J. del Zoppo, MD, from the University of Washington Harborview Medical Center in Seattle, said that, given previous findings from the Nurses' Health Study and other work linking the Mediterranean Diet to a reduced risk for stroke, the lack of relationship in this study is interesting.

"This implies that there may be other factors besides adherence to a Mediterranean-style diet that may be important in stroke risk," Dr. del Zoppo said. "These may include genetic factors that are inherent to the population under study.

"What may be important for the future is to select a group of patients who don't ordinarily use this diet and observe them having changed their dietary habits in the direction of a Mediterranean-style diet for stroke outcomes," he added.

The research is supported by the Evelyn F. McKnight Center for Age-Related Memory Loss and by the National Institute of Neurological Disorders and Stroke. The authors have disclosed no relevant financial relationships.

American Neurological Association 134th Annual Meeting: Abstract M14, Presented October 12, 2009.

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Cite this: Mediterranean Diet Protects Against Vascular Death, but Not Stroke, Across Ethnic Groups - Medscape - Oct 15, 2009.