Olive Oil May Protect Against Stroke

Megan Brooks

June 17, 2011

June 17, 2011 — A diet rich in olive oil may reduce the risk for stroke in older adults, new research suggests.

In roughly 7600 elderly adults, higher olive oil consumption at baseline was associated with a lower incidence of stroke over roughly the next 5 years, after controlling for numerous confounding factors, including lifestyle and nutritional factors, stroke risk factors, and blood lipids.

Cecilia Samieri, PhD, from University of Bordeaux and the National Institute of Health and Medical Research (INSERM) in Bordeaux, France, reported their findings online June 15 in Neurology.

"The high prevalence of stroke in older subjects emphasizes the need for primary and secondary prevention in this age group," they conclude. "Showing a strong association between intensive olive oil use and lower stroke incidence, our study suggests a novel approach of dietary recommendations to prevent stroke occurrence in elderly populations."

But the authors of a linked commentary caution against jumping to any conclusions, noting that the putative health benefits of olive oil, and a Mediterranean-style diet, are complex.

The Three-City Study

Dr. Samieri and colleagues examined the association between olive oil intake and stroke incidence in 7625 people aged 65 and older from Bordeaux, Dijon, and Montpellier, France. They are enrolled in the ongoing, population-based French Three-City Study, which is looking at vascular risk factors for dementia.

At baseline, 1738 (22.8%) participants reported no olive oil use, 3052 (40.0%) reported moderate olive oil use, and 2835 (37.2%) reported intensive olive oil use.

The authors note that moderate and intensive olive oil users (relative to nonusers) were younger than nonusers; they also had lower values or frequencies for several stroke risk factors, weighed less, had lower triglycerides and lower total/high-density lipoprotein cholesterol ratio. They were also more apt to be regular exercisers and ate fish, fruits, and vegetables and omega-3–rich oils more often than nonusers.

Over a median of 5.25 years, 148 incident strokes were recorded (115 ischemic, 28 hemorrhagic, 5 undetermined).

After adjusting for sociodemographic and dietary variables, physical activity, body mass index, and risk factors for stroke, the researchers observed a lower incidence of stroke with higher olive oil use (P for trend = .02). Compared with participants who did not use olive oil, those with intensive use had a 41% lower risk for stroke. No other dietary variable was significantly associated with stroke incidence.

Multivariate Association Between Olive Oil Use and 6-Year Incident Stroke

Olive Oil Use Hazard Ratio (95% CI)* P Value
None Reference  
Moderate (with cooking or dressing) 0.80 (0.53 - 1.20) 28
Intensive (both cooking + dressing) 0.59 (0.37 - 0.94) .03

*Fully adjusted model.

CI = confidence interval

The researchers also examined the association between plasma oleic acid and stroke incidence in a subgroup of 1245 participants. In this group, there were 27 incident strokes during a median follow-up of 5 years, including 20 ischemic and 7 hemorrhagic strokes.

After adjustment for a wide variety of potentially confounding factors, compared to those in the first tertile of plasma oleic acid, those in the third tertile had a 73% reduction in stroke risk (hazard ratio, 0.27; 95% CI, 0.08 - 0.90; P = .03).

However, in the fully adjusted model using "component analysis" of total saturated fatty acids, total omega-3 fatty acids, and other dietary factors, the intensity of the association between plasma oleic acid and stroke was reduced (hazard ratio, 0.25; 95% CI, 0.08 - 0.86; P = .03).

One limitation of the study, Dr. Samieri and colleagues say, is not being able to distinguish between the different types of oil olive consumed. They also say the validity of plasma oleic acid as an indirect marker of olive oil consumption remains to be evaluated.

Olive Oil Pertinent to Neurologic Disease Too?

In their commentary, Nikolaos Scarmeas, MD, from Columbia University Medical Center in New York, New York, and Luc Dauchet, MD, PhD, from Institut Pasteur de Lille in France, comment on the study and the state of research on this topic.

They make the point that exploration of the relation of the Mediterranean-type diet with neurologic diseases has started "only very recently and has suggested potentially beneficial associations for Alzheimer's disease, mild cognitive impairment, cognitive decline, essential tremor, Parkinson disease, and stroke."

Although the current study suggests a protective effect of olive oil in stroke, the authors caution against drawing any firm conclusions from this study, until the observations "withstand the trial of randomized intervention."

They point out that covariate adjustment "can never be complete." Additionally, other potentially beneficial effects of olive oil, not considered in the analyses, may be mediating the association.

They also note that olive oil is not consumed in isolation but with a whole host of potentially healthy foods. "To add further to the complexity, the potentially beneficial biological elements of olive oil are not clear."

Dr. Samieri received support from Institut Carnot LISA (Lipides pour l'Industrie et la Sante [Lipids for Industry, Safety and Health]). A complete list of disclosures for the other authors can be found with the original article. Dr. Scarmeas receives research support from the National Institutes of Health/National Institute on Aging and the Alzheimer's Association. Dr. Dauchet has disclosed no relevant financial relationships.

Neurology. Published online June 15, 2011.

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