Heavy use in cooking and dressings was associated with a 41% lower stroke incidence compared with never using olive oil, Cécilia Samieri of the Université Bordeaux in France and colleagues found.
The top one-third on intake by serum measures had a 73 percent lower stroke risk than those in the bottom third among older adults living in three cities in France.
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Because these results controlled for other dietary and stroke risk factors, olive oil may be considered "a major protective component" of the Mediterranean diet for stroke, the group suggested in the Aug. 2 issue of Neurology.
Intensive olive oil intake could find a place alongside more fruits and vegetables and less salt in the dietary recommendations to prevent stroke in elderly populations, Samieri and colleagues suggested.
"But this can be claimed with confidence only if the observations … withstand the trial of randomized interventions," warned Dr. Nikolaos Scarmeas of Columbia University Medical Center in New York City and Dr. Luc Dauchet of Institut Pasteur de Lille, France, in an accompanying editorial.
The association is plausible because of the benefits of olive oil with regard to diabetes, hypertension, lipid profiles, coronary artery disease, and obesity, the editorialists acknowledged.
However, they cautioned, olive oil can't be entirely separated from the other foods it typically accompanies.
"Olive oil is usually added to other foods (i.e., fruits and vegetables, legumes, cereals, and fish) and may contribute indirect benefits by increasing the palatability and consumption of foods that may have health-promoting potential," they wrote in Neurology.
Samieri's group analyzed olive oil consumption among 7,625 participants 65 and older without a prior stroke in the Three-City Study of community-dwelling residents of Bordeaux, Dijon, and Montpellier.
That prospective cohort study of vascular risk factors for dementia followed participants over a median 5.25 years for independently validated stroke incidence.
At baseline, 22.8 percent of the cohort reported not using olive oil, 40% used olive oil moderately for cooking or dressing food, and 37.2 percent used it intensively for both cooking and dressing.
Higher use yielded lower stroke incidence after adjustment for sociodemographics, diet (including fish, fruit, vegetables, and other types of oils and fats), physical activity, body mass index, and stroke risk factors.
Moderate intake showed a 20 percent reduced incidence of stroke compared with no olive oil intake but the association was not significant.
The study also included 1,245 individuals with plasma oleic acid levels measured as a marker for olive oil intake.
After similar adjustment for dietary, stroke risk, and other factors, higher plasma oleic acid was associated with lower stroke incidence.
Although plasma oleic acid levels were linked to level of olive oil intake in the study, the association wasn't strong.
The researchers suggested cautious interpretation since plasma oleic acid isn't a specific marker for olive oil consumption and in fact was linked to higher intake of butter and goose or duck fat as well as a worse vascular risk profile.
They also cautioned that the study may have missed some strokes, which depended on initial self-report for final validation.
The study didn't distinguish type of olive oil consumed, but Samieri's group noted that nearly all olive oil sold in France is extra virgin olive oil.