Older people who use olive oil for cooking, in salad dressing or with bread may be doing much to protect themselves against stroke, according to a French study of three cities where researchers found seniors whose diet included a lot of olive had a 41% lower risk of stroke compared to those who had never consumed it. While the researchers suggest their findings should prompt new dietary recommendations for the over 65s, at least one expert neurologist cautions we should wait for clinical studies to confirm them first.
Dr Cécilia Samieri, from the University of Bordeaux and the National Institute of Health and Medical Research (INSERM) in Bordeaux, France, is lead author of the study, which appears online in the journal Neurology this week. She told the press their findings may well prompt a change in the dietary recommendations for preventing strokes in people aged 65 and over:
“Stroke is so common in older people and olive oil would be an inexpensive and easy way to help prevent it,” she added.
Samieri and colleagues examined the medical records of 7,625 people aged 65 and over residing in three French cities: Bordeaux, Dijon and Montpellier and who had no history of stroke. They had available two measures of olive oil intake: dietary consumption (from all the participants) and blood levels of oleic acid (as an indirect biological marker; this was available for 1,245 of the participants).
They categorized the participants according to their dietary olive oil consumption into “no use”, “moderate use” and “intensive use”. A moderate user was someone who used olive oil either with cooking or as salad dressing or with bread. An intensive user was someone who used olive oil for both cooking or as a dressing or with bread.
After just over 5 years of follow up, there were 148 strokes in the whole group, with 27 of them occurring in the sub-sample of 1,245 participants.
The researchers then analyzed the data, looking for links between the olive oil intake measures and risk of stroke.
After adjusting for the usual sociodemographic and potential influencing factors such as diet, physical activity, body mass index (BMI), and stroke risk factors, they found:
- An overall lower incidence for stroke with higher use of olive oil (p for trend = 0.02).
- Intensive users of olive oil had a 41% lower risk of stroke compared to never users (95% Confidence Interval CI ranged from 6 to 63%, p = 0.03; absolute risk of 1.5% in six years compared to 2.6%).
- For the sub-sample of 1,245 participants, higher blood levels of oleic acid were linked to lower stroke incidence (p for trend = 0.03).
- Ranking these participants according to top, middle and bottom third in terms of their oleic acid levels, the top third had a 73% lower risk of stroke compared to the bottom third (95% CI ranged from 10 to 92%, p = 0.03).
The researchers concluded that:
“These results suggest a protective role for high olive oil consumption on the risk of stroke in older subjects.”
There are many grades of olive oil, but it is likely that in this study, the participants used mostly extra virgin olive oil, as this is 98% of what is available to buy in France, said Samieri.
However, what is not clear is how this happens: what elements of the oil are protective and whether the effects are direct or indirect, an example of the latter being making other healthy foods tastier. These points were raised in an accompanying editorial by a member of the American Academy of Neurology, Dr Nikolaos Scarmeas of Columbia University Medical Center in New York.
Scarmeas also said we now need clinical trials to confirm the findings before we can rely on them as a basis for changing dietary recommendations.
Funds from several sources helped to pay for the study, including academic, private sector, government, and non-government organizations, all based in France.
“Olive oil consumption, plasma oleic acid, and stroke incidence: The Three-City Study.”
C. Samieri, C. Féart, C. Proust-Lima, E. Peuchant, C. Tzourio, C. Stapf, C. Berr, and P. Barberger-Gateau.
Neurology, Published online before print 15 June 2011, doi: 10.1212/WNL.0b013e318220abeb
Additional source: American Academy of Neurology.
Written by: Catharine Paddock, PhD