The connection between olive oil and a reduced risk of heart disease is well known. A new study suggests that the benefits of olive oil may extend to a lower risk of stroke as well. French researchers found that older adults who use lots of olive oil may have a significantly lower risk of stroke.

Those who reported using olive oil for both cooking and as a dressing were classified as "intensive users" and were found to have a 41% lower incidence of stroke compared to those who never used olive oil.

In the Three-City Study, Cecilia Samieri, PhD, of the University of Bordeaux in France and colleagues looked at the diets of 7,625 adults age 65 and older who had no history of stroke. Those who reported using olive oil for both cooking and as a dressing were classified as "intensive users" and were found to have a 41% lower incidence of stroke compared to those who never used olive oil. Adjustments were made for dietary variables, sociodemographic characteristics, physical activity, body mass index, and major risk factors for stroke. Moderate intake of olive oil showed a 20% reduction in the incidence of stroke when compared with those who never used olive oil, but this was not considered statistically significant.

The researchers also took blood samples from another group of older adults and measured their levels of oleic acid, a fatty acid found in olive oil and some types of nuts. Similar adjustments were made for dietary variables, stroke risk, and other variables. Those with the highest levels of oleic acid in their blood were 73% less likely to have a stroke than those with the lowest levels, but the association is not considered a strong one since blood levels of oleic acid are not a specific marker for olive oil consumption.

Because this was an observational study, the correlation between olive oil and stroke risk cannot be translated as cause-and-effect. It may be that people who consume a lot of olive oil have other characteristics that protect them from stroke. They may have higher incomes, eat a better overall diet, or be more physically active. While the researchers controlled for these differences, olive oil was still associated with a lower incidence of stroke. The results of this observational study will need to withstand the scrutiny of a randomized trial before the connection is considered conclusive.

The study did not differentiate between the types of olive oil used by the participants, but the researchers pointed out that nearly all of the olive oil sold in France is extra virgin olive oil. Extra virgin olive oil is made from the first pressing of the olives, which removes about 90 percent of the juice. There are no chemicals and no high heat used in the production of extra virgin olive oil, and no further processing or refining occurs after the pressing process.

The study was published online ahead of print on June 15, 2011 in Neurology.