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Olive Oil and Stroke Prevention: Is There a Link?By Carol M. Bareuther, RD Elders’ olive oil consumption may lower the risk of stroke, according to a recent study. Olive oil may be a new tool in the healthful diet toolbox to help patients prevent strokes, especially if they are aged 65 and older, according to a study by French researchers published in the August 2011 edition of Neurology.1 Olive oil is made from the olive, a fruit native to the Mediterranean. High consumption of olive oil is one of the key components of the renowned Mediterranean Diet, which consists mainly of fruits, vegetables, dried beans, whole grains, fish, and olive oil with small amounts of dairy and red wine. It has been linked through many studies with a reduced risk of heart disease, diabetes, and cancer.2 Olive oil’s contribution to the Mediterranean Diet’s healthfulness became clear in 2004 when Greek researchers specifically linked the use of this oil with lowered blood pressure in more than 20,000 subjects.3 The new French study marks the first time researchers have examined olive oil’s effect on the risk of stroke. After controlling for socio-demographic and dietary variables, physical activity, and BMI, results revealed that participants in the intensive use group had a 41% lower risk of stroke than those who never consumed olive oil. In a subset of 1,245 participants whose plasma levels were measured for oleic acid, 27 had a stroke. Results of this group showed that higher blood levels of oleic acid were associated with a lowered stroke risk. Oleic acid isn’t a specific blood marker for olive oil. This fatty acid is also found in foods such as beef, pork, duck fat, eggs, and cheese. Preventive Properties While this study wasn’t designed to disentangle the protective effects of either the oleic acid or the polyphenols found in olive oil, says study author Cécilia Samieri, PhD, of the University of Bordeaux and the National Institute of Health and Medical Research in Bordeaux, France, “Oleic acid could prevent strokes by a substituting effect. Increasing oleic acid consumption is associated with a decrease of saturated fat intake, thus beneficially impacting lipid profile.” One of the numerous biological functions olive oil exhibits is the ability to decrease plasma levels of LDL cholesterol and increase HDL cholesterol, hence lessening arterial plaque formation, which could prevent strokes.4 Olive oil contains 55% to 85% monounsaturated fats as oleic acid and about 9% polyunsaturated fats. The flavonoid phenolic compounds in olive oil are natural antioxidants, and these are what contribute to the oil’s bitter taste, astringency, and resistance to oxidation. There are as many as 5 mg of polyphenols in every 10 g (2 teaspoons) of olive oil. In contrast, many nut and seed oils have no polyphenols. Polyphenols offer numerous biological effects that may protect against stroke. These include antiaggregatory platelet activity, antioxidant and free radical scavenging properties, and the ability to act as a power vasodilator through the generation of nitric oxide, which all may interfere with atherosclerotic plaque formation and stability, vascular thrombosis, and occlusion.5 Olive oil also provides anti-inflammatory agents such as oleocanthal, a naturally occurring chemical that blocks Cox-1 and Cox-2 enzymes that cause both pain and inflammation. Vascular inflammation can cause the buildup of plaque, which can lead to ischemic stroke.6 In addition to oleic acid and multiple phenolic compounds, says Nikolaos Scarmeas, MD, an associate professor of neurology in the division of aging and dementia at Columbia University’s College of Physicians and Surgeons in New York City, “Other components in olive oil that may confer stroke protection include vitamin E, carotenoids, squalene, and chlorophyll.” Olive Oil Differences “Both extra-virgin and virgin olive oil contains polyphenols, which have vascular beneficial properties,” says Samieri. “However, it is noteworthy that the French market of olive oil is mainly made of virgin or extra-virgin olive oil rather than refined olive oil.” Extra-virgin and virgin olive oils are produced solely from virgin oil. Olive oils sold as “pure olive oil” and “olive oil” contains a mix of virgin and refined oils. How much olive oil should you recommend your patients consume daily? Substitution is key, says Vandana R. Sheth, RD, CDE, a spokesperson for the Academy of Nutrition and Dietetics (formerly the American Dietetic Association). “Tell your patients to substitute olive oil for the saturated fats in their diet, such as butter and mayonnaise. They should not add olive oil to an already high-fat diet.” Consuming too much of a good thing can be harmful. “Olive oil is rich in calories so the major concern is weight gain,” says Scarmeas. “Although, olive oil does make other foods, such as vegetables either in a salad or cooked, more palatable and therefore aids in increasing consumption.” For stroke prevention, a holistic rather than single-ingredient approach to diet is optimal, says Sheth. “Physicians should advise their clients to consume plenty of colorful fruits and vegetables, whole grains, and dried beans; eat foods with omega-3 fats, such as salmon, twice per week; reduce sodium by using fresh herbs in cooking; and substitute olive oil for animal fats.” Brett Kissela, MD, a professor of neurology at the University of Cincinnati, agrees with this recommendation. “It is not clear if there are direct beneficial effects from individual elements like olive oil or whether the whole Mediterranean dietary pattern is beneficial—for example, might lower risk for developing atherosclerosis—or whether the dietary pattern is part of a bigger picture that might include other confounding factors like exercise.” — Carol M. Bareuther, RD, is a St. Thomas, US Virgin Islands-based writer who contributes to a variety of regional, national, and international publications.
References 2. López-Miranda J, Pérez-Jiménez F, Ros E, et al. Olive oil and health: summary of the II international conference on olive oil and health consensus report, Jaén and Córdoba (Spain) 2008. Nutr Metab Cardiovasc Dis. 2010;20(4):284-294. 3. Psaltopoulou T, Naska A, Orfanos P, Trichopoulos D, Mountokalakis T, Trichopoulou A. Olive oil, the Mediterranean diet, and arterial blood pressure: the Greek European Prospective Investigation into Cancer and Nutrition (EPIC) study. Am J Clin Nutr. 2004;80(4):1012-1018. 4. Alarcón de la Lastra C, Marranco MD, Motilva V, Herrerías JM. Mediterranean diet and health: biological importance of olive oil. Curr Pharm Des. 2001;7(10):933-950. 5. Curin Y, Ritz MF, Andriantsitohaina R. Cellular mechanisms of the protective effect of polyphenols on the neurovascular unit in strokes. Cardiovasc Hematol Agents Med Chem. 2006;4(4):277-288. 6. National Institute of Neurological Disorders and Stroke. Headache: hope through research. NIH Publication No. 09-158. http://www.ninds.nih.gov/disorders/headache/detail_headache.htm. October 2009. |
