Olive Oil Use Reduces Heart Disease
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"those with intensive use had a 41% (95% confidence interval 6%-63%, p = 0.03) lower risk of stroke"
"In the present population-based study, intensive olive oil use was prospectively associated with a lower stroke risk after controlling for numerous confounding factors, including lifestyle and nutritional factors, main stroke risk factors, and blood lipids......The high prevalence of stroke in older subjects emphasizes the need for primary and secondary prevention in this age group. 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."
Olive oil: Pertinent to neurologic diseases too? EDITORIAL "olive oil may result in neurologic health benefits"
Neurology; Prepublished online June 15, 2011
Nikolaos Scarmeas and L. Dauchet
From the Taub Institute for Research in Alzheimer's Disease and the Aging Brain (N.S.), the Gertrude H. Sergievsky Center and the Department of Neurology, Columbia University Medical Center, New York, NY; and the Department of Epidemiology and Public Health (L.D.), Institut Pasteur de Lille, INSERM, Universite Lille Nord de France, Lille, France.
Hundreds of studies on the potentially beneficial effects of the Mediterranean-type diet have focused on vascular disease, several forms of cancer, and overall mortality. Although the Mediterranean-type diet shares many features with many other healthy dietary patterns, it is distinct in its high fat content, mainly from olive oil.1 This feature may partially account for the Mediterranean-type diet's particular gastronomic interest and popular acceptance because olive oil's fatty taste may make the diet more palatable.
The 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 disease, mild cognitive impairment, cognitive decline, essential tremor, Parkinson disease, and stroke. Because these studies were performed mainly in US populations where monounsaturated fatty acid (MUFA) levels and consumption of olive oil are minimal, they do not directly address the potential role of olive oil in relation to neurologic diseases. In a previous report from the Three-City Study (Bordeaux, Dijon, and Montpellier, France), higher consumption of olive oil was associated with better cognitive performance and slower rates of decline in some cognitive domains.2
Regarding cerebrovascular disease, European and US dietary recommendations on stroke primary prevention have suggested various levels of evidence for decrease of salt and saturated fat and increase of potassium, fruits, vegetables, and fiber,3,4 but the potential role of olive oil has not been explored. In this issue of Neurology® , Samieri et al.5 report that higher olive oil consumption is associated with lower incidence of stroke during a about 5-year follow-up in the Three-City Study, a prospective population-based investigation of 7,625 elderly subjects. Underlying mechanisms may include the potentially protective associations between olive oil and multiple vascular risk factors including diabetes, hypertension, lipid profile (reduction of total cholesterol, triglycerides, and low-density lipoprotein, and increase of high-density lipoprotein), coronary artery disease, and obesity.6,7 Indeed, in 2004 the US Food and Drug Administration authorized the use of health claims for olive oil in relation to coronary artery disease based on a series of previously conducted clinical trials. In the current study, the associations between olive oil and stroke risk remained even after controlling for some of the vascular comorbidities. Nevertheless, covariate adjustment can never be complete. Additionally, other potentially beneficial effects of olive oil, not considered in the analyses, may be mediating the associations. They include lower abdominal adiposity (vs body mass index) and metabolic syndrome,6,7 reduction of carotid intima-media thickness, antithrombotic effects and endothelium protection toward development of arteriosclerosis (particularly postprandially),1,6,7 improved insulin resistance, and anti-inflammatory and antioxidative effects.1,6,7
Whether the putative health benefits of a Mediterranean-type diet are due to olive oil itself remains a matter of debate. We are often focused on individual foods but foods are not consumed in isolation. 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.1 Additionally, studies failing to demonstrate associations between olive oil and health outcomes may be limited by the inherent difficulty to assess olive oil consumption accurately (for example, used in variable quantities in cooking, with bread, and as salad dressing) as compared to recording intake of other food items (that tend to be consumed in more readily quantifiable portion sizes) in dietary questionnaires.8
To add further to the complexity, the potentially beneficial biological elements of olive oil are not clear.1,7 Much of the scientific community's and public's attention has been oriented toward nutrients. But foods contain more than a single nutrient, and foods' effects on health may be the result of the combined nutrient effects, or many nutrients' synergistic actions, or intercorrelations. Many of the Mediterranean-type diet- disease associations have been attributed to the high MUFA content of olive oil (namely oleic acid, which represents 70%- 80% of the fatty acids present in olive oil). How- ever, several seed oils (sunflower, soybean, and rapeseed) rich in MUFA and oleic acid have not been as consistently associated with health benefits.1 To address this, Samieri et al.5 analyzed a more restricted sample of 1,245 subjects and demonstrated that plasma oleic acid measurements were related to lower stroke risk, similar to that for olive oil in the whole sample. Using plasma oleic acid as a biomarker of olive oil consumption at individual level remains to be properly evaluated. Oleic acid is not a specific marker of olive oil consumption especially in populations such as the present one, with not extremely high olive oil consumption compared to populations with usual energy intake from MUFA as high as 15%-20%, such as Greeks, Italians, and Spaniards.8
Although oleic acid levels were associated with olive oil use in this study, the intensity of the association was not very strong and oleic acid could have derived from other food sources. Actually, subjects with high levels of plasma oleic acid had higher burden of vascular risk factors, while those with high olive oil use had lower burden of vascular risk factors. This may suggest that olive oil components other than oleic acid may be also conferring stroke protection. Olive oil contains hundreds of nonfat components with potential biological relevance including vitamin E, carotenoids, squalene, chlorophyll, and multiple phenolic compounds (including oleuropein, oleocanthal, and flavonoids).1,9 Extensive re- search has demonstrated potentially biologically relevant effects of such nonfat components of olive oil regarding multiple cardiovascular risk factors, and various mechanisms of arteriosclerosis.1 As an example, oleocanthal, the substance that induces olive oil's stinging sensation in the throat, has COX-1 and COX-2 activities.10 Daily dose of oleocanthal for usual levels of olive oil consumption of Mediterranean populations corresponds to 10% of ibuprofen dosage recommendations for pain relief.10 Nevertheless, health benefits of some of the nonfat components of olive oil, such as vitamin E or carotenoids, have not been confirmed in clinical trials and remain controversial.
The origin of the olive tree is lost in time, coinciding and mingling with the expansion of Greek, Roman, and other Mediterranean civilizations. Its
relation with the Mediterranean culture is so strong that it has been said that "the Mediterranean ends where the olive tree no longer grows." Of course, in modern times, the olive tree is no longer a Mediterranean privilege. Cultivation has spread around the world, including the Americas, Australia, Japan, and China. Spread of consumption of its main culinary product, olive oil may result in neurologic health benefits. But this can be claimed with confidence only if the observations of the study by Samieri et al. withstand the trial of randomized interventions.
Olive oil consumption, plasma oleic acid, and stroke incidence
The Three-City Study - pdf attached
Neurology; Prepublished online June 15, 2011
C. Samieri, PhD C. Fe art, PhD C. Proust-Lima, PhD E. Peuchant, MD, PhD C. Tzourio, MD, PhD C. Stapf, MD C. Berr, MD, PhD P. Barberger-Gateau,
From the Research Center INSERM, U897, Department of Nutritional Epidemiology (C. Samieri, C.F., P.B.-G.), Bordeaux; Research Center INSERM, U897, Department of Biostatistics (C.P.-L.), Bordeaux; University Victor Segalen Bordeaux 2 (C. Samieri, C.F., C.P.-L., P.B.-G.), ISPED, Bordeaux; INSERM (E.P.), U876, Bordeaux; CHU de Bordeaux (E.P.), Hopital Saint-Andre , Department of Biochemistry, Bordeaux; INSERM (C.T.), U708, Neuroepidemiology Unit, University Pierre et Marie Curie Paris VI, Paris; Department of Neurology (C.T., C. Stapf), Hopital Lariboisiere, APHP, Paris; University Diderot Paris VII (C. Stapf), Paris; INSERM (C.B.), U1061, University Montpellier 1, Montpellier; and CHU Montpellier (C.B.), CMRR Languedoc Roussillon, Montpellier, France.
Objective: To determine whether high olive oil consumption, and high plasma oleic acid as an indirect biological marker of olive oil intake, are associated with lower incidence of stroke in older subjects.
Methods: Among participants from the Three-City Study with no history of stroke at baseline, we examined the association between olive oil consumption (main sample, n = 7,625) or plasma oleic acid (secondary sample, n = 1,245) and incidence of stroke (median follow-up 5.25 years), ascertained according to a diagnosis validated by an expert committee.
As in a previous publication,20 3 categories of olive oil consumption were defined: "no use," "moderate use" (using olive oil for cooking or dressing alone), "intensive use" (using olive oil for both cooking and dressing).
Results: In the main sample, 148 incident strokes occurred. After adjustment for sociodemographic and dietary variables, physical activity, body mass index, and risk factors for stroke, a lower incidence for stroke with higher olive oil use was observed (p for trend = 0.02). Compared to those who never used olive oil, those with intensive use had a 41% (95% confidence interval 6%-63%, p = 0.03) lower risk of stroke. In the secondary sample, 27 incident strokes occurred. After full adjustment, higher plasma oleic acid was associated with lower stroke incidence (p for trend = 0.03). Compared to those in the first tertile, participants in the third tertile of plasma oleic acid had a 73% (95% confidence interval 10%-92%, p = 0.03) reduction of stroke risk.
Conclusions: These results suggest a protective role for high olive oil consumption on the risk of stroke in older subjects.
3C Study =Three-City Study; BMI = body mass index; C= confidence interval; HD= high-density lipoprotein; H= hazard ratio; MeD= Mediterranean diet; M= myocardial infarction; MUF= monounsaturated fats.
Cerebrovascular events are responsible for a substantial clinical burden, with their incidence currently exceeding that of coronary heart disease, in particular in older age groups.1 Risk of stroke could be reduced by improvement of lifestyle factors, including diet,2 notably by increas- ing fruits and vegetables consumption3 and decreasing sodium intake, which is strongly corre- lated with hypertension.4 Adherence to the Mediterranean diet (MeDi)5 was related to a lower risk of mortality from cardiovascular diseases6 and to a reduction in major cardiovascular risk factors.7-9 High olive oil consumption is one of the most constant features of the MeDi, and may account for most of its cardioprotective properties.10 Olive oil contains 80% monounsaturated fats (MUFA) in the form of oleic acid, 20% polyunsaturated fats, and several antioxidant components, including phenolic compounds found in virgin olive oil.10 A higher consumption of olive oil has been associated with a decreased risk for myocardial infarction (MI),11 a lower risk of all-cause mortality after MI,12 and a lower carotid intima-media thick- ness.13 Olive oil was the only component of the MeDi specifically associated with lower blood pressure in a large European cohort.14
To our knowledge, the assumption that high olive oil consumption may be associated with a reduced incidence of stroke independently of other dietary habits and stroke risk factors has never been explored. We investigated the rela- tionship between olive oil consumption, plasma oleic acid as a biological marker of oleic acid intake, and 6-year stroke incidence in older participants in the Three-City (3C) Study.
Among the 9,294 subjects from the base- line 3C sample, we excluded 415 subjects with stroke history at baseline (figure 1). Among the remaining 8,879 subjects, the main study sample consisted of the 8,709 participants with available data for olive oil consumption, and the secondary study sample of the 1,364 subjects from Bordeaux who had plasma fatty measurements at baseline. After exclusion of subjects with missing data for the main covariates and those without follow-up assessment, 7,625 subjects were included in the main study sample, and 1,245 in the secondary study sample.
Compared to the subjects without stroke history at baseline not included in the main study sample (n = 1,254), those included (n = 7,625) were younger, more likely to be women, and more educated. They also had a better health status as assessed by several baseline health indicators (table e-1).
Olive oil consumption and stroke incidence. Baseline characteristics of the main study sample as a function of olive oil use (22.8% of nonusers, 40.0% of moder- ate users, and 37.2% of intensive users) are presented in table 1 and table e-2. Intensive users of olive oil were more frequent in Montpellier (Mediterranean Sea, 41.9%) and Dijon (Middle East, 38.5%) than in Bordeaux (Atlantic Ocean, 28.1%).
Moderate and intensive olive oil users were younger and more educated than nonusers. They also had lower values or frequencies for several stroke risk factors, lower BMI (table 1), lower triglycerides, and lower total/high-density lipoprotein (HDL) cholesterol ratio (table e-2). They practiced more often regular physical activity, consumed more often fish and fruits and vegetables, and were more often users of omega-3 rich oils. Conversely, intensive olive oil users consumed less often omega-6 rich oils than non- or moderate olive oil users (table e-2).
In the main study sample, 148 incident strokes occurred over a 5.25-year median follow-up (mean 4.9 years, range 1.5 months- 6 years), including 115 of ischemic etiology, 28 hemorrhagic strokes, and 5 strokes of undetermined cause. A significant trend toward a lower incidence for stroke with higher olive oil use was observed (table 1). This trend was statistically significant for ischemic but not for hemorrhagic stroke (table e-2).
The multivariate association between olive oil use and 6-year incident stroke is shown in table 2. Compared to those who never used olive oil, those with intensive use had a 41% (95% CI 6%-63%) lower risk in the fully adjusted model (model 2). From model 1, further adjustment for regular use of omega-6 rich oils, but no other covariate, slightly increased the strength of the association between olive oil use and stroke risk (see intermediate model in table e-3). No other dietary variable was significantly associated with stroke incidence, considered either separately or together in model 2 (table e-4).
Plasma oleic acid and stroke incidence. Baseline char- acteristics of the secondary study sample from Bordeaux according to tertiles of plasma oleic acid proportion are presented in table 3 and table e-5. Higher plasma oleic acid proportion was signifi- cantly associated with higher olive oil consump- tion. Mean proportion of plasma oleic acid was 19.9% (SD 3.3) in nonusers of olive oil, 20.5% (SD 3.7) in moderate users, and 20.7% (SD 4.2) in intensive users ( p for trend = 0.002, r2 = 1%). The other significant dietary predictors of plasma oleic acid were added fats: omega-6 rich oils (negative association), butter, goose or duck fat (positive associations) (table e-6).
Contrarily to that observed with olive oil con- sumption, participants with higher plasma oleic acid proportion were slightly older and had a more severe burden of vascular risk factors (table 3 and table e-5).
In this secondary study sample, 27 incident strokes occurred over a 5.0-year median follow-up (range 6 months-6 years), including 20 ischemic and 7 hemorrhagic strokes. There was a significant trend toward a lower incidence for stroke with higher plasma oleic acid proportion (table 3). This trend was statistically significant for ischemic stroke. Compared to those in T1, participants with plasma oleic acid in T3 had a 73% (95% CI 10%-92%) to 75% (95% CI 14%-92%) reduction of stroke risk in, respectively, models 2 and 3 (table 4).
Sensitivity analyses. Further adjustment for imputed mean total daily energy intake in the main analysis did not substantially modify the results (e-Results), and the distributions of observed and imputed values conditional on energy intake were very close (figure e-1). Moreover, adjustment for the total/HDL cho- lesterol ratio instead of hypercholesterolemia, or ex- clusion of prevalent dementia cases at baseline (n = 96 in the main study sample and n = 23 in the Bordeaux sample), did not substantially modify the results (data not shown).
In the present population-based study, intensive olive oil use was prospectively associated with a lower stroke risk after controlling for numerous confounding factors, including lifestyle and nutritional factors, main stroke risk factors, and blood lipids.
Several converging arguments suggest a protective role for high olive oil consumption on the risk of stroke in older subjects: 1) olive oil use was associated with lower stroke risk; 2) plasma oleic acid was asso- ciated with lower stroke risk; 3) plasma oleic acid was an indirect marker of olive oil consumption since higher plasma oleic acid was significantly associated with higher olive oil use; 4) no other dietary predictor of plasma oleic acid was significantly associated with stroke risk.
However, our results should be interpreted cautiously, since plasma oleic acid is not a specific marker of olive oil consumption. It can also derive from other food sources and from endogenous hepatic synthesis from saturated fats,26 so that plasma oleic acid may be a marker of olive oil consumption only in populations with moderate to high olive oil use.22 Accordingly, in our study, although higher plasma oleic acid was significantly associated with higher olive oil use, the intensity of the association was very low. Moreover, plasma oleic acid was also associated with higher consumption of butter and goose or duck fat, which are sources of oleic acid as well. This may explain the unfavorable pattern of risk factors associated with higher plasma oleic acid.
While epidemiologic studies published to date do not enable us to disentangle olive oil from other components of the MeDi, probably because they did not use olive oil but the MUFA-to-saturated fatty acids ratio as originally described,27 the current study supports the assumption that within the MeDi, olive oil may be a major protective component independently of other dietary components. It may also partly explain the protective association of olive oil20 and the MeDi28 with cognitive decline observed in the 3C Study. The demonstrated vascular beneficial effects of olive oil include blood pressure reduction, improvement of blood lipid profile, reduction of low-density lipoprotein susceptibility to oxidation, and improvement of oxidative vascular damage and endothelial function,10 possibly through a modulation of key genes implied in vascular inflammation, foam cell formation, and thrombosis.29 These effects were primarily attributed to oleic acid30-32 but also more recently to phenolic compounds found in vir- gin olive oil,33,34 which have a potent anti- inflammatory action.35 The protective association between olive oil use and stroke was significant in ischemic but not hemorrhagic stroke, for which the low number of cases limits study power.
Although vascular events outside the coronary arterial territory encompass acute coronary and peripheral vascular events, in particular in older subjects,1 a single large prospective cohort study found that higher adherence to the MeDi was related to lower stroke incidence.36 However, the associations between each component of the MeDi and stroke incidence were not presented separately. A study reported that higher plasma oleic acid was associated with higher 32-year incidence of stroke,37 a result that seems contradictory to our findings. However, this discrepancy may be explained by different di- etary habits of the studied populations.
The main strengths of the present study include a longitudinal design with a large sample size, low attrition rate, and a standardized and centralized pro- cedure for data recording and validation of clinical outcomes. Another major strength is the use of biological data to complete and validate associations ob- served with dietary data. This study also has some limitations. Since final stroke diagnosis depended on initial self-reporting, some stroke cases may have been missed by our process. Moreover, in spite of a deep investigation of every suspected incident case of stroke by an independent expert committee, we can- not rule out that some confirmed stroke cases may be false positives. Although we used plasma oleic acid as an indirect marker of olive oil intake to support our findings, the lack of quantitative data for olive oil use did not enable an accurate estimation of the association between plasma oleic acid and olive oil intake, which remained very low in our study. Thus, the validity of plasma oleic acid as an indirect marker of olive oil consumption in our population remains to be evaluated. While converging evidence suggests that due to its high content in polyphenols, virgin olive oil provides more cardiovascular benefits than refined olive oil,34 we were not able to distinguish the different types of olive oil consumed. However, olive oil consumers were expected to mostly consume virgin olive oil in our study, since 98% of the French market of olive oil is composed of extra virgin olive oil.38
The high prevalence of stroke in older subjects emphasizes the need for primary and secondary prevention in this age group. 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.