What’s so special about olive oil?
Olive oil contains primarily mono-unsaturated fatty acids, which are linked to better health. In addition, olive oil contains as many as 100 polyphenolic compounds, some of which have been shown to have anti-inflammatory properties. Olive oil may exert its evident health effects via anti-inflammatory and anti-atherogenic effects and by improved blood fat profiles, insulin sensitivity, and blood sugar control.
Monounsaturated fats in olive oil
One of the earliest studies of the effects of monounsaturated fatty acids came from Italian researchers. They used data from 278 non-demented elderly participants in the Italian Longitudinal Study on Aging who ate a traditional Mediterranean diet as evaluated with a food-frequency questionnaire. Cognitive function was evaluated according to global cognitive function (Mini-Mental State Examination), selective attention (Digit Cancellation Test), and episodic memory (Babcock Story Recall Test). High intakes of monounsaturated fatty acids predicted a significant 31 percent greater odds having higher global cognitive function.
If olive oil is good, is more olive oil better?
The PREDIMED randomized controlled trial tested the effects of three diets on various health-related outcomes, one of which was mild cognitive impairment. The three diets included 1) a Mediterranean diet supplemented with extra-virgin olive oil, 2) a Mediterranean diet supplemented with mixed nuts, and 3) a low-fat diet. This trial included 268 community-dwelling Spanish residents at high vascular risk with an average baseline age of 74 years. Dietary compliance was evaluated with food-free frequency questionnaires annually. A battery of 16 cognitive tests lasting 2 hours was administered to the participants after 6.5 years of follow-up. At that time, the diets of participants in the two Mediterranean diet groups differed greatly from that of the low-fat diet group.
At follow-up, the scores for 15 of the 16 cognitive tests were more favorable for the Mediterranean diet with extra-virgin olive oil group compared to the low-fat diet group, but only four of the tests reached statistical significance. Similarly, the scores for 15 of the 16 cognitive tests were more favorable for the Mediterranean diet with extra-virgin olive oil group compared to the Mediterranean diet with mixed nuts group but only three of the tests reached statistical significance. In addition, participants in the Mediterranean diet with extra-virgin olive oil had a significant 66 percent lower risk of developing mild cognitive impairment compared to the control group. Thus, supplementing a Mediterranean diet with extra-virgin olive oil improved cognitive performance compared to the other groups.
More evidence from a PREDIMED trial
Evidence from prospective studies shows that dietary habits are associated with cognitive performance. A report from a randomized clinical trial provides experimental evidence that a Mediterranean diet leads to improved cognitive performance. The study involved 437 individuals who were part of the Barcelona North – PREDIMED study from 2003 – 2009. The participants were between 60 and 80 years of age with high risk of but without cardiovascular disease at baseline. Subjects were randomized to one of three groups: 1) Mediterranean diet with added extra-virgin olive oil, 2) Mediterranean diet with added mixed nuts, and 3) the control group, members of which were advised to reduce dietary fat. Cognitive data were collected at baseline (in 2003) and near the end of the study in 2009.
In multivariate analyses adjusted for potential confounding factors, subjects in the Mediterranean diet plus extra-virgin olive oil group scored significantly higher on the Rey Auditory Verbal Learning Test (an assessment of intermediate and delayed episodic verbal memory) and on the Color Trail Test Part 2 (an assessment of attention, visuomotor speed, and cognitive flexibility) compared to subjects in the control group. No differences among the three groups were found for seven other cognitive tests. For composite scores of cognition, subjects in the Mediterranean diet plus extra-virgin olive oil group had significantly higher scores for frontal and global cognition than members of the control group in the fully adjusted model. For memory, subjects in the Mediterranean diet plus mixed nuts group had significantly higher scores than subjects in the control group. Over a median follow-up period of 4.1 years, no significant differences were observed between the three groups in terms of incident dementia. Overall, the Mediterranean diet with either added extra –virgin olive oil or mixed nuts led to improve cognitive function. The authors attributed the improvement to antioxidants and anti-inflammatory chemicals in the Mediterranean diets.
Evidence from Greece
Extra-virgin olive oil contains high concentrations of phenolic compounds, which may protect against cognitive decline with age. Researchers in Greece conducted a small study with three groups of community-dwelling Greek participants with an average of 70 years. Group 1 was given 50 mL per day of high-phenolic early harvest extra-virgin olive oil plus instruction in consuming a Mediterranean diet. Group 2 was given 50 mL per day of moderate-phenolic extra-virgin olive oil plus instruction in consuming a Mediterranean diet. Group 3 was only given instruction in consuming a Mediterranean diet. A battery of 11 categories of cognitive measures was administered to all participants at baseline and 12 months later.
From baseline to 12 months, participants in Group 1 had significant improvement in 3 of 11 cognitive categories (severity of cognitive function, digit forward, and letter fluency). Similarly, participants in Group 2 had significant improvement in 1 of 11 cognitive categories (severity of cognitive function). Participants in Group 3 had significant improvement in 1 of 11 cognitive categories (letter fluency). In addition, participants in Group 1 and Group 2 had significantly better improvement in severity of cognitive function than Group 3. This pilot study provides preliminary evidence that high-quality extra-virgin olive oil may improve some aspects of cognitive performance over a year’s time.
Can olive oil help you even if you eat a crummy diet?
The Mediterranean dietary pattern appears to confer substantial health benefits compared to the standard American diet. Olive oil forms a central component of the Mediterranean diet. Does higher olive oil consumption predict better health outcomes regardless of overall dietary quality? Researchers at Harvard addressed this question with data from 92,383 participants with a baseline age of 56 years in the Nurses’ Health Study (women) and the Health Professionals Follow-up Study (men). Daily olive oil intake was assessed from 130-item food-frequency questionnaires administered at baseline and every 4 years thereafter.
After 28 years of follow-up and after adjusting for a host of confounding factors, combined women and men participants who consumed at least 7 grams of olive oil (about half a tablespoon) per day had a significant 28 percent lower risk of dying of dementia compared to participants who reported never or rarely consuming olive oil. When data for women and men were analyzed separately, the reduced risk for women increased to 33 percent and remained statistically significant, while that for men declined to 13 percent and became statistically non-significant. These results were not influenced by the presence of the APOE e4 gene that predisposes carriers to greater risk of dementia or by degree of adherence to the Alternative Mediterranean diet or the Alternative Healthy Eating Index. Replacing 5 grams of margarine per day with an equivalent amount of olive oil predicted a significant 10 percent lower risk of dementia death for the studies combined. This result may reflect the abundance of trans-fats in margarine during the study. Previous research using these two cohorts showed that higher consumption of olive oil significantly reduced the risk of all-cause mortality. Thus, shifting oil intake toward olive oil may help you live longer and reduce your chances of dying of dementia.
What to do
After reading about the health benefits of extra-virgin olive oil a decade ago, my wife and I switched from using canola oil to extra-virgin olive oil for most of our eating. We’ve also made the habit of sprinkling olive oil and a low-salt seasoning mix on vegetables to give them more flavor. Thus, we’re inclined to eat more veggies. Join the club!
