191 Virgin Olive Oil Benefits 16.3. How can extra virgin olive oil prevent cognitive decline? “Let Food be thy Medicine and Medicine be thy Food.” Hippocrates (460-377 B. C.). The Greek physician, considered to be the father of medicine, was certainly referring to the Mediterranean diet and extra virgin olive oil (EVOO) when he gave this recommendation more than 2000 years ago. It is so because olive oil represents the hallmark of the Mediterranean diet. EVOO is mainly composed of fatty acids, the most abundant being oleic acid, a monounsaturated fatty acid. EVOO also has 7-10% linoleic acid, a polyunsaturated fatty acid. These fatty acids help to control blood cholesterol and triglycerides levels, thus preventing vascular lesions in AD, vascular dementia, and mixed dementia. Besides fatty acids, EVOO has reduced quantities of more than one hundred minor compounds. Among them, phenolic compounds seem particularly relevant. The beneficial antioxidant and anti-inflammatory effects of these phenolic compounds represent a good preventive strategy against neurodegenerative disease development. It should be highlighted that, despite olive oil and EVOO having a similar fatty acid content, the polyphenol fraction is considerably larger in EVOO given that these compounds are lost in the refinement process. EVOO has different types of phenolic compounds, the most abundant being secoiridoids followed by lignans. EVOO has been demonstrated to have a protective effect on preventing aberrant protein beta-amyloid and tau protein accumulation, and cognitive function impairment in AD animal models. 16.4. What evidence do we have regarding the benefits of extra virgin olive oil on cognitive function, cognitive decline, and dementia risk? Scientific evidence of the protective effect on health of any preventive or curative strategy should be obtained from properly, rigorously performed epidemiological studies. Intervention studies, with randomised, controlled trials (clinical trials with patients or healthy individuals) provide the highest degree of this kind of evidence. Sometimes this type of trials cannot be performed due to ethical or logistic reasons. In such cases, well-designed and analysed prospective observational studies (prospective cohorts) provide the best causal inferences for nutritional approaches. In these cohorts, demographic, physiological and lifestyle (e.g., diet) variables of healthy subjects are recorded at the beginning of the study. Individual follow-ups take place over years to register the occurrence of diseases, events, and/or functional changes
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