1. Amongst older adults in Barcelona, a Mediterranean diet supplemented with either extra virgin olive oil or mixed nuts showed some benefit in slowing down neurocognitive decline.
2. While all adults did have decline in the various neuropsychiatric tests, the amount was lower in the experimental group as compared to the control group.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Cardiovascular and neurodegenerative diseases lead to major morbidity and mortality in the developed world. For most of these diseases, it is thought that addressing them in the pre-clinical state is likely to lead to the best outcomes. The Mediterranean diet, which is largely plant-based and high in antioxidants, has already been shown to have beneficial cardiovascular outcomes. This study, which is based off of a sub-cohort of the original Mediterranean diet study, was conducted to determine whether this diet was associated with cognitive changes in a baseline healthy population. Amongst older adults in Barcelona, a Mediterranean diet supplemented with either extra virgin olive oil or mixed nuts showed some benefit in slowing down neurocognitive decline. While all adults did have decline in the various neuropsychiatric tests, the amount was lower in the experimental group as compared to the control group.
The strength of the study is the standardized design, food counseling for the individual groups, and using a food frequency questionnaire. The weakness includes the fact that many of the patients potentially followed the so-called Mediterranean diet even if in the control group since that might be the norm for them. Also, this sub-cohort was not very large, and there was a significant number that did not complete the second cognitive evaluation. Lastly, the study results are not particularly generalizable.
Relevant Reading: Mediterranean diet and cognitive function: a French study
In-Depth [randomized controlled trial]: This study is based off of a sub-cohort of the original, Prevencion con Dieta Mediterranea (PREDIMED) trial. The study’s cohort came from Barcelona’s study center from 2003-2009. The participants underwent a standardized neuropsychiatric evaluation, were randomly assigned to three groups, and underwent that test a later time point. The three groups were Mediterranean diet supplemented with extra virgin olive oil, Mediterranean diet supplemented with mixed nuts, or a control diet (including counseling on low-fat diet).
Cognitive changes were measured via different tests: Mini-Mental State Exam, Ray Auditory Verbal Learning Test (RAVLT), Color Trial Test, amongst others. There were 447 participants that completed the initial evaluation, but 113 did not complete the subsequent one. The Mediterranean diet with olive oil scored better on the RAVLT (p = 0.049) and Color Trail Test part 2 (p = 0.04) compared with the control group. No significant differences were found in the remaining cognitive tests.
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