Background

Oxidative stress and vascular impairment are believed to mediate in part age-related cognitive decline, a strong risk factor for development of dementia. Epidemiological studies suggest that a Mediterranean Diet, an antioxidant-rich cardioprotective dietary pattern, delays cognitive decline, but clinical trial evidence is lacking.

Objective

To investigate whether a Mediterranean diet supplemented with antioxidant rich foods influences cognitive function compared to a control diet.

Design

Randomized, parallel-group, controlled trial. Barcelona, Spain. Cognitively healthy volunteers (n=447, 52% women, mean age 66.9 years) at high cardiovascular risk enrolled into the PREDIMED nutrition intervention trial underwent neuropsychological assessment at inclusion and were offered retest at the end of the study.

Method

Participants were randomly assigned to a Mediterranean diet supplemented with extra-virgin olive oil (olive oil) (1 liter/week), a Mediterranean diet supplemented with mixed nuts (30 g/day), or control diet (advice to reduce dietary fat).

Result

Rates of cognitive change over time based on a neuropsychological test battery: Mini-Mental State Examination, Rey Auditory Verbal Learning Test (RAVLT), Animals Semantic Fluency, Digit span from Wechsler Adult Intelligence Scale, Verbal Paired Associates from Wechsler Memory Scale, and Color Trail Test. We used mean z scores of change in each individual test to construct three cognitive composites: memory, frontal (attention and executive function), and global cognition. Follow-up cognitive tests were available in 334 participants after intervention (median of 4.1years). In multivariate analyses adjusted for confounders, participants allocated to a Mediterranean diet +olive oil scored better in RAVLT (P=.049) and Color Trail part 2 (P=.044) compared with controls. Similarly adjusted cognitive composites showed that, compared to the control group, the Mediterranean diet+nuts group improved performance above baseline in memory tests (P=.041), while the Mediterranean diet+olive oil group performed better in tests of frontal (P=.003) and global cognition (P=.005). All cognitive composites significantly (P<.05) decreased from baseline in controls.

Conclusion

In an older population a Mediterranean diet supplemented with olive oil or nuts was associated with improved cognitive function.

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