Diet and Brain

Add Olive Oil or Nuts to Guard Brain

By Kathleen Struck, Senior Editor, MedPage Today

Published: May 20, 2013

Reviewed by Zalman S. Agus, MD; Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania

Action Points

• Participants considered to be at high vascular risk were enrolled in a randomised, primary prevention trial with nutritional intervention comparing two Mediterranean diets (supplemented with either extra-virgin olive oil or mixed nuts) versus a low-fat control diet.
• After a mean followup of over 6 years, intervention with a Mediterranean diet enhanced with either extra-virgin olive oil or nuts appeared to improve cognition when compared with a low-fat diet.

A Mediterranean diet heavy on extra-virgin olive oil or nuts does more to keep the aging brain agile than simply switching to a low-fat diet, researchers found.

Participants in the PREDIMED-NAVARRA trial who consumed the Mediterranean diet plus olive oil had significantly better cognitive function scores on a Mini-Mental State Exam (MMSE) (+0.62 versus controls, 95% CI 0.18-1.05, P=0.005), wrote Miguel A. Martinez-Gonzalez, MD, MPH, PhD, of University of Navarra, Pamplona, Spain, and colleagues.

Participants who consumed the Mediterranean diet plus olive oil also did better than controls on clock-drawing tests (CDTs) (+0.51 95% CI 0.20-0.82, P=0.001), the authors wrote in Journal of Neurology Neurosurgery and Psychiatry.

"Our trial suggests that nutritional intervention with MedDiet supplemented with either extra-virgin olive oil or nuts is associated with improved global cognition," the authors wrote . "There are mechanisms that can explain the protective effect of MedDiet on cognitive status, including antioxidative and anti-inflammatory effects and reduced vascular comorbidities."

PREDIMED recruited 522 adults who were at high risk of vascular events. The average age was 75 and 45% were men. The participants were randomized to the MedDiet regimen or a low-fat diet.

They included 224 participants from the MedDiet plus olive oil group, 166 from the MedDiet plus nuts, and 132 from the low-fat control group in their analysis.

Compared with the control group on a low-fat diet typically recommended for the prevention of cardiovascular disease, the "adjusted means of MMSE and CDT scores were also higher for participants allocated to the MedDiet plus nuts versus control (adjusted differences: +0.57 (95% CI +0.11-+1.03, P=0.015 for MMSE and +0.33, 95% CI +0.003-+0.67, P=0.048 for CDT)."

After 6.5 years of nutritional intervention, there were 60 cases of mild-cognitive impairment (18 in MedDiet with olive oil, 19 in Med diet with nuts, and 23 in the control group).

Dementia was diagnosed in 35 participants -- 12 cases in the MedDiet plus olive oil group, six cases in the MedDiet plus nuts. and 17 in the low-fat group.

"These data suggest that the case-ascertainment method based on the review of medical records may be similarly sensitive than the personalised cognitive assessment for dementia diagnosis," the authors wrote. "But sensitivity of medical records review was clearly lower than that for a complete neurological examination for a MCI diagnosis."

Both mini-mental and clock-drawing test scores were lower with inclusion of ApoE4 genotype, female gender, and older age. However, more education was associated with a better mini-mental test scores.

"Oxidative stress has been associated with neurodegeneration. The main components of the MedDiet intervention ... extra-virgin olive oil and nuts, have antioxidant properties and, together with other polyphenol-rich foods in the MedDiet, are suggested to relate to improved cognitive function," the authors wrote.

The authors noted that cognitive function was not assessed at baseline, which limits their findings. Also, they did not control for depression at baseline or cognitive assessment. The sample size was relatively small, they wrote, and true double-blind, long-term trials are not possible when studying nutrition.

Lastly, by study design, the researchers included participants at high risk of CVD, rendering the generalisation of the findings to the average general population "uncertain."

"Future interventional research including both baseline and follow-up assessments of global and multiple domains of cognition is needed to obtain firmer evidence regarding potential benefits of MedDiet on cognition," they concluded.

Martinez-Gonzalez declared no competing interests. Martínez-Lapiscina reported relationships with Novartis, Biogen, Teva, sanofi aventis, Lundbeck and Bayer. Co-authors report relationships with UCB Pharma, GlaxoSmithKline, Lundbeck, Esteve, Novartis, Cerveceros Espana, sanofis aventis, FIVIN-Spain, Nut and Dried Fruit Foundation, the Scientific Advisory Committee of the California Walnut Commission, Flora Foundation, Roche, AMGEN, Merck, DAMM, Abbott, Takeda, Sankyo, Nutrexpa, Feiraco, Unilever UK, Ferrer International, California Walnut Commission, KARO-BIO, DANONE, PACE, AstraZeneca, Rottapharm, and Ricordati. This study was funded by the official agency for funding biomedical research of the Spanish Government.

Primary source: Journal of Neurology Neurosurgery and Psychiatry
Source reference:
Martinez-Gonzalez MA, et al "Mediterranean diet improves cognition: the PREDIMED-NAVARRA randomised trial" J Neurol Neurosurg Psych 2013; DOI: 10.1136/jnnp-2013-305153.