Supplementing the plant-based Mediterranean diet with antioxidant-rich extra virgin olive oil or mixed nuts has been associated with improved cognitive function in a study of older adults in Spain, according to an open-access article published online by JAMA Internal Medicine.

Previous research suggests following a Mediterranean diet may be associated with better cognitive function and a lower risk of dementia. However, the observational studies that have examined these associations have limitations.

The researchers compared a Mediterranean diet supplemented with olive oil or nuts with a low-fat control diet.

The randomized clinical trial included 447 cognitively healthy volunteers (223 were women; average age was nearly 67 years) who were at high cardiovascular risk and were enrolled in the Prevencion con Dieta Mediterranea nutrition intervention.

Of the participants, 155 individuals were assigned to supplement a Mediterranean diet with one liter of extra virgin olive oil per week; 147 were assigned to supplement a Mediterranean diet with 30 grams per day of a mix of walnuts, hazelnuts and almonds; and 145 individuals were assigned to follow a low-fat control diet.

The authors measured cognitive change over time with a battery of neuropsychological tests and they constructed three cognitive composites for memory, frontal cognition (attention and executive function), and global cognition.

Mediterranean-diet subjects showed improved memory or cognition

The study found that individuals assigned to the low-fat control diet had a significant decrease from baseline in all composites of cognitive function. Compared with the control group, the memory composite improved significantly in the Mediterranean diet plus nuts group, while frontal and global cognition improved in the Mediterranean diet plus olive oil group.

At the end of the follow-up, there were 37 cases of mild cognitive impairment: 17 (13.4 percent) in the Mediterranean diet plus olive oil group; eight (7.1 percent) in the Mediterranean diet plus nuts group; and 12 (12.6 percent) in the low-fat control group. No dementia cases were documented in patients who completed study follow-up.

“Our results suggest that in an older population, a Mediterranean diet supplemented with olive oil or nuts may counteract age-related cognitive decline,” the researchers suggest.

“The lack of effective treatments for cognitive decline and dementia points to the need of preventive strategies to delay the onset and/or minimize the effects of these devastating conditions. The present results with the Mediterranean diet are encouraging but further investigation is warranted.”

The researchers are affiliated with the Institut d’Investigacions Biomediques August Pi Sunyer, Hospital Clinic, Barcelona; Ciber Fisiopatología de la Obesidad y Nutrición (CIBEROBN); and Instituto de Salud Carlos III, Madrid.

---

Abstract of Mediterranean diet improves cognition: the PREDIMED-NAVARRA randomised trial

Objective Previous observational studies reported beneficial effects of the Mediterranean diet (MedDiet) on cognitive function, but results were inconsistent. We assessed the effect on cognition of a nutritional intervention using MedDiets in comparison with a low-fat control diet.

Methods We assessed 522 participants at high vascular risk (44.6% men, age 74.6 ± 5.7 years at cognitive evaluation) enrolled in a multicentre, randomised, primary prevention trial (PREDIMED), after a nutritional intervention comparing two MedDiets (supplemented with either extra-virgin olive oil (EVOO) or mixed nuts) versus a low-fat control diet. Global cognitive performance was examined by Mini-Mental State Examination (MMSE) and Clock Drawing Test (CDT) after 6.5 years of nutritional intervention. Researchers who assessed the outcome were blinded to group assignment. We used general linear models to control for potential confounding.

Results After adjustment for sex, age, education, Apolipoprotein E genotype, family history of cognitive impairment/dementia, smoking, physical activity, body mass index, hypertension, dyslipidaemia, diabetes, alcohol and total energy intake, participants allocated to the MedDiet+EVOO showed higher mean MMSE and CDT scores with significant differences versus control (adjusted differences: +0.62 95% CI +0.18 to +1.05, p=0.005 for MMSE, and +0.51 95% CI +0.20 to +0.82, p=0.001 for CDT). The adjusted means of MMSE and CDT scores were also higher for participants allocated to the MedDiet+Nuts versus control (adjusted differences: +0.57 (95% CI +0.11 to +1.03), p=0.015 for MMSE and +0.33 (95% CI +0.003 to +0.67), p=0.048 for CDT). These results did not differ after controlling for incident depression.

Conclusions An intervention with MedDiets enhanced with either EVOO or nuts appears to improve cognition compared with a low-fat diet.