A new study has found that supplementing a plant-based Mediterranean diet with antioxidant-rich extra virgin olive oil or mixed nuts was associated with improved cognitive function in older adults in Spain.
But researchers involved in the study, which was published in JAMA Internal Medicine, warn that more investigation is needed.
For their study, a research team led by Emilio Ros, M.D., Ph.D., of the Institut d’Investigacions Biomediques August Pi Sunyer, Hospital Clinic, Barcelona, and Ciber Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, 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 with an average age of nearly 67 years, who were at high cardiovascular risk and were enrolled in the Prevencion con Dieta Mediterranea nutrition intervention.
The researchers told 155 individuals to supplement a Mediterranean diet with one liter of extra virgin olive oil per week; 147 were told to supplement a Mediterranean diet with 30 grams per day of a mix of walnuts, hazelnuts, and almonds; and 145 were told to follow a low-fat control diet.
The researchers measured cognitive change over time with a battery of neuropsychological tests. They also constructed three cognitive composites for memory, frontal (attention and executive function), and global cognition.
After a median of four years on the diets, follow-up tests were available on 334 participants.
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.
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, while the frontal and global cognition composites improved in the Mediterranean diet plus olive oil group.
The researchers noted the changes for the two Mediterranean diet arms in each composite were more like each other than when comparing the individual Mediterranean diet groups with the low-fat diet control group.
“Our results suggest that in an older population a Mediterranean diet supplemented with olive oil or nuts may counter-act age-related cognitive decline,” the researchers wrote in the study.
“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.”
Source: JAMA Network Journals