A plant-based Mediterranean diet supplemented with extra virgin olive oil or mixed nuts may counteract age-related cognitive decline in older adults, according to a report published online May 11 by JAMA Internal Medicine.

Senior author Emilio Ros, MD, PhD, and colleagues studied 447 cognitively healthy people (223 women; average age, 67 years) who were at high cardiovascular risk and enrolled in the Prevencion con Dieta Mediterranea nutrition intervention in Spain. The participants were randomly assigned to three groups: 155 supplemented a Mediterranean diet with one liter of extra virgin olive oil each week; 147 supplemented a Mediterranean diet with 30 g every day of a mix of walnuts, hazelnuts, and almonds; and 145 followed a low-fat control diet. The authors measured cognitive change over time and constructed three cognitive composites: memory, frontal (attention and executive function), and global cognition. 

At the end of a median of four years of follow-up, the low-fat control diet was associated with a significant decrease from baseline in all three cognitive composites. Compared with the control diet, the memory composite improved significantly when nuts were added to the Mediterranean diet, and the frontal and global cognition composites improved when olive oil was added to the Mediterranean diet. There were no cases of dementia documented among the patients who completed the follow-up.

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