Results of a randomized clinical trial, published earlier this month in the JAMA Internal Medicine, revealed that long-term consumption of the Mediterranean diet supplemented with either extra virgin olive oil or nuts improved cognitive function in older adults.
Although previous observational studies reported a positive relationship between adherence to the Mediterranean diet and improved cognitive function, they compared intake of a control diet versus intake of a Mediterranean diet without a baseline evaluation of the subjects before and after consumption of the Mediterranean diet.
In contrast, findings of the new study are based on repeated neuropsychological assessment of the subjects who consumed a control diet or a Mediterranean diet supplemented with either EVOO or nuts over a four-year period.
Conducted on a small sub-sample of Spanish subjects enrolled at the Barcelona-North PREDIMED center, the study started with 447 cognitively healthy subjects who had either Type 2 diabetes or risk to cardiovascular disease in 2003. However, only 344 subjects completed the study in 2009. The objective of the study was to investigate the effect of an antioxidant-rich Mediterranean diet on cognitive function of the subjects.
The enrolled subjects were randomly assigned to one of the three diets: a Mediterranean supplemented with one liter of extra virgin olive oil per week; a Mediterranean supplemented with intake of 30 grams mixed nuts that included 15 grams of walnuts, and 7.5 grams each of almonds and hazelnuts; or a control diet with advice to reduce fat intake.