Adding extra virgin olive oil or mixed nuts to the Mediterranean diet is associated with a reduced risk of cognitive decline in older adults compared to a low-fat diet alone, according to a study appearing in JAMA Internal Medicine.

Emilio Ros, MD, PhD. 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, and collaborators designed this research to compare a Mediterranean diet supplemented with olive oil or nuts with a low-fat control diet. The clinical trial randomized 447 cognitively healthy volunteers that were enrolled in the Prevencion con Dieta Mediterranean nutrition intervention (average age nearly 67 years) and at high cardiovascular risk to one of the following interventions:

  • Supplement a Mediterranean diet with 1L of extra virgin olive oil per week
  • Supplement a Mediterranean diet with 30g/day of mixed nuts including walnuts, hazelnuts, and almonds
  • Low-fat control diet

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Cognitive change over time was measured with neuropsychological tests and three cognitive composites for memory, frontal, and global cognition. Follow-up tests were available on 334 participants after a median of four years of the intervention. At the end of the follow-up, 13.4% in the Mediterranean diet plus olive oil group were diagnosed with mild cognitive impairment, 7.1% in the Mediterranean diet plus nuts group, and 12.6% in the control group. No dementia cases reported in those who completed the study follow-up. Memory composite improved significantly in the Mediterranean diet plus nuts arm while frontal and global cognition composites improved in the Mediterranean diet plus olive oil arm.

Before the Mediterranean diet plus additional olive oil or nuts can be recommended as a preventative strategy for cognitive impairment and dementia, further studies are needed to confirm the present results.

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