Does olive oil protect your brain against decline?

Extra virgin olive oil as part of the Mediterranean diet appears to protect memory and attention. In the PREDIMED study (334 participants, followed for an average of 4.1 years), people who followed a Mediterranean diet with one litre of extra virgin olive oil per week scored better on memory and attention tests than the control group. That control group, which ate a low-fat diet, declined on every measured cognitive outcome. A longer follow-up measurement in the same trial (522 participants, 6.5 years) confirmed this: the olive oil group scored measurably higher on two standardised cognitive tests than the controls.

A meta-analysis of 23 studies shows that people who adhere closely to the Mediterranean diet have an 11 to 30 percent lower chance of cognitive decline, dementia, or Alzheimer's disease. The strongest figure applies to Alzheimer's: a 30 percent lower risk. These are associations, however, not proven causation. There was also considerable variation between studies, meaning that the precise size of the effect remains uncertain.

Whether olive oil itself makes the difference, or the Mediterranean diet as a whole, has not yet been clarified. A systematic review of 56 studies concludes that olive oil is a promising component, but that the evidence for olive oil as a standalone factor is limited and not definitive. The strongest protection was consistently found for the complete dietary pattern, not for any single ingredient.

How the brain protection works exactly is also unclear. It may be direct, but it may also operate through a healthier cardiovascular system: less arterial hardening also means better blood flow to the brain. A large randomised study specifically testing extra virgin olive oil as protection against Alzheimer's has not yet published its results.