The PREDIMED trial found that substituting lower-grade olive oil for extra virgin olive oil increased polyphenol intake in participants with metabolic syndrome or diabetes.

“um and what happened is what they did was they told people to um they gave people this extra virgin olive oil and the thing is the people on the predimed trial were mostly diabetic um or at least they had to have several parts of the metabolic syndrome they were older and they all when they um surveyed them at the beginning they were all already eating a Mediterranean diet and so they're in Spain and they're they're finding these thousands of people who have been eating olive oil their whole lives now they're diabetic and it was those people that they selected and what they did was they gave them olive oil which they were all already eating so they so what they did was they substituted kind of lower grade olive oil for uh extra virgin olive oil Which is higher in polyphenols”