A new study done by Yale University showed that olive oil rich in polyphenols improved endothelial function while refined olive oil did not. The conclusion was that the biophenols found in real extra virgin olive oil, but not found in refined olive oil, were responsible for the improvement. Endothelial function is the measure of how well blood flows through the vessels, and is an independent predictor of cardiovascular health and type 2 diabetes.

The study took 20 obese people, all with high blood pressure, and gave 3 tablespoons of extra virigin olive oil to half of them and 3 tablespoons of refined olive oil to the other half. After one week their systems were flushed and the groups were reversed. Neither the participants nor the conductors of the study knew who was getting the extra virgin olive oil. After the study the results showed that the endothelial function improved for both groups when taking the real extra virgin olive oil.

From the study:

“Our study demonstrated that a single dose of 50 milliliters of high-polyphenolic extra virgin olive oil, when compared with refined olive oil without polyphenols, was associated with endothelial function improvement among individuals at risk for type 2 diabetes mellitus”.

“The acute effects of extra virgin olive oil on endothelial function observed may be explained by differences in the composition of extra virgin olive oil and refined olive oils”.