Industry-Backed Study Led by Yale Expert Finds Most Olive Oil Is Pure

Like many people around the world, Katerina Karaiskos SPH ’25 uses olive oil every day.

“I have Cypriot roots, so it’s been a cooking staple for as long as I can remember,” Karaiskos said.

Now, Karaiskos says she is shopping with renewed confidence in the olive oil industry. In a report led by Tassos Kyriakides GRD ’99, an assistant professor of biostatistics at Yale and an olive oil sommelier, the pair documented the purity of commercial olive oils.

The report, released in August and backed by the North American Olive Oil Association, or NAOOA, conducted a randomized sampling of 158 representative extra virgin olive oils and 58 olive oils across the market. It found that only two samples, fewer than 1 percent, were adulterated and failed the purity test.

“The message to the consumer is that what you’re buying off the shelf is olive oil. There’s nothing else in it,” Kyriakides said.