Like red snapper, lobster, and Kobe beef, not all olive oils are created equal. In fact, it's been estimated that roughly 73% of the United States' best-selling olive oil brands have been cut with cheaper alternatives, cheapening the $16 billion olive oil industry.
This is all according to a 2011 study from the UC Davis Olive Center, which tested 90 samples of olive oil from Filippo Berio, Bertolli, Pompeian, Colavita, and Star based on the standards set by the International Olive Council. In the end, just over 70% of those tested failed to meet the IOC's standards, which include a sensory test, a chemical review, and an ultraviolet absorption test.
"Olives and olive oil are well-known for their many health benefits, especially for your heart, but using adulterated olive oil will hardly do your health any favors," writes Dr. Joseph Mercola, an osteopathic physician, wellness expert, and New York Times best-selling author of Effortless Healing. "Anywhere from 60 to 90 percent of the olive oils sold in American grocery stores and restaurants are adulterated with cheap, oxidized, omega-6 vegetable oils, such as sunflower oil or peanut oil, or non-human grade olive oils, which are harmful to health in a number of ways."
Dr. Mercola quotes Larry Olmstead, a food critic and investigative journalist, who recommends purchasing Australian, Chilean, South African, and even Californian olive oil to sidestep the so-called "agromafia" that now runs rampant in Italy. Olmstead also pays specific attention to harvest date, color, smell, storage method, and quality seals when selecting a high-quality olive oil. Always opt for extra-virgin instead of the processed "pure" or "light" oils, and favor dark bottles that protect against light.
For more, read up on the only oatmeal brands a nutritionist will eat.
UC Davis Olive Center at the Robert Mondavi Institute. Report: Evaluation of Extra-Virgin Olive Oil Sold in California. Updated April 2011.
Gaforio JJ, Visioli F, Alarcón-de-la-lastra C, et al. Virgin Olive Oil and Health: Summary of the III International Conference on Virgin Olive Oil and Health Consensus Report, JAEN (Spain) 2018. Nutrients. 2019;11(9).doi:10.3390/nu11092039