Most avocado oil sold in the United States — including that labeled “pure” or “extra virgin” — is either stale before its expiration date or mixed with other oils, according to a study published recently in the journal Food Control.

In fact, some of the samples tested in the study contained almost no avocado oil.

“Most people who buy avocado oil are interested in the health benefits, as well as the mild, fresh flavor, and are willing to pay more for the product,” says Selina Wang, one of the study’s authors and a food scientist at the University of California, Davis, in a released statement. “But because there are no standards to determine if an avocado oil is of the quality and purity advertised, no one is regulating false or misleading labels.”

“These findings highlight the urgent need for standards to protect consumers and establish a level playing field to support the continuing growth of the avocado oil industry,” she adds.