“White tuna” does not exist! Whoa. You weren’t expecting us to spring that on you right off the bat, were you? But the fact is that any Japanese restaurant serving white tuna (and there are a lot of them here in the U.S.) is lying to you — plain and simple.

What exactly is the fish you just ordered at your neighborhood sushi joint? “People hope it is albacore,” says chef Yoshihiko Kousaka of New York City’s omakase-only hot spot Kosaka. “But when you see something that says ‘white tuna’ and not ‘albacore,’ it is not albacore. White tunas are usually ‘oilfish,’ ‘butterfish’ or ‘escolar.’”

So just why does “white tuna” appeal to people in the U.S.? Its variations taste like a rich fatty tuna, giving diners the impression that it’s a flavorful alternative to seemingly similar, yet much more expensive options, like chu-toro (mid-fatty tuna) and o-toro (fatty tuna).

There are myriad issues with eating these types of fish. “Human bodies cannot digest their oil, which is toxic wax ester and leads to keriorrhea,” explains Kousaka, referring to a very less-than-pleasant side effect. (Indeed, there is a distinct waxy texture to escolar.) Just how risky is it to consume these fish? “The Japanese government considers them toxic…. It is prohibited to sell or serve these ‘white tunas.’ It is that dangerous!” exclaims the chef. He adds that he personally would never purchase any fish marked “white tuna.”

Meanwhile, serving oilfish, butterfish and escolar is not banned in the U.S. Lower-end sushi places “tend to use falsely named fish to save cost,” says chef Masaki Saito of top-notch omakase-only establishment Sushi Ginza Onodera. Labeling escolar as “white tuna to mislead consumers is not exactly uncommon,” Saito adds.

Chef Kousaka adds that he believes the mislabeling of fish at sushi restaurants in the U.S. is “huge.”

Still need convincing that you should stay away from any fish labeled “white tuna”? Feel free to Google the term “keriorrhea.” Then again, we know you already did.