Escolar is not white tuna, but it is frequently sold and served as “white tuna,” especially at sushi restaurants. True white tuna is albacore, a completely different species from a different biological family. The two fish look similar when served as sashimi or in a roll, which is why the mislabeling is so common. One study found that 84% of fish sold as “white tuna” in the U.S. was actually escolar.
Two Completely Different Fish
Albacore (the real white tuna) belongs to the mackerel family and is a true tuna species. Escolar belongs to a separate family called Gempylidae, sometimes known as snake mackerels. They are no more closely related than a house cat and a hyena.
The confusion starts at the plate. Raw albacore has a pinkish hue, while raw escolar is opaque white with a buttery, rich texture. Ironically, escolar looks more like what most people imagine “white tuna” should look like, which makes it easy to pass off under that name. Escolar also goes by butterfish, walu, and oilfish depending on the restaurant or market.
Why Escolar Causes Digestive Problems
Escolar’s flesh is roughly 20% indigestible oil by weight. This oil is made up of wax esters, a type of fat the human body simply cannot break down. The substance is sometimes called gempylotoxin, though the name is misleading: it’s not actually toxic. Your digestive system just has no way to process it, so the waxy oil passes straight through.
The result is a condition called keriorrhea, essentially oily, orange diarrhea that can arrive without warning. Symptoms typically start about two hours after eating, though they can appear as quickly as 20 minutes or take up to four hours. The episode usually resolves within two days, but it can be dramatic and uncomfortable while it lasts. Some people experience no symptoms at all, particularly if they eat a small portion, while others are highly sensitive.
Where Escolar Is Banned or Restricted
Japan and Italy have banned the sale of escolar outright. Canada, Sweden, and Denmark allow it but require warning labels so consumers know what they’re eating. In the United States, the FDA advises against selling escolar under misleading names, but enforcement is inconsistent. There is no outright ban, and many sushi restaurants continue listing it as “white tuna” or “super white tuna” on their menus without any mention of its real identity.
How to Tell What You’re Actually Eating
If you’re at a sushi restaurant and the “white tuna” is strikingly white, almost waxy looking, and melts on your tongue with an intensely buttery richness, you’re almost certainly eating escolar. Real albacore is leaner, firmer, and has a subtle pink tint even when raw. The flavor is milder, closer to what you’d expect from canned tuna’s upscale cousin.
Price can also be a clue. Escolar is cheaper than albacore, which gives restaurants a financial incentive to substitute it. If a sushi spot is offering unusually inexpensive white tuna, that’s worth questioning. You can always ask your server directly whether the fish is albacore or escolar. Restaurants that know the difference will usually tell you honestly.
Eating Escolar Safely
Plenty of people enjoy escolar on purpose once they know what it is. The key is portion size. Keeping your serving to around six ounces or less significantly reduces the chance of digestive trouble. Some sushi chefs recommend treating it like a rich appetizer rather than a main course.
Cooking method matters too. Grilling or broiling escolar allows some of the waxy oil to render out, which can reduce the oily load your gut has to deal with. Eating it raw as sashimi delivers the full fat content. If you’ve never had escolar before and want to try it, start with a few pieces rather than ordering an entire roll. That gives you a chance to see how your body handles it before committing to a larger portion.