Perhaps you've seen escolar at your local fishmonger or on the menu at restaurants. With some varieties of fish in danger of being overfished and other species becoming undesirable due to their high mercury content, seafood purveyors need a fish that's delicious, cheap, sustainable, and low in mercury. And escolar fits the bill. It's economical and politically correct; it's also extremely tasty.
But before you eat it, there is something important you need to know.
But, First: What Is Escolar?
Escolar is a type of snake mackerel. Sometimes it's under the name "butterfish," "oilfish," or "waloo/walu." Sushi restaurants occasionally serve it as "super white tuna" or "king tuna." As mentioned above, it is, in many ways, the perfect fish: It's cheap, it's sustainable, and it's buttery and succulent.
So, what's the problem?
The Problem with Escolar
Escolar cannot metabolize the wax esters naturally found in its diet. These esters are called gempylotoxin, and this is what gives the flesh of escolar its oily texture. The downside is that these esters are are very similar to castor or mineral oil, and when full portions of escolar are consumed, they can cause gastrointestinal symptoms.
To be frankly and bluntly specific — and I'm sorry for this — consumption of escolar causes explosive, oily, orange diarrhea. People have reported that the discharges are often difficult to control and accidents can happen while passing gas.
I personally know someone who ate an escolar steak one night, unaware of its side effects. The next day he was riding the elevator to his office when out of nowhere his bowels unleashed a surprise attack on his pants. As he said later, "Thank God I had my gym bag with me, which had a clean pair of underwear in it." This explains why escolar is also called the "olestra fish" and the "ex-lax fish."
The Japanese and Italian governments have banned the importation and sale of escolar for these reasons. The governments of Canada, Sweden, and Denmark require that all escolar come with warning labels. The FDA lifted the escolar ban in 1992 because the fish is nontoxic (sure, it causes embarrassing things to happen in your pants, but it won't hurt or kill you).
So, Should You Eat Escolar?
In spite of all this, escolar is indeed very buttery and delicious, and should be enjoyed, but never in portions larger than six ounces. Portions below six ounces will not cause gastrointestinal distress. Don't say we didn't warn you.