Escolar, a fish prized for its rich, buttery taste, is known for causing digestive discomfort in some individuals. This often leads to questions about why this appealing fish can have such unpleasant effects. The reason lies in a specific type of fat that the human digestive system struggles to process.
The Role of Wax Esters
The high concentration of wax esters in its flesh is the primary reason escolar can cause illness. Escolar accumulates these wax esters because it cannot metabolize them effectively from its diet. These indigestible oils can make up 14% to 25% of the fish’s body weight, with over 90% of that fat being wax esters.
Wax esters are a type of lipid formed when a fatty acid combines with a fatty alcohol. Unlike typical dietary fats, such as triglycerides, the human digestive system lacks the enzymes to break down and absorb these long-chain wax esters. Consequently, these compounds pass through the stomach and small intestine largely unchanged. They then accumulate in the rectum, leading to characteristic gastrointestinal symptoms.
Recognizing the Symptoms
Consumption of escolar can lead to a range of gastrointestinal symptoms, most notably an oily discharge known as keriorrhea. This condition is characterized by the involuntary passage of an oily, orange or yellowish substance from the rectum. Since this oil is less dense than water, it floats, appearing as orange oil droplets in the toilet.
Other symptoms that may accompany keriorrhea include abdominal cramps, nausea, vomiting, stomach gurgling, and headaches. Symptoms manifest within a few hours of consumption, usually between 30 minutes and 36 hours, and resolve within 24 to 48 hours. While unpleasant, these effects are not life-threatening and do not cause significant fluid loss like other forms of diarrhea. The severity of symptoms depends on the amount of escolar consumed and individual sensitivity.
Minimizing the Risk
To reduce adverse effects from escolar, consuming it in very small portions is recommended. Health authorities and seafood experts suggest limiting a single meal to 6 ounces (approximately 170 grams) or less. For those trying it for the first time, even smaller initial portions of 3-4 ounces are advised. For some, avoiding escolar entirely may be the safest approach.
It is also important to be aware of potential mislabeling, as escolar is sometimes sold under other names like “white tuna,” “butterfish,” or “oilfish.” Cooking methods, such as grilling, do not reliably break down or eliminate the wax esters, as these compounds are heat-stable. While some suggest deep-skinning or removing dark meat might help, there is limited evidence to support these claims.