Is Butterfish Okay to Eat? What You Need to Know Before You Dine

December 9, 2025 •

4 min read

While U.S. wild-caught butterfish is considered a sustainable and healthy seafood choice, a different fish often mislabeled as 'butterfish,' known as escolar, can cause severe digestive issues. The key to safety is understanding which species you are actually consuming, particularly when ordering at restaurants or sushi bars.

Quick Summary

Authentic butterfish is a healthy, low-mercury fish rich in omega-3s, but a mislabeled fish called escolar contains indigestible wax esters that can cause oily diarrhea. Careful sourcing and identification are essential to safely enjoy this buttery-tasting seafood.

Key Points

Misidentification is Common: The fish most associated with digestive problems, escolar, is often mislabeled as butterfish, especially in restaurants and sushi bars.
Authentic Butterfish is Safe: Species like U.S. wild-caught Atlantic butterfish or pomfret are safe, healthy, low-mercury options rich in protein, B vitamins, and selenium.
Escolar Causes Keriorrhea: Escolar contains indigestible wax esters that cause gastrointestinal distress, leading to oily diarrhea (keriorrhea) and abdominal cramps.
Ask Your Vendor: Always verify the specific species with your fishmonger or restaurant server to avoid mislabeled escolar.
Be Cautious with "White Tuna": Any fish labeled as "super white tuna" or "walu" is likely escolar and should be avoided due to the associated health risks.
Vulnerable Individuals Should Avoid Escolar: Pregnant women, people with bowel conditions, and those with malabsorption issues should strictly avoid escolar due to increased risk of adverse effects.
High-Omega-3 Alternatives Exist: For a similar rich flavor profile without the risk, opt for Alaskan black cod (sablefish), which is sometimes also called butterfish.

The Butterfish Identity Crisis: Separating the Safe from the Risky

In the world of seafood, the name "butterfish" can be a source of confusion and even health problems. While the true butterfish is a delicious and healthy choice, other species, most notably escolar, are frequently mislabeled and can cause significant digestive distress. The primary issue with misidentified fish is the presence of indigestible wax esters, particularly in escolar, which pass through the body unchanged and lead to a condition called keriorrhea, or oily diarrhea. This has even led to bans on the sale of escolar in some countries, like Japan.

To ensure a safe and enjoyable dining experience, it is crucial to understand the characteristics of true butterfish and its common impersonators. True butterfish species include the Atlantic butterfish (Peprilus triacanthus) and various pomfret species (Stromateidae family), which are generally smaller, silver, and found closer to coastlines. Conversely, the impostor, escolar (Lepidocybium flavobrunneum), is a large, deepwater fish sometimes sold as "super white tuna," "walu," or "oilfish". Learning to differentiate these fish is the most important step in protecting your health and avoiding unpleasant side effects.

The Nutritional Benefits of Authentic Butterfish

When you are confident that you are consuming a true butterfish species, you can enjoy its many health benefits without concern. For instance, the U.S. wild-caught Atlantic butterfish is a great source of protein, vitamin B12, niacin, and selenium. Similarly, black cod, also known as sablefish, is often called butterfish for its rich, oily flavor and is packed with omega-3 fatty acids, even more than salmon.

High in Omega-3 Fatty Acids: Many species of fish colloquially called butterfish, like black cod, are exceptionally high in heart-healthy omega-3s, which are essential for brain function and reducing inflammation.
Rich in Vitamins and Minerals: True butterfish is a good source of vital nutrients, including vitamin B12, selenium, and niacin, which contribute to overall health and well-being.
Low in Mercury: Unlike some larger predatory fish, butterfish are small and typically have very low levels of mercury contamination, making them a safe choice for regular consumption.

Health Risks Associated with Escolar

Escolar's claim to fame is its high oil content, a delicious but dangerous property. The oil is composed of wax esters that the human body cannot digest. Eating even a small amount can lead to a range of gastrointestinal symptoms.

Keriorrhea (Oily Diarrhea): This is the most well-known symptom and involves a sudden, involuntary oily discharge. It is often described as an orange or yellow liquid and can be accompanied by abdominal cramps and nausea.
Digestive Intolerance: Some individuals are more sensitive to the wax esters and may experience significant discomfort after consuming escolar, even in small portions.
Risk for Vulnerable Groups: People with pre-existing bowel conditions, malabsorption issues, or who are pregnant are at an increased risk of severe symptoms and should avoid escolar entirely.

Comparison of Butterfish and Escolar


Feature	True Butterfish	Escolar (Misidentified as Butterfish)
Family	Stromateidae (Atlantic, Pacific Pomfret)	Gempylidae (Snake Mackerel)
Primary Distinguishing Feature	Contains easily digestible fats and oils.	Contains indigestible wax esters (gempylotoxin).
Size	Typically smaller, often sold whole or as small fillets.	Larger, deepwater fish, typically sold as thick, white fillets.
Flavor	Delicate, clean, and mildly buttery.	Rich, very oily, and intensely buttery.
Health Risks	Very low levels of contaminants; safe for most people.	High risk of keriorrhea and digestive upset.
Appearance (Filet)	Can vary depending on species, but often delicate and white/translucent.	Opaque white, with a notably firm yet creamy, buttery texture.
Global Regulation	No widespread restrictions.	Banned or restricted in several countries (e.g., Japan).

Practical Advice for Safe Butterfish Consumption

For a safe and healthy dining experience, consider the following:

Know Your Source: When purchasing fish labeled as "butterfish," ask your fishmonger for the specific species name. Trustworthy suppliers and reputable retailers will know the difference. In North America, true Atlantic butterfish is a safe option.
Verify at Restaurants: When ordering sushi or a dish featuring "white tuna" or "butterfish," confirm with the chef or server that it is not escolar. Look for dishes made with Alaskan black cod (sablefish) as a safer, rich alternative.
Start with Small Portions: If trying a type of butterfish for the first time, especially if the species is uncertain, eat a very small portion to gauge your body's reaction.
Opt for Cooking Over Raw: While cooking may not eliminate the wax esters in escolar, it can help reduce the oil content. For true butterfish, pan-frying, baking, or grilling are popular methods that highlight its moist texture.

Conclusion

Navigating the world of seafood can be challenging due to common mislabeling practices. While the rich, buttery flavor of fish is highly desirable, consumers must be aware of the stark difference between authentic butterfish and its troublesome imposter, escolar. By sourcing from reputable vendors and asking clarifying questions, you can confidently enjoy the nutritional benefits of real butterfish, or a safe alternative like black cod, while completely avoiding the digestive issues associated with escolar. Your health and enjoyment depend on informed choices, so be an advocate for your own dining safety.

More information on safe seafood consumption:

For further guidance on choosing and preparing fish, consult reputable resources such as the U.S. National Oceanic and Atmospheric Administration (NOAA) for information on sustainable and safe seafood choices.

Resource: U.S. National Oceanic and Atmospheric Administration (NOAA)
URL: https://www.fisheries.noaa.gov/topic/sustainable-seafood

Frequently Asked Questions

Fish often mislabeled as butterfish, especially escolar, contain indigestible wax esters. These fats cannot be absorbed by the human body and pass through the digestive system, causing an oily, orange or yellow diarrhea called keriorrhea, along with possible abdominal cramps.

Authentic butterfish species are generally smaller and have fine, flaky, white flesh. Escolar is a larger, deepwater fish typically sold as thick, firm, and creamy white fillets. For certainty, ask your retailer or server for the specific species name and be wary of generic terms like 'white tuna' or 'super white tuna'.

Yes, true butterfish, like the U.S. wild-caught variety, is considered a safe and healthy seafood choice for pregnant women. It is low in mercury and a good source of protein and other nutrients. However, all pregnant women should avoid the mislabeled escolar fish.

No, cooking does not remove the indigestible wax esters in escolar that cause keriorrhea. While methods like grilling and draining the oil might reduce the effect for some, the risk of digestive issues remains.

Escolar is banned or regulated in some countries, like Japan and Italy, due to the high likelihood of it causing keriorrhea and other severe digestive issues in consumers. These regulations help prevent food poisoning and consumer deception.

Authentic butterfish is a source of high-quality protein, niacin, vitamin B6, vitamin B12, and selenium. Certain species, such as black cod, are also very high in omega-3 fatty acids, which are beneficial for heart and brain health.

For a similar rich, oily, and buttery flavor profile without the digestive risks, consider opting for Alaskan black cod (sablefish), which is often called butterfish for its texture and taste. True Atlantic butterfish is also a safe choice.