- Recently, the Centre for Food Safety has received complaints of oily diarrhoea after consumption of fish products labelled as "codfish" by members of the public. The symptoms are suspected to be related to the presence of indigestible wax ester (gempylotoxin) in certain species of fish (e.g. escolar and oilfish), which are marketed as codfish or using names similar to codfish.
- There have been reports of oily diarrhoea associated with the consumption of ocean-fish in Australia and the United States. Common names of fish associated with such reports include oilfish and escolar.
Food Safety and public health significance
- The fat content of codfish is not high. According to the food nutrient data from USDA, 100g of raw cod contains 0.63-0.67g fat (<1%). On the other hand, escolar (Lepidocybium flavobrunneum) and oilfish (Ruvettus pretiosus) are rich in fat (about 20%) and contains a naturally present wax ester known as gempylotoxin. In humans, wax esters are indigestible and thus accumulate in the rectum causing oily diarrhoea (keriorrhoea).
- Keriorrhoea, as opposed to diarrhoea, does not cause loss of body fluid and is therefore not life threatening. Not all people are affected by the wax ester. However, if it does, it causes significant discomfort ranging from stomach cramps to rapid loose bowel movements, with onset 30 minutes to 36 hours after consumption. Recovery is expected within 24 to 48 hours.
- There is no well-proven ways to reduce wax esters in the fish to guarantee a no-effect level, although certain cooking methods that separate a large proportion of oil from the fish (such as grilling) coupled with discarding the cooking liquid may reduce the risk to some extent.
Advice to the Trade
- If you are engaged in a business of fish trading, confirm the species of the fish that you are importing and marketing, including oilfish and related species.
- When selling fish and fish products, verify the correct fish names, especially the prepackaged ones, before they are properly marked and labelled.
- If you are a food caterer or manufacturer, obtain your fish supplies from reliable sources, such as approved fish wholesale markets and familiar fish importers. Avoid buying fish from improper channels.
- As escolar, oilfish and related fish species may cause oily diarrhoea in some people, they are not suitable for catering purposes if proper labelling and advice cannot be provided to the customers.
- Check incoming materials carefully including reading of labels to ensure escolar, oilfish and related fish types are not sold as codfish to you.
Advice to the Public
- When selecting foods, consumers should be aware of the possible health effects associated with eating escolar and oilfish. Consumers who eat these fish for the first time should eat a small portion to determine their susceptibility.
- Should you have any doubt about the type of fish, seek more information and clarification from the seller before buying.
- Maintain a balanced diet with a variety of food.
Risk Assessment Section
Centre for Food Safety