Fans of fish oil supplements might want to take a further look at what they’re consuming.
A report from Labdoor—an independent testing company—has found that a large amount of such supplements sold on the market can be heavy in oxidized oils, which makes them rancid in both taste, smell, and leaves them in poor quality. As reported by The Guardian, 60 popular retail brands were tested and more than 10% were found to be rancid. Of the brands, some had oxidized oil levels 11 times higher than recommended.
“It was fairly frequent,” Dan Mark, Labdoor’s research director, said to the publication. “For us, they would start to smell and feel off.”
In the past, results have been similar, as an average of 20% of fish oil products—which are consumed by over a third of adults using dietary supplements— were found to have excess oxidation in a combination of global studies since 2015.
“That means if you go out and buy fish oil, there is at least a one in five chance of you getting an oil more oxidized than the recommended level,” Dr. Ben Alber of the University of Auckland said, adding that the smell doesn’t always give it away. “… Flavoring is added to fish oils to help mask fishy smell and taste, and … might make more oxidized oils more palatable for people to take, so it could also be used to hide oxidation of the oil.”
Notably, Labdoor’s analysis between 2014 and 2018 found that those from brands Carlson Labs and Puritan’s Pride, which are sold in retail chains, saw rancidity grades significantly higher than suggested. Brand Oceanblue was in the same ballpark. As for standard oxidation levels, the process is normal “in all oils that contain polyunsaturated fatty acids,” per The Guardian.
“To prevent oxidation, you have to focus on it from the beginning when the fish is caught, because when the oil is oxidized you can’t restore it back to freshness,” said Bo Martinsen, co-founder of fish oil company Omega3 Innovations.
