Again, however, the research is not conclusive. He points to changes in the chemical composition of highly oxidised oils that may reduce their benefits. Whether it is harmful or not, rancid oil is likely to be less effective than fresh fish oil, according to Martinsen. “The fact that we know from animals that the effects change when it’s oxidised would mean that a reasonable human consumer would want to avoid oxidised oils – but they can’t do that themselves.” “It certainly tells us that oxidation changes the way these oils work,” Albert said. When tested in high doses in animals, the oils were shown to have toxic effects. So far, sporadic studies have shown that highly oxidised fish oil capsules can have a negative impact on cholesterol levels. Whether rancid fish oil is harmful remains unclear. “To prevent oxidation, you have to focus on it from the beginning when the fish is caught, because when the oil is oxidised you can’t restore it back to freshness,” said Bo Martinsen, an omega-3 specialist and co-founder of the fish oil company Omega3 Innovations. At each step, the oil must be handled quickly and at low temperatures. Once harvested, the oil is often sent to China for extraction and distillation, before coming back to North America or Europe to be packaged. Photograph: Enrique Castro-Mendivil/Reuters Most fish oil comes from Peruvian anchovetas. Unloading anchovies at Peru’s northern port of Chimbote. Annual catches exceed 4m tonnes, mainly used for aquaculture, with an estimated 38,000 tonnes of anchovy oil extracted for supplements, according to GOED. Most fish oil comes from anchovetas in Peru. It is also prone to oxidisation because of its long supply chain, which often lacks appropriate preventive measures. Fish oil is particularly susceptible to oxidising, which happens faster when exposed to heat, air or light. Oxidation is a normal process in all oils that contain polyunsaturated fatty acids. Half of all products tested by Labdoor bordered on the GOED limit, at an average of 24.4. Other brands that exceeded limits were Oceanblue, with an oxidation value of 73.9, and Nature’s Answer, which tested at 34.4. The GOED maintains that the majority of its members’ fish oil products are within the limits.īut according to Labdoor’s analysis, conducted on products between 20, fish oils under the brand names Carlson Labs and Puritan’s Pride, which retail in chains such as Walmart and Amazon, had rancidity grades significantly higher than the suggested limits: 281.8 for Carlson’s Norwegian cod liver oil and 37.1 for Puritan Pride’s soft-gel fish oil. So, the higher the number, the more rancid the oil, though it is important to note that it is an indication of quality, not safety. The recommended limit was set at 26, an arbitrary and unitless measure of oxidation, and is the most common and strictest worldwide benchmark for fish oil quality. Given that the supplement market is largely unregulated, voluntary limits for oxidative quality were created by the Global Organization for EPA and DHA Omega-3 (GOED), an industry body with about 170 members that aims to increase consumption of omega-3s. “Some fish oils will smell more than others, but if they don’t smell bad, that doesn’t tell you it’s not oxidised,” he said. “Flavouring is added to fish oils to help mask fishy smell and taste, and … might make more oxidised oils more palatable for people to take, so it could also be used to hide oxidation of the oil,” said Albert.Īlbert said smell was not a reliable indicator of oxidation. Vitamins and health supplements at a Walmart store in the US, where fish oils are a very popular supplement.
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