“It was previously widely thought that farmed salmon contained more environmental pollutants than wild salmon, but this proves not to be the case,” Anne-Katrine Lundebye, study co-author and senior scientist at the National Institute of Nutrition and Seafood Research (NIFES), said in a NIFES article.

Lundebye explained that the differences between wild and farmed were due to their diets. “Fish are what they eat, both in terms of environmental pollutants and nutrients. This can be controlled in farmed fish, while what fish eat in the wild varies,” Lundebye was quoted as saying.

The relatively low level of organic pollutants in farmed salmon has been attributed to changes in the composition of fish feed, among others. Today’s fish feed contains less fish oil, which was previously the main source of many of the undesirable substances in the feed, said the NIFES report.

The study, Lower levels of Persistent Organic Pollutants, metals and the marine Omega 3-fatty acid DHA in farmed compared to wild Atlantic salmon (Salmo salar), demonstrated that the concentrations of dioxins, polychlorinated biphenyls (PCBs), DDT, dieldrin, lindane, chlordane, Mirex, toxaphene and mercury in wild Atlantic salmon were higher than in farmed Atlantic salmon.

The same findings also applied to the levels of the essential elements selenium, copper, zinc and iron, and the marine Omega-3 fatty acid, docosahexaenoic acid (DHA). DHA and EPA (eicosapentaenoic acid) are kinds of Omega-3 fatty acids that are found in certain fish.

“The PBDE (polybrominated diphenyl ethers), endosulfan, pentachlorobenzene, hexachlorobenzene, cadmium and lead levels were low and comparable in both wild and farmed ﬁsh and there was no signiﬁcant diﬀerence in the EPA concentration,” said the study.

PBDEs organobromine compounds are used as flame retardant. PCBs are a group of man-made chemicals that are either oily liquids or solids, clear to yellow in color, with no smell or taste.

Both are safe to eat

“The total fat content was signiﬁcantly higher in farmed than wild salmon due to a higher content of both saturated and monounsaturated fatty acids, as well as a higher content of Omega-6 fatty acids. The Omega-3 to Omega-6 fatty acid ratio was considerably lower in farmed than wild salmon due to the high level of Omega-6 fatty acids,” it said.

Analyses indicated that the contaminant concentrations in wild, escaped and farmed salmon are well below maximum levels applicable in the European Union. This makes Atlantic salmon – regardless of origin – safe for consumption and a good source of EPA and DHA. A 200-gram portion per week contributes 3.2 grams of EPA or 2.8 grams of DHA, almost double the intake considered adequate by the European Food Safety Authority.

Fish samples of wild, escaped farmed and farmed salmon, caught in Norway, were analyzed for polybrominated diphenyl ethers (PDE), pesticides and metals. Homogenized samples were extracted for total lipid determination.

“Total arsenic levels were higher in wild Atlantic salmon than in farmed salmon in the present study, in contrast to higher arsenic concentrations found by Foran et al (2004) in farmed Atlantic salmon compared to wild salmon,” the researchers said.

Despite the different levels of nutrients and environmental pollutants in Norwegian farmed and wild salmon, Lundebye recommends both types of salmon to consumers.

“Consumers have nothing to worry about because both types are a good source of omega-3 fatty acids and do not contain alarming levels of environmental pollutants. We can safely say that they are both healthy,” Lundebye said in the NIFE report.

The study was funded by the National Institute of Nutrition and Seafood Research, the Institute of Marine Research (IMR) and the Norwegian Food Safety Authority’s (NFSA) monitoring program for directive 96/23 on farmed ﬁsh. The analysis of scale samples was funded by the European Union, through the Kolarctic Salmon ENPI CBC project.

— Ruby Gonzalez