Polychlorinated biphenyls (PCBs) contamination and aryl hydrocarbon receptor (AhR) agonist activity of omega-3 polyunsaturated fatty acid supplements: implications for daily intake of dioxins and PCBs.
Article Type: Report
Subject: Dietary supplements (Research)
Dietary supplements (Chemical properties)
Polychlorinated biphenyls (Research)
Polychlorinated biphenyls (Measurement)
Omega-3 fatty acids
Pub Date: 09/01/2011
Publication: Name: Alternative Medicine Review Publisher: Thorne Research Inc. Audience: Academic; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2011 Thorne Research Inc. ISSN: 1089-5159
Issue: Date: Sept, 2011 Source Volume: 16 Source Issue: 3
Topic: Event Code: 310 Science & research
Product: Product Code: 2834730 Nutrient Preparations; 2866672 Polychlorinated Biphenyls NAICS Code: 325412 Pharmaceutical Preparation Manufacturing; 325192 Cyclic Crude and Intermediate Manufacturing SIC Code: 2833 Medicinals and botanicals; 2834 Pharmaceutical preparations; 2869 Industrial organic chemicals, not elsewhere classified
Accession Number: 269531000
Full Text: Bourdon JA, Bazinet TA, Arnason TT, et a l. Food and Chemical Toxicology 2010;48:3093-3097.

Omega-3 polyunsaturated fatty acid (n-3 PUFA) rich oils derived primarily from fish are frequently consumed as supplements. Due to the tendency of persistent organic pollutants (POPs) to accumulate in exposed organisms, n-3 PUFA supplements can contain sufficient POPs to present a risk to consumers. Here we investigated PCB concentrations and aryl hydrocarbon receptor (AhR) agonist activity in 17 n-3 PUFA supplements available in Canada. PCBs ranged from <0.8 to 793 ng/g oil, with salmon- and seal-derived products yielding the highest values. AhR agonist activity from a reporter gene assay ranged from 1.3 to 72.2 pg TEQ/g oil, with salmon and tuna yielding the highest values. When consumed at the recommended doses and as a supplement to the average Canadian diet, seal-derived oil can contribute to exceedance of the tolerable daily intake of 20 ng PCBs/kg-BW/day, and salmon , tuna-, and sea herring-derived oils can contribute to exceedance of the tolerable daily intake limit of 2.3 pg TEQ/kg- BW/day. The beneficial properties of fish and n-3 PUFA supplements, and the results of this study suggest that it is prudent to consume supplements derived from small, cold- water fatty fish. Further research will be necessary to draw firm conclusions.


Multiple studies have documented the contamination offish with PCBs and other persistent pollutants. Studies also indicate that regular consumption of Atlantic salmon, or other PCB-contaminated fish, results in detection of multiple PCBs in serum. This study indicates that these lipophilie toxicants can also be found in fish oil supplements. Because of the health problems associated with PCB exposure, it is imperative that clinicians recommending fish oil supplements be aware of the potential for PCB contamination. This issue is also pertinent to health-conscious consumers buying fish oil supplements, especially pregnant women (who often take such supplements in hopes of having smarter children), since PCB contamination during pregnancy has been associated with lower IQs in offspring and increased incidence of ADHD. A wise consumer would only purchase fish oil supplements from companies that provide bona fide testing for contaminants for each of their lots offish-oil capsules.

Salmon and cod liver oil products consistently had high levels of PCBs. This result is not surprising for salmon oil, since all commercially available salmon oil products are from farmed Atlantic salmon, and studies have indicated that farmed salmon is high in PCBs. The highest detected PCBs levels were in a seal oil product. Seal oil products ranged from one of the lowest to the highest PCB levels, giving it a higher mean level than salmon. This highlights the fact that levels of these toxicants can vary widely in non-farmed sea creatures, as would be expected by carnivores (e.g., seals in this case) that can eat a widely varying diet in terms of location and type of food consumed. The PCB contamination level in farmed fish is likely more consistent, since they are fed the same diet every day."Mixed small fish"had the lowest average PCB content, as would be expected because lipophilic contaminants, like PCBs, bioaccumulate as they move up the food chain. Compared to carnivorous fish like salmon, cod, and tuna, small fish are much lower on the food chain.

This study also investigated the in vitro agonist activity of aryl hydrocarbon receptors (AhR) produced from these supplements. AhR-agonist activity is the primary mechanism of dioxin toxicity. Chemical toxicants, other than dioxins, also produce damage via this mechanism. For these non-dioxin compounds, the AhR-agonist activity is measured; thus, their toxicity can be compared to dioxins. The researchers provided ratings for both the total PCB levels and the AhR-agonist activity of each of the oils tested, including ratings for these oils based on normal daily consumption. Salmon oil capsules had the highest level of AhR-agonist activity (i.e., dioxin-like activity), followed closely by tuna and sea herring oils."Mixed small fish"had the lowest AhR-agonist activity.

Overall, of the various fish oil supplements tested, the mixed small fish rated best (i.e., lowest in PCBs and AhR- agonist activity), leading the authors of the study to conclude that, should one choose to supplement with fish-derived oils, "... it is prudent to consume supplements derived from small, cold-water fatty fish." The other clear winner for lowest toxicity in this study was flax oil. In this study, flax oil supplements were the only omega-3 products that were free of PCBs.
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