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# Fish oil benefits can be null when polluted with PCBs
- URL: https://www.foodconsumer.org/fish_oil_benefits_0214150320/
- Published: 2015-02-14T16:18:00.000Z
- Updated: 2026-09-22T15:59:51.000Z
- Description: Swedish researchers followed 33,446 women free of heart disease for 12 years to test whether PCB contamination offsets the heart benefits of long-chain omega-3s from fish and fish oils, and suggest polluted fish or oil may not protect against heart attack.
- Author: Food Consumer
- Tags: Supplements, Nutrition, #vivvo-import

Saturday Feb 14, 2015 (foodconsumer.org) -- Agneta Åkesson at Institute of Environmental Medicine Karolinska Institutet in Stockholm, Sweden and colleagues published a study that suggests that fish or fish oil with high levels of polychlorinated biphenyls present may not provide protection against heart disease or cardiovascular events such as myocardial infarction.

Fish consumption or taking fihs oil which is high in omega-3 fatty acids like docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), is believed to be beneficial for heart health. The new study suggests that contaminants in fish or fish oil such as polychlorinated biphenyls (PCBs) may negate the omega-3 benefits.

Polychlorinated biphenyls are a group of persistent organic pollutant, which have been recognized by the U.E. Environmental Protection Agency as a probable human carcinogen. These toxic pollutants had once found their ways to many applications in the industry and the household environment. Although these chemicals have been banned for many years now, they can still show up as pollutants in fish/seafood and agricultural products. 

The current study was intended to examine how dietary PCB exposure through intake of long chain mega-3 fatty acids like EPA and DHA from fish, fish oils, egg oil, squid oils, and krill oil may affect the risk of myocardial infarction or heart attack. Note that short chain omega -3 fatty acids are found in other foods such as flaxseed and hemp, they can be converted into long chain DHA and EPA at a very low rate.

For the study, 33,446 middle-aged and elderly women enrolled in the Swedish Mammography Cohort who were free of cardiovascular disease, cancer and diabetes mellitus at baseline were followed up for a period of 12 years during which 1386 incident cases of myocardial infarction were identified.

The researchers found women in the highest quartile of dietary PCB exposure or intake of 286 ng per day were 21 percent more likely to suffer myocardial infarction, compared to those in the lowest quartile or intake of 101 ng per day. 

The association came when the analysis was not adjusted for omega-3 fatty acids EPA and DHA. After adjustment for these fatty acids, the risk was found 58% higher in those in the highest quartile of PCB exposure.

Intake of dietary EPA and DHA was found inversely associated with risk of myocardial infarction after including dietary PCB in the analysis, but not before adjusting for dietary PCB. 

EPA and DHA are mainly found in fish and other seafood like krill. The findings seem to suggest that fish oil may not render a protect effect against myocardial infarction when pollutants like PCBs are present in fish or fish oil.

The researchers concluded that exposure to PCBs was linked with increased risk of myocardial infarction while intake of EPA and DHA may provide some protection. In order to maximize the protective effect of fish or fish oil, PCBs should be reduced. (David Liu, PHD)

*Bergkvist C, Berglund M, Glynn A, Wolk A, Åkesson A. Dietary exposure to polychlorinated biphenyls and risk of myocardial infarction - A population-based prospective cohort study. Int J Cardiol. 2015 Jan 27;183C:242-248.*