Measurement of Organochlorines in Commercial Over-the-Counter Fish Oil Preparations: Implications for Dietary and Therapeutic Recommendations for Omega-3 Fatty Acids and a Review of the Literature

Archives of Pathology & Laboratory Medicine, Jan 2005 by Melanson, Stacy Foran, Lewandrowski, Elizabeth Lee, Flood, James G, Lewandrowski, Kent B

Context.-The consumption of fish high in omega-3 fatty acids is advocated by the American Heart Association to decrease the risk of coronary artery disease. However, fish contain environmental toxins such as mercury, polychlorinated biphenyls, and organochlorine pesticides, which may negate the beneficial cardiovascular effects of fish meals. Toxin levels vary depending on both the fish source and the specific toxin, and neither farm-raised nor wild fish are toxin free. Fish oil supplements also prevent the progression of coronary artery disease and reduce cardiovascular mortality. However, only sparse data exist on the level of toxins in fish oil. In a previous study we showed that the amount of mercury in 5 over-the-counter brands offish oil was negligible.

Objective.-To determine the concentrations of polychlorinated biphenyls and other organochlorines in 5 overthe-counter preparations of fish oil.

Design.-The contents of 5 commercial fish oil brands were sent for organochlorine analysis.

Results.-The levels of polychlorinated biphenyls and organochlorines were all below the detectable limit.

Conclusions.-Fish oil supplements are more healthful than the consumption of fish high in organochlorines. Fish oils provide the benefits of omega-3 fatty acids without the risk of toxicity. In addition, fish oil supplements have been helpful in a variety of diseases, including bipolar disorder and depression.

(Arch Pathol Lab Med. 2005;129:74-77)

Fish possess antiatherogenic properties, presumably because of their high content of essential omega-3 polyunsaturated fatty acids (ie, eicosapentaenoic acid or docosahexaenoic acid). Several studies demonstrate the benefits of fish consumption in patients with cardiac disease, including a decreased mortality following myocardial infarction.1-16 In addition, regular fish intake is recommended to decrease the risk of coronary artery disease.6 On the other hand, many studies have illustrated that certain fish contain high levels of environmental toxins, such as mercury, polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides, and related compounds.6,7 Some of these toxins may negate the cardiovascular health advantages of fish meals.6

Concentrated omega-3 fatty acids are found in fish oil supplements and may provide benefits similar to fish without the exposure to harmful environmental toxins.1 Daily fish oil ingestion slows the progression of coronary artery disease.5 Furthermore, fish oil supplements have been shown to stabilize mood in bipolar disorder, relieve depression in pregnancy, and decrease inflammation in some autoimmune diseases.8-15 In a previous study, we showed that several over-the-counter brands of fish oil supplements contained negligible amounts of mercury compared with fish and suggested that the consumption of fish oils may be preferable to eating fish.16 However, mercury is not the only toxin potentially in fish oil supplements.

Organochlorines have at least 1 aromatic ring and include PCBs, which have 2 aromatic rings. Organochlorines can be divided into pesticide OCs (ie, dichlorodiphenyltrichloroethane [DDT]) and nonpesticide OCs (ie, PCBs). PCBs are unwanted byproducts of a variety of industrial processes and are still found in transformers and capacitors that were manufactured before PCBs were banned in 1977. PCBs persist in the environment because of their resistance to degradation, and they bioconcentrate in fish along the food chain. PCBs and related compounds have adverse dermatologic, reproductive, developmental, endocrine, hepatic, and immunologie effects.17-19 DDT is the best-known OC pesticide. Similar to PCBs, OC pesticides such as DDT are resistant to degradation and accumulate in fish and in the environment. Exposure to OC pesticides may cause neurotoxicity and cardiac and pulmonary dysfunction.17,18,20

The levels of PCBs, OC pesticides, and related compounds in fish have received considerable attention in the press recently.21,22 Articles warn the public about the hazards of toxins in certain fish and discuss the use of fish oil as an alternative. Commercially available fish are either farm raised or wild. Researchers have addressed concerns about the source of fish and its associated contaminants. A recent Wall Street journal article stated that farm-raised salmon had higher levels of certain toxins than wild salmon. Consequently, people who regularly consume farmraised salmon may have an increased risk of cancer later in life. On the other hand, toxins such as mercury are detected at equal or higher concentrations in wild fish, so neither farm-raised nor wild fish appear superior.17,23-27 In this study, we examined the levels of a common group of environmental toxins, organochlorines, in 5 over-the-counter fish oil preparations to further evaluate whether advocating fish oil over fish is potentially warranted.

MATERIALS AND METHODS

Five commercial over-the-counter brands of fish oil supplements were purchased from retail or Internet sources. The brands included Omega Brite (Waltham, Mass), Natrol (Chatsworth, Calif), Sundown (Boca Raton, Fla), Kirkland (Houston, Tex), and CVS (Woonsocket, RI). The capsules were punctured, and approximately 5 mL of the liquid contents were sent in a citrate tube to National Medical Services (Willow Grove, Pa) for OC analysis (a-chlordane, 1,1 -dichloro-2,2-bis(;i-chlorphenyl)ethane [DDD], dichlorodiphenyldichloroethene [DDE], DDT, dieldrin, ychlordane, heptachlor, heptachlorepoxide, hexachlorobenzene, lindane, methoxychlor, oxychlordane, polybrominated biphenyls (PBBs), PCBs, trans-nonachlor). The OC levels were measured by gas chromatography with electron capture detection. This methodology has been described previously.28-30 The lower limits for detection of PCBs and other OCs in this assay are 400 parts per billion (ppb) and 200 ppb, respectively.