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," write Stacy Foran Melanson, MD, PhD, from the Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, and colleagues. "However, fish contain environmental toxins such as mercury, polychlorinated biphenyls, and organochlorine [OC] pesticides, which may negate the beneficial cardiovascular effects of fish meals."

The authors estimate that compared with fish oil supplementation, regular consumption of fish from the Great Lakes would expose humans to at least 70 times more PCBs and 120 times more OC pesticides. OC analysis of the contents of five commercial fish oil brands revealed that the levels of polychlorinated biphenyls (PCBs) and OCs were all below the detectable limit.

"Fish oil supplements are more healthful than the consumption of fish high in organochlorines," the authors write. "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."

Fish oil contains at least five times less PCB and 25 times less DDT than the FDA daily recommended limits and less OC than fish high in the food chain.

The authors note that of the PCBs produced in the U.S. before 1976, 1.2 billion pounds entered rivers, lakes, and oceans, where they accumulate in bottom-feeding fish and become more concentrated higher up on the food chain (0.6-20 parts per million [ppm] in edible fish high in the food chain). In 1984, the Food and Drug Administration (FDA) lowered the limit to 2.0 ppm for edible fish.

Similarly, OC pesticides entered the air, water, and soil when they were sprayed on crops and forests and concentrate more than 1,000-fold in fish and marine mammals. These pesticides, including DDT, were banned in 1973 because of their neurotoxic properties.

Although consumption of 200 to 400 g of oily fish each week has been recommended to protect against cardiovascular disease, regular fish intake presents potential problems, particularly in children and pregnant women.

"Our data concerning the levels of OCs suggest that fish oil supplements may be preferable to fish consumption as a dietary guideline for the general population and as a therapeutic source of omega-3 fatty acids in patients with cardiovascular disease and depression," the authors conclude.

Source: Diabetes In Control.com: Arch Pathol Lab Med. 2005;129:74-77.