Fish oil and mercury 9. May 2007 William Davis (2) I often get questions about the mercury content in fish oil. I've even had patients come to the office saying their primary care doctor told them to stop fish oil to avoid mercury poisoning. Manufacturers of fish oil also make claims that this product or that ("super-concentrated", "pharmaceutical grade", "purified", etc.) is purer or less contaminated than competitors' products. The manufacturers of the "drug" Omacor, or prescription fish oil, have added to the confusion by suggesting that their product is the most pure of all, since it is the most concentrated of any fish oil preparation (900 mg EPA+DHA per capsule). They claim that "OMACOR is naturally derived through a unique, patented process that creates a highly concentrated, highly purified prescription medicine. By prescribing OMACOR® (omega-3-acid ethyl esters), a prescription omega-3, your doctor is giving you a concentrated and reliable omega-3. Each OMACOR capsule contains 90% omega-3 acids (84% EPA/DHA*). Nonprescription omega-3 dietary supplements typically contain only 13%-63% EPA/DHA." How much truth is there in these concerns?Let's go to the data published by the USDA, FDA, and several independent studies. Let's add to that the independent (and therefore presumably unbiased) analyses provided by Consumer Reports and Consumer Labs (www.consumerlab.com). How much mercury has been found in fish oil supplements?None.This is different from the mercury content of whole fish that you eat. Predatory fish that are at the top of the food chain and consume other fish and thereby concentrate organic methyl mercury, the toxic form of mercury. Thus, shark, swordfish, and King mackerel are higher in mercury than sardines, herring, and salmon. The mercury content of fish oil capsules have little to do with the method of processing and much more with the animal source of oil. Fish oil is generally obtained from sardines, salmon, and cod, all low in mercury. Fish oil capsules are not prepared from swordfish or shark. Thus, concerns about mercury from fish oil--regardless of brand--are generally unfounded, according to the best information we have. Eating whole fish--now that's another story for another time. But you and I can take our fish oil to reduce triglycerides, VLDL, IDL, small LDL, and heart attack risk without worrying about mercury.