Purified Fish Oil

Fish oil supplements contain oil from the fatty tissues of fish. Because contaminants in the ocean also accumulate in the fatty tissues, you may worry about the potential for contamination with methylmercury or polychlorinated biphenyls, also called PCBs, in fish oil supplements. Commercial fish oil supplements undergo purification to remove contaminants in one of several ways. Most methods produce adequately purified and safe products, according to the Environmental Defense Fund.

Molecular distillation is the most effective method for reducing contaminants in fish oil to far below acceptable industry standards, according to Bioriginal Food & Science Corporation, a Canadian company that produces fish oil supplements. Molecular distillation concentrates the omega-3 fatty acids in the fish oil, creating supplements with more omega-3 fatty acids than the original product. This process separates the fatty acids from their original triglyceride form and converts them into ethyl esters, which may have less bioavailability and are also less stable and oxidize more readily than triglycerides, Ascenta Health reports.

Oil refining does not concentrate the amount of omega-3 fatty acids in the oil and removes fewer contaminants, although the amounts still fall below acceptable industry standards, the Bioriginal Food & Science Corporation explains. Because higher temperatures are used to purify the product, increased oxidative damage could occur. On the other hand, this method preserves the original triglyceride form of the oil rather than turning it into ethyl esters. The amounts of omega-3 fatty acids cannot be increased or changed using this method.

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