Natural Medicines Newsletter

Volume 1, Issue 30, 08/13/2009

Question

Do fish oil (omega-3 fatty acid) supplements contain mercury?

Answer

Mercury (Hg) is a well known heavy metal that was historically used in thermometers, barometers and sphygmomanometers.  Unfortunately, mercury (especially methylmercury) has been linked to varying degrees of toxicity if ingested or inhaled in large amounts.(1-5)  More recently, the risk has been linked to the ingestion of certain types of fish and shellfish, which has led some regulatory authorities to recommend that women who are pregnant, planning to become pregnant or breastfeeding as well as young children should avoid certain types of fish and shellfish.(6,7)  All fish and shellfish contain methylmercury with some species containing more than others.(6,7)  Conversely, the consumption of fish has also been linked to reduced cardiovascular disease which has led to the development of both prescription and nonprescription omega-3 fatty acids supplements that are now used to treat hyperlipidemia as well as reduce cardiovascular-related mortality.(8-11) 

Why do fish contain mercury (specifically methylmercury)?
One of the main mechanisms of contamination of fish and shellfish with mercury is....

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