The Claim: Fish Oil Supplements Can Contain Mercury

Posted on Aug 1, 2010 in Heavy Metals

by Anahad O’Connor


Fish oil supplements are increasingly popular with people who don’t like seafood but are attracted by claims of cardiac benefits. But could they also expose you to the harmful pollutants found in some species of fish?

The concern is a common one, but studies have found that most of the widely available supplements contain little or no mercury, dioxins or PCBs. For one thing, most companies use species of fish that are lower on the food chain, like cod and sardines, which accumulate less mercury. And many companies distill their oils to help remove contaminants.

A report by, which conducts independent tests of supplements, examined 41 common fish oil products and found none contaminated with mercury or PCBs.

Another report, by researchers at Harvard Medical School and at Massachusetts General Hospital, studied five popular brands of fish oil, including Nordic Ultimate, Kirkland and CVS. They found that the brands had “negligible amounts of mercury, suggesting either that mercury is removed during the manufacturing of purified fish oil or that the fish sources used in these commercial preparations are relatively mercury-free.”

Test results for various fish oils can also be found on the International Fish Oil Standards Web site.


Studies suggest that fish oil products contain little or no contaminants.