Fish-Oil Supplements Contain Contaminants

Levels of fire retardants found in cod liver oil-based dietary supplements are on the rise, a new British study claims.

Fire retardants are added to various consumer products, including furniture, computers and fabrics, to reduce the risk of fire. The chemicals have already been found in breast milk and peregrine falcon eggs. Some researchers contend the chemicals are responsible for health problems in humans.

The British study also found that levels of PCBs and pesticides in the supplements have declined in recent years, but only slightly.

The research appears in the April 7 issue of the Journal of Agricultural and Food Chemistry.

"Really, these contaminants shouldn't be there in the first place," says lead author Miriam Jacobs, a lecturer in food safety at the University of Surrey in Guildford, England.

Other experts, however, question the validity of the findings.

"These are not U.S. supplements. That's a big one," says Charles Santerre, an associate professor of foods and nutrition at Purdue University and a technical consultant for the industry group, Salmon of the Americas.

"Also, they [the researchers] didn't compare [flame retardants] in supplements. They compared salmon feed to supplements, which is apples and oranges. You can't ascribe an increase in [flame retardants] in fish oil supplements. They actually might be going down."

For her study, Jacobs measured for levels of the flame retardants in salmon feed four years ago, then compared those findings to levels found recently in supplements. Her conclusion: Levels of the retardants were more than twice as high in the cod liver oil supplements than in the salmon feed.

Annette Dickinson, president of the Council for Responsible Nutrition, says levels of all the contaminants in the study were below the council's tolerance levels. The cod liver oil figures were higher, she adds, but "they are a relatively cruder extract... The liver does concentrate these contaminants so whole-fish oils are inherently less contaminated and also are processed differently."

Many people supplement their diet with fish and vegetable oils because they contain omega-3 fatty acids, which have been shown to reduce the risk of heart disease as well as certain immunological and arthritic diseases.

But, if the fish from which the oil is taken are caught in polluted waters, the oils can turn out to be contaminated. And this contamination can have health effects. According to the study authors, there is evidence that flame retardants interfere with hormone function in wildlife and may be implicated in developmental difficulties in children.

Eight years ago, Jacobs assessed the levels of pesticides and polychlorinated biphenyls (PCBs) in different dietary supplements. She did not measure for fire retardants back then.

"Those samples eight years ago were not analyzed for flame retardants because the analytical techniques hadn't been worked up and they weren't known to be an environmental issue," she explains.

For the new study, Jacobs and her team looked at levels of PCBs, pesticides and polybrominated diphenyl ethers (PBDEs), which are widely used as flame retardants, in 21 dietary supplements containing fish and vegetable oils rich in omega-3 fatty acids. These were the same brands from the same stores in London that she had analyzed eight years ago.

Supplements based on vegetable oil and whole body fish oil showed little or no contamination in the current and previous studies, with vegetable oils containing the lowest level of contaminants.

"There was evidence of a slight reduction [of PCBs and pesticides] in the cod liver oils, but only very slight," Jacobs says. "It was still the same magnitude, but they're still present and people would still be taking in a relatively high level of PCBs compared to other sources in the diet."

The flame retardant levels in cod liver oils, however, were more than double the levels she had found four years ago in salmon feed. But whether these figures are comparable is still a question.

Santerre feels manufacturers need to set up a better system for identifying how well a product bound for supplements is refined.

As for public health implications, Jacobs says the new study "suggests that more steps need to be taken to reduce the environmental release of these compounds. The second thing is that manufacturers need to do more to try and reduce the contaminant levels."

This is not impossible, she adds. The brand that was one of the most contaminated eight years ago was, this time around, one of the cleaner supplements. "The fact that oils could be reformulated to have reduced levels is perfectly possible," Jacobs says.

More information

The Environmental Working Group has a report on fire retardants in breast milk.