Salmon fillets rich in Omega-3 fatty acids. (Photo: Stock File)

Mercury 'will never outweigh' the benefits of Omega-3

CANADA
Friday, October 16, 2009, 23:30 (GMT + 9)

The head scientist of a study released earlier this month on the benefits of Omega-3 fatty acids in fish uncategorically recommended that consumers eat fish despite the role played by mercury-in-seafood contamination in elevating human blood pressure and cardiac frequency.

Eric Dewailly, a professor in the department of social and preventive medicine at Laval University in Quebec and lead author of a report in the 5 October issue of Hypertension, stated that "the small increase of blood pressure due to methylmercury [in fish] will never outweigh the benefits of Omega-3 fatty acids," HealthDay reports.

Omega-3-rich diets from oily fish, such as fatty sardines, herring, trout and salmon, are associated with a reduced risk of death from heart attack, stroke and other cardiovascular disease,

Fish can also contain high levels of methylmercury, which can interfere with the normal development of the nervous system and brain in human fetuses and newborns. For this reason, the US Food and Drug Administration (FDA) advises pregnant women, those trying to get pregnant, nursing women and children to limit their intake of fish.

Dewailly and his colleagues conducted a survey of Inuit residents of 14 Nunavik communities in northern Quebec, where the traditional diet is based on fish and marine mammals.

It found an average blood mercury level of 50 nanomoles per litre of blood, much higher than the 4-nanomole level of the general population of the United States. It also found a relationship between blood mercury levels and blood pressure after adjusting for other factors.

Dewailly said that studies have shown that exposure to environmental mercury can affect the delicate lining of blood vessels, and decrease the ability of smooth muscles to relax, which could explain the slight increase in blood pressure seen in the study.

It was not a great effect, he said. "For every 10 per cent increase in blood mercury level, there is a 0.2 millimeter increase in blood pressure," Dewailly said.

A 10 per cent increase in blood mercury would therefore raise a blood pressure reading from 120/80 to 120.2/80, Dewailly indicated. That is not a reason to avoid fish "if you look at the fish nutrients that are reported to be associated with so many benefits.”

Another heart expert concurred. Penny Kris-Etherton, professor of nutrition at Pennsylvania State University and a member of the American Heart Association Council on Nutrition Metabolism and Physical Activity Committee, concurred with Dewailly.

"Many Americans can safely enjoy eating fish as a regular part of  their diet to achieve the health benefits of omega-3 fatty acids,” she said.

"And this includes canned light tuna, which is significantly lower in mercury than white tuna."

Related Articles:

- Mercury counteracts benefits of Omega-3
- Mercury higher in deepwater fish: study
- Marine methylmercury levels in seafood rising: study

By Michel Loubet
editorial@fis.com
www.fis.com

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