New Findings On Mercury Content In Salmon

A new study published in Environmental Toxicology
and Chemistry
finds that although mercury levels in both wild
and farmed salmon from British Columbia are substantially below human
health consumption guidelines, the levels found in wild salmon were
three times higher than in farmed salmon.

A large proportion of the farmed salmon consumed in the United States
originates in British Columbia, Canada. Over the years, there have been
health concerns because high levels of methylmercury have been found in
long-lived fish species nearer to the top of the food chain – such as
tuna and salmon. High mercury levels have been associated with an
increase in the risk of cancer, and this has led many people to avoid
consuming certain fishes.

This most recent study has determined that levels of mercury and other
trace metals measured in both farmed and wild salmon were significantly
Health Canada’s consumption guidelines. Compared to wild salmon, the
researchers found that farmed salmon did not
have significantly higher concentrations of metals such as arsenic,
cobalt, copper, or
cadmium. The threefold higher mercury concentration observed in the
flesh of wild salmon than in farmed salmon is potentially explained by
farmed salmon’s low gastrointestinal absorption efficiency, its
negligible transfer of metals to muscle tissue, and its rapid growth
cycles (growth dilution). In farmed fish, there were no differences in
metal levels found between pre- and post-processing.

For comparison to other parts of the human diet, the researchers
indicate that total mercury levels were slightly
higher in wild or farmed salmon than in chicken, beef, or pork and
about the same as in fruit, vegetables, honey, and eggs. Compared to
other foods, salmon contains lower levels of other trace elements. The
average dietary intake of mercury and trace metals from salmon still
remains a paltry 0.05% to 32% compared to the 68% to 99% that is
absorbed from meat, poultry, fruit, and vegetables. Salmon
also contains its own protection against mercury in the form of the
element selenium. The moderate surplus of this metal can counteract
mercury’s toxicity.

“Estimates of human dietary exposure indicate that human health risks
associated with trace metal exposure via consumption of farmed and wild
British Columbia salmon are negligible,” conclude the authors. “The
current scientific evidence therefore supports the weekly consumption
of oily fish species (including all British Columbia salmon sources) as
recommended by the American Heart Association.”

Mercury and Other Trace Elements in Farmed
and Wild Salmon from British Columbia, Canada

Barry C. Kelly, Michael
G. Ikonomou, David A. Higgs, Janice Oakes, and Cory Dubetz
Environmental Toxicology and Chemistry (2008). Vol.
here to view paper

Written by: Peter M Crosta

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