The study was funded by the Canadian fishing industry, which supplies much of the farmed salmon eaten in the United States.
In recent years, concerns have been raised about the safety of farmed salmon vs. wild, and there have also been suggestions that Canadian and other Atlantic-farmed salmon contains more contaminants than farm-raised fish from other areas, such as Chile. The newly published study was conducted in an attempt to address these concerns.
Researchers measured mercury levels as well as levels of 18 other trace metals in commercial salmon feed and farmed and wild salmon from British Columbia fisheries and waters.
They found that levels of all the metals tested were well below recommended consumption guidelines.
"(These findings) further validate the relative safety of farmed and wild British Columbia salmon," write Barry C. Kelly and colleagues from Canada's Institute of Ocean Sciences. "The current scientific evidence therefore supports the weekly consumption of oily fish species as recommended by the American Heart Association."
Concerns About PCBs
But the new study did not examine levels of polychlorinated biphenyls (PCB) in the fish, a chemical compound once widely used in manufacturing.
In a widely reported 2004 study, researchers examined PCB levels in farmed and wild salmon from around the world, concluding that farmed salmon contained significantly higher levels of the chemical than wild varieties of the fish.
The study found the greatest PCB levels in salmon from farms in northern Europe and the lowest levels in fish farmed in Chile. They concluded that eating farmed Atlantic salmon, "may pose health risks that detract from the beneficial effects of fish consumption."
That same year, the FDA and EPA issued a recommendation that pregnant women and young children eat no more than two servings, or 12 ounces, of salmon and other low-mercury fish each week.
Harvard Medical School nutritionist George Blackburn, MD, PhD, tells WebMD that although the risks associated with contaminants in farmed or wild salmon have yet to be proven, the health benefits of eating salmon are well established.