Alaska News

Mercury levels in Yukon River sled dogs linked to salmon-rich diet

New research that compared Yukon River village sled dogs to kennel-fed huskies in Salcha found an inverse link between a diet rich in salmon and the level of healthful antioxidant substances in their canine blood.

As their exposure to trace mercury went up through eating lots of salmon (along with black bear, moose and pike,) the "total antioxidant status" of the huskies went down, say the authors of the study, published this month in the journal Environmental Research Letters.

The results don't suggest that village mushers should stop feeding their animals wild game and fish -- or that people should consider reducing their consumption of salmon, explained lead author Kriya Dunlap, an assistant professor of chemistry and biochemistry at the University of Alaska Fairbanks, in an email message to Alaska Dispatch.

"These are all performance animals and are all highly competitive," she wrote. "In fact, the kennel in Russian Mission with the highest mercury and lowest (total antioxidant levels) was in excellent shape and were undefeated in the races that year. Of course the fish he was feeding the dogs looked beautiful, healthy (and) strong, and I would have gladly (eaten) the salmon."

The levels of mercury and other contaminants in wild Alaska salmon and other game remain far below concentrations thought to cause health problems. All of the reasons that people have been given to eat Alaskan subsistence foods -- more healthy, lower dollar cost, spiritually and culturally satisfying -- continue to trump comparable store-bought food.

In fact, Alaska wild salmon is so healthy, with such high concentrations of omega-3 fatty acids, antioxidants and protein, that people (and their dogs) should eat as much of it as they can scarf down, according to the latest guidelines posted by the state Department of Health and Social Services.

But the troubling relationship found between mercury and the antioxidants in these dogs merits further investigation, and Dunlap and her associates plan to conduct additional research.

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"The amounts of mercury in the salmon are well below Environmental Protection Agency limits and the health benefits compared to processed food are still quite significant," Dunlap explained in this release about the research. "However, the fact that health indices may be impaired by mercury levels indicates mercury generation should be monitored."

The study is part of a broader scientific effort over the past couple of decades to gauge health impacts of eating Alaskan wild food in the face of industrial contamination carried on air and ocean currents from far outside the region.

"Before adopting modern corn-and-grain-based western processed diets, circumpolar people had a high fat and protein subsistence diet and exhibited a low incidence of obesity, diabetes and cardiovascular disease," the authors wrote in the paper. "Pollution, both global and local, is a threat to wild foods, as it introduces contaminants into the food system. … The sled dogs in Alaskan villages are maintained on the same subsistence foods as their human counterparts, primarily salmon, and therefore they can be used as a food systems model for researching the impact of changes in dietary components."

In this study, Dunlap and her UAF team examined hair and blood samples of 12 dogs from four villages along the Yukon River, spread from close to the mouth to hundreds of miles upriver -- Russian Mission, Galena, Rampart and Fort Yukon. They also examined a group of dogs that ate only commercial food at kennel based in Salcha, on the road system near Fairbanks.

Dunlap said they aren't sure yet why the salmon-fed dogs showed such differences. One hypothesis focuses on the fact that salmon don't eat as they travel hundreds of miles up the river toward their spawning grounds.

"So the fish at the mouth are teeming with the 'healthy' omega-3 fatty acids but still have not mobilized and eliminated their mercury, while salmon that have migrated for hundreds of miles might have less mercury, but might also have less of the 'healthy' omega-3 fatty acids," she told Dispatch. "Mercury is known to interfere with endogenous antioxidant systems, so it makes sense that dogs with higher mercury might also have less overall antioxidant capacity. It may very well be a risk/benefit relationship."

Contact Doug O'Harra at doug(at)alaskadispatch.com.

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