News Coverage
Advice sounds fishy
Published October 22, 2002
DEAR DR. BLONZ: I read with interest your answer to the question about fish oils and omega-3 fatty acids. My concern with eating more salmon not raised in farms is about mercury. My understanding -- but I cannot cite a specific source -- is that deep-sea ocean fish are becoming dangerously high in mercury. Can you comment on this topic? --A.S., Hanover, N.H.
Dear A.S.: Mercury is a naturally occurring element in our environment, so it is impossible to avoid it entirely. A contaminant, such as mercury, enters the food chain when industrial pollution gets into the water and becomes incorporated into basic forms of life, such as algae or plankton. The "you are what you eat" adage holds as true in the ocean as it does on land. Pollutants work their way up the food chain as smaller creatures become the food source for increasingly larger creatures. The contaminant levels in a given fish depend on how long it has been in polluted waters and how much of the contaminant is in the food it has consumed.
Measurements of mercury levels from the 1999 National Health and Nutrition Examination Survey found that approximately 10 percent of the women tested were bordering the safety margin. In light of these numbers, reducing exposure to sources of mercury in food seems prudent.
Pregnant and lactating women, infants and young children are at higher risk because mercury poisoning can cause kidney problems and irreversible neurological damage in a growing body. In fact, the National Academy of Sciences estimates that every year 60,000 babies are born with neurological damage brought about by mercury poisoning.
Fish sitting atop the oceanic food chain tend to have the highest levels of contaminants. In the case of mercury, the Food and Drug Administration issued an advisory that women of childbearing age should not consume shark, swordfish, king mackerel and tilefish.
The risk of mercury poisoning from eating salmon appears to be minimal. In fact, the Food and Drug Administration states that consumption advice is unnecessary for salmon, canned tuna, shrimp, pollock, cod, catfish, clams, flatfish, crabs, and scallops. These fish make up about 80 percent of the seafood we eat. The FDA claims that these varieties typically contain low-enough mercury levels and that few people exceed the suggested weekly limit of fish (2.2 pounds) with this level of mercury contamination.
There is no consensus that this is all that needs to be done. The Environmental Working Group, a not-for-profit environmental research organization, has a more extensive list of fish to avoid. They recommend that pregnant women, nursing mothers and all women of childbearing age avoid tuna steaks, sea bass, oysters from the Gulf Coast, marlin, halibut, pike, walleye, white croaker and largemouth bass -- in addition to the FDA's recommendations.
The EWG goes on to state that women in these groups should eat the following foods no more than once a month: tuna, mahi-mahi, blue mussel, Eastern oyster, cod, pollock, salmon from the Great Lakes, blue crab from the Gulf of Mexico, wild channel catfish and lake whitefish. The "safe" fish for mercury, according to their data, include farmed trout or catfish, shrimp, fish sticks, flounder, wild Pacific salmon, croaker, haddock and blue crab from the mid-Atlantic.
Canned tuna represents an interesting issue. On one side we have the fact that tuna that goes into cans is usually caught in the ocean, far away from polluted areas. The flip side of the argument is that the tuna is high up on the food chain, and they don't have to hang around the polluted waters if the fish they dine upon contain the dangerous pollutants.
It make sense to be cautious, but do so with a reasoned approach.
Fish are good food, but we don't want to eat anything that can cause harm.
We can all benefit from the high-quality protein and healthful omega-3 fats found in seafood. There are many choices when it comes to seafood, and eating a wide variety of foods continues to be the best advice.