Mercury in seafood: Is fish safe to eat?

March 27, 2:22 PMSeattle Healthy Food ExaminerKristen Rezabek, MS, RD, CD, CDE

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Health experts talk about the benefits of eating fish and shellfish – they are good sources of protein, low in saturated fat, and contain omega 3 fats essential to the body. Eating fish and shellfish may help to lower risk for heart disease and is important for the growth and development of infants and children. Unfortunately almost all seafood contains traces of toxins such as mercury, along with other environmental contaminants like cancer causing PCB’s (polycholorinated biphenyls) and dioxins.

Some mercury is found naturally in the environment, but most is a byproduct of industrial pollution. Mercury released into the air makes its way into streams and oceans. The mercury is converted into a substance called methylmercury. Fish absorb this methylmercury into their flesh. As smaller fish are eaten by larger fish the mercury toxin accumulates. Typically older, larger, predatory fish contain the highest levels of mercury and other contaminants. The same thing happens to people when we eat fish, particularly larger fish such as shark and sword fish, overtime the mercury level builds up in our bodies.

According to the Environmental Protection Agency (EPA) and Food and Drug Administration (FDA), the populations most at risk from eating mercury are young women and children. The reason being, high levels of mercury can damage a baby’s or young child’s developing nervous system. According to Centers for Disease Control and Prevention (CDC) - 10% of women of child bearing age have high enough levels of methylmercury to put their unborn children at risk for learning disabilities and developmental delays. The EPA and FDA advise women who may become pregnant, pregnant women, nursing mothers, and young children to follow three recommendations when eating seafood to lower the amount of mercury they are exposed to:

1. Avoid Shark, Swordfish, King Mackerel, or Tilefish - they contain high levels of mercury.

2. Eat no more than 8-12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in mercury.

3. Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If there are no warnings, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but don't consume any other fish during that week.

Other groups such as the Environmental Working Group (EWG) say these restrictions don’t go far enough to prevent the damaging effect of high mercury levels. Added to the above list of fish for young women and children to limit are; tuna, including canned albacore tuna (canned light tuna has less mercury), halibut, sea bass, Gulf coast oysters, marlin, pike, walleye, white croaker, and largemouth bass.

Fish is a healthy food, containing the omega 3’s fats we need, along with vitamin D and other nutrients important for our health. The American Heart Association recommends eating 2 servings of fish per week. Choose fish that contain low levels of mercury such as; Sardines, Wild Alaska Salmon, Rainbow Trout, Mussels, Clams, Oysters, and Bay Scallops. To see how much tuna is safe to eat - check out the EWG's tuna calculator.

For more info: Natural Resources Defense Council Mercury in Fish Guide