What You Need to Know About Mercury and Seafood

Eating seafood offers many health benefits. For example, it is an excellent way to get more heart-healthy omega-3 fatty acids into your diet. Cold-water fish like herring, sardines, anchovies, fresh-water trout, and wild-caught salmon are especially high in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), omega-3s that help reduce inflammation, prevent blood clots, and ultimately lower the risk of heart attack or stroke. Mercury, however, can be a real concern when it comes to eating fish and shellfish.

Seafood can become contaminated with a type of mercury called methylmercury, which results from industrial pollution. The seafood that has the highest levels of methylmercury tend to be the larger fish that live the longest, since they absorb methylmercury throughout their lifetimes and accumulate additional amounts of the toxin from the smaller fish they feed on.

While cooking food can sometimes help reduce or kill certain bacteria, it does not have any effect on methylmercury. But since the benefits of seafood are so great, health experts agree that it is better to seek out varieties with lower concentrations of methylmercury than to try to replace them with fish oil supplements or plant-based sources of omega-3s, like flax or chia seeds.

Dr. Arthur Agatston, creator of the South Beach Diet, recommends eating at least two servings of seafood each week, including the oily varieties like those mentioned above, as well as shrimp, scallops, hake, and pollock, for example, which are among the fish and shellfish that contain the least methylmercury.

Do make an effort to avoid the following fish with the highest mercury concentration, and especially if you are pregnant, trying to get pregnant, or nursing.


  • Bigeye and ahi tuna
  • Canned albacore and yellowfin tuna
  • King mackerel
  • Marlin
  • Orange roughy
  • Shark
  • Swordfish
  • Tilefish


For more information on which seafood to buy and avoid, and to learn about sustainable varieties, visit the Monterey Bay Aquarium Seafood Watch.

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