Does Fish Contain Too Much Mercury?

Written By: Gloria Tsang, RD

Title: Founding Registered Dietitian

Alumni: University of British Columbia

Last Updated on:

Fish and seafood have long been a center of controversy, and these days many of us are left wondering – are fish still safe to eat?

What’s in fish?

Fish and shellfish contain high-quality protein and other essential nutrients, are low in saturated fat, and contain omega-3 fatty acids. A well-balanced diet that includes a variety of fish and shellfish can contribute to heart health and children’s proper growth and development.

However, nearly all fish and shellfish contain traces of mercury. For most people, the risk from mercury ingested by eating fish and shellfish is not a health concern. Yet, some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child’s developing nervous system.

In addition, fish also contain polychlorinated biphenyls (PCBs), toxic industrial compounds that were banned in 1979, but that persist in the environment. Fish absorb PCBs from contaminated sediments and from their food. You can limit exposure to PCBs simply by trimming, skinning and cooking your catch to reduce fatty tissue. But, unlike mercury, which you can eliminate from your body over time, PCBs are stored in body fat for many years.

FDA Recommendation on Mercury and Fish

In March 2004, the Food and Drug Administration and Environmental Protection Agency revised their advisories on mercury in fish. Here is a summary:

  • Women who are pregnant or who may become pregnant, nursing mothers, and young children should avoid some types of fish and eat fish and shellfish that are lower in mercury.
  • Shark, swordfish, king mackerel, and tilefish contain high levels of mercury, and therefore should be avoided by the above groups.
  • It’s okay to eat 12 oz. (about 2 servings) of low-mercury fish per week. Low-mercury fish include shrimp, crab, cod, clams, scallops, canned light tuna, canned salmon, pollock, and catfish, among others.
  • Albacore “White” tuna contains more mercury than other kinds of tuna. Stick to 6 oz or less of albacore tuna per week (about 1 serving).
  • For a complete list of fish and recommended portions, go to the National Resources Defense Council guide.

Key Message: Fish offers benefits in heart health. Indeed, the American Heart Association recommends fish and fish products for prevention of heart disease. So don’t give up fish completely, but do choose wisely for an average of 2 meals a week.


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