Diet and Nutrition

Fish & Mercury: Cause for Concern?

Include fish

Why should I include fish in my diet?

Fish and shellfish are nutrient-rich foods that are good sources of high quality protein and several vitamins and minerals, such as calcium, phosphorus, iron, copper, vitamin A, vitamin D, and B vitamins. Some fish, such as salmon, trout, and herring, are excellent sources of omega-3 fatty acids, which may play a role in the prevention and treatment of heart disease. The American Heart Association recommends 2 servings of fish per week, as part of a low-fat, heart-healthy diet.

Should I be concerned about mercury found in fish?

Fish are the main sources of methylmercury, a highly toxic form of mercury that is transformed by bacteria in the water. Almost all fish contain traces of methylmercury, but the exact levels depend on what the fish eat, how long they live, and how high they are in the food chain. In the United States, the Environmental Protection Agency regulates commercial fishing to help ensure that fish meet certain standards for contaminants, including mercury. Each state monitors its waters and issues advisories if contaminants are found.

For most people, the level of mercury in a balanced diet that includes fish is not a health concern. However, high levels of mercury may have harmful effects on the developing brain and nervous systems of unborn babies and young children, potentially causing problems with memory, attention, language, fine motor skills, and visual spatial skills.

Who should limit the amount of fish in their diet?

A consumer advisory was issued by the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) in 2004. If you are a woman who might become pregnant, a pregnant woman, a nursing mother, or a young child, should follow these rules to avoid or limit certain types of fish:

Do not eat shark, swordfish, king mackerel, or tilefish due to their high levels of mercury.
Eat up to 12 ounces (two average meals) per week of a variety of fish and shellfish that are lower in mercury, such as shrimp, salmon, pollock, catfish, and canned light tuna. (Note: Albacore "white" tuna should be limited to 6 ounces per week due to its higher mercury content).
Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) of fish from local waters, but do not consume any other fish that week.

How can I find out more about the risks associated with eating fish?

For information about fish from local waters, visit the EPA Fish Advisory website or the FDA Food Safety website.

This article originally appeared in Nutri-bytes (May 2007), a service of the University of Cincinnati College of Nursing and was adapted for use on NetWellness with permission.

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Last Reviewed: May 02, 2007

Bonnie J Brehm, PhD, RD
Professor of Nursing
College of Nursing
University of Cincinnati