Mercury is a metal found naturally in the environment. Human activities, such as farming, burning coal, and using mercury in manufacturing, increase the mercury cycling through the air, water, and soil. In water, mercury changes its form and becomes methylmercury. Fish absorb this mercury. When you eat fish containing mercury, you absorb the mercury, and at high levels it can be harmful. Mercury will leave the body over time in the urine, feces, and breast milk.
For most people, the level of mercury absorbed by eating fish and shellfish is not a health concern. Overall, fish and shellfish are healthy foods. They contain high-quality protein and other essential nutrients, are low in saturated fat, and contain omega-3 fatty acids, a type of essential fatty acid. A balanced diet that includes fish and shellfish can contribute to heart health and children's growth and development.
Nearly all fish and shellfish contain traces of mercury. But some contain high levels. Eating large amounts of these fish and shellfish can result in high levels of mercury in the human body. In a fetus or young child, this can damage the brain and nerves (nervous system).
Because of the mercury found in fish, the U.S. Food and Drug Administration (FDA) and U.S. Environmental Protection Agency (EPA) advise the following people to avoid eating fish high in mercury and to eat limited amounts of fish and shellfish that are lower in mercury:
If you are concerned about your or your child's mercury level, talk to your doctor or local health department about testing.
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 oz (170 g) a week (one average meal) of fish caught from local waters, but don't eat any other fish during that week.
Mercury accumulates in your bloodstream over time and slowly leaves the body through urine, feces, and breast milk. If you eat a lot of fish high in mercury, it may take up to a year for your mercury levels to drop after you stop eating the fish. If you decide to become pregnant or if you have an unplanned pregnancy, you may have high levels of mercury. While elevated levels of mercury usually do not cause significant health problems, they may affect a developing fetus. If you are of childbearing age, try to follow the guidelines above when you eat fish.
For specific information on:
For general information on mercury in fish, see:
- U.S. Food and Drug Administration (2004). What you need to know about mercury in fish and shellfish: 2004 EPA and FDA advice for women who might become pregnant, women who are pregnant, nursing mothers, young children. Available online: http://www.epa.gov/fishadvisories/advice.
- U.S. Department of Health and Human Services, U.S. Environmental Protection Agency (2011). Mercury Levels in Commercial Fish and Shellfish. Available online: http://www.fda.gov/Food/FoodSafety/Product-SpecificInformation/Seafood/FoodbornePathogensContaminants/Methylmercury/ucm115644.htm.
|Primary Medical Reviewer||Sarah Marshall, MD - Family Medicine|
|Specialist Medical Reviewer||Siobhan M. Dolan, MD, MPH - Reproductive Genetics|
|Last Revised||April 4, 2012|
Last Revised: April 4, 2012
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