Guidelines on Mercury in Fish

by Food and Drug Administration (FDA)

One minute you hear that eating fish is good for your heart. The next, you find out that eating certain types of fish can be harmful.

Actually, there are benefits and risks to eating fish. Fish and shellfish are an important part of a healthy diet. They contain high-quality protein, other essential nutrients, and omega-3 fatty acids, and fish are low in saturated fat. A well-balanced diet that includes a variety of fish and shellfish can contribute to a healthy heart and to healthy, well-developed children.

However, nearly all fish and shellfish contain traces of methylmercury, a type of mercury found in water that can be harmful, especially to unborn babies and young children whose nervous systems are still developing. Some types of fish and shellfish contain higher levels of mercury. The risks depend on the amount of fish and shellfish eaten and the levels of mercury in the seafood.

The Food and Drug Administration and the Environmental Protection Agency (EPA), through a joint consumer advisory, warn that women who may become pregnant, pregnant women, nursing mothers, and young children should avoid the types of fish and shellfish with higher levels of mercury and eat only those that have lower levels.

Here's more information about the mercury in fish and shellfish, and what you should know.

Q. What is mercury and methylmercury?

A. Mercury occurs naturally in the environment and also can be released into the air through industrial pollution. Mercury falls from the air and can accumulate in streams and oceans. Bacteria in the water cause chemical changes that transform the mercury into methylmercury. It is this type of mercury that can be harmful to unborn babies and young children. Fish absorb the methylmercury as they feed in these waters. Methylmercury builds up in the tissue of some types of fish and shellfish more than others depending on what the fish eat. That's why levels vary among species and locations.

Q. Should a woman who is not pregnant, but could become pregnant, be concerned about methylmercury?

A. Yes. If you regularly eat types of fish high in methylmercury, the substance can accumulate in your blood over time. Methylmercury is removed from the body naturally, but it may take more than a year for the levels to drop significantly. Therefore, it may be present in a woman even before she becomes pregnant. That is why women who are trying to become pregnant also should avoid eating certain types of fish.

Q. Do all fish and shellfish contain methylmercury?

A. Nearly all fish and shellfish contain traces of methylmercury. However, larger fish that have lived longer have the highest levels of methylmercury because it has accumulated over time. Large fish such as swordfish, shark, king mackerel, and tilefish pose the greatest risk. Other types of fish and shellfish may be eaten in the amounts recommended by the FDA and EPA.

Q. Where can I get information about the types of fish I eat?

A. Information about the levels of methylmercury in the various types of fish you eat can be found at the FDA food safety Web site: www.cfsan.fda.gov/~frf/sea-mehg.html or the EPA Web site at www.epa.gov/ost/fish/.

Q. Should I be concerned about fish sticks and fast food sandwiches that are made with fish?

A. Fish sticks and fast food sandwiches are commonly made from fish low in mercury.

Q. Although advice is provided about canned tuna, what is the advice about tuna steaks?

A. Because tuna steak generally contains higher levels of mercury than canned light tuna, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces of tuna steak per week.

Q. What will happen if I eat more than the recommended amount of fish and shellfish in a week?

A. One week's consumption of fish does not change the level of mercury in the body much. If you eat a lot of fish one week, you can cut back for the next week or two. Just make sure to average the recommended amount per week.

Q. Where can I get information about the safety of fish caught recreationally in lakes, streams, and rivers?

A. Before you go fishing, check the appropriate fishing regulations booklet for information about recreationally caught fish. You can also contact your local health department for information about advisories in your area. Check local advisories because some kinds of fish and shellfish caught in local waters may have widely varying levels of mercury, depending on the levels of mercury in the water. Fish with much lower levels may be eaten more frequently and in larger amounts.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.