Fish and Shellfish: Consumer's Guide to Healthy Choices

Fish (and shellfish) play an important role in a healthy diet. They are high in proteins and nutrients, low in saturated fats and stocked with omega-3 fatty acids which a veritable flood of recent studies shows lowers the chance of heart attack, makes babies smarter, wards off dementia and stroke in the elderly, and even seems to guard against dry-eye syndrome. Fish is an excellent choice for a heart healthy diet and can help maintain overall health.

While it is still recommended to include fish in your diet, it is important to follow some general guidelines to protect yourself from mercury and other pollutants. Consumption of food containing mercury has been identified as a health risk by the U.S. Environmental Protection Agency (U.S. EPA) and the National Academy of Sciences. Nearly all fish and shellfish contain traces of mercury yet for most people the risk is not a health concern.

However, some fish and shellfish contain more mercury that can harm the nervous system of developing children fetuses and children affecting blood vessel contraction and heart rhythms. Two common pollutants found in fish - mercury and PCBs - are linked to learning and memory problems in children, heart problems, and possibly cancer. Mercury is known to affect the migration of brain cells in fetuses and might prevent signal transmission pathways from developing properly. The guidelines for pregnant and nursing mothers and young children are helpful for anyone concerned about mercury levels in the fish they eat.

Mercury occurs naturally in the environment and is also produced by industrial pollution. Mercury pollution comes from power plant smokestacks, mining, and other industrial activities. It accumulates in streams and ocean water, is eaten by bacteria and undergoes a chemical reaction that turns it into a very toxic form of the element methylmercury. Some pollutants remain as inorganic mercury, the liquid kind found in old-style thermometers, is excreted rapidly by the body. But methyl mercury binds very tightly to muscle tissue and is much more toxic for that reason. Pollution that reaches our lakes, streams, rivers, and oceans end up in the fish there. Fish absorb methylmercury as they feed in polluted waters and become contaminated. The levels of pollution, type of fish and their feeding habits all determine the mercury levels of the fish and the potential harm to humans.

The three basic recommendations in regard to mercury for fish or shellfish allow the benefits of eating fish without harmful exposure to mercury. First avoid top of the food chain fish like Shark, Swordfish, King Mackerel and Tilefish. These fish have high levels of mercury due to ingesting other mercury laden fish. Second, eat up to 12 ounces or two meals per week of a variety of fish and shellfish that are low in mercury. These include shrimp, canned light tuna, salmon, Pollock and catfish. Albacore tuna has more mercury than canned light so if this is your preference one meal per week is suggested. Fast food fish and frozen "fish sticks" tend to be made from inexpensive fish that is also low in mercury. Third it's important to stay current on local advisories. As a rule 6 ounces or one meal of fish from local stock is the maximum you should ingest.

These recommendations are meant for pregnant or nursing moms and the same can apply to young children in smaller portions. They are set as a guideline because just like in fish, methylmercury can accumulate in the human body over time. It is removed from the body naturally but can take over a year to leave the blood stream. For this reason, women who are trying to conceive should plan ahead to ensure low methylmercury levels in their body.

PCBs are the other concern when eating fish and shellfish. These industrial chemicals are now outlawed but remain in soils and water. PCBs are found in fatty parts of certain fish like salmon, bluefish and other fatty fishes. PCBs can be reduced by trimming away fatty areas such as the belly. Also removing or puncturing the skin will allow fat to drain off as will broiling, grilling and roasting on a rack. It is not recommended to fry large, fatty fish nor to use the fat drippings for other cooking.

The key to remember is not to avoid fish altogether, it is an important part of a healthy diet. By following a few simple guidelines fish can remain part of a healthy lifestyle as long as consumers understand the different issues. In general, eating fish lower on the food chain is the best choice, is good for your health and good for the environment.