Eating fish: being healthy and safe

You should eat fish, but avoid unlimited consumption.

By Deborah Swackhamer

From eNews July 19, 2007

Fish is an important part of a healthy, balanced diet. High in heart-healthy omega 3 fatty acids, fish is a low-fat source of protein and nutrients. Reports about chemical contamination in water, however, raise questions about how these chemicals may affect your health. It's a balancing act: to be both healthy and safe, you should eat fish, but avoid unlimited consumption.

All fish--whether caught locally or purchased in restaurants and stores--contain some environmental chemical contaminants. Three types of chemicals are found in Minnesota fish: mercury, polychlorinated biphenyls (PCBs), and perfluorinated compounds (PFCs). These chemicals come largely from industrial sources and man-made products that pollute air and landfills. Over time, they enter lakes, rivers, or oceans and move up through the food web, eventually accumulating in fish. Fish that are bigger, older, or higher in the food web have the most contaminants.

The government regulates the safety of commercially sold fish and issues advisories about fish consumption. Minnesota was one of the first states to develop these advisories and has some of the most rigorous procedures for determining advice it provides. The Minnesota Department of Health's Web site includes a fish consumption advice section, offering resources for anglers and fish consumers.

Mercury, PCBs, and PFCs have negative effects on human health, particularly on early development. Because of the impact of these chemicals on developing fetuses, infants, and young children, fish consumption guidelines are stricter for women who are pregnant or might become pregnant, women who are breastfeeding, and children under the age of 15 than they are for the general population. For example, women of childbearing age and children should avoid shark, swordfish, tilefish, and king mackerel because they have high mercury levels, while the general population should limit consumption.

At the University of Minnesota, scientists are studying why fish have higher levels of chemical contamination than other meats, such as beef or chicken. The length of the food web appears to be important. While cows and poultry are part of a short food web, fish are near the end of a longer food web. Because each step in a food web has an additive effect on chemical build-up, contaminants can reach significant concentrations in the fish on your dinner table. Understanding this "bioaccumulation" of chemicals may be the first step in developing strategies to interrupt or minimize the process, improving food safety.

When it comes to eating fish:

• eat a balanced diet that includes some fish;
• choose smaller varieties when eating local fish; and
• remove skin and fat to lower the level of PCBs. Mercury cannot be removed by cooking or cleaning fish.

Deborah Swackhamer is professor of environmental health sciences in the School of Public Health and interim director of the Institute on the Environment.

Edited from Health Talk & You, an educational service produced by the University of Minnesota Academic Health Center.