Fish: What’s Healthy and What’s Not

Dr. Karen Sokal-Gutierrez, M.D., M.P.H.
Pediatrics
Adults and children need to eat a nutritious diet for overall health, energy for daily activities and growth. It can be confusing, however, to know what’s healthy and safe to eat. It seems that the news is constantly filled with conflicting reports about food—especially when it comes to fish.

We’re told, for example, that it’s important to eat fish as part of a balanced diet, but then we learn that some fish is contaminated with mercury and other pollutants. If you’re confused about how to make this food source a healthy part of your diet, consider the following fish facts.

What is healthy about fish?
Fish and shellfish are excellent sources of protein. Protein is needed to maintain healthy tissue, which is especially important for pregnant women and children who are growing rapidly. Fish is low in the artery-clogging saturated fats found in meat. It is also rich in healthy omega-3 polyunsaturated fatty acids, which can decrease triglycerides and plaque in the arteries, lower blood pressure and reduce the risk of heart disease and stroke. In babies they promote the development of the central nervous system.

What is unhealthy about fish?
Since fish live in oceans, lakes, rivers and bays, they are exposed to pollutants that enter the water from different sources. Industries and cities pump waste into the water; factories send smoke into the air, which rains down into the water; and rain washes run-off from agriculture, mines and waste disposal sites into the water. As a result, fish can become contaminated with toxic chemicals and infectious diseases. Contaminated fish poses health risks for anyone who eats it, but it is most dangerous for young children, whose growth, development and immune systems are most vulnerable, and pregnant women. Some of the contaminants in fish include:

Mercury
Mercury is a naturally occurring heavy metal and a waste product of industries such as coal-burning power plants. Once mercury enters the water, it is consumed by microorganisms, which are eaten by small fish, and these, in turn, by bigger fish. At each step up the food chain, the mercury is retained in the muscle meat of the fish, resulting in the highest concentrations of mercury in large, long-lived predatory fish, such as swordfish and shark. Mercury has a toxic effect on the human nervous system and can cause problems with learning and coordination. It is particularly dangerous for pregnant women (who can pass the mercury to the fetus through the placenta), breastfeeding women (who can pass the mercury to the baby through breast milk) and young children, whose nervous systems are developing.

PCBs
Polychlorinated biphenyls (PCBs) are a chemical produced in electronics and other industries. In 1977 the manufacture of PCBs was banned due to their toxicity. Since then, PCB levels in the environment have been slowly declining, but significant amounts continue to be discovered in fish. For example, farm-raised salmon has been found to have high levels of PCBs. Similar to mercury, PCBs accumulate and become more concentrated in larger fish, collecting in the fatty parts of the fish. PCBs also accumulate over time in the human body, particularly in fatty tissues, and are concentrated in breast milk. Like mercury, PCBs can be toxic to the developing nervous system, so they are especially harmful for pregnant and nursing women as well as children. In addition to causing developmental problems in children, PCBs have been shown to cause cancer in laboratory animals, and may cause cancer in humans as well.

Infectious Diseases
Fish and shellfish can be contaminated by infections of bacteria, parasites and viruses such as hepatitis A and norwalk virus. Shellfish, such as oysters and clams, are particularly risky. Contaminated fish and shellfish can typically cause diarrhea, but they can also cause more severe illness, particularly in pregnant women, young children and people with immune problems.

How can we make fish a healthy part of our diet?
In order to maximize its health benefits and minimize its health risks, pregnant women, nursing mothers and young children should eat fish that is low in contaminants and prepared in the healthiest manner. The following recommendations combine the 2003 guidelines from the U.S. Food and Drug Administration and the U.S. Environmental Protection Agency to reduce mercury exposure, as well as the recommendations of the U.S. centres for Disease Control and other health authorities to reduce the exposure to PCBs, other chemical contaminants and infectious diseases carried by fish and shellfish. They apply to women who are trying to get pregnant as well as those who already are, nursing mothers and children. (Note: The portion sizes listed below are for adults and should be reduced depending on a child’s size.):

1. Select fish that is least likely to be contaminated.

• Do not eat fish that contain high levels of mercury: shark, swordfish, king mackerel and tilefish.
• You may eat up to 12 ounces (two average meals) a week of fish and shellfish that are low in mercury, e.g., shrimp, canned light tuna, salmon, catfish and pollock (commonly used in fish sticks).
• Or, you may eat up to 6 ounces (one average meal) a week of fish that has moderate levels of mercury, e.g., lobster, grouper, fresh tuna or canned white albacore tuna. (Canned light tuna—which comes from smaller, younger fish—is preferable since it has less mercury.).
• If you plan to eat fish caught by family and friends from local lakes, rivers and coastal areas, first check local advisories regarding contamination levels.
• Inspect fish carefully before buying it. Don’t buy fish that looks or smells spoiled.

2. Prepare fish and shellfish in a manner that minimizes contamination.

• Avoid raw fish and shellfish. Cook both thoroughly.
• Keep fish refrigerated or frozen until preparing it. Cook refrigerated fish within two to three days. If it smells spoiled, do not use it.
• Wash your hands, utensils and cutting boards thoroughly before and after handling raw fish.
• Before cooking fish, remove the skin and fat.
• Broil, grill, roast or steam fish on a rack to allow the fat to drain away. Serve less fried fish, since frying seals in the chemical contaminants in the fat.
• Don’t reuse fat drippings from fish in other dishes.
• Use a clean platter and utensils for the cooked fish. Serve fish warm or cold, but don’t let it sit out at room temperature for more than one hour.

How can we make fish safer to eat?
Recent changes in EPA policies have weakened controls on pollutants, particularly mercury, entering the environment and our food supply. Help protect your family’s health by urging your legislators and public health officials to implement tighter regulations on mercury and other pollutants.

For more information, visit the following websites:

FDA Food Safety website: www.cfsan.fda.gov/seafood1.html

EPA’s Fish Advisory website: www.epa.gov/ost/fish.

Mercury Action Now: www.mercuryaction.org/fish/learn_more.html

Environmental Defense website: www.environmentaldefense.org