News Coverage
FAQ on the risks, benefits of fish
Published March 17, 2004
Fish have been causing a lot of confusion lately.
For years, nutrition experts and doctors touted the omega-three fatty acids found in certain types of fish, which have been useful in helping treat conditions such heart disease. More studies are emerging on the benefits of these acids for other diseases and conditions.
Now researchers are finding that some fish that are sources of these acids also contain levels of mercury and contaminants.
Here are some questions and answers about fish, fish oils and pollutants:
What are fish oils and omega-three fatty acids?
Fish oils are the natural oils usually found in fish such as mackerel, lake trout, herring, sardines, albacore tuna and salmon. These oils contain two types of omega-three fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA), both of which provide health benefits.
Are there plant-based sources of omega-three fatty acids?
Yes. Soybeans, canola, walnut and flaxseed and oils made from them contain alpha-linolenic acid (ALA), But this type of omega-three fatty acid is less potent, according to a report from the American Heart Association.
Why are omega-three fatty acids getting attention?
The typical U.S. diet does not contain a lot of omega-three fatty acids, yet some researchers consider these fatty acids ''wonder food,'' said Mary Ellen Camire, professor of food science and human nutrition at the University of Maine-Orono. "They play a role in proper brain development of the fetus, help prevent premature births and are important in the health of infants," she said. They are also linked to the development of the eye's retina.
Studies have shown that they can benefit the heart, whether or not we have heart disease. They can decrease risk of abnormal heart rhythms, decrease levels of triglycerides -- the chemical form of fat in the body, decrease the growth rate of plaque in arteries and slightly lower blood pressure.
More studies are needed to determine whether fatty acids can help conditions such as asthma, depression, early rheumatoid arthritis and Alzheimer's disease.
I've heard reports about harmful levels of chemicals in salmon. What have studies shown?
Astudy released by the non-profit Environmental Working Group (EWG) found that farm-raised salmon contained levels of polychlorinated biphenyls (PCBs) that exceeded Environmental Protection Agency limits. PCBs are cancer-causing chemicals that were banned in the United States in 1976 but persist in the environment.
Tests of farmed salmon from U.S. grocery stores showed that on average, farmed salmon have 16 times the amount of PCBs found in wild salmon, four times the levels in beef and 3.4 times the PCBs found in other seafood.
The farmed-salmon industry has disputed the findings.
Why are the PCB tolerance levels of the FDA and EPA different?
The FDA sets the tolerance cutoffs for commercial fish, including those sold in many supermarkets. The EPA sets limits for recreationally caught fish.
What should I do to reduce PCBs in salmon?
Trim fat from fish before cooking. Choose broiling, baking or grilling over frying, because those methods allow PCB-laden fat to cook off.
There seem to be conflicting reports on mercury in tuna. What is the FDA's stance?
Mercury levels in tuna vary, according to the FDA. Tuna steaks and canned albacore tuna generally contain higher levels than canned light tuna. The FDA says tuna can be included safely in a typical adult diet.
What about other fish?
Shark, swordfish, king mackerel or tilefish contain high levels of mercury, according to the FDA. If you regularly eat fish high in methylmercury, it can accumulate in your bloodstream over time. Methylmercury is removed from the body naturally, but it may take more than a year for levels to drop significantly. This is why the FDA recommends that women who are pregnant, might become pregnant or who are nursing avoid these fish.
How much fish is safe to eat?
The heart association and the American Dietetic Association recommend that adults eat two servings of fish per week. The FDA recommends mixing the types of fish so you avoid eating the same type more than once a week. The Environmental Working Group recommends eating farmed salmon no more than once a month.
What else can I do to limit my exposure to contaminants and pollutants?
Whenever possible, find out where the fish is from. That isn't always easy. But in the fall, a new federal law goes into effect requiring that labels on seafood sold in grocery stores and supermarkets contain information about country of origin, where the fish was processed and whether it is farmed or wild.