News Coverage
Q&A about fish, fish oils and pollutants
Published February 24, 2004
Are they potion or poison?
Fish have been causing a lot of confusion lately.
Nutrition experts and doctors have been saying in recent years that oils found in certain types of fish contain omega-three fatty acids, which have been found to be useful in helping treat conditions such heart disease. And more studies are emerging on the benefits of these acids for other diseases and conditions.But researchers also are finding that some fish that are sources of these acids also contain levels of mercury and contaminants that may be harmful to health. Here, questions and answers about fish, fish oils and pollutants:
Q: What are fish oils and omega-three fatty acids? A: Fish oils are the natural oils found usually 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 have been found to provide health benefits.
Q: Are there plant-based sources of omega-three fatty acids? A: 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.
Q: Why are omega-three fatty acids getting a lot of attention? A: The typical American diet does not contain a lot of omega-three fatty acids, yet some researchers consider these fatty acids "wonderfood," said Mary Ellen Camire, professor of food science and human nutrition at the University of Maine in Orono. "Studies have shown that what these fatty acids can do is amazing," she said. "They play a role in proper brain development of the fetus, help prevent premature births and are important in the health of infants." They are also linked to the development of the eye's retina. Studies have shown that these "good fats" can benefit the heart, whether or not we have heart disease, according to the heart association. 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 even slightly lower blood pressure. More studies are needed to determine whether the fatty acids can help in treating conditions such as asthma, depression, early rheumatoid arthritis and Alzheimer's disease.
Q: I've heard reports about harmful levels of chemicals in salmon. What have the studies shown? A: Several weeks ago, the Environmental Working Group (EWG), a nonprofit organization, released a study that 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. These 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 disputes these findings, stating among others, that the amount of PCBs in farmed salmon is less than the amount found in other products such as beef and milk, and that the levels of PCBs fall well within the limits set by the Food and Drug Administration.
Q: Why are the PCB tolerance levels by the FDA different from those of the EPA? A: The FDA sets the tolerance cutoffs for commercial fish, including those sold in many supermarkets and grocery stores. The EPA sets limits for recreationally caught fish.
Q: What should I do to reduce PCBs in salmon? A: Trim fat from fish before cooking. Choose broiling, baking or grilling over frying, as these cooking methods allow the PCB-laden fat to cook off the fish.
Q: There seem to be conflicting reports on mercury in tuna. What is the FDA's stance? A: Mercury levels in tuna vary, according to the FDA. Tuna steaks and canned albacore tuna generally contain higher levels of mercury than canned light tuna. The FDA says that tuna can be safely included in a typical adult diet.
Q: What about other types of fish? A: Shark, swordfish, king mackerel or tilefish contain high levels of mercury, according to the FDA. If you regularly eat types of fish that are 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 the levels to drop significantly. This is why the FDA recommends that women who are pregnant, might become pregnant or who are nursing should avoid these types of fish.
Q: How much fish is safe to eat? A: The heart association and the American Dietetic Association recommend that adults eat two servings of fish per week. The FDA recommends mixing up the types of fish you eat and to not eat the same type of fish more than once a week. The EWG recommends eating farmed salmon no more than once a month.
Q: What else can I do to limit my exposure to contaminants and pollutants? A: Whenever possible, find out where the fish is from, said Dr. Muhammad Sheikh of the University of California, Irvine, a board-certified in clinical nutrition. That isn't always easy to do because the place of origin of fish sold in stores need not be clearly stated. In the fall, a new federal law goes into effect requiring that labels on seafood sold in grocery stores and supermarkets contain country of origin, where it was processed and whether it was farmed or wild.
Q: Are omega-three fatty acid supplements a good alternative? A: Some experts, such as Camire, believe that fish-oil supplements from a reputable manufacturer are an alternative. Camire recommends one gram of fish oil a day for healthy adults. Sheikh said those who want to use it to lower triglycerides may need to take more, from three to four grams per day, but they should consult their doctors first. The safety, effectiveness and dosage of these supplements for children is not known. Some companies, such as Consumerlab.com, test various brands of supplements to find out if they contain enough fatty acids and their levels of certain pollutants or contaminants. These reports can be purchased.
Q: Are omega-three fatty acids being added to food? A: Yes, they are. Some infant formulas have added omega-three fatty acids. Eggs that contain these acids also are available. Expect to see in stores more food products such as mayonnaise with added omega-three fatty acids, Camire said.
Q: Are there any precautions concerning these fatty acid supplements? A: Yes. They have some blood-thinning properties, so those who are taking anticoagulant medications or are scheduled for surgery should consult their doctor before taking fish-oil supplements.
Q: Where can I get more information? A: Try the following: Food and Drug Administration: www.fda.gov/oc/opacom/mehgadvisory1208.html Environmental Protection Agency: www.epa.gov Environmental Working Group: www.ewg.org/issues/ Salmon of the Americas: www.salmonoftheamericas.com/ US Tuna Foundation: www.tunafacts.com/