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Good Fish, Bad Fish


Updated July 08, 2014

Slow roasted salmon with caper and herb relish and asparagus
James Baigrie/The Image Bank/Getty Images

Both fresh water and ocean fish are available in every grocery store and are served in many restaurants. The American Heart Association suggests eating fish at least twice each week in place of red meat.  Fish is mostly good for you, but there are a couple of time when fish can be bad. 

Let me explain.

When Fish is Good

Fish contains omega-3 fatty acids, but is still low in total fat.  Omega-3 fatty acids help reduce your risk of cardiovascular disease and may reduce inflammation. Replacing red meat with fish may be doubly good - you'll get more omega-3's and reduce your saturated fat intake at the same time. While a little bit of saturate fat may be okay, eating large amounts is associated with an increased risk of heart disease. 

The fat in fish is comprised of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A diet rich in fish oil may help reduce inflammation, which is part of the reason fish lowers your risk of cardiovascular disease. 

Cooking Your Fish

So does it matter how you cook your fish? It might. Prepare your fish in a healthy manner - baked, poached or sautéed is best. Skip the battered and deep fried fish that are high in fat and calories.  Our Low Fat Cooking Expert has some healthy recipes for fish.

The type of fish matters too. Oily ocean fish, like salmon, has the most omega-3 fat. If you prefer white fish, choose trout. Of course, you also want to avoid the fish that are contaminated with mercury. The worst offenders are marlin, orange roughy, tilefish, swordfish, shark, and king mackerel. Anchovies, butterfish, catfish, flounder, haddock, perch, trout and tilapia have the least amount of mercury. 

Fish is also an excellent source of lean protein, plus most types of fish contain various vitamins and minerals.

When Fish Isn't Good

Almost all fish is contaminated with trace amounts of mercury and other contaminants. While most healthy adults have no problem eliminating the mercury from their bodies, children and women who are pregnant or breastfeeding should avoid some types of fish and shellfish to reduce their risk of mercury exposure.

Fish that contain the highest level of mercury are larger and older sharks, swordfish, king mackerel, and tilefish. Choose shrimp, pollock, canned light tuna, salmon and catfish instead -- they're all much lower in mercury. The United States Environmental Protection Agency has a complete listing of the mercury levels in commercial seafood and fish.

It is also interesting to note that deep-frying fish may increase the concentration of mercury in fish.

Besides mercury, fish can be a problem if it isn't prepared properly. Eating undercooked fish may lead to a parasitic infection. Make sure you cook your fish until it is flaky and tender; the meat should show no signs of translucency. And do not cross contaminate raw fish with uncooked or ready to serve foods.

What About Fish Oil Supplements?

Most people can get all the omega-3 fatty acids they need from fish, but EPA and DHA are also available as dietary supplements.

The DHA supplements may be the most beneficial for babies. The developing brain accumulates large amounts of DHA during the third trimester of pregnancy through the first three months of infancy. Women can take DHA supplements during their pregnancy and in the initial months of breastfeeding to be sure their babies receive enough DHA for normal brain development.

Although fish oil supplements are safe, speak to your health care provider first if you're nursing, pregnant or have any health conditions.


Burger J, Dixon C, Boring CS, Gochfeld M. "Effect of deep-frying fish on risk from mercury." J Toxicol Environ Health A. 2003 May 9;66(9):817-28.

Cetin I, Koletzko B. "Long-chain omega-3 fatty acid supply in pregnancy and lactation." Curr Opin Clin Nutr Metab Care. 2008 May;11(3):297-302.

FDA/Center for Food Safety & Applied Nutrition. "What You Need to Know About Mercury in Fish and Shellfish." Updated February 2005.

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