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What to Know About Omega-3s and Fish

Experts explain which fish are best for omega-3s, and which you should limit due to mercury.

To Fish or not to Fish: Weighing the Benefits and Risks continued...

The higher on the food chain, the greater the accumulation of toxins. Fish that eat plants are less contaminated than those that eat other fish. That's why it's better, in general, to eat smaller fish lower on the food chain or smaller portions of fish that may be contaminated.

The FDA released an advisory about fish. The alert wasn't meant for everyone. It was directed at women who were planning to become pregnant, were already pregnant, or were nursing a young child. For this group of people, the FDA advised against eating shark, swordfish, king mackerel, or tilefish -- which contain high levels of mercury.

The FDA didn't throw all the proverbial fish back in the water, though. It recommended eating two meals, or up to 12 ounces a week, of a variety of fish and shellfish containing lower amounts of mercury. Safer sources cited were:

  • canned light tuna
  • catfish
  • pollock
  • salmon, especially wild salmon
  • shrimp

The FDA also made similar recommendations for feeding fish and shellfish to young children, but in smaller portions. It recommended checking local advisories for information about locally caught fish.

Questioning Conventional Wisdom About Fish

Muddying the waters, though, are research results outside the U.S. Some of these studies challenge U.S. assumptions and advice about fish consumption by pregnant women.

In a U.K. study, children of mothers who ate more than 12 ounces a week actually scored better on tests of verbal I.Q., social behavior, and development and communication than children of mothers who ate none.  In the Seychelles Islands, where people average 12 fish meals -- not ounces -- a week, there are no reports of links between mercury exposure and poor outcomes in children. These studies suggest that eating less than 12 ounces of fish each week could do more harm to a child's developing neurological system than mercury poisoning.

Unfortunately, fears about mercury and other pollutants may have caused Americans to start eating less fish. Following the FDA's advisory, the Center for Food, Nutrition, and Agriculture Policy at the University of Maryland took an opinion poll of more than 1,000 Americans. What they found was this:

  • A little more than a third ate fish occasionally.
  • More than 1 in 10 were eating less fish and feeding less to their children than before the advisory came out.
  • Most people didn't realize the FDA aimed its advisory at only certain groups: women who are pregnant, nursing babies, or planning to get pregnant soon.

Reaping the Best Benefits of Fish and Omega-3s

You can take several steps to get the best benefits from fish.

Deep-six the omega-6s. Foods high in polyunsaturated fats, such as soybean, corn, sunflower, or safflower oils hurt you in more ways than one. Apparently these omega-6 fatty acids, when eaten in excess, can reduce your body's ability to metabolize the beneficial omega-3 fatty acids.

Cast about for healthy canned tuna. Think all tuna is created equal? Think again. Choose canned light tuna instead of tuna steaks or albacore tuna. It tends to have less mercury. Albacore may contain three times the mercury of chunk light tuna. Check fish guides for the latest information about foods low in toxins but high in omega-3. Two good online sources are:

  • Monterey Bay Aquarium's Seafood Watch web site
  • Environmental Defense Fund web site

Do the sniff test. Buy the freshest fish you can find. The longer a fish is exposed to oxygen, says Bost, the more it loses some of its omega-3 benefits. 

Cook it up right. You can't remove toxins by cooking, but you minimize exposure to PCBs by removing fish skin and surface fat before eating.

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Reviewed on October 17, 2011

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