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Heard Any Good Fish Stories Lately?


October 23, 2014


By Julie Redfern, R.D., L.D.N.
Brigham and Women's Hospital

Heard any good fish stories lately? Here's one: Certain fats in fish and seafood may be fantastic for your health — they may even prevent heart disease.

Now here's a bad fish story: Some fish may contain high levels of harmful toxins. Moreover, our hearty appetite for the fruit of the sea has helped to create a new fish-farming industry. While this makes fish more readily available, large-scale production has brought to light similar problems faced by corporate farming, including the spread of disease and negative environmental impact.

So, should you go for the catch of the day or sail on for better waters?

The Great News About Seafood

Seafood is chock full of lean protein, zinc and heart-healthy fats. These heart-healthy fats may lower the risk of heart disease when substituted for meat. Seafood is a particularly great source of omega-3 fats called EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). EPA has heart-protective properties, and DHA benefits the nervous system.

Omega-3 fats are essential to good health, and since we cannot make them in our body, we must get them from our foods. The most efficient way for your body to get these fats is to eat fish and seafood. Do you need more reasons to go for grilled halibut instead of the porterhouse? The friendly fats in fish and seafood:

  • Keep inflammation — which plays a role in many disease processes — in check
  • May help to combat some cancers, depression, and autoimmune disorders such as asthma, rheumatoid arthritis, lupus and inflammatory bowel disease
  • Promote optimal brain, retinal and motor development in the fetus

Our fish story gets more complicated, however. Because of contaminants in fish and seafood, especially mercury, some fish may be, alas, harmful to our health.

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The Not-So-Great News About Seafood

In addition to those good fats, fish and seafood also can contain a not-so-healthy toxin, mercury. While most fish and seafood contain traces of mercury, those near industrialized cities, or larger predator species such as swordfish, mackerel and shark, usually contain more. Skinning, trimming and cooking fish does not reduce the toxin concentration since it is distributed throughout the muscle.

High levels of the metal can accumulate in brain tissue and cause neurological problems. Your body has a hard time getting rid of it — a bit like cleaning up a toxic waste site. Pregnant and nursing women should be especially careful. High levels of mercury may affect the sensitive nervous system of a developing fetus (methylmercury easily crosses the placenta). Equally, infants or very young children who are breast-fed can absorb mercury through their mothers' milk.

But we are not out of the deep end yet. To complicate our decision-making even further, we must consider farm-raised versus wild fish.

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Old MacDonald Had a Fish Farm

Like cattle in pens, fish are bred and raised in contained environments, typically close to the shore of a lake or river. To help keep up with high demand for seafood, the farm-raised fish business (or aquaculture) has soared. Is there a difference in the quality of fish, levels of omega-3 fats, and levels of mercury in farm-raised versus wild fish?

All fish, whether farm-raised or wild, contain omega-3 fats, but the levels vary with environmental factors such as their species and type of feed. Farm-raised species usually have lower levels of mercury, but may contain other contaminants. Farm-raised fish can breed illnesses that warrant the use of antibiotics. The feed is not the same as that of wild fish — additives are used in the feed, and the flesh is dyed to help the fish obtain the usual pink color consumers find familiar. The farms are packed tightly, which lowers the fish's immunity to parasites. Excrement and excess food pollute the ocean floor. If a farm fish escapes, these ill fish can potentially contaminate their wild companions.

Fish farmers are already improving methods of farming to fix some of these issues. Some have started using closed, circulating tanks that redirect wastes for future use. Fish farmers also are looking at using more eco-friendly feed.

The bottom line: There is a place for both farm-raised and wild fish in our future as the stocks of wild fish are replenished and farming methods are improved. If you are concerned about this issue, be sure to ask your grocery store or market about the sort of fish they stock.

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Tips: From the Lake to Your Lunch

  • Chose the safest kinds of seafood. Anchovies, herring, cod, crab, oysters, pollock, haddock, halibut, sardines, shrimp, and tilapia are all good choices. Look or ask for specific varieties of the following: tuna (canned white or canned light albacore), salmon (coho, wild or canned pink ), catfish (channel farmed), flounder/sole and trout (farmed or wild).
  • Take note, mothers and young children: Pregnant and breast-feeding women as well as young children should avoid the following types of fish: swordfish, shark, king mackerel, tilefish (golden bass/golden snapper), and fresh tuna steaks. Further, these folks should not eat any more than 12 ounces of "safe" fish (above) per week.
  • Check local fish advisories. Most state Web sites will list advisory updates about high levels of contamination in fish or seafood.
  • Consider other sources of omega-3 fats. If you don't eat fish but want the benefits of those healthy fats, you can take a fish-oil supplement (look for products that include 200 milligrams of DHA, docosahexaenoic acid), and 300 milligrams of EPA (eicosapentaenoic acid).
  • Get more information. In addition to only shopping for fish at grocery stores or markets that you trust, become better educated about seafood safety.

    www.aboutseafood.com
    Provides good information about buying and preparing fish

    www.mbayaq.org/cr/
    Provides information about choosing eco-friendly fish

    www.cfsan.fda.gov or 888-SAFEFOOD (888-723-3366)
    Provides FDA food safety information

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Julie Redfern, R.D., L.D.N. is a registered dietitian in the nutrition consultation service at the Brigham and Women's Hospital. She specializes in nutrition counseling for the Obstetrics and Gynecology Department. She is a graduate of the University of Vermont, and completed her internship at the University of Cincinnati Medical Center.

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