Health Matters: Beware of Mercury Levels in Fish
Enjoy seafood — but watch how much and what kind you eat
In New England, summer is a prime time for enjoying fresh-caught seafood, but consumers need to be careful: fish and shellfish can contain high levels of mercury, a dangerous chemical that affects the nervous system.
Mercury is a naturally occurring element in the environment that is released into the air through industrialized pollution — when power plants burn fossil fuel, for example. Mercury then accumulates in streams and oceans, and when aided by bacteria undergoes a chemical transformation into methylmercury. Small fish absorb methylmercury in the water, bigger fish eat the smaller fish, and when humans eat the bigger fish, poisonous methylmercury accumulates in our bodies.
Stephanie Spaide, director of outpatient nutrition services at Boston Medical Center, warns that young children with high levels of mercury are at risk of severe brain damage, seizures, and visual problems, and adults with high amounts of mercury can experience a “pins and needles” feeling in the hands and feet, as well as impaired speech, vision, hearing, and walking.
Cooking does not affect mercury levels. Some fish are more susceptible to mercury contamination than others. The Massachusetts Office of Health and Human Services offers a guide to fish safety from different regions in the state, and the EPA and the FDA recommend following these general guidelines:
Avoid or limit shark, swordfish, king mackerel, or tilefish — they contain high levels of mercury.
Eat up to 12 ounces, or two average meals, a week of fish and shellfish that are lower in mercury. These include shrimp, canned light tuna, salmon, pollack, and catfish.
Note that albacore (white) tuna has more mercury than canned light tuna. When choosing your two meals of fish and shellfish, you may eat up to six ounces, or one average meal, of albacore tuna a week.
But don’t let high mercury levels deter you from eating fish at all this summer. A 2006 study in the Journal of the American Medical Association found that the benefits of eating fish outweigh the risks. Fish is high in protein and omega-3 fatty acids, which are necessary for cognitive and behavioral function. Regular consumption of fish lowers the risk of heart disease by 36 percent and lowers mortality by 17 percent.
“Americans have stopped eating fish because of the fear of mercury,” Spaide says. “I recommend people be aware of the amount of mercury in their fish, but realize there are a lot of other options in the types of fish they eat.”
Amy Laskowski can be reached at amlaskow@bu.edu.
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