Mercury in Seafood

For years, the media has underlined the valuable dietary contributions of fish, and the positive press is well deserved. "Brain food" and "heart-healthy," fish is high in protein and low in saturated fat. It contains omega-3 fatty acids as well as nutrients like DHA, EPA and selenium. Recent studies by doctors at Harvard Medical School and Brigham and Women's Hospital conclude that just one or two servings of fish per week (especially those high in fatty acids, like salmon) cuts the risk of death by 17 percent and the risk of coronary death by 36 percent.

All fish-related news hasn't been upbeat, though. Stories about the dangers of mercury in fish and shellfish might have you wondering if fish remains a good food choice after all. There are plenty of variables to consider and debate to be found, but most experts agree that the benefits of eating fish outweigh the possible risks of mercury contamination—as long as you make well-informed decisions about which fish you eat and in what quantities. Here are some answers you might find useful:

How does mercury get in fish?
Mercury is a naturally occurring metal, but it's also released into the environment via industrial pollution. Once rained or melted into the waterways, mercury is converted by bacteria into a more toxic form of the metal, methylmercury. As fish feed in these waters, they absorb the methylmercury. Most fish and shellfish have at least trace levels of it. And some fish—those that eat other fish, are larger, and live longer—have higher levels than others. These include swordfish, king mackerel, shark, some kinds of tuna and tilefish. The Chilean sea bass, which is often sold in restaurants, and big-eye tuna, which is sometimes used to make sushi, also test high in mercury. Fish and shellfish low in mercury include catfish, cod, crab, flounder/sole, grouper, haddock, herring, lobster, mahi-mahi, ocean perch, oysters, rainbow trout and farmed trout, salmon, sardines, scallops, shrimp, tilapia, and pollock. Cooking does not affect the mercury content of fish.