Seafood lovers concerned about sustainability may already be familiar with the popular Monterey Bay Aquarium Seafood Watch's pocket and mobile guides, which divide up fish caught in the United States into easy-to-follow "Best Choices," "Good Alternatives," and "Avoid" lists based on the management of the fisheries for each species, population data, and fishing methods. While helpful, these lists leave out a component also worth considering when making seafood choices: toxin levels and omega-3 levels.
But now there's a new list, dubbed "The Super Green List," which attempts to take all of these factors into account and boil them down to a "top 10" list. The fish that make this list have fewer than 216 parts per billion mercury and 11 parts per billion PCBs (a toxic byproduct of industrial activities), and yield at least 250 milligrams of omega-3 fatty acids per day based on a weekly consumption of eight ounces of fish per week. To put some of these numbers in perspective, according to the Food and Drug Administration's (FDA) study on mercury levels in commercial fish and shellfish, the worst offender, tilefish from the Gulf of Mexico, has 1,450 parts per billion mercury, and one of the least offenders, anchovies, has 17 parts per billion. These fish also fall under the old list's "Best Choice" category.
"The Super Green List" attempts to combine the best of both worlds — establishing a connection between concern over the environment and health. Prior to the creation of this list, one would have had to cross-reference the Seafood Watch's old list with the FDA's study.
The importance of minimizing mercury and PCB exposure cannot be emphasized enough for at-risk groups including children, pregnant or nursing women, women of childbearing age (ages 18 to 45), and women who are about to become pregnant. The inclusion of the last two groups may seem a bit surprising, however, studies have shown that it can take at least five years for women of childbearing age to eliminate PCBs from their bodies, and between 12 and 18 months to lower mercury levels by a measurable amount. According to the Environmental Protection Agency (EPA), up to one in 12 American women have mercury levels that would cause brain damage or other birth defects during pregnancy.
Mercury contamination is a prevalent, pervasive, and ongoing problem in the world's seafood stock. Much of the mercury that ends up in fish comes from industrial activities, particularly the burning of coal by power plants. Airborne mercury can travel long distances, and once it makes its way into the water table and the oceans through precipitation or runoff, it is converted into methylmercury, a particularly problematic form because it concentrates as it moves up the food chain. And this form of mercury is not a form that can be separated from the flesh, as it binds itself to the muscles and tissues of the fish. Repeated consumption of fish with high concentrations of methylmercury can also cause the compound to accumulate to high levels in humans as well. (Photo courtesy of flickr/nino63004)
Fish absorb methylmercury mostly from their food, but also from the water as it passes over their gills. Hence, larger fish (those higher up in the food chain) tend to have the highest levels of mercury — just look at the FDA's list of fish to avoid, which consists of king mackerel, shark, swordfish, and tilefish from the Gulf of Mexico. So it's no surprise that according to the EPA, mercury concentrations in fish can be anywhere between 1 to 10 million times that of the surrounding water.
This begs the question, what can be done to minimize one's exposure to methylmercury when eating fish? Nearly all fish contain some level of mercury. However, many health experts argue that, on balance, the health benefits of eating fish can still outweigh the risks if care is taken to pick the right fish. Fish are generally low in saturated fat, are a great source of protein as well as omega-3 fatty acids, and contribute to cardiovascular health. But, if memorizing the list doesn't seem practical, the Food and Drug Administration and Environmental Protection Agency have issued a joint advisory which counsels people to generally eat lower on the food chain — smaller fish are better. Larger and older fish tend to have higher concentrations of methylmercury in their tissues.
Furthermore, the two agencies recommend that adults eat at most 12 ounces (two 6-ounce portions) of fish per week, and eat a variety of fish that are low in mercury content. Young children should still eat fish as well, but in smaller portions. Eating more than the recommended weekly amount of fish doesn't pose an immediate health risk, but make sure to cut back the following week.
By following these recommendations diligently, one can still enjoy fish (and its numerous health benefits) without having to worry too much about the risks. After all, the only thing worse than a mouthful of scales is a stomach full of mercury. But for the list that takes it all into account (not just mercury levels)…