Alice Park
There are a lot of good reasons to eat seafood—recent studies have linked the omega-3 fatty acids found in deep water fish to a lower risk of heart disease; fish are a good source of protein, and early studies hint that pregnant women who eat fish or take fish oil supplements are more likely to carry babies to full term, and to enhance their babies’ cognitive development.
But eating more fish isn’t easy. The healthy bonus that comes from fish, it seems, has a price. The same fats that make fish so good for the heart and the body also attract dangerous toxins, from dioxins to polychlorinated biphenyls (PCBs), the man-made byproducts of the electrical industry. (While PCBs have not been created since the 1970s, trace amounts still linger in waters.) In addition, the lean muscle of the ocean’s biggest and most powerful swimmers can become sinkholes for methylmercury, a potentially brain- and liver-damaging metal formed when salts are processed by certain anaerobic bacteria. Is it safe to eat fish at all? Are the benefits of eating fish enough to outweigh these risks? How much fish is safe to eat? Which kinds of fish and seafood have the most omega-3 fatty acids and the lowest levels of contaminants?
Two reports released this week may finally provide some answers for those trying to decide between surf or turf. Both the Institute of Medicine and researchers at Harvard School of Public Health report that more Americans could be benefiting from the high protein and healthier fat found in fish, and that for most people, these benefits do indeed outweigh the risks of consuming contaminants. Not surprisingly, both studies note that some populations, including pregnant women and young children who may be at greatest risk of suffering from contaminant poisoning, should avoid consuming too much of the larger fish species that are likely to have the highest levels of methylmercury or PCBs.
The IOM report, Seafood Choices, Balancing Benefits and Risks, provides recommendations for four populations—women who are or may become pregnant or who are breast-feeding; children younger than 12; adult women who are not planning to become pregnant and adult men; and adults at risk of heart disease—but the core advice for all groups is the same: it’s safe, and healthy, to eat up to two 3 oz. servings of fish each week. Young children and pregnant women, however, should make sure that these servings don’t include shark, swordfish, tilefish or king mackerel, the largest predatory species that contain the highest levels of methylmercury.
The Harvard authors, whose report appears in the Journal of the American Medical Association, also found that eating fish carries significant health benefits. Based on their review of several years of previously published studies, they found that eating 3 oz. of farmed salmon a week could reduce the risk of death from heart disease by 36% and the risk of overall death by 17%. While contaminants like methylmercury and PCBs can indeed cause neurological problems, the benefits gained from eating fish often outweigh the smaller risk these toxins pose.
What it means: While Americans are eating more fish on average today than at the turn of the century, we’re not eating the healthiest kinds of seafood. The most popular form of seafood, shrimp, is high in cholesterol and contains low levels of omega-3 fatty acids. And that cafeteria staple, fish sticks, contain very low levels of methylmercury but are equally poor sources of omega-3 oils; a 3.5 oz serving contains one-twelfth the amount of oils found in the same-sized portion of farmed salmon.
So if you’ve been eating too much of the less healthy offerings from the sea, or avoiding fish altogether because you’ve been worried about the contaminants they may contain, take some advice from the Harvard researchers. The best way to avoid the potential dangers of an all-surf diet, they say, is to vary the types of fish you eat. Atlantic herring, wild salmon, sardines and Atlantic cod are among the fish with the lowest methylmercury levels; while the larger species, like king mackerel and swordfish, contain some of the highest levels. For more on the IOM’s report, visit www.iom.edu.
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