The term "seafood” includes a broad category of marine animals that live in the sea and in freshwater lakes and rivers. It includes fish, such as salmon, tuna, trout and tilapia, as well as shellfish, such as shrimp, crab, oysters, mussels and clams. Beyond that, there are still choices to make at the supermarket when you're shopping for seafood—fresh, frozen, canned, or prepared, and farmed versus wild—and things you should know to make your choices count the most.
Seafood and your health
Seafood provides high-quality protein and is low in saturated fat; some shellfish, like clams and oysters, are rich in iron. Seafood also contains special long-chain omega-3 fats that go by the names eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fats are not found in other foods, and the best seafood sources are fatty fish such as salmon, anchovies, herring, sardines, trout and mackerel.
Marine sources of omega-3 fats may help prevent arrythmias (irregular heart beats) and blood clots, reduce chronic inflammation and help lower triglycerides and blood pressure. These fats are also vital for the brain development of infants and young children. Preliminary research suggests that these omega-3s may help relieve rheumatoid arthritis and other inflammatory conditions, reduce the risk of macular degeneration, help preserve cognitive function in older people and help treat depression and certain other mental disorders, though some studies have not shown benefits.
Concerns have been raised, however, about contamination of seafood with harmful chemicals, such as PCBs (polychlorinated biphenyls) and heavy metals (such as mercury), which are byproducts of industrial pollution. Toxins tend to be cumulative affairs with seafood, the amount present depending on the water where the fish live and what they eat. Following this logic, when a fish eats other fish, it accumulates toxins in amounts that depend on where those other fish lived and what they had fed upon. Large fish like swordfish, albacore tuna and shark are more likely to contain contaminants, notably mercury, than smaller fish like trout and sardines. Still—and this is key—the benefits of consuming a variety of seafood outweigh the potential health risks.
Then there’s the question of cholesterol. Like all animal foods, most seafood contains moderate amounts (about 55 to 90 milligrams per 4 ounces). Shellfish, including lobster and shrimp, have a bad reputation because they are higher in cholesterol (about 160 milligrams per 4 ounces). But that still leaves room on your plate for shellfish, considering that the recommended cholesterol limit is 300 milligrams a day (or even up to 500 milligrams a day, some experts think), and 200 milligrams if you have heart disease or coronary risk factors. Just watch your consumption of cholesterol from other sources on days you eat shellfish. Moreover, shrimp and lobster are very low in saturated fat, which is the bigger culprit behind high blood cholesterol levels.
The 2010 Dietary Guidelines for Americans and the American Heart Association recommend that most Americans consume at least two servings (a “serving” is 3.5 ounces, cooked) of seafood a week to reduce the risk of cardiovascular disease. According to the FDA, it’s safe for women of childbearing age and young children to eat up to 12 ounces a week of a variety of fish and shellfish that are lower in mercury (such as shrimp, pollock and catfish), but they should avoid tilefish, shark, swordfish and king mackerel and limit albacore (white) tuna to no more than 6 ounces a week because of mercury concerns.
It’s important to be sure that the seafood you buy has been handled and stored properly to reduce the risk of foodborne illness. Only buy fresh fish or shellfish that is refrigerated or properly iced. Fresh fish should be displayed in a case on a thick bed of fresh ice. The eyes of the fish should be clear and bulge a little. Whole fish and fillets should have firm, shiny flesh and bright red gills, free of slime. Fish fillets should not be dark or dry around the edges. Don’t buy frozen seafood if the package is open, torn or crushed on the edge.
Country of Origin Labeling (COOL), required on fresh seafood, helps you identify its source—where in the world it comes from and whether it was farmed or wild-caught. The labels are required in supermarkets but, oddly enough, not in fish markets or on processed fish products. Though there is no fail-safe rule for picking the safest seafood, farmed domestic fish is generally a better option than imported. In particular, you may want to limit or avoid imported Asian shrimp and prawns, and all seafood from Vietnam (a big exporter of basa or “Asian catfish”), which is more likely to contain veterinary drug residues (often drugs banned in U.S. aquaculture operations), according to an analysis from Johns Hopkins University. This is advice we don’t give lightly, since such exports help the economies of developing countries. Farmed imports, especially from Asia, are cheaper (think affordable shrimp), so foregoing them may also mean a higher fish bill.
Healthy grocery shopping tips for seafood
- Before you shop, download a pocket seafood guide from the nonprofit Environmental Defense Fund or Monterey Bay Aquarium to help steer you toward environmentally friendly and safe seafood choices. Choose a variety of fish and shellfish. Seek out those that are higher in omega-3s and lower in mercury.
- Choose wild salmon over farmed, when you can (as revealed by COOL labeling). Wild salmon costs more and is available fresh mainly in the summer months, but you can find it year-round frozen or, more cheaply, canned.
- If you like shrimp, look for domestic wild-caught rather than imported farmed shrimp. Frozen shrimp must also have COOL labeling, so you know its origins, but not if it’s breaded or mixed with other seafood.
- Buy only live oysters, clams or mussels. Do a “tap test” at the store: Live clams, oysters and mussels close up when the shell is tapped; if they don’t close, don’t buy them. And if they don’t pass the test once you get home, discard them. Crabs and lobsters spoil rapidly after death, so if buying fresh, choose only those that show some leg movement.
- Try calamari (squid), which is sold fresh or frozen. It’s an inexpensive and omega-3-rich seafood choice. Don’t overlook canned seafood, such as canned salmon, sardines and herring. They can be high in sodium, but there are “low sodium” and even “very-low-sodium” options. If you eat a lot of canned tuna, choose “light” rather than “white” (albacore) tuna, which is higher in mercury.
- Fish sticks are low in mercury, but they can be high in fat and sodium. Plus, they are generally low in heart-healthy omega-3 fats because they are made from lean whitefish, such as pollock.
- Check out the prepared fish your store may offer. This can save you time at home, but depending on how the fish is seasoned, it could be high in sodium and fat. Some stores sell raw marinated fish and fish kabobs that just need to be cooked at home.
- Stop at the produce section for lemons. Most seafood is delicious simply cooked and then finished with a good squeeze of lemon.
Published August 15, 2013