By Markham Heid
With all the talk about the disease-fighting, life-extending superpowers of the Mediterranean diet, a lot of people are trying to cram more seafood into their meals. But while there are endless articles extolling the healthful glories of fatty, omega-3-rich fish like salmon and mackerel, there’s not much talk about shellfish—or whether these sea creatures deserve space on your shopping list.
As it turns out, they do. “Shellfish are high-quality protein sources—just like land animals—meaning they have all the essential amino acids,” says Faye Dong, professor emerita of food science and human nutrition at the University of Illinois. Those “essential” amino acids are ones your body can’t make on its own but are needed to support proper cellular function and muscle health—making them a crucial component of a healthy diet.
Like meat from land animals, shellfish have a range of cholesterol levels; shrimp, lobster and crab have a bit more than mussels, oysters and other mollusks. But there’s ongoing debate about whether dietary cholesterol really contributes to unhealthy levels of blood cholesterol. And, in any case, the amount in shellfish is much lower than in land animal sources of protein, like chicken or beef.
Shellfish meat is also low in fat. “And the fat it has falls under the category of healthy fats, meaning it’s low in saturated fat and high in the omega-3’s DHA and EPA,” says Ann Yaktine, director of the Food and Nutrition Board at the National Academy of Sciences. Shellfish aren’t nearly as impressive on the omega-3 front as salmon. But oysters, shrimp, crab, lobster and mussels have about 25%-50% the omega-3s per serving as the healthiest fatty fish.
Depending on the type of shellfish you’re eating, most have varying amounts of some hard-to-get micronutrients. Selenium—a trace mineral important for cognitive and immune function—is most abundant in seafood. Shellfish are also rich sources of B vitamins, which help support nerve structure and cell function.
Finally, shellfish are good sources of some healthy minerals. Zinc, copper and iron can be difficult to get, Dong says, but they’re found in shellfish. Copper is especially abundant in lobsters and oysters, and it helps the body to make collagen, hemoglobin and other proteins necessary to human health and functioning. Zinc is important for immune function and wound healing, and oysters contain more zinc per serving than any other food. (Eat just two oysters, and you’ll meet the government’s recommended daily intake for zinc.) Clams, meanwhile, are great sources of iron.
That’s the good news. The bad news is that depending on the type of shellfish you’re eating and where it comes from, there are some potential contamination concerns.
Shrimp and lobster can accumulate heavy metals, namely lead and the metal cadmium, which is sometimes used in industrial manufacturing. And research suggests that fried preparations (as opposed to boiling or steaming) can heighten an eater’s exposures. More research has turned up elevated levels of cadmium in some Pacific oysters.
There’s also some concern about the use of antibiotics in shrimp, says Larry Olmsted, author of Real Food, Fake Food, a book about food provenance and safety. Shrimp is the most popular seafood in America, but much of it is farmed in Southeast Asia at facilities that are known to use banned antibiotics, says Olmsted. “If I buy shrimp, I get wild caught shrimp from the Gulf of Mexico,” he says. If you’re concerned about over-fishing and sustainability, Olmsted recommends looking for the blue Marine Stewardship Council (MSC) seal. MSC is a non-profit that audits seafood producers for sustainable fishing practices.
Finally, one of your best safeguards against any potential risk is to vary the types of shellfish you consume. “Moderation goes a long way,” Dong says, adding that you’re probably safe eating any type of shellfish once or twice a week. “Even if you’re eating something that’s contaminated, your body can clear that out,” she says.
Yaktine agrees. “Variety is a good rule of thumb,” she says. In terms of food safety, nutrition and the avoidance of over-fishing a species, “spreading the wealth” when it comes to dining on shellfish is a prudent course.