Is shellfish as healthy as regular fish?
The answer, according to a new report published in a Harvard Medical School newsletter, depends on the nutrient and which type of fish, seafood or shellfish on your plate.

The report, published in the Harvard newsletter Healthy Eating for a Healthy Heart, found that fish – such as baked salmon and swordfish – is a very healthy food choice. It’s loaded with omega-3 fatty acids and lean protein, and when eaten in moderation poses no significant risks from mercury.
But when it comes to lobster, shrimp, or clams, the benefits may vary, the Harvard report said. Researchers consulted the U.S. Department of Agriculture's nutrient database to calculate the nutritional value of a three-ounce serving of various seafood varieties. Among their findings:
Omega-3s: Lobster contains very few omega-3s, and shrimp and clams also have only modest levels. Calamari, blue crab, and oysters have just one-fourth of the omega-3 content of salmon.
Protein: Once for ounce, clams and lobsters are comparable to salmon. But octopus has more protein than any of the 10 main species of fish in the USDA’s nutrient database.
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Cholesterol: People with high blood cholesterol levels might want to watch their consumption of shrimp and fried calamari. Shrimp has 166 mg of cholesterol per three ounces and fried calamari has about 221 mg. But clams, crab, mussels, and oysters may actually lower cholesterol levels because they contain compounds called sterols that block the body’s absorption of cholesterol.
Calories: Most shellfish are low in calories, as long as they’re not breaded or fried.
Other nutritional benefits: Oysters are loaded with zinc. Clams contain a lot of iron and vitamin B12. And crustaceans are full of choline, which accelerates the synthesis of acetylcholine, a neurotransmitter important in memory and muscle control.
Toxins: Toxins in some shellfish can be a problem. The organisms responsible for "red tides" make a toxin that collects in clams, crabs, mussels, and scallops that can cause paralytic shellfish poisoning. In 2008, the FDA also warned against eating tomalley, the soft green substance in lobster, because of red-tide conditions. About 30 cases of shellfish poisoning are reported each year in the United States.
Allergies: About 2 percent of Americans are food allergies – with shellfish being among the most common.