How healthy are shellfish?

Philip J. Goscienski, M.D.

December 2011

Shellfish is an odd term. No animals of this group are fish and it includes everything from oysters to octopus, clams to crabs. They are among the most ancient animals on the planet and humans have been harvesting them for at least a couple of hundred thousand years.

Except for octopuses, all members of this group have an external skeleton or a shell, unlike their sea-dwelling neighbors such as fish and oceanic mammals. With limited ability to move, shellfish were probably the first marine foods enjoyed by our Stone Age ancestors. Some anthropologists credit the incorporation of seafood into the human diet with the sudden spurt in the cultural advances of the human race. Specifically, they point to the presence of omega-3 fatty acids, major components of the human brain and eye, as the responsible factor.

Besides being a good source of protein and omega-3 fats, shellfish contain several B vitamins, including B12 as well as vitamin D and the minerals zinc and selenium. Shrimp do contain some cholesterol but it is about one-third as much as is found in an equivalent weight of eggs. To keep the cholesterol issue in perspective, dietary cholesterol intake has little effect on blood levels unless it is truly excessive. The major cause of elevated blood cholesterol levels is saturated fat, which is abundant in meat and dairy products.

Shellfish tend to be low on the food chain and are thus unlikely to contain environmental toxins such as mercury and cancer-causing PCBs (polychlorinated biphenyls) that contaminate large fish. On very rare occasions, shellfish become contaminated with tiny but toxic organisms that sometimes are labeled red tide. Public health authorities monitor this phenomenon carefully and the risk of any toxicity of shellfish is minuscule relative to its nutritional benefits.

About one in 50 persons in the U.S. has seafood allergy. It is most often related to shellfish but it is usually mild. The most common symptoms are itching, hives, wheezing and swelling of the area around the mouth. Unfortunately, one does not "grow out of" seafood allergy, although it is usually a specific form of shellfish or other fish that causes the symptoms.

Omega-3 fat is the most common nutritional deficiency in the modern Western diet. For persons with an aversion to fish, the wide variety and high nutritional value of shellfish should be an encouragement to incorporate it into the regular diet.

Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at