Health Guide: the Benefits and Risks of Shellfish

Do shellfish always have a special place at your dinner table?  Do you like them shucked or peeled, and sauteed or skewered?

For years, shellfish has been wrongly branded a dietary villain.  But it is making a comeback as a heart-healthy food.  You may, however, be reeling in some risks, including bacteria, viruses, and pollutants.  Learning to cook smart can reduce the dangers and keep deep-sea delights on your menu.

The benefits:

Shellfish was long thought to contain dangerously high levels of cholesterol, but the levels, according to health experts, are actually comparable to those in lean cuts of beef and chicken.  Dietitians say that your daily cholesterol intake should not exceed 300 milligrams and saturated fat should be no more than 10 percent of daily calories.  So a 3-ounce (85-gram) serving of shrimp (about 15 shrimps), for example, with 166 milligrams of cholesterol and almost no saturated fat, gets the thumbs-up.

Your heart will love shellfish, too.  Studies have shown a significantly reduced risk of sudden cardiac death among men who ate shellfish at least once a week.  Another study showed that subjects who ate 10 ounces (280 grams) of shrimp daily for three weeks had reduced levels of triglycerides, blood fats that can clog arteries.  One reason is that crustaceans (such as lobsters and shrimp) and mollusks (oysters, clams, and mussels) contain omega-3 fatty acids, which may control blood pressure and cholesterol levels.  Among shellfish, oysters, mussels, and crabs contain the most.  Shellfish is also rich in protein and bone-friendly calcium, as well as zinc (linked with prostate health), iron, and B vitamins.  And it is relatively low in sodium and calories.

The risks:

Experts warn that shellfish are quick to absorb contaminants from the sea, including bacteria, such as salmonella, and viruses, such as hepatitis A.  Uncooked oysters may also contain a bacterium called ‘Vibrio vulnificus,’ which can cause serious illness, mainly in people with liver disease, diabetes, gastrointestinal disorders, or compromised immune systems.

Thoroughly cooking oysters and other shellfish usually kills bacteria, although steamed oysters may still contain V. vulnificus.  Because bacteria thrive in warm water, experts recommend eating oysters only in the colder months – those with an R in their name – and steaming clams at least six minutes to eliminate any bacteria.

If you’re careful in preparing your shellfish, the odds are in your favor:  studies show that fewer than one-quarter of 1 percent of all food-borne illnesses can be attributed to seafood.

Doctors add one caution:  Shellfish absorb pollutants if they live in contaminated water.  Don’t eat the green tomalley, or liver, in lobsters or the "mustard" in blue crabs; they may contain high levels of harmful chemicals known as PCBs or other toxins.

Finally, experts offer some precautionary measures:  Since raw shellfish is highly perishable, it has to be kept from spoiling with these techniques:

- Raw mussels and clams should be alive, with their shells tightly-closed, before cooking.  Discard those with open shells.

- Store fresh shellfish in the coldest part of the refrigerator as soon as you get home.

- Live shellfish need ventilation.  Store in open containers; cover with a damp cloth.

- Eat fresh shellfish within one or two days of purchase.