Eating Raw Clams: Is It Risky?

Americans love clams, scallops and other seafood, raw or cooked. But how safe is a trip to the raw bar?

Experts say that any time you eat something raw, there's a risk. The U.S. Food and Drug Administration (FDA ) notes that shellfish, especially mollusks such as oysters, clams, musselsand scallops, are more likely to cause foodborne illness than fish because shellfish pump water through their bodies. The water contains nutrients, but it also can contain contaminants. Contaminated shellfish that are eaten raw -- or only lightly cooked -- boost the risk for foodborne illness.

The Centers for Disease Control and Prevention (CDC) offers this advice for those contemplating a trip to the raw bar: Don't.

If you can't give up your favorite delicacies, here's some advice from the experts. Don't ever eat raw shellfish if you have one of the following conditions:

• Gastrointestinal disorders

• Diabetes

• Immune disorders; if you are taking an immunosuppressant medication for an organ transplant or if you have HIV/AIDS

• Liver disorders, such as hepatitis

• Chronic kidney disease

• Inflammatory bowel disease,including ulcerative colitis and Crohn’s disease

• Cancer

• A condition that requires you to take steroid drugs

• Chronic alcohol abuse

• Pregnancy or breast-feeding

Infants, children and elderly adults also should avoid raw shellfish, the CDC says.

People in these high-risk groups are vulnerable to bacteria sometimes found in shellfish. The most deadly of these bacteria is called Vibrio vulnificus, which is found in oysters and continues to multiply even during refrigeration. These bacteria can be detected in the laboratory, but so far there's no screening process to keep infected oysters off the market. Because these bacteria are not associated with polluted waters, even "clean" oysters may contain Vibrio vulnificus .

In addition to Vibrio species, contaminated shellfish potentially may carry organisms that cause hepatitis A, hepatitis E,cryptosporidium, salmonella, shigella, Norwalk-like virus and enterovirus .

Stomach acids in healthy people are usually strong enough to destroy the Vibrio bacteria. But people with intestinal problems or weak immune systems may not be able to resist the bacteria. Symptoms of infection by the Vibrio bacteria include sudden chills, fever and nausea. It can be fatal in people with certain medical conditions, such as liver disease.

Thoroughly cooking the shellfish to an internal temperature of 145 degrees F will kill the bacteria.

If you're healthy and want to eat raw shellfish, here's the expert advice on how to do so as safely as possible:

• Buy only high-quality, very fresh live mollusks and use within two days. Buy from a reputable, licensed dealer. When a clam, oyster, mussel or scallop is alive, the shells will be closed tightly or will close when tapped lightly, experts say. Another test for freshness is to hold the shell between your thumb and forefinger and press as though sliding the two halves of the shell across one another. If the shells move, throw the mollusk away.

• Always ask to see the tag that certifies the shellfish were taken from waters approved by the National Shellfish Sanitation Program. Federal officials closely monitor shellfish beds for pollution.

• Discard dry oyster meat. Oyster meat should have a creamy tan color, say experts at the National Fisheries Institute. The meat should be plump and should smell fresh and mild.