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, mussels, and scallops, are likely to cause foodborne illness because they filter water through their bodies and absorb contaminants. 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 which can lead to intense abdominal pain, nausea, vomiting and diarrhea. 

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 breastfeeding

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

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. Because these bacteria are not associated with polluted waters, even "clean" oysters may contain Vibrio vulnificus. Reports of illnesses can help officials close contaminated water areas.

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. 

In healthy people, the Vibrio bacteria can cause vomiting, diarrhea, and abdominal pain. 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 shellfish to an internal temperature of at least 145 degrees F will kill the bacteria. Shells of clams, oysters, and mussels should open with cooking. Shells that don't open should be thrown out.