Fishing for safe seafood - includes related articles on purchasing, storing, health tips and fraud - Cover Story

Nutrition Action Healthletter, Nov, 1996 by David Schardt, Stephen Schmidt

Last May, a 38-year-old Los Angeles man with diabetes developed fever, chills, nausea, and muscle pain two days after eating raw oyster from Texas. Three days later, in a hospital intensive care unit, he died of blood poisoning.

A week later, 46-year-old Los Angeles man with cirrhosis of the liver came down with fever, sweats, and nausea one day after eating raw ousters from a different source in Texas. Despite antibiotics and hospital care, he, too, died within days.

And later that month, also in Los Angeles, a 51-yeat-old woman with hepatitis developed fever, nausea, and muscke aches a day after she ate raw oysters from Louisiana at a party. Two days later she was dead from blood poisoning.

Each day in the United States, hundreds - perhaps thousands - of people get sick from eating seafood. For most, it's an inconvenience, maybe an unpleasant day or two of diarrhea and stomach cramps. Others are disabled for weeks ... or even years. And a small number - mostly those who eat raw shellfish - die.

All the from one of the healthiest foods you can eat. Seafood is remarkably low in (heart-damaging) saturated fat. And it's the richest source of omega-3 fatty acids, which could protect against heart attacks.

The trick is to get the most benefit ... at the least risk.

Contaminated seafood causes about 113,000 cases of food poisoning each year in the U.S., according to the Food and Drug Administration (FDA). But that's clearly an underestimate. "There are probably many incidents that are not reported," says Sean Altekruse, an FDA epidemiologist who tracks seafood poisoning for the Centers for Disease Control (CDC) in Atlanta.

Unlike with meat, where ground beef is the chief culprit, the most popular varieties of seafood are among the safest. Canned tuna, for example, poses little or no risk of illness. The same goes for shrimp, cod, imitation crabmeat, breaded fish filletss and fish sticks, flounder and haddock, catfish, and salmon (canned or fresh). That takes care of more than two-thirds of the seafood that Americans buy. Some of the other third can be a bit dicier.

RAW SHELLFISH

"The biggest seafood hazard by far is raw or undercooked shellfish," says Morris Potter of the CDC. About 20 million Americans eat raw shellfish, says the FDA. And it's raw shellfish that accounts for more than 90 percent of seafood poisoning cases.

"One has to bear in mind that when you eat raw shellfish you're eating a whole living organism complete with its GI tract," Potter points out. "That would be equivalent to plucking a live chicken and eating it whole, guts and all."

What's more, shellfish feed by filtering two to three gallons of water an hour. That means they take in whatever's floating by - not only plankton and other food, but viruses, bacteria, mercury, and who-knows-what-else.

Here's what could be waiting for you in your next oyster, mussel, or clam:

*Norwlak Virus. The most common cause of shellfish poisoning comes from human sewage. It causes nausea, vomitting, or diarrhea, but most of the 100,000 or so people who are attacked each year recover within a day or two.

"In general, it's a mild illness," says Melvin Kohn of the Louisiana Department of Health and Hospitals, "People get very sick for a couple of days but they usually don't die."

As with just about all seafood contamination, you can't see or smell Norwalk. And stewing or steaming doesn't necessarily solve the problem.

"We know that high degrees of heat clearly can kill it and low degrees of heat don't," says Kohn. "But how many degrees it has to be has not been determined."

*Vibrio. The nastiest strain found in the U.S. is Vibrio vulnificus, which kills about 10 to 15 people each year. Vibrio bacteria thrive in the waters of the Gulf of Mexico, so seafood that comes out of that environment, particularly when the waters are warm, have Vibrio on them," notes Morris Potte

In fact, every case that the CDC has traced since 1990 came from raw shelifish harvested in the Gulf.

Only a small percentage of the population is susceptible to Vibrio vulnificus infections, but about half of those who get it die. "There aren't very many trivial Vibrio vulnificus infections," says Potter. The most vulnerable: people suffering from liver disease, liver damage caused by too much alcohol, or iron-overload disease (hemochromatosis), and people with diabetes, AIDS, or cancer.

Fortunately, heat destroys Vibrio. So as long as you avoid raw or undercooked Gulf Coast shellfish, especially from May through November, you're probably safe.

FINFISH

While most seafood poisoning is caused by raw shellfish, fish with fins aren,t always squeaky clean. And cooking may not make a contaminated fish safer.

*Ciguatera. "It's the most common finfish food poisoning in the United States," says W. Robert Lange of the Johns Hopkins School of Medicine.

Some 8,000 Americans a year are made ill by the ciguatera toxin, which is produced by plankton that grow on tropical reefs. Small fish that eat the plankton also eat the toxin, and large predatory fish that eat the small fish end up carrying even more ciguatera. In the U.S., ciguatera poisoning cases are concentrated in Florida, Hawaii, Puerto Rico, the Virgin Islands, and Guam.