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There's a splendid restaurant chain out of Boston that calls itself Legal Seafoods, and I used to imagine the name originated because eating fish can be so dangerous at times, and only "legal" seafood would do. Even their slogan, "If it isn't fresh, it isn't legal" made that idea seem legitimate. They gently explained to me, however, a more prosaic reason. The name comes from a kind of green discount stamp, a "Legal stamp," predecessor (and by the same people) to the wildly popular green stamps of the 1950s and 1960s, enough of which got you a dinnerware set at the supermarket.

But my idea persists that eating fish can be dicey at times. Even the U.S. government feels it necessary to warn people not to buy fish "from trucks and wagons," and to advise when it's safe to eat the fish you catch yourself. Fear of mercury poisoning is a big deterrent, of course, the results on babies being so devastating. Another cause for disquiet: 80% of the seafood we eat is imported, and a full 18% comes from China.

In addition to being sure the fish you order is fresh, here are some tips on avoiding becoming sick as a result of eating fish (including shellfish) while you are on the road (or at home, for that matter):

1. To avoid mercury poisoning, smaller is better, and some fish are better than others. Mercury poisoning results from smaller fish (or even algae) ingesting mercury found in water, some mercury natural, some man-made. Then, as each fish gets eaten by bigger fish, the amount accumulates, so that the danger is greater in larger fish. Mercury cannot be eliminated by cooking or any other form of food preparation. Big predators who gobble up smaller ones, for instance, are swordfish, shark, king mackerel and tile fish, so avoid them altogether. Considered to have the least mercury are summer flounder, haddock, farmed trout, wild Pacific salmon and farmed catfish.

2. Much seafood poisoning is due to toxins found in small marine organisms throughout all the oceans, especially near coral reefs. It follows, therefore, that warm water fish are more likely to be dangerous, though you can't say all coldwater fish are safe, either.

3. Avoid the following that can and often do contain ciguatera, which can cause nausea, vomiting, diarrhea and more. The toxins in the fish can't de destroyed by cooking, smoking, freezing or any other method of food preparation. Large fish (more than six pounds) are more likely to contain ciguatera. So avoid them, and the innards (liver, roe, etc.) even of smaller fish, as the toxin is concentrated there. Especially avoid amberjack, barracuda, grouper, parrotfish, sea bass, snapper, surgeon fish and ulua. Areas where most of the 50,000 to 100,000 people who become ill yearly include the Caribbean, Florida, Australia and the South Pacific. If you have it, head for the hospital quickly.

4. Scromboid poisoning results from improperly handled fish that convert a natural bacteria therein to histamine, which makes the body react in an allergic manner, causing flushing, headaches, diarrhea and more. This occurs worldwide in the tropics and temperate regions. Most commonly associated with it are the following: yellowfin tuna, mackerel, skipjack and bonito; also mahi-mahi, herring bluefish, sardines, anchovies and amberjack. Recovery usually takes place within a few hours.

5. Avoid raw shellfish, which may contain a cholera-related bacteria, the vibrio, the worst of which is vibrio vulnificus. This can enter the body through eating raw oysters, clams, lobster and the like (even through open wounds in the body if you swim in vibrio-infested water). If you have a compromised immune system, it can be fatal. By the way, anyone over about 50, and certainly over 65 ("the elderly"), has a compromised immune system, as the hydrochloric acid in your stomach is no longer strong enough to kill such bad bacteria. Also, if you have diabetes, cirrhosis or other related illness that compromise stomach acids, stay away no mater how young you may be. Your immune system is also compromised if you are taking heavy steroids (prednisone, etc.), are an alcoholic, have liver disease or HIV.

6. Avoid raw fish, including sushi and sashimi, as uncooked or partially cooked seafood may harbor worms (anisakis, for example) and other parasites, bad enough, but may cause intense diarrhea from vibrio parahaemolyticus and vibrio cholerae. When I developed worms while living in Tokyo, my experienced doctor there told me to lay off sushi and sashimi if I wanted to prevent a recurrence. Freezing the raw fish before turning it into sushi or sashimi does not always kill all the worms and parasites, either. To be safe at all times, you should avoid raw or undercooked meats, poultry or eggs, as well as seafood and shellfish, all raw protein, in fact, to avoid illness.

7. If you don't fall victim to vibrio, you may just have a few days of discomfort as you suffer upset stomach, headache, loss of muscle coordination, nausea, diarrhea, etc. This can be cause by red tide, which can occur anywhere in the world. Contaminated shellfish can be found in both temperate and tropical waters, usually during or shortly after algae blooms ("red tides") associated with warm weather. If you're unlucky, you could die from the paralysis that can set in, in severe cases. Be sure to ask where you go if there is any problem with red tide when you order fish or shellfish.

8. On restaurant menus, look for warnings about consuming raw proteins, which indicate the establishment is taking its obligations to its customers seriously. Legal Seafood is one such chain (in seven eastern states and D.C.), saying also on its menus "More information about the safety of consuming raw food is available upon request." It's the law to give such a warning in at least four states, though in one such, Florida, there doesn't seem to be any penalty for flouting it (no penalty clause in the law, all too common an occurrence everywhere), the last time I looked into the matter, anyhow.

What's Left to Eat?

Avoid the fish and shellfish mentioned above, and enjoy the many other dishes on the seafood menu. There's plenty of fish in the sea, as everyone's mother said to her children, usually in a different context, but apropos here.

Contacts

The Centers for Disease Control and Prevention (CDC) site is www.cdc.gov.

The hardworking Environmental Working Group site is www.ewg.org.

Legal Seafoods can be reached at www.legalseafoods.com.

Notes

I am indebted to the CDC for much of the material above, as found in their excellent CDC Health Information for International Travel 2008, which can be found on their website, www.cdc.gov, or in print (order through the web site). Also to IAMAT, the International Association for Assistance to Travellers, www.iamat.org. And to the Environmental Working Group (EWG) for data on mercury in fish.

Full disclosure: the author is pro bono vice president of IAMAT.

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