To Eat or not to Eat Fugu

Gary Podolsky MD

In Japan and also in Korea, some restaurants serve that infamous and intriguing fish, fugu, a local delicacy, a dish where if your preparer is poorly trained or overloaded with saki, the meal could easily be your last.

But, today, more likely, eating fugu will cost you merely an arm and a leg (figuratively speaking, of course). While the fish is very expensive, fugu chefs are well trained and licensed. Moreover, according to most non-connoisseurs, the taste is very ordinary, and will leave you wondering why all the hoopla. Albeit, the experience of eating a potentially lethal dish makes for an impressive tale that travellers can tell back home, a tale of the magnitude of having challenged a sumo wrestler to a match.

The fish. In English, fugu is variously called blow/globe/puffer fish because of its ability to enlarge itself several times and assume a spherical shape, a defensive mechanism designed to ward off predators. The fish does this by filling its mouth with water, sealing its mouth and then pushing the water down the esophagus into an extremely elastic stomach. Depending on the species (there are 40 different types), the fugu can achieve an almost perfectly spherical shape.

In Japan, about 10,000 tons of fugu is consumed yearly, much of it grown in cages suspended in the ocean. Fugu prices rise in the fall and peak in winter, which is the best time to eat fugu, as they fatten to survive the cold. The fugu is shipped to restaurants alive and stored in large tanks, usually prominently displayed. As fugu are aggressive and have sharp teeth, their mouths are often sewn shut to prevent them from injuring each other. Allegedly, the most poisonous fugu, "tora-fugu," is the most delicious and very expensive. One fish can cost over one hundred dollars at a fish market, and much more at good restaurants.

Most fugu sold nowadays comes from fish with low concentrations of toxin. Selling or serving the toxic organs, especially the liver, is illegal in Japan, but it does happen, most often the work of amateur sellers or chefs, and sometimes with fatal results. After several homeless people died from eating organs discarded into an insecure trashcan, restaurants in Japan are now required to store the organs in specially locked barrels that are later burned as hazardous waste. Prepared fugu is now available in grocery stores. The stores must display official documents that they are licensed to so.

To become a licensed fugu chef requires two years of training, followed by a written test, a fish identification test, and a practical test of preparing fugu - and then eating it. Only 30 percent of applicants pass. The other 70 percent do not die from poisoning but fail, usually the result of making a minor mistake in the long and complicated procedure of preparing the dish.

Serving fugu. The most popular way of preparing the fish is fugu sashimi, also called fugu sashi or tessa. The fish is sliced so thin that the pattern of the plate can be seen through the meat. It is served with ponzu dipping sauce (a mixture of citrus juice and soy sauce). The plates are beautifully decorated giving diners pleasure to their palates as well as their eyes.

Another method of preparing fugu is to simmer it with vegetables and soup, fugu-chiri. Often the rather weak taste of the fish is difficult to detect with these other substances.

The toxin. Tetrodotoxin (anhydrotetrodo-toxin 4-epitetrodotoxin) is what makes fugu potentially lethal, and in spite of this _ or, perhaps, because of it _ fugu is considered a delicacy. The highest concentrations of the toxin are found in the organs, especially in the liver and ovaries (which are never served, knowingly), but toxins also reside in the skin and muscles. Apparently, the skin and muscles are the tastiest parts of the fish, the parts which deliver just the right amount of toxin to give the desired and pleasing feelings of tingling and numbness on the diner's tongue.

The toxin is produced by a type of pseudomonas bacteria. Fugu acquires the toxin by eating other fish already contaminated with the bacteria, without itself being affected. Tetrodotoxin is also found in other marine animals, the blue-ringed octopus, cone snails and some newts, for example. Blue octopus bites and cone snail envenomations are medical emergencies, and can be lethal.

Tetrodotoxin is a potent neurotoxin, paralyzing muscles by shutting down electrical signaling in nerves. Some fish contain enough tetrodotoxin to kill 30 adults. The toxin is stable and not deactivated by heat. It does not cross the blood-brain barrier, leaving victims fully conscious while gradually paralyzing the rest of the body.

Symptoms of poisoning appear between 15 minutes to several hours after ingestion but, rarely, may surface up to 20 hours after ingestion. The earliest signs include paresthesias of the lips and tongue, which then spreads to the face and extremities, causing speech difficulties and numbness. This is generally followed by increased salivation, and gastrointestinal symptoms.

Examination of patients reveals the following: progressive loss of sensory and motor neuron function, ascending paralysis with respiratory depression, and cyanosis and hypotension. There are also various electrocardiographic abnormalities due to myocardial dysfunction. Severely toxic patients develop deep coma and loss of brain stem reflexes. Victims remain fully conscious throughout but cannot speak or move. Those that survive 24 hours usually recover completely. There is no known specific antidote - though much research is underway to find one. Treatment consists of emptying the stomach, administrating activated charcoal to bind the toxin, and providing standard life-support measures to keep the victim alive until the toxin effects dissipate.