Death on the Half-Shell: The Health Hazards of Eating Shellfish

PERSPECTIVES IN BIOLOGY AND MEDICINE Volume 33 ¦ Number 3 · Spring 1990 DEATH ON THE HALF-SHELL: THE HEALTH HAZARDS OF EATING SHELLFISH ROBERT C. NOBLE * "He was a bold man that first eat an oyster," said Jonathan Swift [1, p. 296]. Oysters and bivalve molluscs have been a source of food for man since prehistoric times. Native Americans in coastal habitats left giant mounds of shells as evidence of this, and, in Europe, refuse heaps or kitchen middens indicated the popularity of shellfish for early man. How nutritious are oysters? One hundred grams of eastern raw oysters (five to eight oysters) yield about 66 calories, of which 8.4 grams are protein, 3.4 grams are carbohydrate, and 1.8 grams are fat [2, p. 52]. Eating raw shellfish is not only a nutritional but a sensory experience as well. Eleanor Clark writes about the taste of a variety of French oyster, the Amoricaine. "You can't define it," she says. Music and the color of the sea are easier to describe than the taste of one of these Amoricaines, ... It is briny first of all, and not in the sense of brine in a barrel, for the preservation of something; there is a shock of freshness to it. Intimations of the ages of man, some piercing intuition of the sea and all its weeds and breezes shiver you a split second from the little stimulus of the palate. You are eating the sea, that's it, only the sensation of a gulp of sea water has been wafted out of it by some sorcery, and are on the verge of remembering you don't know what, mermaids or sudden smell of kelp on the ebb tide or a poem you read once, something connected with the flavor of life itself. ... [3] Hardly anyone says such things about the other bivalve molluscs. What are the molluscs? The Mollusca are a phylum of soft-bodied *Division of Infectious Diseases, Department of Medicine, University of Kentucky College of Medicine, Lexington, Kentucky 40536.© 1990 by The University of Chicago. All rights reserved. 0031-5982/90/3303-0683$01 .00 Perspectives in Biology and Medicine, 33, 3 ¦ Spring 1990 | 313 invertebrate animals that includes snails, periwinkles, whelks, and conchs (the Gastropoda), octopuses, squids, and nautiluses (the Cephalopodia ), and the Bivalvia, animals with two separate shells, the oysters, mussels, cockles, scallops, and clams. The Bivalvia live at the seashore in the intertidal zones, although there are freshwater varieties as well. Because of the manner in which the Bivalvia take in food, they become a problem for humans. The Bivalvia are suspension feeders. Feeding is accomplished by filtration of small particles from the surrounding water. An oyster has constantly lashing cilia, and a large specimen can force several liters of water per hour through the openings of its gill plates [4, p. 271]. Particles of only 2 µp? in diameter are trapped and transported into the mouth. The bivalve gill is a fabulous device for concentrating the innumerable microscopic plants and animals that form the base of the aquatic food chain. Unfortunately for man, the food-gathering mechanisms also concentrate other things as well, including plant toxins, viruses, and bacteria pathogenic to man. Oysters have long been considered a delicacy and were cultivated by the Greeks and Romans a century before Christ. "Oyster dear to the gourmet," wrote Seneca, "beneficent Oyster, exciting rather than sating, all stomachs digest you, all stomachs bless you!" [3]. Oysters continued in popularity, and through the ages were thought to be an aphrodisiac. It is said that Cassanova ate 50 oysters every evening with his punch [3]. No doubt this gave him the energy for his perpetual tumescence. But Cassanova was an amateur in comparison to the Roman emperor Vitellius, who is said to have eaten 1,000 oysters at a single sitting, or Henry IV, who had 400 oysters before dinner, or Balzac, who would eat 100 oysters before his meal [5]. Our idea of a dozen oysters for dinner would be ludicrous to the ancients. But not everyone in history was thrilled by eating raw oysters. "Mme. Denis will eat your oysters tomorrow," Voltaire wrote in a letter. "I...