Web edition: October 9, 2001
For chefs who savor the flavor of fresh, organic ingredients, what could be better than cooking just-picked mushrooms for dinner?
That attitude appears to have gotten a few French gourmands in trouble—big trouble, according to a report in the Sept. 13 New England Journal of Medicine. Over a 9-year period, a dozen people were poisoned, three of them lethally, by consumption of a local mushroom. Until the new report, the species they ate had had a global reputation for being tasty and safe.
Toxicologist Edmond E. Creppy of the University of Bordeaux in France and his colleagues reviewed case reports that had been accumulating on severe fungal poisoning. Each of the seven women and five men had been hospitalized about a week after consuming three or more consecutive meals of woodland mushrooms known locally as bidaou or canari. Scientists refer to these golden-capped fungi as either Tricholoma equestre or Tricholoma flavovirens. Though these wild mushrooms grow throughout much of the world, the poisoning victims had all harvested theirs from beneath pine trees in late fall or winter at spots along the sandy coast of southwestern France.
Their initial symptoms were identical. Within 1 to 3 days of eating their last meal containing the mushrooms, the victims became fatigued and started complaining of weakness—a problem that continued to worsen over the next 3 or 4 days. During this time, their muscles stiffened, and their faces reddened. They also reported nausea, darkening urine, and in eight cases, profuse sweating.
Blood tests indicated that the mushroom aficionados were suffering from severe rhabdomyolysis—a condition where the iron-containing red pigment called myoglobin leaks out of muscle cells and into the blood. Another tell-tale sign: the victims’ red-brown urine.
As myoglobin degrades, it produces kidney poisons that, untreated, can lead to kidney failure. Doctors typically treat the problem by filling the patient with fluids to quickly flush the poisons from the kidneys.
To confirm that the victims had correctly identified the fungus that poisoned them, Creppy’s team sought out trained mycologists—fungi experts—to collect some bona fide T. equestre. Then, they fed to mice an extract of these mushrooms in amounts that were comparable by weight to what the diners had reported consuming.
Within 72 hours of being fed the extract, two mice died. The rest developed increased blood concentrations of certain enzymes, classic markers of rhabdomyolysis. These laboratory experiments “confirmed” the role of T. equestre in the muscle disease, Creppy’s team says. However, because most of the people survived despite having massive enzyme increases in the blood, the researchers conclude that “a genetic muscular susceptibility may be unmasked by the direct muscle toxicant . . . when the amount of mushrooms ingested exceeds a certain threshold.”
As word of the new report began circulating among U.S. mushroom enthusiasts, reports on the Internet defended the mushrooms, arguing that the delectable species in question had never been associated with disease and therefore may reflect the French species having been misidentified.
“Every source I have ever seen lists these species as good edibles,” notes Michael Wood, a past president of the Mycological Society of San Francisco and developer of a leading Web site on fungi http://www.mykoweb.com/. “I have never heard of an adverse reaction.” Indeed, he told Science News Online, “Out of over 150 species of fungus that I have eaten, Tricholoma flavovirens stands out as being one of the very best.”
Fred Stevens, who photographed the mushroom we show here, also points out that “there is disagreement among professional mycologists [mushroom experts] whether Tricholoma flavovirens and Tricholoma equestre are one and the same.” In fact, he told Science News Online that he hopes the new report provides “the impetus for U.S. and European mycologists to get together and settle once and for all the taxonomic status of this ‘species pair.’”
For now, Marilyn Shaw, a mushroom-toxicology consultant to the Rocky Mountain Poison Center in Denver and member of the North American Mycological Association’s toxicology committee, recommends that unless further research exonerates the species growing in this country, “Don’t eat Tricholoma equestre/flavovirens.”
Indeed, that’s the name of a review of the French report that she authored in this month’s Spores Afield, a newsletter of the Colorado Mycological Society. After all, she cautions, it’s better to be safe than sorry.
Edmond E. Creppy
Department of Toxicology
University Bordeaux 2
146 Rue Leo-Saignat