Sharks Can Get Cancer: Tumor Found In Great White Shark For First Time Ever
Researchers in Australia have discovered tumors on two sharks, a great white and a bronze whaler. This is the first time a tumor has been found on a great white shark, according to Rachel Robbins, one of the researchers from Fox Shark Research Foundation in southern Australia. The great white shark's tumor was particularly nasty, measuring one foot long and wide.
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The idea that sharks don't get cancer, and that their cartilage is thus effective at fighting cancer in humans, dates back to the studies of two Johns Hopkins School of Medicine in the 1970s. The shark cartilage myth was further popularized by a 1992 book called "Sharks Don't Get Cancer." Practitioners of alternative medicine have latched onto the myth, which has led to a lot of people getting phony medical treatment.
"Available scientific evidence does not support claims that shark cartilage products sold as dietary supplements are an effective treatment for cancer, osteoporosis, or any other disease," reads the American Cancer Society's website. "Although some laboratory and animal studies have shown that some components in shark cartilage have the ability to slow the growth of new blood vessels, these effects have not been proven in humans. The clinical studies of shark cartilage products published to date have not proven any benefit against cancer."
David Shiffman, a shark researcher and doctoral student at the University of Miami, in Florida, put it more bluntly: "Sharks get cancer....Even if they didn't get cancer, eating shark products won't cure cancer any more than me eating Michael Jordan would make me better at basketball." (Shiffman wasn't involved in the study.)
The researchers aren't sure what caused the great white and bronzer shark tumors. Studies suggest that cancerous tumors in marine mammals have increased in recent years due to pollution. For example, beluga whales in the St. Lawrence River, which connects the Great Lakes to the Atlantic Ocean, have contracted intestinal cancer as a result of the human pollutant polycyclic aromatic hydrocarbons.
The first shark tumor was found in 1908 in the liver of a blue shark. Only a small percentage of shark species are known to get cancer--23 species out of 1,168, or about two percent--which may further bolster the sharks-don't-get-cancer myth.
The study, "First reports of proliferative lesions in the great white shark, Carcharodon carcharias L., and bronze whaler shark, Carcharhinus brachyurus Günther," was published in the November issue of Journal of Fish Diseases.
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