The rising popularity of shark cartilage extract as an
anti-cancer treatment is a triumph of marketing and
pseudoscience over reason, with a tragic fallout for both
sharks and humans, according to a Johns Hopkins biologist
writing in the Dec. 1 issue of Cancer Research.
"Since shark cartilage has been promoted as a cancer
cure, not only has there has been a measurable decline in
shark populations, but cancer patients also have been
diverted from proven, effective treatments," said Gary K.
Ostrander, a research professor in the Krieger School's
Biology Department
and the School of Medicine's
Department of Comparative
Medicine.
In the paper, titled "Shark Cartilage, Cancer and the
Growing Threat of Pseudoscience," Ostrander writes, "Crude
shark cartilage is marketed as a cancer cure on the premise
that sharks don't get cancer. That's not true, and the fact
that people believe it is an illustration of just how
harmful the public's irrationality can be."
Ostrander's paper details more than 40 examples of
tumors in sharks and related species, dating back to the
mid-1800s.
In the paper, Ostrander and a team of researchers from
the Registry of Tumors in Lower Animals not only dissect
what they call the "fallacious arguments" that have
successfully convinced desperate cancer patients to
purchase and ingest crude shark cartilage extract, but they
also sound a "wake-up call" for society to become more
scientifically literate and, thus, less vulnerable to
skillfully mass-marketed illogical claims.
"People read on the Internet or hear on television
that taking crude shark cartilage extract can cure them of
cancer, and they believe it without demanding to see the
science behind the claims," Ostrander said. "This shows how
the electronic media has increased the potential harm of
pseudoscience, turning what would otherwise be quaint
cultural curiosities into potential serious societal and
ecological problems. The only way to combat this is to
ensure that government leaders and media professionals
receive adequate scientific training based on reason, and
that they also develop critical thinking skills."
Ostrander traces the popularity of crude shark
cartilage as a cancer treatment and preventive measure to
I. William Lane's 1992 book titled Sharks Don't Get Cancer,
which was further publicized by the CBS News program 60
Minutes in 1993. Though Lane acknowledges in the book that
sharks do, in fact, get cancer, he bases his advocacy of
crude cartilage extracts on what Ostrander calls
"overextensions" of some early experiments in which the
substance seemed to inhibit tumor formation and the growth
of new blood vessels that supply nutrients and oxygen to
malignancies.
"The fact is that it is possible that highly purified
components of cartilage, including from sharks, may hold
some benefit for treatment of human cancers," Ostrander
said. "The key will be to isolate these compounds and
design a way to deliver them to the site of the tumor. Lane
and others ignore these existing barriers and suggest that
consuming crude cartilage extracts by mouth or rectum could
be curative of all cancers--an approach for which there is
no scientific basis. It is worth noting that despite more
than a decade of evaluation of shark cartilage, not a
single controlled clinical study has established that it
works as an anti-cancer agent."
The National Cancer Institute funded a portion of this
work.