THURSDAY, Dec. 2, 2004 (HealthDayNews) -- Although shark cartilage products remain widely available to the public, there's no scientific evidence to show they cure cancer, as advocates claim.

That's the conclusion of a paper in the Dec. 1 issue of Cancer Research, in which Johns Hopkins University researchers highlight the "falsehoods" that have led some people to believe that crude shark cartilage extracts may be an effective, alternative cancer treatment.

"All of us working in cancer would love for this to work as they say; it would solve a lot of problems," said Gary K. Ostrander, a research professor in the departments of Biology and Comparative Medicine at Hopkins. "But the fact is, it doesn't."

Ostrander's paper builds on preliminary work presented at a April 2000 meeting of the American Association for Cancer Research, where he began to describe the disconnect between the actual science and the public's perception of shark cartilage as a cancer therapy.

Ostrander blames "pseudoscience" -- studies based on flawed methodologies -- for building false hope. He traces the popularity of shark cartilage as a cancer cure to William Lane's 1992 book Sharks Don't Get Cancer and the subsequent publicity it received on the CBS News program "60 Minutes."

Early experiments by the acclaimed Harvard Medical School researcher Dr. Judah Folkman examining shark cartilage's ability to block the development of blood vessels that nourish tumors -- a process called angiogenesis -- also ignited interest in the substance. But Ostrander and colleagues said claims that crude cartilage extracts are effective against cancer represent an "overextension" of that work.

Yet Ostrander and others said it is possible that high purified components of cartilage may one day show some benefit. Two angiogenesis inhibitors have been purified from shark cartilage, according to the National Cancer Institute, which is sponsoring two clinical trials examining the use of shark cartilage. Existing evidence is inconclusive regarding the effectiveness of cartilage as a cancer treatment, it said.

Mary Ann Richardson, vice president of research and development at the National Foundation for Alternative Medicine, said the use of shark cartilage products begs for more research. "I think the whole issue is if people are using these things, we need to investigate them and we need to validate them," she said.

Shark cartilage has been marketed as a cancer cure on the premise that sharks don't get cancer. Actually, sharks and their relatives do develop both benign and malignant tumors: Ostrander's paper offers more than 40 examples, dating back to the mid-1800s.

And while shark cartilage distributors insist that sharks rarely get cancer, the actual rate of cancer among sharks is not known, the authors noted.

Even if sharks were less susceptible to cancer than other organisms, it would not support the use of crude cartilage extracts to treat cancer in humans, they continued.

Yet, Ostrander said, the products on the market today consist mainly of processed, powdered cartilage. "You're going to be consuming crude cartilage containing lots and lots of things in it," he explained. And even if you increase the dose, you may not be consuming enough of the key component, he added.

While particular components of shark cartilage ultimately may prove beneficial, Ostrander said more research is needed to identify the key substances, their cause of action, potential side effects, best routes of delivering these substances, and their effectiveness.

More information

The National Cancer Institute can provide more detail on past studies examining the use of shark cartilage as a cancer treatment.

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