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© Copyright 2002, Jim Loy
Reportedly, sharks do not get cancer. This is false; sharks do get cancer, although they get cancer less frequently than most other animals. Well, what is it about sharks that reduces the risk of cancer? What is different about sharks? One might leap to the observation, sharks have no bones; their entire skeletons are made of cartilage. So, one might leap further, shark cartilage prevents cancer. This is the contention of a book and a large shark cartilage industry. It is a good theory, which needs to be tested, and apparently has been tested. And, so far, there is no evidence at all that shark cartilage prevents cancer. None. The use of probability would allow us to deduce that (within a reasonable amount of certainty) shark cartilage does not prevent cancer.
Some other fish have cartilage instead of bones. Some of us have been accidentally ingesting tuna cartilage for years, but no claims have been made about tuna and cancer. So sharks are not particularly different from many other fish. And so, the logical leap from sharks having less cancer, to shark cartilage preventing cancer is beginning to look like a particularly illogical leap.
Maybe you have been taking shark cartilage and have never gotten cancer. And maybe someone else who you know has not taken shark cartilage and has gotten cancer. This may convince you. But it is not convincing at all, statistically. Large tests must be done, with thousands of patients. And, for any real conclusions to be drawn, the tests must be double blind (some patients getting shark cartilage and others getting a placebo), and other factors (use of vitamin C, for example) must be taken into consideration too. In other words, while anecdotal evidence may sometimes be suggestive, it is seldom convincing. Anecdotal evidence may be a good reason to do serious testing.