A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Does shark cartilage prevent cancer?

October 22, 2004

Dear Cecil:

I saw a bottle at the pharmacist's today that said "Shark Cartilage" on it. My curiosity was piqued, so I asked if it really was shark cartilage. My pharmacist said it most certainly was and that a lot of people take it for its alleged immunity benefits. She told me that sharks don't get cancer, parasites, infections, etc, because their internal organ setup consists almost exclusively of a liver, and that sharks only die from being eaten or from starvation after they lose their teeth. Is this true? Am I missing the boat by not stocking up on shark innards, or is this a bunch of aquatic bunk?

Cecil replies:

Your first thought is: Oh, right, shark cartilage — that definitely sounds like it'd be effective against the big C. Your second thought is: Hey, they laughed at the guy who tried to make an antibiotic out of bread mold. (Guide for the perplexed: We're talking about penicillin, goof.) A lot of pharmaceuticals were invented using some process that on first hearing sounded pretty stupid. Trouble is, a lot of stupid things start out pretty stupid, too.

I go on about this because shark cartilage seems like your classic quack nostrum — Cecil's creakier readers will recall laetrile, the cancer panacea of the 1970s, which was derived from apricot pits and in large enough doses could give you cyanide poisoning. However, as with laetrile, there's just enough plausible science behind cartilage therapy that it can't be summarily dismissed. The current booming market for shark cartilage is largely the work of William Lane, who's cowritten several books on the subject, notably Sharks Don't Get Cancer (1992) and Sharks Still Don't Get Cancer: The Continuing Story of Shark Cartilage Therapy (1996). The first book describes a study of 29 terminally ill cancer patients in Cuba, many of whom allegedly improved when treated with shark cartilage. In 1993 60 Minutes reported favorably on this study and on Lane's work generally; sales of powdered shark cartilage promptly took off, and Lane and his allies have been touting cartilage and fending off their numerous critics ever since.

It must be said that Lane was perhaps not the ideal person to be conducting research of this sort, since although he holds a PhD, it's in agricultural biochemistry and nutrition, not, say, marine biology. Were he more knowledgeable in the latter field, he might have recognized earlier on that, as has now been unambiguously established, sharks do get cancer, sometimes in their cartilage. You're thinking: Kinda puts the kibosh on that line of scientific development, huh? Don't be too hasty — it seems sharks don't get cancer very often, for reasons that have yet to be fully elucidated. The phenomenon of most interest here is angiogenesis, the formation of new blood vessels that enable a tumor to grow. Long ago cancer researchers reasoned that (a) if angiogenesis could be retarded, tumors would cease to grow and might even shrink; (b) cartilage contains few if any blood vessels, so maybe cartilage contains antiangiogenetic agents; and (c) if so, since a shark skeleton is all cartilage, sharks must contain antiangiogenetic agents in prodigious amounts. If the logic wasn't quite a total reach, it wasn't exactly airtight either, as even its pre-Lanian exponents would agree.

Lane, however, has been the boldest advocate for the power of shark cartilage, making him either a daring medical pioneer, a flake, or worse, depending on whom you ask. To date the evidence is trending against pioneer. In 1998 a study published in the Journal of Clinical Oncology found that 60 cancer patients treated with shark cartilage enjoyed no detectable benefit. Cancer experts generally agree that taking cartilage powder orally is useless — digestive juices destroy the supposedly cancer-fighting compounds before they can do you any good. In 2000 the Federal Trade Commission ordered a firm owned by Lane's son Andrew (and for which Lane himself is a consultant) to stop claiming therapeutic benefit for a shark-cartilage product it sold under the name BeneFin and pay a million-dollar fine. Evidently this did not have the desired inhibitory effect: in July 2004 a federal court ordered Andrew's company to halt sales of BeneFin (and two other dubious products) and give customers their money back. Meanwhile, outraged shark advocates — what, you think nobody should speak up for the sharks? — say the $100 million shark-cartilage industry is hastening the extinction of many shark species.

Articles still show up in the medical journals reporting that a shark-cartilage derivative called neovastat inhibits angiogenesis — as I say, Lane wasn't pulling his claims out of thin air. To date there's no conclusive evidence the drug increases cancer survival rates, but who knows, maybe one day some variant of neovastat will find its place in the anticancer pharmacopoeia. That stuff your pharmacist is hawking, on the other hand — dunno if she's spent too much time sniffing the ginseng (she thinks sharks are immortal?), but she's spreading a discredited yarn.

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