Sharks & Rays
Myth 1: Sharks Must Swim Constantly or They Die!
Myth 2: Sharks are the Number One Cause of Animal-Related Deaths!
Myth 3: All Rays Have Poisonous Stingers!
Myth 4: All Sharks are Like the Great White!
Myth 5: Sharks Can Detect a Single Drop of Blood in the Ocean!
Myth 6: Sharks Do Not Get Cancer!

Certain sharks are...

Myth 6:

Sharks Do Not Get Cancer!

The idea that sharks don't get cancer seems to stem from scant clinical evidence that cartilage has antiangiogenic properties--i.e., it inhibits the development of blood vessels, which are crucial to the growth of cancerous tumors--and since shark skeletons are made of cartilage, it follows (albeit somewhat loosely) that they can't get cancer. Recent studies and literature reviews have found that while the incidence of cancer in sharks and related fishes such as rays does seem to be low, cancerous tumors, including chondromas (cancers of the cartilage), have in fact been found in sharks. The reasons for the apparently low incidence are not necessarily related to their high cartilage content, but may simply be a matter of lack of directed research on cancer in sharks and related fishes.

While cartilage may have antiangiogenic properties, orally ingesting powdered shark cartilage has not been shown to be an effective cancer treatment or prevention, because none of the constituent parts of the powder appear to be absorbed across the intestine wall into the bloodstream.

Besides the lack of evidence that shark cartilage prevents or cures cancer in humans, the fishing of sharks for manufacturing shark cartilage products endangers shark populations and upsets fragile marine ecosystems. The myth that "sharks don't get cancer" is thus both a medical fallacy and results in the pointless slaughter of sharks, jeopardizing the existence of the species.