Shark cartilage is a dietary supplement made from the dried and powdered cartilage of a shark; that is, from the tough material that composes a shark's skeleton. Shark cartilage is marketed under a variety of brand names, and is marketed explicitly or implicitly as a treatment or preventive for various illnesses including cancer.
Shark cartilage is widely used as a cure for cancer although there is no scientific evidence that it is effective.
The Mayo Clinic trial stated that it "was unable to demonstrate any suggestion of efficacy for this shark cartilage product in patients with advanced cancer."
The National Cancer Institute trial showed no difference in survival between patients receiving shark cartilage and those taking a placebo. Some of the enthusiasm for shark’s cartilage came from the reported observation that sharks do not get cancer; many varieties of cancer have been identified in sharks. It is claimed that molecules with anti-angiogenic activity have been isolated from the cartilage, but these macromolecules would not be absorbed from commercially available preparations.
Shark cartilage contains potentially toxic compounds linked to Alzheimer disease and amyotrophic lateral sclerosis.
Woodruff R. Palliative medicine evidence-based symptomatic and supportive care for patients with advanced cancer. Fourth edition. Oxford University Press, 2004. (p. 489)