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, including Carticin, Cartilade, or BeneFin, and is often[when?] explicitly or implicitly marketed as a treatment or preventive for various illnesses including cancer.
There is no scientific evidence that shark cartilage is useful in treating or preventing cancer or other diseases. Controlled trials have shown no benefit to shark cartilage supplements, and shark cartilage contains potentially toxic compounds linked to Alzheimer disease and amyotrophic lateral sclerosis. However, shark cartilage supplements remain popular on the basis of the misconception that sharks do not get cancer, popularized in the 1992 best-selling book Sharks Don't Get Cancer.
Tumors of many kinds, some metastatic, have been found in numerous species of sharks. The first shark tumor was recorded in 1908. Scientists have since discovered 40 benign and cancerous tumors in 18 of the 1,168 species of sharks. Scarcity of studies on shark physiology has perhaps allowed the myth to be accepted as fact for so many years.
While shark cartilage does not seem to be an effective treatment for cancer, some studies suggest that intake of one of its key components, chondroitin sulfate, may have positive effects on patients suffering from arthritis. That substance, however, is found in all animal cartilages, and not just that of sharks.
The ongoing consumption of shark cartilage supplements has been linked to a significant decline in shark populations, and the popularity of these supplements has been described as a triumph of pseudoscience and marketing over scientific evaluation.
Criticism and controversy
Proponents[who?] of shark cartilage are encouraged by anecdotal evidence from users as to its efficacy. The proponents[who?] also cite studies that show that shark cartilage has had some success in preventing angiogenesis, the growth of new blood vessels from pre-existing vessels. While angiogenesis is often a normal function, it is also consistent with the growth of malignant tumors. They[who?] argue too, that very little research (in the quantity and quality of studies) has been conducted, and thus the benefits cannot be scientifically disputed.
Opponents cite existing studies of shark cartilage on a variety of cancers that produced negligible to non-existent results in the prevention or treatment of cancer. Most notable among these was a breast-cancer trial conducted by the Mayo Clinic that stated that the trial "was unable to demonstrate any suggestion of efficacy for this shark cartilage product in patients with advanced cancer."  The results of another clinical trial were presented at the 43rd annual meeting of the American Society for Clinical Oncology. In that study (sponsored by the National Cancer Institute), "researchers did not find a statistical difference in survival" between patients receiving shark cartilage and those taking a placebo. Scientific evidence does not support the efficacy of shark cartilage nor the ability of effective components to remove cancer cells. The fact that people believe eating shark cartilage can cure cancer shows the serious potential impacts of pseudoscience.
Detractors also purport that previous beliefs in regards to sharks and cancer have been overturned, as forty-two varieties of cancer have now been discovered in sharks and related species. Also, many opponents[who?] feel that non-existent (or even limited) results do not justify the rampant over-fishing of many endangered species of sharks, further threatening their extinction.
The protein involved in inhibiting angiogenesis would have to be injected into the bloodstream to have any effect on the cancer in the body. When a patient takes shark cartilage orally the protein is digested before it reaches the area of the tumor. Not all cancers rely on angiogenesis for energy.
In the summer of 2004, Lane Labs, the manufacturers of BeneFin, was ordered to cease the promotion of BeneFin as a treatment or cure for cancer, as they had not conducted any research as to their claims for the product, much less reported any potential side effects. Thus, the FDA ordered Lane Labs to "pay restitution to all of its customers from September of 1999 to the present."
- Ostrander GK, Cheng KC, Wolf JC, Wolfe MJ (December 2004). "Shark cartilage, cancer and the growing threat of pseudoscience". Cancer Res. 64 (23): 8485–91. doi:10.1158/0008-5472.CAN-04-2260. PMID 15574750.
- "Shark Cartilage". American Cancer Society. November 1, 2008.
- Szabo, Liz (June 4, 2007). "Shark cartilage flounders; flaxseed shows promise". USA Today. Retrieved March 8, 2012.
- Mondo K, Hammerschlag N, Basile M, Pablo J, Banack SA, Mash DC (2012). "Cyanobacterial Neurotoxin β-N-Methylamino-L-alanine (BMAA) in Shark Fins". Marine Drugs 10 (2): 509–520. doi:10.3390/md10020509.
- O'Connor, Anahad (March 8, 2012). "Shark Cartilage May Contain Toxin". New York Times. Retrieved March 8, 2012.
- Natterson-Horowitz, MD., Barbara; Bowers, Kathryn (2012). Zoobiquity, What Animals Can Teach Us About Health and the Science of Healing. New York: Alfred A. Knopf. p. 44. ISBN 978-0-307-59348-1.
- "Sharks and Cancer". sharksavers.org. Retrieved 2013-06-22.
- "Efficacy and tolerability of chondroitin sulfate 1200 mg/day vs chondroitin sulfate 3 x 400 mg/day vs placebo.". US National Library of Medicine, National Institutes of Health. May 6, 1998.
- "Shark Cartilage Shows No Benefit as a Therapeutic Agent for Lung Cancer". University of Texas M. D. Anderson Cancer Center. June 1, 2007.
- Loprinzi CL, Levitt R, Barton DL, et al. (July 2005). "Evaluation of shark cartilage in patients with advanced cancer: a North Central Cancer Treatment Group trial". Cancer 104 (1): 176–82. doi:10.1002/cncr.21107. PMID 15912493.
- "Shark Cartilage, Not a Cancer Therapy". New York Times. June 3, 2007.
- Ostrander, G. K.; Cheng, KC; Wolf, JC; Wolfe, MJ (2004). "Shark Cartilage, Cancer and the Growing Threat of Pseudoscience". Cancer Research 64 (23): 8485–91. doi:10.1158/0008-5472.CAN-04-2260. PMID 15574750.
- "Facts endangering sharks: Cartilage". Shark Foundation, Foundation for research and the preservation of sharks. 26 January 2006.
- "Warning Against BeneFin". About.com. 26 January 2006.[dead link]
- Information on shark cartilage, from WebMD.com
- Shark Cartilage, American Cancer Society
- "Operation Cure.all" Nets Shark Cartilage Promoters, Federal Trade Commission