• Shark skeletons are made almost entirely of cartilage.shark 2 image by cherie from Fotolia.com
  
  Shark cartilage is the main component of shark skeletons. Harvested from their heads and fins, it contains proteoglycans, glycoproteins as well as calcium salts and other proteins. It is sold as a capsule, powder or liquid under such brand names as Cartilade and BeneFin. Taking shark cartilage supplements is believed by some to be an alternative to conventional cancer treatments.
  
  

Claims

• Shark cartilage is said to contain proteins that stop the process of blood vessel development, also known as angiogenesis. Tumors rely on blood vessels to survive in the body, so the theory goes that when blood vessel development is inhibited, the tumor starves and shrinks or disappears. Osteoperosis, arthritis, macular degeneration, psoriasis and inflammation of the intestinal tract are also said to be helped by shark cartilage. It may be taken by mouth or as an enema, and manufacturers recommend that it be taken in doses as large as one cup per day.
  
  

Evidence

• Many studies on the effects of shark cartilage on cancer have not been published because their records of data is incomplete. No special benefit was found in a recent clinical trial testing shark cartilage versus a placebo in more than 80 patients with advanced-stage cancer. In general, researchers agree that the protein molecules found in shark cartilage are too large to be absorbed by the human digestive tract. One study showed that orally taken liquid shark cartilage extract slowed the growth of new blood vessels in healthy men; however, further tests did not show any overall effect on survival in patients suffering from various cancers.
  
  

Complications

• Since shark cartilage is sold as a dietary supplement and not a drug, the Food and Drug Administration does not regulate manufacturers' claims and ingredients as long as they do not claim that shark cartilage cures any specific disease. Most "dietary supplements" have also not been tested for adverse reactions with foods or drugs, and some may contain contaminants not listed on the labels. Allergic reactions are also possible, and although shark cartilage is not known to be toxic, it can cause nausea, indigestion or dizziness. It may also affect liver function, and growth and development in children. Pregnant women and people with low white blood cell counts should not take shark cartilage.