What is shark cartilage?
Just what its name implies: Shark cartilage is simply the skeletal material of a shark. But many people believe this substance does far more than keep ocean creatures together. Ever since the book Sharks Don't Get Cancer hit the market, shark cartilage has been touted as a powerful cancer fighter in human beings. People also take cartilage in hopes it will relieve the pain and inflammation of arthritis.
Cartilage supplements are available in pills, powders, and liquid extracts, among other forms. If you prefer, you can receive your shark skeleton via enemas, intravenous infusions, or injections under the skin, into the abdomen, or between muscles. But before you rush to your health food store, you should take a close look at what shark cartilage can and can't do.
Can shark cartilage help fight cancer?
The phrase "sharks don't get cancer" has become a rallying cry among people who package and sell shark cartilage. A more accurate, if less stirring, phrase would be "sharks do get cancer, but nobody knows exactly how often." According to the National Cancer Institute and the University of Pennsylvania, sharks have been known to suffer from melanomas, sarcomas, brain tumors, cancer of the blood, and even cancer of the cartilage.
Of course, the fact that sharks do get cancer doesn't necessarily mean the supplements are worthless. There is even some reason for optimism. Since the 1970s, many test-tube and animal studies have found that shark cartilage can stop or slow the growth of the blood vessels that feed tumors. (In a study that made headlines in 1998, Dr. Judah Folkman of Children's Hospital in Boston found that the drugs angiostatin and endostatin could shrink tumors in mice through the same mechanism.) Cartilage may also be able to ward off cancer by preventing damage to the genetic material in healthy cells.
Unfortunately, the triumphs of shark cartilage in the laboratory have not translated well to treatment of the human body. A Cuban study covered on 60 Minutes found that many cancer patients "felt better" after taking shark cartilage, but the National Cancer Institute called the study "incomplete and unimpressive." A more recent and thorough study of 379 lung cancer patients, funded by the National Center for Complementary and Alternative Medicine and the National Cancer Institute, found that shark cartilage supplements did not improve overall survival rates. A 2005 study of 88 patients with advanced colorectal or breast cancer similarly found no benefit, although the study was stopped early because half the patients couldn't stomach the supplement.
After over two decades of such studies, there's still no clear-cut evidence that shark cartilage can fight cancer in humans.
Can shark cartilage ease arthritis?
Scientists have scarcely studied the ability of shark cartilage to ease arthritis, but they have taken a close look at one of its key components: chondroitin sulfate. This compound is an alternative-healing phenomenon in its own right, although the chondroitin sulfate in supplements at your health food store often comes from cows instead of sharks.
Research to date suggests that chondroitin sulfate may have some curative powers. A study of 120 patients at the Centre Hospitalier Universitaire in Toulouse, France, found that those who took the compound for three months felt less joint pain and took fewer pain relievers than patients who took a placebo. A similar study of 87 patients with osteoarthritis of the knee conducted at Pitii Salpjtrihre Hospital in Paris found that chondroitin sulfate eased pain, and both the patients and their doctors noticed overall improvement in their condition.
Since one of its components seems to help patients with arthritis, it makes sense that shark cartilage would be beneficial to sufferers. But for arthritis relief, it might make more sense to buy your chondroitin sulfate straight. Be aware that it can cause gastric pain and nausea in some cases.
Is shark cartilage dangerous?
Nobody has studied the long-term effects of shark cartilage, but the majority of people seem to tolerate the supplement in small doses. Some do experience side effects, which can include nausea, vomiting, dizziness, abdominal cramps and bloating, constipation, fever and fatigue. It may also lower blood pressure and raise blood sugar levels. Taking shark cartilage can lead to an overload of calcium in the blood, particularly if you use calcium supplements. There was also one report of hepatitis occurring in someone who took shark cartilage.
For some people, shark cartilage isn't worth the risk. According to a report from the University of Pennsylvania, children and pregnant women should avoid the supplement because it could slow the normal growth of children and fetuses. People who have recently had surgery are also advised not to take it, as it may slow healing. Finally, having a shark-cartilage enema could trigger a life-threatening infection in those with a low white blood cell count.
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Mazieres B; Loyau G; Menkes CJ et al. Le chondroitine sulfate dans le traitment de la gonarthrose et de la coxarthrose. Rev Rhum Mal Osteartic 59:466, 1992.
National Cancer Institute. Cartilage (Bovine and Shark). February 2006.
National Cancer Institute. Questions and Answers About Cartilage (Bovine and Shark). August 2007.
American Cancer Society. Shark Cartilage. June 2005.
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National Center for Complementary and Alternative Medicine. Shark cartilage supplement does not extend the lives of lung cancer patients. October 2007.