Shark Cartilage Receives IOM Draft Monograph

WASHINGTON--A draft prototype monograph was released Sept. 19 for shark cartilage, the controversial supplement that became popular after the book Sharks Don't Get Cancer (Avery Publishing, 1992) caught the public's eye. This is the second monograph released by the Committee on the Framework for Evaluating the Safety of Dietary Supplements, which falls under the Institute of Medicine (IOM). The draft serves as a compendium of shark cartilage's possible adverse events, as well as an overview of other issues, including how cartilage supplements are prepared. This and the other four monographs still to be published are not intended to evaluate the benefits of shark cartilage.

Worldwide, different species of shark are used for the cartilage found in these supplements. IOM reported that in North American-made supplements, the spiny dogfish shark is used, and in supplements imported into the United States, sharks from Asian-Pacific, Pacific equatorial and South American waters are used. Unlike shark fin soup, shark cartilage dietary supplements are prepared from the backbone and head cartilage of the shark. Different processing methods make compositions between supplements varied. Products come in forms ranging from liquids and tablets to enemas and suppositories, and there are no generally accepted dosages for preparations such as aqueous extracts and powder.

Based on the limited number of published clinical investigations for shark cartilage, evidence has not shown a direct association between use of this supplement and adverse event reports (AERs). Only one case report has been published discussing an AER of a possible link between liver damage and the supplement, although the preparation and amount used were unknown. Four AERs have been reported to the government's SN/AERS, including some where cartilage users cited side effects such as lymphoma and jaundice, although causality was not able to be proven. Non-serious AERs included gastrointestinal distress such as nausea, diarrhea and flatulence.

However, the monograph reported that there was clear evidence demonstrating shark cartilage has anti-angiogenic activity, which destroys or interferes with the fine network of blood vessels needed by tumors to grow and spread. Even though this is good news on the cancer front, it is bad news for reproduction since angiogenesis is critical for limb and skeletal formation of a fetus. Drugs with known anti-angiogenic activity have adverse events such as hypertension, depression and leukopenia, an abnormal decrease in white blood cells.

Safety concerns for shark cartilage products go beyond AERs. Shark cartilage has a high risk for contamination during the collection and processing periods. The cartilage may become contaminated when in contact with decomposing tissue or other shark byproducts, such as the liver and blood. This concern has already been recognized by the Food and Drug Administration (FDA), which sent an alert in 1996 to field personnel to detain shark cartilage powder preparations being imported into the country except from firms who had already provided the agency with quality control assurances.

Another safety concern is that products made from any sea creature, including sharks, may be contaminated with heavy metals such as mercury. Also, shark cartilage can become contaminated in the same vein as uncooked animal products. Batches of shark cartilage with a strong odor may be contaminated with squalamine, another anti-angiogenesis compound found in the shark's liver and blood. Because of the strong smell, some manufacturers use chlorine to cover the odor and bleach the cartilage. However, this practice could result in chemical contamination.

The monograph noted that, currently, one shark cartilage product is being used as an investigational new drug (IND), and not as a dietary supplement. Patients with advanced inoperable cancer are participating in trials using the IND. Besides cancer, shark cartilage products are being marketed for joint inflammation, athletic performance, diabetic retinopathy and skin conditions. According to Nutrition Business Journal, these supplements are the 19th most popular in the United States, logging $120 million in sales for 1999. In a 2001 Prevention magazine survey, 4 percent of 2,000 respondents said they had used shark cartilage supplements within the previous 12 months.

The draft in its entirety can be found here. Written comment regarding the draft will be open until October 6, 2002, and can be posted at www4.nas.edu/iom/fnbcomment.nsf/comment?openform.