Several very different products are marketed as “shark cartilage,” including aqueous extracts of the homogenized cartilage, and the processing of powdered shark cartilage preparations may include extensive washing, soaking, and/or bleaching. These processes may deplete the product of any readily water-extractable components. While one aqueous extract and a powdered shark cartilage preparation are presently being used in clinical trials to investigate its antitumor potential, information about the composition of this or any other product is not currently available in the public domain. In the absence of information about the specific composition of a shark cartilage product, it must be assumed that adverse effects seen in one product apply to all products labeled as shark cartilage.
Human data: Shark cartilage dietary supplements are taken for a variety of conditions. Case reports occasionally mention nonserious side effects such as nausea, vomiting, diarrhea, constipation, and flatulence, but it is unclear whether such effects are due to the supplement, palatability issues, or placebo effects. Serious adverse effects, such as hepatotoxicity, have been anecdotally reported, but specific susceptibility, confounding causes, or other contributing factors were not adequately assessed in the reports. Serious adverse effects have not been observed in clinical trials of specific shark cartilage preparations, but most of these studies are in progress. The studies published to date have not been randomized, double-blind, placebo-controlled trials.
Animal data: Animal toxicity studies have been conducted using various types and amounts of shark cartilage preparations and using various routes of administration and laboratory animal species. Details of these studies are not published or available to assess the adequacy of animal toxicity; however, information from summaries and abstracts of nonpublished data do not indicate overt toxicity.
In vitro data: Shark cartilage extracts have been shown to inhibit angiogenesis in cell culture experiments. Extracts specifically inhibit the proliferation of endothelial cells in culture media and inhibit the activities of vascular endothelial growth factor and basic fibroblast growth factor in accepted assays for angiogenesis. In vitro studies and other data also demonstrate that shark cartilage powder and extracts possess matrix metalloprotease inhibitors; inhibition of metalloproteinases inhibits angiogenesis. Antiangiogenesis activity of shark cartilage has been confirmed in chick embryonic chorioallantoic membrane (CAM), an accepted assay for angiogenesis. There are no published studies demonstrating antiangiogenic activity in whole animals using shark cartilage via the oral route.