There are no scientifically proven benefits to using shark cartilage, but there are many negatives regarding the endangered status of sharks and their welfare. GNC gets their cartilage from Australia, where sharks are often caught, have their fins cut off, and are left to drown mercilessly. Also, the overfishing of sharks could cause major ecological problems, including an overabundance of their prey, and a decline in shellfish. The false statements that shark cartilage promotes joint health and that it acts as a tumor suppressant are unfounded in scientific studies. The only studies that found a positive correlation were non-random. There is no need for the suffering of sharks and the ecosystems they are part of, and GNC should not support the shark fishing industry.
Loprinzi, C. et al. 2005. Evaluation of shark cartilage in patients with advanced cancer. Cancer, 104.1, 176-182. (http://onlinelibrary.wiley.com/doi/10.1002/cncr.21107/full)
Miller, DR., Anderson, GT., Stark JJ., Granick, J.L., Richardson, D. 1998. Phase I/II trial of the safety and efficacy of shark cartilage in the treatment of advanced cancer. Journal of Clinical Oncology, Vol 16, 3649-3655 (http://jco.ascopubs.org/content/16/11/3649.short)
William D. Robbins, Mizue Hisano, Sean R. Connolly, J. Howard Choat, Ongoing Collapse of Coral-Reef Shark Populations, Current Biology, Volume 16, Issue 23, 5 December 2006, Pages 2314-2319, ISSN 0960-9822, 10.1016/j.cub.2006.09.044.