Cartilage extracts are just what you think they are – from sharks (the fins are typically used), while cartilage from the trachea (windpipe) of cows is used in bovine cartilage supplements. The cartilage is then pulverized, powdered and packed into capsules with various claims made for preventing/treating cancer, promoting wound healing, and relieving the pain and stiffness of arthritis.
Cartilage consumption has been linked to healing of connective tissue injuries since the middle part of the century (much as HCP/gelatin, glucosamine and chondroitin are today). In the early 1980s, cartilage extracts became a popular alternative treatment for reducing the pain and stiffness associated with arthritis (although gelatin, SAMe and glucosamine all appear to be more effective in this regard). Today, the most common use of cartilage supplements is as a cancer treatment. As the theory goes, cartilage supplements inhibit tumor growth by inhibiting angiogenesis (growth of new blood vessels) and “choking off” the blood supply that the tumor needs to survive and grow. This popular, but unproven, theory generated a wave of media attention in the 1980s following publication of a popular pseudo-scientific book entitled, “Why Sharks Don’t Get Cancer” (but they actually do).
At this time, cartilage extracts do not appear to provide significant value as a dietary supplement. As research into this area progresses, perhaps new findings will provide evidence of cartilage extracts in preventing angiogenesis in cancer patients (an experimental new drug derived from shark cartilage, Neovastat, is under investigation as an anti-tumor agent). Until then, consider other supplements with proven benefits in joint health/wound healing (HCP/Gelatin, SAMe, glucosamine and chondroitin) and cancer prevention (green tea and soy isoflavones).
Cancer tumors generally need new blood vessels to grow, and some researchers have theorized that cartilage, which does not have blood vessels, might be a cancer preventive. Shark cartilage is known to harbor certain compounds that seem to slow down the growth of the new blood vessels needed for tumors to grow and spread. Several processes are thought to be involved. First, shark cartilage interferes with a group of enzymes known as matrix metalloproteases (MMPs), which are thought to be secreted by tumors to break down surrounding tissue and allowing the tumors to spread. Vascular endothelial growth factor activity (which promotes the formation of new blood vessels) is low shark cartilage. Some rodent studies have used injected shark cartilage extracts and have shown promising initial results (Horsman et al. 1998) – but when shark cartilage is taken by mouth, not enough of the active ingredients may be absorbed from the gastrointestinal tract to be very effective. Controlled studies of either oral or injected products in patients with advanced cancer that had been treated with conventional drugs, however, did not demonstrate effectiveness from shark cartilage in producing complete or partial responses (Miller et al. 1998). No studies involving patients with less advanced or previously untreated cancer have been published, but clinical research is ongoing.
Although there is certainly no shortage of testimonials for “miracle” cartilage products that “cure” cancer, the scientific evidence for such effects is lacking. Despite shark and bovine cartilage supplements being touted as cancer cures, careful scientific study in people with advanced tumors have shown these claims to be wildly optimistic at best and completely bogus in many cases. It is interesting to note, however, that for all the outlandish and unsubstantiated claims for shark cartilage to “cure” cancer, a growing number of laboratory and early-stage clinical studies (Davis et al. 1997) indicate that shark cartilage does indeed contain compounds which can inhibit tumor angiogenesis (growth of new blood vessels to feed the tumor). This means that something in cartilage prevents the growth of new blood vessels toward tumors, thereby restricting tumor growth. The inhibitor is probably not a typical protein, but may be a heat-stable form of proteoglycans (long chains of sugars and amino acids). Whatever this factor happens to be, it turns out that there is quite a lot of it in shark cartilage compared to cartilage from mammalian sources (such as cows). A major problem with the shark cartilage theory of tumor prevention, however, has always been the lack of clinical proof that this anti-angiogenesis factor could even get into the body when consumed as a dietary supplement.
However, studies reported recently suggest that oral administration of liquid cartilage extract delivers a similar anti-angiogenic effect in humans that has previously been observed in lab animals and test tube studies (Berbari et al. 1999). In one study, subjects (29 healthy males) received either a placebo or a liquid shark cartilage extract (7-21ml) each day for 3-4 weeks (Berbari et al. 1999). Midway through the supplementation period (day 12), a special sponge was inserted subcutaneously (under the skin of each subject’s arm) and removed on Day 23. Researchers then counted the number of cells which had grown into the sponge as an indirect measurement of angiogenesis. Results from the study found that cell density was significantly lower in subjects who had received the liquid cartilage extract compared to subjects who had received the placebo. These results are the first to show that the anti-angiogenic component of cartilage extracts is bioavailable in humans by oral administration and that oral intake of such extracts can actually reduce blood vessel growth in the body. The next step will be to conduct controlled clinical trials in cancer patients to see whether cartilage extracts can indeed “choke off” cancerous tumors (as those underway for the experimental drug, Neovastat are attempting to do) and live up to the claims made for many of the supplement currently on the market (Batist et al. 2002).
Although no specific safety studies have been conducted on cartilage extracts, the doses commonly suggested are not expected to cause any significant side effects (or dramatic benefits). In some isolated cases, bovine tracheal cartilage has been associated with contamination by thyroid tissue (the trachea is located adjacent to the thyroid gland) and could potentially lead to thyroid hormone toxicity. For patients who do choose to supplement with cartilage extracts, typical dosage suggestions are likely to be in the range of 250-1000mg/day although significant differences may exist between products.
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EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.