Shark Cartilage FAQs
What is cartilage and what is it used for?
Cartilage is a flexible connective tissue that forms the skeleton of sharks and parts of the skeletons of other animals. Traditionally, shark cartilage has been eaten as a food and health supplement in the Far East. Commercial shark cartilage supplements are primarily composed of chondroitin sulphate, a key component in human cartilage that is essential to joint health. Shark cartilage is believed to help a variety of conditions, including arthritis, shingles, rheumatism, haemorrhoids, psoriasis and inflammatory disorders. One of the most commonly suggested uses of shark cartilage is to help treat cancer.
Shark cartilage and cancer
The promotion of cartilage to treat cancer has arisen from the false claim that sharks, which have cartilaginous skeletons, do not suffer from cancer. Cartilage naturally has few blood vessels, and cartilage from all species rarely develops malignant tumours; this appears to be due to substances in cartilage inhibiting angiogenesis (see box for explanation [1]) . Consequently, claims have arisen that solid forms of shark cartilage may be efficient in the treatment of human cancer. Several studies over the last 30 years have attempted to assess the effect of cartilage in cancer treatment. Most of these studies have been viewed with scepticism due to a lack of rigorous trials, and in rare cases where a significant number of patients were involved in a trial, no consistent improvement was observed [2].
Two large glycoproteins (sphyrnastatin 1 and 2), identified in hammerhead shark cartilage, have been found to have anti-angiogenic properties that could in theory be helpful in the treatment of cancer [3] . However, large glycoproteins are normally broken down in the body, rather than absorbed, so they are unlikely to reach the bloodstream when cartilage is administered orally. Furthermore, commercially available supplements contain varying amounts of cartilage, and contain binding agents that do not have anti-angiogenic properties [4]. The potential for the active components of cartilage to inhibit angiogenesis in human cancers depends on whether their biological activity can be preserved following their extraction, and used in a treatment that delivers an effective concentration of the active substance to target tissues [2].
To date only one extract – AE-941 (Neovastat), which was developed as a pharmaceutical and is NOT a commercially available supplement – has been through both laboratory trials and clinical in-patient trials, with the following result: “In the first study of its kind, shark cartilage extract, AE-941 or Neovastat, has shown no benefit as a therapeutic agent when combined with chemotherapy and radiation for patients with advanced non-small cell lung cancer” [5]. In short, no scientific studies by independent researchers using proper controls have been able to substantiate claims that shark cartilage supplements are effective in treating human cancer. Similarly, there is no published experimental data to suggest unprocessed shark cartilage supplements are effective in the plethora of other conditions that they are used to treat.
Processing, trade and markets
Cartilage may be boiled and sun-dried, frozen, or dried using industrial fan driers, depending on the scale of the operation. Cartilage of the vertebrae and fins are commonly used, but jaws and head may also be processed. Cartilage is commonly procured from Spiny Dogfish, Tope and hammerhead sharks. The cartilage of Blue Sharks is also valued for its consistency. Cartilage from different species is usually sold in products of similar strength and the source is not usually named. In general cartilage is a byproduct of shark fisheries and the shark fin trade so species composition reflects fisheries catch [6].
In 1995 the global market for shark cartilage was worth over US$30 million, with over 40 products on the market [7]. Shark cartilage products are commonly sold over the internet, but are also sold in health food stores, including Holland and Barrett. In the UK, cartilage is sold as a food supplement, and not as a drug. In Europe cartilage is commonly available but there is little information available on source of supply. In America there are several companies manufacturing shark cartilage powder, which is sold worldwide under various brand names [8]. Trade data are often unavailable due to the nature of the market and lack of regulatory procedures. Tracing trade and assessing the volume of production is difficult as although a relatively small number of companies manufacture cartilage powder, these may purchase cartilage from a variety of domestic or overseas sources including vessels, processors, shark fin dealers or other sources that handle these products. They may also supply ground cartilage to other domestic or overseas companies. Research by TRAFFIC suggests major producing nations include the USA, Japan and Australia.
Shark cartilage is not unique; mammal and bovine cartilage also have similar properties, yet as sharks have entirely cartilaginous skeletons they are seen to represent a more viable source for pharmaceutical use. Shark cartilage is less valuable than other shark products – one report lists the financial returns from a 23kg shark as follows: cartilage US$2; fins US$25; meat US$12.508 [8]. As a result it is argued that cartilage products are a by-product and are not a major driver of the shark fishing industry. However, commercial products provide added incentive for unsustainable shark fisheries, and serve to boost the value of dead sharks rather than encourage the value of live sharks. Although the Shark Trust supports full utilisation of sharks landed, unsustainable shark fishing is a threat to shark populations worldwide, and the sale of products from such fisheries threatens to deplete vulnerable species.
UK health food retailer Holland and Barrett have announced they will no longer be selling shark cartilage due to large public opposition; the product is now no longer available in shops or on their website.
Holland and Barrett stated in June 2007 that their shark cartilage product was sourced from Spiny Dogfish (Squalus acanthias), a species listed in the 2006 IUCN Red List assessment as globally Vulnerable, with North Atlantic, North Pacific and South American stocks all Threatened (Vulnerable, Endangered or Critically Endangered).
In August 2007, Holland and Barrett stated that while their product had historically been a by-product of the Spiny Dogfish, it was now a by-product of the Blue Shark (Prionace glauca). In the 2006 IUCN Red List assessment the Northeast Atlantic population of the Blue Shark was listed as Vulnerable, which means it is considered to be facing a high risk of extinction in the wild. The Blue Shark is a highly migratory species; records from the Atlantic show regular clockwise migration with the prevailing currents [9], therefore it is likely that the entire Atlantic population of Blue Sharks is under threat of extinction. Blue Sharks are among the most heavily fished sharks in the world, and are often caught as bycatch. As with most sharks, the species is slow to grow and reproduce, making it highly vulnerable to overfishing, and slow to recover once depleted.
A customer services representative at Holland & Barrett went on to state that, “Holland & Barrett takes the threat and welfare to endangered species very seriously and would not be selling any product that contained a by-product of an endangered shark”. However, the letter continued to say that, “Holland & Barrett will continue to sell shark cartilage due to customer demand, until such time that the species is classed as an endangered species”. The Shark Trust responded to this statement to ensure that Holland & Barrett was aware of the conservation status of both the Spiny Dogfish and Blue Shark.
There are also many other retailers who stock shark cartilage and the Shark Trust will continue to approach these companies about the sustainability of this product, so please check our website for campaign updates.
References
1. Alsner J and Overgaard J (1998) The effect of shark cartilage extracts on the growth and metastatic spread of the SCCVII Carcinoma, Acta Onologica 37.
2. Gingras D, Renaud A, Mousseau N and Beliveau R (2000) Shark cartilage extracts as antiangiogenic agents: smart drinks or bitter pills?, Cancer and Metastasis Reviews 19: 83-86
3. Ernst E and Cassileth BR (1999) How Useful are Unconventional Cancer Treatments?, European Journal of Cancer 35 (11)
4. Holt S (1995) Shark cartilage and neutriceutical update, Alt Compl Ther 1: 414-416, cited in Ernst (1998) Shark cartilage for cancer?, The Lancet 351: 298
5. Science Daily, 4 June 2007, www.sciencedaily.com/releases/2007/06/070603215346.htm
6. Rose DA (1996) An overview of world trade in shark and other cartilaginous fishes. TRAFFIC International. 106pp
7. Ernst E (1998) Shark cartilage for cancer?, The Lancet 351: 298
8. Rose DA (1996) An overview of world trade in shark and other cartilaginous fishes. TRAFFIC International. 106pp
9. Leonard J. V. Compagno (1984). Sharks of the World: An annotated and illustrated catalogue of shark species known to date. Food and Agriculture Organization of the United Nations, 521-524, 555–61, 590.
|
