Natural Products from the Sea: Ethnopharmacology, Nutrition and Conservation

Townsend Letter for Doctors and Patients, Feb, 2001 by Tim Batchelder

Shark cartilage is taken to ease the pain and inflammation of arthritis, osteoarthritis, and other bone and joint ailments. Intestinal inflammations such as enteritis may respond to shark cartilage supplementation. Shark cartilage is also a popular alternative treatment for cancer, taken both to slow the growth of existing tumors and in smaller daily doses to prevent new cancers.

Canadian researchers found that a topical shark cartilage preparation had an anti-inflammatory effect when applied to the forearms of subjects, suggesting a potential role in the treatment of the common inflammatory skin condition psoriasis (Dupont 1998). Brazilian researchers using mice for subjects demonstrated a dose-dependent pain-relieving effect for shark cartilage.

A series of studies in 1998 have produced mixed results on the use of shark cartilage as an anti-cancer supplement. At high doses of as much as 1 g of shark cartilage supplement per kilogram of bodyweight, taken orally in three divided doses for six weeks, some studies have not found beneficial effects. However, this may be due to the low life expectancy of the study population. (Horsman 1998, Miller 1998)

Shark cartilage is known to contain glycoprotein compounds that strongly inhibit the process of angiogenesis, which is the growth of new blood vessels. Anti-angiogenic compounds have garnered increasing scientific attention among cancer researchers because these substances can potentially retard the growth of existing cancerous tumors by denying them the necessary blood-derived nutrients and oxygen. Inhibiting the development of new blood vessels may also account for shark cartilage's healing actions on joint, bone, and skin conditions. (Sheu 1998) Shark cartilage's effects may also be due to the immune-boosting action of its polysaccharide components. (Fontenele 1997)

Capsules and tablets range from approximately 250 to 800 mg. Shark cartilage is also available as a powder and "liquivial" extract. Prominent shark cartilage companies use cartilage from sharks caught for food, or from nonendangered shark species such as spiny dogfish. Shark steaks are a popular seafood but do not contain significant levels of cartilage.

Squalene

Squalene is an unsaturated hydrogen/carbon compound (a terpene) that is widely distributed in nature. It occurs in high concentrations in the oil derived from the livers of certain deep-sea sharks and in olive oil. Squalene is widely distributed in human tissues, most prominently in human sebum, the oily lubricant secreted by the skin's tiny sebaceous glands. Squalene supplements taken orally are a promising anti-cancer agent, although human trials have yet to be performed that could verify its usefulness in cancer therapy. As an ingredient in bodycare products squalene is an effective moisturizer, wrinkle remover, and wound healer. (see Kelly 1999 for a review of the clinical use of squalene.)

People take squalene to enhance the function of the immune system and to promote resistance to cancer. Researchers believe that squalene may be the constituent of olive oil that is responsible for the reduced cancer and mortality rates among populations, such as some traditional Mediterranean societies, that consume lots of olive oil. (Newmark 1997) Animal studies suggest that squalene can lower blood levels of fats and cholesterol, and a recent human study found that squalene promoted the effectiveness of a statin-type cholesterol-lowering drug. (Chan: 1996) Topically squalene is used to soothe and soften rough and dry skin and to promote the healing of wounds and sores.