Claw-like thorns are what gave the South American climbing vine its name—cat's claw. Also known as una de gato, cat's claw first emerged on the international herb market in the 1980s, but it was hardly a "new" herb—the rain forest tribes of the Amazon basin have been using it for thousands of years to treat everything from cancer to arthritis. Now, new research has documented the botanical's ability as an immune booster and anti-inflammatory.
There are 14 species of cat's claw, but the botanical commonly sold for medicinal purposes as cat's claw is Uncaria tomentosa, which grows in the highland jungles of Peru. Occasionally the species Uncaria guianensis has been marketed under the same name, but it doesn't contain the same alkaloids that are responsible for many of Uncaria tomentosa's apparent benefits.
Recent research on cat's claw has led to several U.S. patents on its immuno-stimulating effects, and even to a cat's claw symposium sponsored by the World Health Organization. This greater recognition has led to widespread availability of the herb, but also to overharvesting of the root, which threatened the viability of the species in its native habitat. Research shows that the vine bark is as high in essential compounds as the root and can safely be harvested without destroying the plant itself, which is now protected in Peru.
Cat's claw's ability to stimulate immune function has been the most-studied of the plant's many uses. In addition to general immune support, cat's claw has been suggested by many herbalists, particularly in Europe, as a cancer remedy and as an adjunct to AZT treatment for HIV. The active constituents of the plant that impact the immune system appear to be six or more pentacyclic oxindole alkaloids, including isopteropodine, pteropodine, mitraphylline and isomitraphylline. Evidence suggests that even relatively small amounts of these compounds can significantly increase immune function. In vitro studies have shown these alkaloids to stimulate phagocytosis, in which immune cells ingest and digest microorganisms and cell debris (Planta Medica, 1985). Animal studies conducted on mice given cat's claw extract have shown increases of up to 40 percent in immune cell activity.
In addition, several of the oxindole alkaloids have documented antileukemic properties, and in vitro studies of the bark extract suggest antitumor and antimutagenic properties as well. One study showed that cat's claw extract in vitro is a potent antimutagen in relation to breast cancer cells (Anticancer Research, 2001). Another study suggested that cat's claw can inhibit the growth of both leukemia and lymphoma cells (Anticancer Research, 1998). Though not a published study, a European clinical trial suggested that cat's claw was effective in reducing many of the symptoms, including weight loss, nausea and hair loss, associated with chemotherapy and other allopathic therapies.
In addition, its immune-enhancing and antiviral properties may have a positive effect on viral diseases such as herpes and shingles (Alternative Medicine Review, 2001).
Though less well-known by the public, cat's claw's ability to fight inflammation rivals its immuno-stimulating properties. Some of this effect is due to sterols that function as antioxidants, but the primary active ingredients in regard to inflammation appear to be phytochemicals known as quinovic acid glycosides. In vitro studies and in vivo tests involving mice have suggested that these compounds can provide as much as a 70 percent reduction of inflammation.
One recent double-blind, human study showed cat's claw to be much more effective than a placebo in treating painful joints related to rheumatoid arthritis (Journal of Rheumatology, 2002), while another showed success in reducing pain associated with osteoarthritis of the knee (Inflammation Research, 2001). These studies support traditional use, which recommends cat's claw for inflammation of the joints associated with arthritis and rheumatism, as well as for gastritis—which is essentially an inflammation of the stomach lining—and acne.
Capsules and tinctures are the most common methods of ingesting cat's claw. It does not appear to be toxic, even in relatively high dosages. In capsule form, 500 mg to 1 gram of the dried herb daily are suggested for general immune benefits, while for bowel problems and arthritis, dosages of 3 to 4 grams daily are not uncommon. Higher dosages should not be continued indefinitely and should be monitored by a health professional.
Cat's claw was traditionally used as a method of birth control (though only in extremely high doses) and to cause miscarriage in cases of unwanted pregnancy. Given this history, it's essential that cat's claw not be used by pregnant women. The herb is also contraindicated in people suffering from autoimmune illness (such as lupus), multiple sclerosis and tuberculosis.
Mitchell Clute is a poet, musician and freelance writer based in Louisville, Colo.
Natural Foods Merchandiser volume XXIV/number 1/p. 48-9