What Is It?
Cat's claw, also known as Uno de Gato csp (its Spanish name), is a high-climbing, woody vine that grows profusely in the upper Amazon regions of Peru, Columbia, Ecuador, and other South American countries. At the base of the plant's leaves are two curved thorns that resemble the claws of a cat (hence its name); these allow the vine to climb up trees and other vegetation into the forest canopy. The herb's botanical name, Uncaria, is from the Latin uncus, for "hook."
Two species of cat's claw are harvested for medicinal purposes, Uncaria guianensis, used mainly in Europe, and Uncaria tomentosa, commonly imported into the United States. Among the herbal practitioners of South America, the two species are considered interchangeable.
For hundreds of years, people in the Amazon basin have used cat's claw to treat a broad range of ailments, ranging from cancer, arthritis, and stomach and liver disorders to skin conditions and even contraception. Traditionally, the herb's primary medicinal form has been a decoction, or crude extract, prepared by boiling the inner bark of the stem and parts of the root.
Scientific interest in cat's claw centers on the plant's immune-boosting and anti-inflammatory properties. There is early and speculative evidence that cat's claw may have antiviral and cancer-fighting potential as well.
In recent years researchers have identified two separate subspecies of U. tomentosa, which have important differences in their chemical properties. One contains mainly pentacylic alkaloids, substances responsible for the most well-researched effect of cat's claw, namely immune stimulation. The other type of U. tomentosa contains tetracylic alkaloids, which affect the brain and central nervous system and actually counteract the immune-stimulating effects of the pentacylic group.
In the mid-1990s, once it became known that cat's claw had potential value for the treatment of serious conditions such as cancer, arthritis, and even HIV infections, it became one of the top-selling herbs in the United States. Unfortunately, this enthusiasm was not backed up by much clinical evidence. Very few well-designed clinical trials with human subjects have been done on cat's claw, but some laboratory and animal studies have been conducted.
Most of the anecdotal evidence (word of mouth only) indicates that it may help to improve inflammatory problems such as osteoarthritis (OA) and prostatitis, immune disorders such as lupus and rheumatoid arthritis (RA), and situations in which a stronger immune system is desired, such as cancer and HIV. On the other hand, some herbal researchers also point out that long-term use of cat's claw might overstimulate the immune system and do more harm than good for some of these conditions.
According to a 2001 article in Alternative Medicine Review, cat's claw also warrants further research because of the worldwide concern over viral diseases. Although these areas have not been fully explored, some experts believe that cat's claw may eventually have potential in fighting chronic viral infections such as AIDS, and also in combating cancer and immune-related conditions associated with aging.
Specifically, cat's claw may help to:
Reduce inflammation. In several laboratory experiments, cat's claw has been shown to demonstrate anti-inflammatory effects; few clinical studies of these properties have been conducted, however. One small four-week trial, reported in the 2001 Inflammation Research journal, found that 30 people with OA of the knee had significant relief from pain during daily activities but no easing of nighttime pain or pain during rest; the control group had no pain relief at all. A number of other inflammatory conditions are also being investigated in association with cat's claw, including allergies and asthma, Crohn's disease, rheumatoid arthritis, bursitis, and tendinitis.
Support cancer therapy. In Germany and Austria, standardized extracts of cat's claw, available by prescription only, are given to some cancer patients under a doctor's care. As an immune-boosting agent, cat's claw may strengthen the general health of people undergoing chemotherapy, radiation, or other treatments for cancer, although this effect has not been thoroughly proven. It is not known whether forms other than standardized extracts would be beneficial for cancer patients.
--In Germany and Austria, the standardized extract of cat's claw is available only by physician's prescription, and it is used almost solely to stimulate a patient's immune system. Recently, the Austrian product, known as Immodal, was sold to a U.S. supplement manufacturer and is available under the brand name Saventaro. The root bark and stem are imported from South America and manufactured according to Austrian standards.
--Purchase only products that label the plant's species as Uncaria tomentosa. A common plant found in the American Southwest, acacia greggi, is also called cat's claw, but it is highly toxic. Some unscrupulous marketers try to pass it off as the real thing.
--Look for products certified to contain only the pentacylic form of Uncaria tomentosa. The standardized extract (sold under the brand name Saventaro) contains a minimum of 1.3% pentacylic oxindole alkaloids (POAs) and is free of tetracylic oxindole alkaloids (TOAs).
For osteoarthritis: Take 1 capsule or 15-30 drops of liquid extract twice a day.
For cancer support: Take 1 capsule 3 times a day for the first 10 days, and 1 capsule daily thereafter.
Guidelines for Use
Take cat's claw between meals.
If you are taking high blood pressure medication, cat's claw can increase its action, which can be dangerous.
Possible Side Effects
Mild nausea may occur if you take a crude extract or use cat's claw tea.
There have been no reports of toxicity when cat's claw is taken at recommended dosages. However high doses may cause diarrhea, bleeding gums, excessive bruising, and a dangerous drop in blood pressure.
Never take cat's claw if you are pregnant, lactating, or are even considering pregnancy. It may bring on a spontaneous miscarriage.
Do not take cat's claw if you have high blood pressure.
Some, but not all, herbalists recommend against using the herb in any condition which may be adversely affected by an overstimulating the immune system. These might include autoimmune disorders, such as lupus or multiple sclerosis.
Avoid cat's claw if you have had, or are scheduled to have, an organ or tissue transplant