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Other Common Name(s): una
de gato
Scientific/Medical Name(s):
Unicaria tomentosa
Description
Cat's claw is a woody vine that winds its way up trees at
higher elevations in the Peruvian rain forests. The plant's name comes
from the claw-like thorns that grow on the plant's stem, which can
reach up to 100 feet. The root (which can grow to the size of a
watermelon) and the inside of the bark are the parts of the plant used
in herbal remedies. Because demand for this herb has increased greatly
in the past few years, the Peruvian government now forbids harvesting
the roots of the plant. Since the same compounds are present in the
bark as the root, the plant is now harvested 3 feet above the ground.
This preserves the plant so that it can be harvested again a few years
later.
Overview
Cat's claw has been promoted as a remedy to boost the body's
immune system, but available scientific evidence in humans does not
support claims of immune-stimulating effects. Available scientific
evidence also does not support cat's claw's effectiveness in preventing
or treating cancer or any other disease. There are some serious side
effects associated with cat's claw although the extent of these effects
is not known.
How is it promoted for use?
The most common claims for cat's claw are that it boosts the
immune system and increases the body's ability to fight off infections,
including yeasts, parasites, and herpes, as well as other viruses. The
herb also is promoted as a remedy for arthritis, allergies,
inflammatory bowel disorders, cancer, cardiovascular disease, diabetes,
asthma, and menstrual disorders. South American folk medicine holds
that cat's claw is a contraceptive, and some practitioners claim that
it can significantly decrease AIDS-related symptoms. Available
scientific evidence does not support these claims.
What does it involve?
Cat's claw is taken by mouth and is available in capsules,
tablets, tinctures, elixirs, and tea. Sometimes it can be found as a
cream. Practitioner recommendations for how much to take vary widely.
Some suggest a dosage of 3,000 to 6,000 milligrams (mg) per day in pill
form, or 4 strong cups of tea. Herbalists may prescribe up to 20 g per
day for seriously ill patients. Because herbs are not regulated in the
United States, different brands of cat's claw may contain very
different amounts of active ingredients.
What is the history behind it?
For centuries, South American native tribes have used cat's
claw medicinally. Awareness of the herb grew in the United States and
Europe during the 1970s when an Austrian Scientist, Klaus Kiplinger,
traveled to the rain forests of Peru and learned about the plant from
local priests. Kiplinger eventually received patents for isolating the
active ingredients within the herb. Recently, cat's claw has become an
extremely popular herbal supplement among consumers in the United
States and Europe.
What is the evidence?
Rigorous scientific study of cat's claw in humans is not
available. The reported positive effects of the herb are either
individual reports (anecdotal) or the result of lab experiments.
Researchers have found chemicals in cat's claw called
alkaloids. One Canadian lab study concluded that some of the alkaloids
can stimulate the white blood cells of rats. Similar studies found that
the alkaloids increase phagocytosis, the process in which white blood
cells seek out and destroy invading germs. Also found were
antioxidants--compounds that block the action of activated oxygen
molecules, known as free radicals, which can damage cells.
Certain alkaloids (organic compounds) that are present in
cat's are thought reduce inflammation, slow the heart rate, slow the
growth of tumors, and possibly lower blood pressure. Human studies have
not yet confirmed that cat's claw, or its extracts, has any of these
actions. Peruvian researchers in the 1970s claimed that cat's claw was
an effective treatment for children with leukemia, but available
scientific evidence does not back up those reports. A 2006 laboratory
study suggested this plant is not effective in killing leukemia cells,
and may actually help the leukemia cells to survive longer.
Animal and lab studies may show promise, but further studies
are necessary to find out if the results apply to humans. Until
clinical trials in humans are completed, the true value of cat's claw
remains uncertain. Available scientific evidence does not support
claims that this herb can treat cancer or other diseases in people.
Are there any possible problems
or complications?
These products are sold as a dietary supplement in
the United States. Unlike drugs (which must be tested before being
allowed to be sold), the companies that make supplements are not
required to prove to the Food and Drug Administration that their
supplements are safe or effective, as long as they don't claim the
supplements can prevent, treat, or cure any specific disease.
Some such products may not contain the amount of the
herb or substance that is written on the label, and some may include
other substances (contaminants). Actual amounts per dose may vary
between brands or even between different batches of the same brand.
Most such supplements have not been tested to find
out if they interact with medicines, foods, or other herbs and
supplements. Even though some reports of interactions and harmful
effects may be published, full studies of interactions and effects are
not often available. Because of these limitations, any information on
ill effects and interactions below should be considered incomplete.
More research is needed to be sure that cat's claw is safe.
Thus far, animal studies suggest that it is unlikely to be very toxic
to humans. Mild rash, lowered blood pressure, sleepiness, and diarrhea
may be possible.
Herbalists warn people who are taking blood pressure
medicines, blood thinners (anticoagulants), hormones, or insulin not to
take cat's claw. This herb may also affect a common route by which the
body excretes drugs, so it is possible that it may raise the blood
levels of certain sedatives and sleeping medicines. The potential
interactions between herbs and drugs or other herbs should be
considered. Some combinations may be dangerous. Always tell your doctor
and pharmacist about any herbs you are taking.
Other people who should not take the herb include those who
have low blood pressure or an autoimmune disease (such as lupus or
multiple sclerosis), or those who have had an organ or bone marrow
transplant. Kidney failure has been reported in one person with lupus.
Studies have also shown that cat's claw contains tannins which, in
large amounts, may cause upset stomach or even kidney damage. Small
children and women who are pregnant or breast-feeding should not use
this herb.
Additional Resources
More Information From Your
American Cancer Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be ordered
from our toll-free number (1-800-ACS-2345).
References
Cassileth B. The Alternative Medicine Handbook.
New York, NY: W. W. Norton & Co; 1998.
Gruenwald J, Brendler T, Jaenicke C, eds. PDR for
Herbal Medicines, Third Edition. Thomson PDR, Montvale NJ,
2004.
Fetrow CW, Avila JR. Professional's Handbook of
Complementary and Alternative Medicines. Springhouse, Pa:
Springhouse Corp; 1999.
Lemaire I, Assinewe V, Cano P, et al. Stimulation of
interleukin-1 and -6 production in alveolar macrophages by the
neotropical liana, Uncaria tomentosa (una de gato). J Ethnopharmacol.
1999;64:109-115.
MD Anderson Cancer Center. Cat's Claw. Available at:
http://www.mdanderson.org/departments/CIMER/display.cfm?id=A0AAF589-ECA2-11D4-810100508B603A14&method=displayFull&pn=6EB86A59-EBD9-11D4-810100508B603A14.
Accessed April 11, 2007.
Memorial Sloan Kettering. Cat's Claw. Available at:
http://www.mskcc.org/mskcc/html/69166.cfm. Accessed April 11, 2007.
Moss R. Herbs Against Cancer. New York,
NY: Equinox Press; 1998.
Riva L, Coradini D, Di Fronzo G, et al. The antiproliferative
effects of Uncaria tomentosa extracts and fractions on the growth of
breast cancer cell line. Anticancer
Res. 2001;21:2457-2461.
Sandoval-Chacon M, Thompson JH, Zhang XJ, et al.
Anti-inflammatory actions of cat's claw: the role of NF-kappaB. Aliment Pharmacol Ther.
1998;12:1279-1289.
Spaulding-Albright N. A review of some herbal and related
products commonly used in cancer patients. J Am Diet Assoc.
1997;97:S208-S215.
Styczynski J. Wysocki M. Alternative medicine remedies might
stimulate viability of leukemic cells. Pediatric Blood & Cancer.
2006;46:94-98.
Valerio LG Jr, Gonzales GF. Toxicological aspects of the South
American herbs cat's claw (Uncaria tomentosa) and Maca (Lepidium
meyenii): a critical synopsis. Toxicol
Rev. 2005;24:11-35.
Note: This information may not
cover all possible claims, uses, actions, precautions, side effects or
interactions. It is not intended as medical advice, and should not be
relied upon as a substitute for consultation with your doctor, who is
familiar with your medical situation.
Revised: 06/26/2007
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