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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 have traditionally been used in
herbal remedies. Because of increased demand, the plant can now only be
harvested above ground.
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. Cat’s claw is
associated with some serious side effects, although the extent of those
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.
What does it involve?
Cat's claw is taken by mouth and is available in capsules,
tablets, tinctures, elixirs, and as a tea. Sometimes it can be found as
a cream for application to the skin. Practitioner recommendations for
how much to take vary widely. Some suggest a dosage of 3,000 to 6,000
milligrams per day in pill form, or 4 strong cups of tea. Herbalists
may prescribe up to 20 grams 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 plant. Recently, cat's claw has become an
extremely popular herbal supplement among consumers in the United
States and Europe. Because demand for this herb has increased greatly
in the past few years, the Peruvian government now forbids harvesting
the roots of the plant. The same compounds are present in the bark as
in the root, and so 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.
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
anecdotal reports or the results of laboratory experiments.
In laboratory and animal studies, researchers have been able
to identify certain substances in cat’s claw that may lead to
further discovery. Among these are chemicals called alkaloids. One
Canadian laboratory 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 in cat’s claw
were antioxidants—compounds that block the actions of free
radicals, which can damage cells.
Certain alkaloids in cat's claw are thought to 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 have any of these effects. Peruvian
researchers in the 1970s claimed that cat's claw was an effective
treatment for children with leukemia, but available scientific evidence
does not confirm those reports. Results of laboratory studies have been
inconsistent. A 2006 study suggested this plant is not effective in
killing leukemia cells and may actually help the leukemia cells to
survive longer. A study published in 2007 suggested that chemicals from
cat’s claw might help kill cells from 2 forms of nervous
system cancer
Available scientific evidence does not support claims that
this herb can treat cancer or other diseases in people. Animal and
laboratory studies may show promise, but further studies are necessary
to find out whether the results apply to humans. Until clinical trials
in humans are completed, the true value of cat's claw remains
uncertain.
Are there any possible problems or
complications?
This product is sold as a
dietary supplement in the United States. Unlike companies that produce
drugs (which must provide the FDA with results of detailed testing
showing their product is safe and effective before the drug is approved
for sale), the companies that make supplements do not have to show
evidence of safety or health benefits to the FDA before selling their
products. Supplement products without any reliable scientific evidence
of health benefits may still be sold as long as the companies selling
them do not 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). Though the FDA has written new rules
to improve the quality of manufacturing processes for dietary
supplements and the accurate listing of supplement ingredients, these
rules do not take full effect until 2010. And, the new rules do not
address the safety of supplement ingredients or their effects on health
when proper manufacturing techniques are used.
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 that people who are taking blood pressure
medicines, blood-thinning medications, hormones, or insulin should not
take cat's claw. This herb may also have an effect on the way 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 other medications or 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 cat’s claw 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 breastfeeding should not use
this herb. Relying on this type of treatment alone and avoiding or
delaying conventional medical care for cancer may have serious health
consequences.
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 found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
Cassileth B. The
Alternative Medicine Handbook: The Complete Reference Guide to
Alternative and Complementary Therapies. New York, NY:
W.W. Norton; 1998.
Cat's Claw. Memorial Sloan-Kettering Cancer Center Web site.
http://www.mskcc.org/mskcc/html/69166.cfm. Accessed June 4, 2008.
Garcia Prado E, Garcia Giminez MD, De la Puerta Vazquez R,
Espartero Sanchez JL, Saenz Rodriguez MT. Antiproliferative effects of
mitraphylline, a pentacyclic oxindole alkaloid of Uncaria tomentosa on
human glioma and neuroblastoma cell lines. Phytomedicine.
2007;14:280-284.
Gruenwald J. PDR
for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR;
2004.
Fetrow CW, Avila JR. Professional's
Handbook of Complementary & Alternative Medicines.
Philadelphia, PA: Lippincott Williams & Wilkins; 2004.
Herbal/plant therapies: cat's claw detailed scientific review.
Complementary/Integrative Medicine Education Resources, The University
of Texas M.D. Anderson Cancer Center Web site.
http://www.mdanderson.org/departments/CIMER/display.cfm?id=A0AAF589-ECA2-11D4-810100508B603A14&method=displayFull.
Accessed June 4, 2008.
Lemaire I, Assinewe V, Cano P, Awang DV, Arnason JT.
Stimulation of interleukin-1 and -6 production in alveolar macrophages
by the neotropical liana, Uncaria tomentosa (uña de gato). J Ethnopharmacol.
1999;64:109-115.
Moss R. Herbs
Against Cancer: History and Controversy. New York, NY:
Equinox Press; 1998.
Riva L, Coradini D, Di Fronzo G, De Feo V, De Tommasi N, De
Simmone F, Pizza C. The antiproliferative effects of Uncaria tomentosa
extracts and fractions on the growth of breast cancer cell line. Anticancer Res.
2001;21:2457-2461.
Sandoval-Chacón M, Thompson JH, Zhang XJ, Liu X,
Mannick EE, Sadowska-Krowicka H, Charbonnet RM, Clark DA, Miller MJ.
Antiinflammatory 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. Pediatr Bloood 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.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
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