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Cat's Claw

Other common name(s): una de gato

Scientific/medical name(s): Uncaria tomentosa (There are other plants that are called cat’s claw, including some from the same area in South America, but this information only pertains to Uncaria tomentosa)


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.


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 linked to 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 can be made into 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. Note that 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. People in the United States and Europe began to hear of the herb during the 1970s after an Austrian investigator, Klaus Keplinger, traveled to the rain forests of Peru. He learned about the plant from healer-priests of the Ashinaka tribe. Keplinger eventually received patents for isolating the active ingredients from the plant.

Cat's claw has become an extremely popular herbal supplement in the United States and Europe. Because demand for this herb has increased greatly in recent 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 reports from individuals or the results of experiments in the lab.

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. But human studies have not yet confirmed that cat's claw or its extracts have any of these effects.

Available scientific evidence does not confirm reports that cat’s claw can treat childhood leukemia. Results of laboratory studies have been inconsistent. A 2006 study suggested this plant does not kill leukemia cells and may actually help them to survive longer.

A lab study published in 2007 suggested that chemicals from cat’s claw might help kill cells from 2 forms of nervous system cancer. A 2010 lab study suggested that the same chemical could slow the growth of breast cancer cells and Ewing’s sarcoma cells, but no studies in humans have been done. Also, it is important to note that purified or concentrated plant extracts often do not have the same effects as the whole herb.

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 be tested before being 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 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. In 2007, the FDA wrote new rules to improve the quality of manufacturing for dietary supplements and the proper listing of supplement ingredients. But these rules do not address the safety of the ingredients or their effects on health.
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 affect 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.

To learn more

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 (1-800-227-2345).

Dietary Supplements: What Is Safe?

The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

Complementary and Alternative Methods and Cancer

Placebo Effect

Learning About New Ways to Treat Cancer

Learning About New Ways to Prevent Cancer


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Garcia Prado E, Garcia Giminez MD, De la Puerta Vazquez R, et al. Antiproliferative effects of mitraphylline, a pentacyclic oxindole alkaloid of Uncaria tomentosa on human glioma and neuroblastoma cell lines. Phytomedicine. 2007;14:280-284.

García Giménez D, García Prado E, Sáenz Rodríguez T, et al. Cytotoxic effect of the pentacyclic oxindole alkaloid mitraphylline isolated from Uncaria tomentosa bark on human Ewing's sarcoma and breast cancer cell lines. Planta Med. 2010 Feb;76(2):133-6.

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Memorial Sloan-Kettering Cancer Center Web site. Cat's Claw. Accessed at www.mskcc.org/mskcc/html/69166.cfm on April 6, 2011.

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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: 09/12/2011
Last Revised: 09/12/2011