Cat's Claw

Claims, Benefits: Boosts the immune system, has anti-cancer effects, reduces inflammation, inhibits blood clotting, and lowers blood pressure.

Bottom Line: It is untested, unpredictable, and risky, so we don't recommend it.

Full article, Wellness Letter, November 2001:

Ask the Experts

Q: Will the herb cat's claw help the immune system?
C.V., VIA THE INTERNET

A: The herb contains many interesting compounds, but as with most herbal remedies, there have been no good studies on its effects in humans. It's hard to predict what the cat's claw supplements (capsules, tablets, creams, teas, and liquids made from various parts of the plant) sold in health-food stores will do.

Known as cat's claw because of its clawlike thorns, this woody vine is native to the Amazon, where it has been used medicinally for centuries. There are several species; two (Uncaria guianensis and Uncaria tomentosa) are supposed to have therapeutic effects.

Some of its compounds are alleged to help boost certain aspects of the immune system, have anti-cancer effects, reduce inflammation, inhibit blood clotting, or lower blood pressure. That sounds pretty miraculous, but the evidence comes only from test-tube studies and animal research, and the results have not been consistent. In Germany, where the herb is standardized, some doctors prescribe it for certain people with compromised immune systems, such as those undergoing chemotherapy for cancer.

As with many herbs, there are as many potential risks as possible benefits. High doses may cause diarrhea, bleeding gums, excessive bruising, and a dangerous drop in blood pressure. Do not try it if you are pregnant (or may become pregnant), breastfeeding, have HIV, or are taking a drug that affects blood clotting. Cat's claw may also interfere with certain widely used prescription medications.

Because it is untested, unpredictable, and risky, we don't recommend cat's claw.

UC Berkeley Wellness Letter, November 2001