Supplement analysis backed by scientific evidence · PT

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Limited evidenceJoints & skin

Cat's Claw

Two small randomized trials from the early 2000s found modest pain relief in knee osteoarthritis and rheumatoid arthritis, and essentially nothing has confirmed them in the two decades since. The immune and anticancer claims have no clinical support.

What the science says

  • Knee osteoarthritis pain Limited evidence

    A 4-week randomized placebo-controlled trial in 45 adults using 100 mg/day of freeze-dried Uncaria guianensis reported reduced pain on activity within the first week, with no change in resting or night pain and no effect on knee swelling. It is one small, short, single trial — and it tested U. guianensis, a different species from the U. tomentosa in most supplements.

  • Rheumatoid arthritis Limited evidence

    In a 52-week trial, 40 patients on sulfasalazine or hydroxychloroquine were randomized to a pentacyclic-alkaloid-chemotype U. tomentosa extract or placebo for 24 weeks; the extract group had a significant reduction in the number of painful joints (by about 53% versus 24%) but no significant change in swollen joints or in disease-activity biomarkers. Add-on effect only, in a very small sample.

  • Immune support and anticancer effects Limited evidence

    Oxindole alkaloids from cat's claw modulate immune cells and inhibit NF-κB in vitro, and small studies have reported increases in lymphocyte counts. No controlled clinical trial shows it prevents infection, treats cancer, or improves any hard outcome in humans.

Dosage & safety

Studied doseOsteoarthritis trial: 100 mg/day of freeze-dried Uncaria guianensis. Rheumatoid arthritis trial: 60 mg/day of a pentacyclic-alkaloid-chemotype U. tomentosa extract. Commercial products commonly supply 250-1,000 mg/day of bark extract, often standardized to 1.3-3% oxindole alkaloids — well above the doses actually tested. Chemotype matters: the tetracyclic-alkaloid chemotype antagonizes the pentacyclic one, and few labels state which is present.
SafetyUsually well tolerated at trial doses; headache, dizziness, nausea and diarrhoea are reported. Case reports include acute kidney injury in a lupus patient and hypotension. It inhibits CYP3A4 in vitro and has been reported to raise levels of antiretrovirals such as atazanavir, ritonavir and saquinavir — avoid with protease inhibitors. Theoretical additive risk with anticoagulants and antihypertensives. Its immune-stimulating reputation means caution in autoimmune disease and it should be avoided with immunosuppressants and after organ transplant. Contraindicated in pregnancy and lactation (traditional contraceptive/abortifacient use). Avoid before surgery. Note that "cat's claw" also refers to unrelated plants including Acacia greggii, so botanical name on the label matters.

Scientific references

Where to buy

Solaray, Vital Extracts, Cat's Claw, 30 VegCaps

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