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Western herbalism

Cat's clawUncaria tomentosa

Cat’s claw bark is sold for gut lining and cleanse formulas; its human trials are in arthritis, and we could find none for the gut.

Botanical name
Uncaria tomentosa
Part used
inner bark (also root)
Also called
Una de gato, Uncaria guianensis (related species)
Used in
Western herbalism
Taken for
The gut lining, Antimicrobial use
Sold as
capsules, tea, tincture, extract, powder

The plant

Cat’s claw is a woody vine of the madder family (Rubiaceae) from the Amazon rainforest and other parts of South America, named for the paired, hooked thorns along its stems. Two species are sold, Uncaria tomentosa and Uncaria guianensis. The part used is the inner bark of the stem, sometimes the root. The traditional preparation is a bark decoction; supplements are capsules of ground bark, bark tea, tinctures and standardized extracts, and cat’s claw is an ingredient in some gut-lining and cleanse formulas.

Products differ more than the name suggests. Researchers describe three chemotypes of U. tomentosa, grouped by the profile of their oxindole alkaloids (pentacyclic or tetracyclic), and the water extracts that have been studied for inflammation contain almost no alkaloids at all, less than 0.05 percent in one analysis. A capsule labeled “cat’s claw” may therefore contain a different mix of compounds from the extract used in a trial.

How the traditions use it

Western herbalism

Indigenous people of the Amazon rainforest have used cat’s claw for centuries, in the words of the National Center for Complementary and Integrative Health, to ward off disease. A paper on its water extracts lists the traditional targets as chronic inflammation, gastrointestinal dysfunction such as ulcers, tumors and infections. The Natural Medicines database adds colitis, diverticulitis and parasites to the list of conditions people take it for, and rates the evidence for each as insufficient to rate.

What is in it

Cat’s claw contains oxindole alkaloids in pentacyclic and tetracyclic forms, plus, in water extracts, quinic acid esters that one laboratory group identified as the active part of its water extract C-Med-100. In cells, that extract slowed cell growth without killing the cells, which the authors link to immune-stimulating and anti-inflammatory effects. In a comparison of the three alkaloid chemotypes, they differed in how selectively they harmed cancer cells versus normal white blood cells. All of this is laboratory work; none of it has been shown to carry over to the human gut.

What the human trials show

We could find no randomized trial of cat’s claw for a gut outcome. The Natural Medicines database rates the evidence for colitis, diverticulitis, ulcers and parasites as insufficient to rate, and the National Center for Complementary and Integrative Health states there is no conclusive scientific evidence from studies in people that supports using cat’s claw for any health purpose, because few high-quality human studies exist.

The human trials are in joint disease. In a randomized trial of 40 patients with active rheumatoid arthritis who were already taking sulfasalazine or hydroxychloroquine, a 24-week double-blind phase compared an extract of the pentacyclic alkaloid chemotype of U. tomentosa with placebo; the number of painful joints fell 53.2 percent on the extract and 24.1 percent on placebo (p = 0.044), and only minor side effects were reported. Natural Medicines rates knee osteoarthritis pain with activity and rheumatoid arthritis symptoms as possibly effective, with doses of 100 mg once a day for osteoarthritis and 60 mg a day in three doses for rheumatoid arthritis. These are small trials of specific extracts.

What has not been tested: any form of cat’s claw for ulcerative colitis, Crohn’s disease, diverticulitis, intestinal permeability, irritable bowel syndrome or intestinal parasites; the effect on the gut microbiome in people; and whether the water-extract chemistry found in the gut-lining products matches the chemistry used in the arthritis trials.

StudyDoseWhat it found
Randomized trial, 40 patients with active rheumatoid arthritis on sulfasalazine or hydroxychloroquine (24-week double-blind phase; joints, not gut) PMID 11950006Extract of the pentacyclic alkaloid chemotype; Natural Medicines lists 60 mg a day in 3 dosesPainful joints fell 53.2% vs 24.1% with placebo (p = 0.044); only minor side effects
Laboratory characterization of cat's claw water extract C-Med-100 PMID 15619581In vitro and in vivo (not in gut disease)Active components identified as quinic acid esters; alkaloids under 0.05% of the extract; no human gut data
Laboratory comparison of three oxindole-alkaloid chemotypes in human cell lines PMID 27180878In vitroChemotypes differed in selectivity for malignant versus normal white blood cells; shows products are not interchangeable
Case report: acute interstitial nephritis after a ketogenic-diet shake containing Uncaria tomentosa PMID 36465572Product dose not statedCreatinine 3.6 mg/dL from a baseline of 0.7; confirmed on biopsy; improved after stopping the shake and corticosteroids
NCCIH review of cat's claw evidenceNot applicableNo conclusive evidence from studies in people for any health purpose; few high-quality trials

How much the studies and the texts used

No gut trial gives a dose. The Natural Medicines database lists the doses used in other conditions: 100 mg once daily of a freeze-dried U. guianensis extract for knee osteoarthritis, 60 mg a day split into three doses of an extract without tetracyclic oxindole alkaloids for rheumatoid arthritis, and 100 mg three times a day in cancer. The traditional preparation is a decoction of the inner bark. The National Center for Complementary and Integrative Health says oral use appears safe for short periods, up to about 6 months. Because chemotypes and extracts vary, a bark capsule cannot be matched to the extract used in a trial.

Doses here describe what studies and pharmacopoeias used. They are not a recommendation for any person; a clinician or pharmacist who knows your medicines and conditions is the right person to ask.

Side effects and cautions

The National Center for Complementary and Integrative Health says cat’s claw may stimulate the immune system, which could worsen autoimmune disease, and may slow clotting, raising bleeding risk around surgery. It says some studies suggest it is unsafe in pregnancy and that little is known about breastfeeding. Natural Medicines lists headache, dizziness and vomiting, rates pregnancy possibly unsafe, and advises caution with autoimmune disease, bleeding disorders, low blood pressure and leukemia, and stopping at least two weeks before surgery. Case reports describe an acute interstitial nephritis confirmed on biopsy, and a woman who developed severe delirium and a heart rate of 29 to 40 beats per minute after trying to stop a high-dose supplement.

Interactions

The National Center for Complementary and Integrative Health names theoretical interactions with anticoagulant, antiplatelet and blood pressure drugs. Natural Medicines rates these classes moderate: immunosuppressants such as cyclosporine, tacrolimus and prednisone, because immune stimulation might blunt them; blood thinners and antiplatelets, because of slowed clotting; blood pressure drugs including calcium channel blockers, because of added lowering; HIV protease inhibitors; and drugs cleared by the liver enzyme CYP3A4, such as lovastatin and ketoconazole, because cat’s claw might slow their breakdown. These ratings rest on theory and lab work rather than interaction trials.

Medicines the quiz checks cat's claw against

When a quiz taker names one of these medicines, the rule below fires. Each comes from a published interaction reference; none is a diagnosis:

Cat's claw on the shelf: the products that contain it

The products here name cat's claw among their actives. How much of it a serving holds, and whether that matches any trial, is on each page.

Designs for Health GI Revive Peach Powder 4.8 out of 5 from 248 ratings from iHerb · $89.49 for 225 g (28 servings), about $3.20 a day Designs for Health GI Revive Capsules 4.8 out of 5 from 57 ratings from iHerb · $99.99 for 210 capsules, about $3.33 a day at 7 capsules

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Often paired or compared

Western Pau d'arco Tabebuia impetiginosa (Handroanthus impetiginosus) Western Black walnut Juglans nigra Ayurvedic / TCM / Western Turmeric Curcuma longa Western Goldenseal Hydrastis canadensis

Questions people ask

Is cat's claw used for the gut?

Traditional use includes ulcers and gastrointestinal dysfunction, and people take it for colitis, diverticulitis and parasites. The Natural Medicines database rates the evidence for each of those as insufficient to rate, and we could find no trial for any gut outcome.

What have human trials of cat's claw actually tested?

The trials are in joint disease. A 40-patient trial in rheumatoid arthritis found painful joints fell 53.2 percent on the extract and 24.1 percent on placebo (p = 0.044), and Natural Medicines rates knee osteoarthritis pain as possibly effective.

Should people on immunosuppressants avoid cat's claw?

The National Center for Complementary and Integrative Health notes it may stimulate the immune system and could worsen autoimmune disease. Natural Medicines rates the interaction with immunosuppressants such as cyclosporine, tacrolimus, azathioprine and prednisone as moderate.

Is cat's claw safe in pregnancy?

The National Center for Complementary and Integrative Health says some studies suggest it is unsafe during pregnancy and that little is known about breastfeeding. Natural Medicines advises avoiding it in both.

Why do cat's claw products differ so much?

There are three chemotypes of Uncaria tomentosa based on alkaloid profile, and the water extracts studied for inflammation contain under 0.05 percent alkaloids. Extracts of different chemistry, and the bark powder in capsules, are not the same material.

Sources