Short answer
Cat's claw (Uncaria tomentosa, called una de gato in Peru and Ecuador) is an Amazonian vine whose inner bark has been used for generations for joint comfort and general resilience. Small human trials suggest it may modestly ease joint pain, and animal studies show it lowers some inflammation markers, but there are no large trials and it is not a treatment for any disease. [1] [2] [3]
Key takeaways
- Best-supported use: joint comfort. Two small trials found less joint pain than placebo, one in rheumatoid arthritis (40 people) and one in knee osteoarthritis (45 people, using a close relative species). [1] [2]
- A 2024 review of 24 animal studies found cat's claw extracts lowered the inflammation messengers IL-6 and NF-κB, but not TNF-α or IL-1. Animals are not people. [3]
- It is not a cancer treatment. One phase II study found better quality of life and less fatigue in advanced-cancer patients, with no tumor response. [4]
- Safety is not zero: a documented case of kidney injury, plus lab evidence that it can affect drug-handling proteins. Talk to a clinician first if you take medication. [5] [6] [7]
- Traditional preparation is a decoction (a simmer), not a quick steep.
Search for cat's claw and you will find two very different kinds of pages. One promises that a bark can fix almost anything. The other says there is no evidence at all. Both are wrong in the same way: they skip the actual studies.
This guide reads the studies. Every claim below links to a PubMed record you can open yourself, and where the evidence is thin we say so plainly. We sell cat's claw bark, so you should know where we stand: we think it is a plant worth respecting, and we think respecting it means telling you what has and has not been shown.
What is cat's claw?
Cat's claw is a woody climbing vine of the Amazon basin and Central America. It gets its name from the paired, hooked thorns it uses to haul itself up into the forest canopy, sometimes thirty meters or more. The species sold most often is Uncaria tomentosa, a member of the coffee family (Rubiaceae). A close relative, Uncaria guianensis, is used the same way and shows up in some of the clinical research.
The part used is the inner bark of the stem, harvested in strips and dried. Roots and leaves are also studied, but the bark is the traditional material. Its flavor is woody, earthy and a little astringent, closer to a forest broth than a floral tea.
One detail matters for anyone reading research papers: Uncaria tomentosa comes in at least two chemical types. One carries mostly pentacyclic oxindole alkaloids, the other mostly tetracyclic ones, and the two behave differently in lab tests. [8] That is a big reason results vary between products and between studies.
Traditional uses of cat's claw (una de gato)
In Peru, Ecuador and neighboring countries, bark, root and leaf have been prepared as a decoction for a long list of complaints. A 2025 review of the ethnobotanical record lists arthritis and rheumatism, weakness, viral infections, skin problems, abscesses, allergies, asthma, fevers, gastric ulcers, inflammation, menstrual irregularity, urinary tract inflammation and wounds. [9]
That list is a record of what people have used the plant for, not a record of what it has been proven to do. Traditional use is a reason to study a plant, and that is what researchers have done. The honest summary of the studies is in the next section.
What the research says about cat's claw benefits
Joint comfort: the best-supported use
Two small randomized trials point the same direction. In the first, 40 people with active rheumatoid arthritis, all already taking sulfasalazine or hydroxychloroquine, received either a purified Uncaria tomentosa extract or placebo for 24 weeks. The number of painful joints fell by 53.2% on the extract versus 24.1% on placebo (p = 0.044). Side effects were minor. The authors called it a small preliminary study showing modest benefit to tender joint count. [1]
In the second, 45 people with knee osteoarthritis took freeze-dried cat's claw or placebo for four weeks. Pain during activity and clinician and patient assessment scores improved, with effects starting within the first week. Pain at rest, night pain and knee swelling did not change significantly. Note that this trial used Uncaria guianensis, the sister species, though the lab portion of the paper found the two species behave alike. [2]
Neither trial is large enough to settle the question, and both tested concentrated extracts, not a home-simmered bark. That is the honest ceiling on this claim: promising, small, and in need of bigger studies.
Inflammation and immune signaling
Most of the inflammation research is in cells and animals. An early study found a cat's claw bark extract blocked activation of NF-κB, a master switch for inflammatory genes, and reduced intestinal damage in rats given an inflammatory drug. [10] A 2024 systematic review pooled 24 animal studies and found the extracts lowered IL-6 and NF-κB, while IL-1, IL-10 and TNF-α did not change significantly. The authors also reported low toxicity across the studies and noted the effects did not trace to one class of compounds. [3]
What this means in practice: there is a plausible mechanism and consistent animal data, which supports the traditional use. It does not tell you what a cup of bark tea does in your body.
Cell protection and DNA repair
In a small randomized human study, 12 healthy adults took a water extract at 250 mg or 350 mg a day for eight weeks. After a standard hydrogen peroxide challenge, the supplement groups showed less measured DNA damage and more DNA repair than controls, and there were no drug-related toxic responses. [11] This is a lab biomarker in twelve people. It is interesting, not a health outcome.
Advanced cancer: quality of life, not treatment
Cat's claw is often promoted online as a cancer remedy, so this one needs precision. A phase II study followed 51 people with advanced solid tumors who had no further treatment options and gave them 100 mg of dry extract three times a day. Overall quality of life, social functioning and fatigue scores improved. No tumor responded, inflammatory blood markers did not change, and four people had stable disease for more than eight months. [4]
Lab studies on cancer cells, including breast cancer cells [12] and skin squamous carcinoma cells [13], show extracts can slow growth or trigger cell death in a dish. Cells in a dish are not people. Nobody should delay or replace cancer care with an herb.
| Claim | Evidence level | What we know |
|---|---|---|
| Joint comfort | Small human trials | Two trials (n = 40 and n = 45) found less joint pain than placebo with extracts. Larger trials needed. [1] [2] |
| Lowering inflammation markers | Animal studies, pooled | 24 animal studies: IL-6 and NF-κB lower, TNF-α not significantly changed. [3] |
| Immune support | Lab and animal data, tiny human study | Mechanisms plausible; human outcomes not established. [11] |
| Quality of life in advanced cancer | One phase II study (n = 51) | Less fatigue, better quality of life, no tumor response. [4] |
| Treating or curing disease | No credible evidence | None of the studies show cat's claw treats or cures any disease. |
How to prepare cat's claw bark
Cat's claw bark is dense. Steeping it like a tea bag for five minutes barely extracts anything. The traditional method is a decoction: you simmer the bark in water.
Our label directions, which follow the traditional method: bring 1 1/2 cups of water to a boil, add 1 heaping teaspoon of bark, reduce to low, cover and simmer for 30 minutes, then strain and drink warm. We suggest taking it an hour before or after meals. A slice of ginger in the pot is the usual way to soften the taste.
For more on method, our tea preparation guide covers decoctions, infusions and storage.
Cat's claw bark vs capsules and extracts
People often ask whether whole bark, capsules or a standardized extract is better. Honestly, the studies cannot say. The trials in this guide used standardized extracts, some of them chemotype-specific (for example a purified pentacyclic-alkaloid extract). [1] A bark decoction is a different material with a different, unmeasured amount of active compounds.
Quality varies in every format. An analysis of 18 commercial Uncaria tomentosa bark products sold in Costa Rica and Spain found the same basic polyphenol profile, but most samples had low proanthocyanidin levels (about 255 to 603 micrograms per gram) while one sample had about 2,400 micrograms per gram. [14] The practical lessons: check the species and plant part on the label, prefer a seller that names its origin, and do not assume a capsule is stronger or safer than bark.
| Whole bark (decoction) | Capsules and extracts | |
|---|---|---|
| What you can verify | The bark itself: curls, color, aroma, species on the label | Only what the label says |
| Dose control | Approximate, set by your measuring | Defined per capsule, which is how trials were done |
| Preparation | 30-minute simmer | Swallow |
| Evidence | Traditional use; no trials of bark tea | Small trials used extracts [1] [2] |
Cat's claw side effects, safety and drug interactions
In the clinical trials, side effects were generally minor. The knee osteoarthritis trial reported no harmful effects on blood or liver tests compared with placebo. [2] The 24-study animal review also reported low toxicity. [3] Still, "mostly mild in small trials" is not the same as "safe for everyone."
- Kidney: a 2022 case report describes a person who developed biopsy-proven acute interstitial nephritis (a kidney inflammation) while using diet shakes containing Uncaria tomentosa. Kidney function returned to near baseline after stopping it and treatment with steroids. It is a single case, but it is a documented one. [5]
- Drug interactions (lab evidence): in cell experiments, cat's claw extract inhibited several drug transporter proteins, and its alkaloids activated a receptor (PXR) that increases the drug-metabolizing enzyme CYP3A4. Either could change how some medications are absorbed or cleared. This is lab data, not proven in people, but it is the reason to check with a pharmacist. [6] [7]
- Immune-active: because it is studied for immune effects, people with autoimmune conditions or who take immunosuppressants should ask their clinician first.
- Pregnancy and breastfeeding: there is not enough safety data. Avoid it.
- Surgery and blood thinners: tell your care team you use it, since herbs can matter around procedures and anticoagulants.
Who might consider cat's claw, and who should skip it
Cat's claw suits an adult in good general health who wants to try a traditional Amazonian bark as part of a considered routine, and who has checked with their clinician or pharmacist if they take medication. It is a poor fit for anyone pregnant or nursing, anyone with an autoimmune condition or a transplant, anyone on blood thinners or other medication with a narrow safety margin, and anyone hoping it will replace medical treatment.
Cycling is traditional: a few weeks on, then a break, rather than indefinite daily use. Nothing in the research says a break is required, but it is a reasonable way to keep the plant occasional.
How to buy cat's claw bark well
Cat's claw became a commodity decades ago, and quality varies. Here is what to check:
- Species and part named on the label: Uncaria tomentosa inner bark, not an unspecified "cat's claw."
- Whole bark, not unlabeled powder: you can see what you are buying.
- Named origin and harvest practice: selective harvest from mature vines, without killing them, keeps wild stands alive.
- Honest claims: avoid any seller that says it treats arthritis, cancer or any named disease.
Our bark is wild-harvested by Indigenous partner harvesters in the Ecuadorian Amazon and sold as whole bark in small batches. You can read more about our approach in wildcrafted versus commercial herbs.
Cat's claw vs similar Amazonian herbs
People searching for cat's claw often compare it with chuchuhuasi, another Amazonian bark with a long record in joint-focused traditions, and with graviola (soursop), which is sold for very different reasons. They are different plants with different chemistry and different evidence. Cat's claw is the one with human trials for joint comfort; the others are mostly traditional use plus lab work.
Frequently asked questions
What is cat's claw good for?
What are the side effects of cat's claw?
Trials report mostly minor side effects, but a documented case of kidney inflammation exists, and lab studies show it can interact with drug-handling proteins. Pregnant or nursing people, people with autoimmune conditions or transplants, and people on blood thinners or other prescription drugs should not use it without clinician advice. [5] [6]
How do you make cat's claw tea?
Simmer, do not steep. Bring 1 1/2 cups of water to a boil, add 1 heaping teaspoon of bark, reduce to low, cover and simmer for 30 minutes, strain and drink warm.
Does cat's claw help with arthritis?
Is cat's claw the same as una de gato?
Yes. Una de gato is the Spanish name for Uncaria tomentosa. Some products use the related species Uncaria guianensis, so check the label.
Can you take cat's claw every day?
There is no established safe long-term daily amount. Traditional use cycles it for a few weeks at a time with breaks. If you want to take it regularly, check with a clinician, especially if you use any medication.
What is the difference between cat's claw bark and cat's claw capsules?
Is cat's claw a cancer treatment?
No. A phase II study in advanced cancer found improved quality of life and less fatigue but no tumor response, and lab results in cancer cells do not show it works in people. Do not delay or replace cancer treatment with an herb. [4]
Where can I buy cat's claw bark in the USA?
Look for whole Uncaria tomentosa inner bark with a named origin. Kawsaypac sells wild-harvested cat's claw bark shipped across the United States: view Cat's Claw.
References
- Mur E, Hartig F, Eibl G, et al. (2002). Randomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of uncaria tomentosa for the treatment of rheumatoid arthritis. J Rheumatol. PubMed 11950006
- Piscoya J, Rodriguez Z, Bustamante SA, et al. (2001). Efficacy and safety of freeze-dried cat's claw in osteoarthritis of the knee: mechanisms of action of the species Uncaria guianensis. Inflamm Res. PubMed 11603848 · DOI
- Arado GM, Amatto PPG, Marins M, et al. (2024). Anti-inflammatory and/or immunomodulatory activities of Uncaria tomentosa (cat's claw) extracts: A systematic review and meta-analysis of in vivo studies. Front Pharmacol. PubMed 38881881 · DOI
- de Paula LC, Fonseca F, Perazzo F, et al. (2015). Uncaria tomentosa (cat's claw) improves quality of life in patients with advanced solid tumors. J Altern Complement Med. PubMed 25495394 · DOI
- Portalatin G, Shettigar S, Carrion-Rodriguez A, et al. (2022). Ketogenic-Diet Shake Containing Uncaria tomentosa-Associated Acute Interstitial Nephritis. Case Rep Nephrol Dial. PubMed 36465572 · DOI
- Szilvásy N, Lajer P, Horváth A, et al. (2024). Modulation of Multispecific Transporters by Uncaria tomentosa Extract and Its Major Phytoconstituents. Pharmaceutics. PubMed 39598486 · DOI
- Lei S, Lu J, Cheng A, et al. (2023). Identification of PXR Activators from Uncaria Rhynchophylla (Gou Teng) and Uncaria Tomentosa (Cat's Claw). Drug Metab Dispos. PubMed 36797057 · DOI
- Reinhard KH (1999). Uncaria tomentosa (Willd.) D.C.: cat's claw, uña de gato, or savéntaro. J Altern Complement Med. PubMed 10328636 · DOI
- Marques O, Figueirinha A, Pina ME, et al. (2025). Uncaria tomentosa as a Promising Natural Source of Molecules with Multiple Activities: Review of Its Ethnomedicinal Uses, Phytochemistry and Pharmacology. Int J Mol Sci. PubMed 40725012 · DOI
- Sandoval-Chacón M, Thompson JH, Zhang XJ, et al. (1998). Antiinflammatory actions of cat's claw: the role of NF-kappaB. Aliment Pharmacol Ther. PubMed 9882039 · DOI
- Sheng Y, Li L, Holmgren K, et al. (2001). DNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study. Phytomedicine. PubMed 11515717 · DOI
- Riva L, Coradini D, Di Fronzo G, et al. (2001). The antiproliferative effects of Uncaria tomentosa extracts and fractions on the growth of breast cancer cell line. Anticancer Res. PubMed 11724307
- Ciani F, Tafuri S, Troiano A, et al. (2018). Anti-proliferative and pro-apoptotic effects of Uncaria tomentosa aqueous extract in squamous carcinoma cells. J Ethnopharmacol. PubMed 28964869 · DOI
- Navarro M, Arnaez E, Moreira I, et al. (2019). Polyphenolic Composition and Antioxidant Activity of Uncaria tomentosa Commercial Bark Products. Antioxidants (Basel). PubMed 31450810 · DOI