- Turkish rhubarb
- Chinese rhubarb
- Tai huang
- Da huang
For Patients & Caregivers
How It Works
Rhubarb acts as a stimulant laxative, but has not been shown to treat or prevent cancer.
Rhubarb is a perennial herb, and the stalks are sometimes consumed as food. In Traditional Chinese Medicine (TCM), the rhizome and roots are used as laxatives and to treat ulcers, constipation, diarrhea, high blood pressure, and cancer. In lab animals, compounds in rhubarb called anthraquinones reduced pain, inflammation, and some tumors.
Studies in humans are limited, but suggest rhubarb can improve feeding tolerance and relieve gastrointestinal dysfunction in very ill patients. It may also reduce excess blood levels of pancreatic enzymes and pancreatitis events caused by some procedures. Other initial studies suggest it can treat mouth sores or help reduce radiation side effects. Additional studies are needed to determine safety and effectiveness.
Rhubarb is considered to be a stimulant laxative. It is also a component of Essiac tea. Patients and physicians should be aware of the potential for additive effects.
- To reduce cancer treatment side effects One study suggests that a rhubarb extract may reduce side effects from radiation therapy in lung cancer patients. Additional studies are needed.
- To relieve constipation Rhubarb acts as a laxative, although clinical trials have not tested this use.
- As a fever reducer There is no scientific evidence to support this claim.
- To suppress the immune system Laboratory data shows that rhubarb decreases the activity of isolated immune cells.
- To reduce inflammation Some studies suggest that rhubarb has anti-inflammatory effects.
- To treat infections There is no scientific evidence to support this claim.
- To treat ulcers A small study suggests rhubarb may be useful for treating oral ulcers. More studies are needed.
Do Not Take If
- You are taking digoxin: Potassium loss due to the laxative effect of rhubarb means it may increase the risk of low potassium levels.
- You are taking cytochrome P450 substrate drugs: Rhubarb may reduce the effectiveness of these drugs, but clinical significance has yet to be determined.
- You are taking melatonin: Lab studies suggest that using both products together may affect the way melatonin is metabolized, but clinical relevance is not yet known.
- You are taking cyclosporine: In lab studies, rhubarb decreased cyclosporine bioavailablity. Clinical relevance is not yet known.
- You are taking methotrexate: In lab studies, rhubarb increased exposure to methotrexate. However, clinical relevance is not clear.
- You have kidney disease: Rhubarb is high in oxalates and may cause kidney problems in some individuals.
- Kidney damage/failure: In a type-1 diabetic patient with normal kidney function following excess ingestion of rhubarb and in a 75-year-old man from excess intakes of rhubarb stew over a few weeks.
- Dark pigment deposits in the colon: In a 67-year-old woman with long-term use of a natural fiber supplement containing rhubarb. This condition is often associated with chronic laxative use. It was reversed after a long period of product discontinuation and repeat colonoscopy.
For Healthcare Professionals
Rhubarb, a perennial herb, is cultivated in many parts of the world. The stalks are consumed as food, and the rhizome and root are widely used in Traditional Chinese Medicine for a variety of conditions including cancer, constipation, diarrhea, gastrointestinal ulcers, and hypertension (1) (3). The anthraquinones and tannins in rhubarb are thought responsible for its laxative and constipating effects, respectively (4).
In preclinical studies, rhubarb demonstrated anticancer (20), antimetastatic (21), radioprotective (22), and estrogen-receptor-modulating (13) effects. The constitutent aloe-emodin has demonstrated anticancer (5) (6) (27) and anti-leishmanial (30) effects. It was also shown to enhance the effects of sorefenib (28) and cisplatin (29).
Evidence for safety and efficacy in humans is limited. Preliminary studies suggest rhubarb may have added benefits for patients with sepsis when used with the protease inhibitor ulinastatin (34), or help treat recurrent aphthous stomatitis (25). Other data suggest it may improve feeding tolerance and relieve gastrointestinal dysfunction in critically ill patients (23) or help prevent procedure-related pancreatitis and hyperamylasemia in high-risk patients (24). A meta-analysis suggests that rhubarb adjuvant to early enteral nutrition may benefit patients with severe acute pancreatitis (35), but a systematic review does not support its use for gastrointestinal failure in ICU patients (36). In a small study of lung cancer patients, a rhubarb extract reduced radiation-induced lung toxicity and increased pulmonary function (7).
Mechanism of Action
When used in small doses, the tannin content in rhubarb has a constipating effect. At higher doses, however, the hydrolyzed metabolites of emodin and sennidin stimulate the gastrointestinal tract and produce a laxative effect (4). The actions of anthraquinones on rheinanthrone, which is transformed from sennoside A, may promote the purgative effects of sennoside A (16).
The anti-inflammatory activity of emodin may mediate rhubarb’s hepatoprotective effects in rats with cholestatic hepatitis (11). Lindeyin, a phenolic gallylglucoside, exhibits analgesic and anti-inflammatory properties in animal models. Catechin, epicatechin, procyanidins, and gallylglucose were also shown to inhibit hyaluronidase (10) (12).
Additional studies show that aloe-emodin exerts anti-proliferative activity, inducing cell cycle arrest in cancer cell lines (6). Anthraquinone extracts of rhubarb were shown to induce cytotoxicity in cancer cell lines (5) and tumor (sarcoma 37, mammary, and Ehrlich) necrosis in mice (1), although this has not been demonstrated in humans. Another study showed that emodin inhibits human cancer cell invasiveness by specifically antagonizing the adenosine 5’-triphosphate (ATP)-gated Ca(2+)-permeable channel P2X7 receptor (P2X7R) (17).
- Kidney failure: In a type-1 diabetic patient with normal kidney function following excess ingestion of rhubarb (18), and in a 75-year-old man from excessive intakes of rhubarb stew over a few weeks (37). Rhubarb is high in oxalates.
- Melanosis coli: In a 67-year-old woman with long-term use of a natural fiber supplement containing rhubarb. This condition is often associated with chronic laxative use and causes dark cellular pigment deposits in the colon. It was reversed after product discontinuation and upon repeat colonoscopy 1.5 years later (38).
- Digoxin: Potassium loss due to rhubarb’s laxative effect can increase the risk of hypokalemia. (9)
- Cytochrome P450 substrates: In animal models, rhubarb induces CYP3A and CYP2D6 (15) (19), while the compound rhein inhibits CYP2E1, CYP3A, and CYP2C9, and to a lesser extent CYP1A2 and CYP2D6 (39). Clinical relevance is not known.
- Melatonin: A study using human primary hepatocytes showed that concomitant use can cause metabolic disorder of melatonin (31). Clinical relevance is not known.
- Cyclosporine: Rhubarb decreased the bioavailablity of cyclosporine in a murine model. Clinical relevance is not known (32).
- Methotrexate: Rhubarb was shown to increase exposure to methotrexate in a murine model. Clinical relevance is not clear (33).