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Rhubarb

Scientific Name

Rheum palmatum, Rheum officinale

Common Name

Turkish rhubarb, turkey rhubarb, Chinese rhubarb, tai huang, da huang

Clinical Summary

Rhubarb, a perennial herb, is cultivated in many parts of the world. The stalks are consumed as food; the rhizome and root of Rhubard are widely used in Chinese medicine for a variety of conditions including cancer ⁽¹⁾, immunosuppression, constipation ⁽²⁾, diarrhea, gastrointestinal ulcers, and hypertension ⁽³⁾. The anthraquinones and tannins are thought responsible for the laxative and constipating effects, respectively ⁽⁴⁾. Limited human clinical data are available for the claims made. Majority of the studies were conducted in China, often using formulations of rhubarb along with other herbs.

Cytotoxic ⁽⁵⁾ and cytostatic ⁽⁶⁾ ⁽¹⁴⁾ effects have been reported in cancer cells in vitro. Antitumor effects were also shown in mice ⁽¹⁾. One study found that a rhubarb extract reduced radiation-induced lung toxicity and increased pulmonary function in lung cancer patients ⁽⁷⁾.

Adverse effects are primarily gastrointestinal in nature. Chronic consumption can cause hypokalemia due to diarrhea, possible renal and hepatic damage from oxalates ⁽⁸⁾, theoretical hypokalemia when combined with diuretics, and altered response to digoxin ⁽⁹⁾. Rhubarb should be used under medical supervision.

Purported Uses

Cancer treatment
Constipation
Fever
Hypertension
Immunosuppression
Inflammation
Microbial infection
Peptic ulcers

Constituents

Anthraquinones: Rhein, physcion, aloe-emodin, emodin, chrysophenol, sennoside A-F
Tannins: Rheum tannic acid, gallic acid, glucogallin, catechin, epicatechin
Other: Calcium oxalate, lindeyin, fatty acids, rutin, starch, trace volatile oils
⁽²⁾ ⁽⁸⁾ ⁽¹⁰⁾

Mechanism of Action

When used in very small doses the tannin content has a constipating effect. At increased doses, however, the hydrolyzed metabolites of emodin and sennidin cause stimulation of the gastrointestinal tract and produce a laxative effect ⁽⁴⁾; in vitro tests show suppression of TNF, IL-1, and IL-6 production. Reductions in blood pressure and cholesterol have been seen but are due to unknown mechanisms. Anti-inflammatory activity of emodin may mediate its hepatoprotective effects in rats with cholestatic hepatitis ⁽¹¹⁾. In addition, aloe-emodin possesses anti-proliferative activity, inducing cell cycle arrest in cancer cell lines ⁽⁶⁾. Anthraquinone extracts have been shown to induce cytotoxicity in cancer cell lines ⁽⁵⁾ and tumor necrosis in mice (sarcoma 37, mammary, and Ehrlich) ⁽¹⁾, although this has not been demonstrated in humans. Lindeyin, a phenolic gallylglucoside exhibits analgesic and anti-inflammatory activity in animal models. Catechin, epicatechin, procyanidins, and gallylglucose inhibit hyaluronidase in vitro ⁽¹⁰⁾ ⁽¹²⁾.

Warnings

Stimulant laxative products such as rhubarb should not be used for more than a week without medical supervision.
⁽⁸⁾ ⁽⁹⁾ ⁽¹²⁾

Contraindications

Patients with arthritis, kidney or hepatic dysfunction, history of kidney stones, inflammatory bowel disease, or intestinal obstruction should not take this herb.
Rhubarb may cause uterine stimulation and therefore should not be consumed by women who are pregnant.
Patients with hormone-sensitive cancers should avoid rhubarb because estrogenic activity has been reported ⁽¹³⁾.

Adverse Reactions

Reported: Abdominal cramps, nausea, vomiting, diarrhea leading to possible hypokalemia, anaphylaxis, renal and hepatic damage.
⁽⁸⁾

Herb-Drug Interactions

Diuretics: Potassium loss due to stimulant laxative effect can increase potential risk for hypokalemia.
Digoxin: Potassium loss due to stimulant laxative effect can increase potential risk for hypokalemia. ⁽⁹⁾
Cytochrome P450 substrates: Rhubarb induces CYP3A and CYP2D6 and can affect the intracellular concentration of drugs metabolized by these enzymes ⁽¹⁵⁾.

Herb Lab Interactions

Anthraquinones can cause discoloration of the urine interfering with urinalysis.

Literature Summary and Critique

Yu HM, et al. Effects of rhubarb extract on radiation induced lung toxicity via decreasing transforming growth factor-beta-1 and interleukin-6 in lung cancer patients treated with radiotherapy. Lung Cancer. Feb 2008;59(2):219-226.
In this randomized, double-blind, placebo-controlled study, 80 lung cancer patients undergoing radiation therapy also received a rhubarb extract (20 mg/kg daily) or placebo for 6 weeks. Radiation-induced lung toxicity (RILT), pulmonary function, and circulating TGF-beta and IL-6 levels were measured after 6 weeks and 6 months. In the intervention group, decreased RILT, improved pulmonary function, and reduced circulating TGF-beta and IL-6 were detected as compared to the control group, suggesting that rhubarb reduces RILT through attenuation of TGF-â and IL-6. In addition, no adverse events were reported. Larger studies are required to determine the mechanism by which rhubarb extracts exert their effect on RILT as well as the component responsible for these effects.

References

Mantani N, et al. Rhubarb use in patients treated with Kampo medicine—a risk for gastric cancer? Yakugaku Zasshi 2002;122:403-5.

Huang KC. The Pharmacology of Chinese Herbs, 2^nd ed. New York: CRC Press; 1999.

Zhang ZJ, Cheng WW, Yang YM. Study on low-dose of processed rhubarb in preventing pregnancy induced hypertension. Chung-Hua Fu Chan Ko Tsa Chih [Chinese Journal of Obstetrics & Gynecology] 1994;29:463-4, 509.

Peigen X, Liyi H, Liwei W. Ethnopharmacologic study of chinese rhubarb. J Ethnopharmacol 1984;10:275-93.

Cui XR, Tsukada M, Suzuki N, et al. Comparison of the cytotoxic activities of naturally occurring hydroxyanthraquinones and hydroxynaphthoquinones. Eur J Med Chem. Jun 2008;43(6):1206-1215.

Guo JM, Xiao BX, Liu Q, Zhang S, Liu DH, Gong ZH. Anticancer effect of aloe-emodin on cervical cancer cells involves G2/M arrest and induction of differentiation.Acta Pharmacol Sin. Dec 2007;28(12):1991-1995.

Yu HM, Liu YF, Cheng YF, Hu LK, Hou M. Effects of rhubarb extract on radiation induced lung toxicity via decreasing transforming growth factor-beta-1 and interleukin-6 in lung cancer patients treated with radiotherapy. Lung Cancer. Feb 2008;59(2):219-226.

Newall CA, et al. Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press; 1996.

Brinker F. Herb Contraindications and Drug Interactions, 3^rd ed. Sandy (OR): Eclectic Medical Publishing; 2001.

Tamayo C, et al. The chemistry and biological activity of herbs use in Flor-essence herbal tonic and Essiac. Phytother Res 2000;14:1-14.

Ding Y, Zhao L, Mei H, et al. Exploration of Emodin to treat alpha-naphthylisothiocyanate-induced cholestatic hepatitis via anti-inflammatory pathway. Eur J Pharmacol. Aug 20 2008;590(1-3):377-386.

Blumenthal M, Goldberg A, Brinckmann J. Herbal Medicine, Expanded Commission E Monographs. Austin: American Botanical Council; 2000.

Kang SC, Lee CM, Choung ES, et al. Anti-proliferative effects of estrogen receptor-modulating compounds isolated from Rheum palmatum. Arch Pharm Res. 2008 Jun;31(6):722-6.

Li WY, Chan SW, Guo DJ, et al. Water extract of Rheum officinale Baill. induces apoptosis in human lung adenocarcinoma A549 and human breast cancer MCF-7 cell lines. J Ethnopharmacol. 2009 Jul 15;124(2):251-6.

Tang JC, Zhang JN, Wu YT, Li ZX. Effect of the water extract and ethanol extract from traditional Chinese medicines Angelica sinensis (Oliv.) Diels, Ligusticum chuanxiong Hort. and Rheum palmatum L. on rat liver cytochrome P450 activity. Phytother Res. 2006 Dec;20(12):1046-51.

How It Works

Bottom Line: Rhubarb is not an effective treatment for cancer or any other medical condition. It can act as a stimulant laxative, but is not safe to use for long periods of time.

Rhubarb is a perennial herb the stalks of which are consumed as food. The rhizome and roots are used as laxatives and to treat ulcers, constipation, diarrhea, hypertension, immunesuppression, and cancer in Chinese medicine. In laboratory experiments, rhubard showed biological effects, but scientists are still unsure how rhubarb works. Chemicals in rhubarb called anthraquinones cause tumor death in mice implanted with some solid tumors. Lindeyin, a chemical found in rhubarb, was found to reduce pain and inflammation in laboratory animals.
More studies are needed.

Purported Uses

To treat cancer
No scientific evidence supports this use.
To reduce the severity of side effects from anticancer therapy
One small study suggested that a rhubarb extract may reduce side effects associated with radiation therapy in lung cancer patients, but further studies are needed to draw a conclusion.
To relieve constipation
Rhubarb act as a laxative, although clinical trials have not tested this use. Prolonged use of rhubarb as a laxative may lead to dangerous blood electrolyte imbalances.
As a fever reducer
There is no research to validate this claim.
To lower high blood pressure
One study in China found that low-dose rhubarb could prevent high blood pressure in pregnancy, but there is no other evidence that rhubarb can lower high blood pressure.
To suppress the immune system
Laboratory data shows that rhubarb decreases the activity of isolated immune cells, but there is no proof from clinical trials that this effect occurs in the human body.
To reduce inflammation
No scientific evidence supports this use.
To treat infections
This claim is not backed by research.
To treat stomach ulcers
Rhubarb is often used in traditional Chinese medicine to treat gastrointestinal disturbance, but there is no proof from clinical trials to support this use.

Research Evidence

Reducing side effects associated with radiation therapyIn this study, 80 lung cancer patients undergoing radiation therapy also received a rhubarb extract or placebo for 6 weeks. Side effects associated with radiation therapy, such as cough, shortness of breath, fever and lung function were measured after 6 weeks and 6 months. Patients receiving rhubarb reported decreased side effects and improved lung function. No negative side effects were reported. Larger studies are needed to confirm these effects.

Patient Warnings

Rhubarb is considered to be a stimulant laxative, and therefore should not be used for more than seven days without medical supervision.
This product is regulated by the FDA as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. This product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.

Do Not Take If

You have kidney or liver problems, a history of kidney stones, inflammatory bowel disease, arthritis, or intestinal obstruction.
You are pregnant (Rhubarb may cause stimulation of the uterus and may increase the risk of miscarriage).
You have hormone-sensitive cancers such as breast, prostate, cervical, and uterine cancers (Rhubarb may have estrogenic activity).
You are taking potassium-wasting diuretics (Rhubarb can have a stimulant laxative effect, which can lead to additional potassium loss when used for prolonged periods).
You are taking digoxin (Rhubarb can have a stimulant laxative effect, which can lead to potassium loss when used for prolonged periods. Low potassium levels in the blood can interfere with the activity of digoxin and cause toxicity).
If you are taking drugs that are substrates of Cytochrome P450 (Rhubarb may reduce the effectiveness of these drugs).

Side Effects

Abdominal cramps
Nausea and vomiting
Diarrhea, which can possibly lead to low blood potassium levels if prolonged.
Anaphylactic shock
Kidney and liver damage

Special Point

Rhubarb contains chemicals that can change the color or urine, interfering with urinalysis. Do not take rhubarb for a few days before having a urinalysis.
Rhubarb is one of the herbs found in Essiac tea.

Dosage (Inside MSKCC Only)

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Aliases

Da Huang

Rheum Officinale

Turkey Rhubarb

E-mail your questions and comments to aboutherbs@mskcc.org.

Last updated: August 15, 2011