About Herbs

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

Rhubarb is a root extract that has traditionally been used as a laxative. In laboratory experiments, it shows additional biological effects, but scientists are still unsure how rhubarb works. Rhubarb extracts appear to suppress the activity of isolated immune cells in the laboratory. Chemicals in rhubarb called anthraquinones have been shown to induce tumor death in mice implanted with certain solid tumors. Lindeyin, a chemical found in rhubarb, was found to reduce pain and inflammation in laboratory animals. However, none of these effects have been seen in humans. 

Preventing progression of kidney failure
In a clinical trial conducted in China, researchers studied the ability of rhubarb, taken with or without captopril (a medication used to lower blood pressure), to prevent the progression of chronic kidney failure. Eleven patients took rhubarb alone, nine took rhubarb plus captopril, and ten took captopril alone. The researchers found that rhubarb, with or without captopril, appeared to slow the progression of the disease after ten months, but actually all three groups of patients reported improvements in quality of life. However, because this is such a small study, it is difficult to say whether these results are due to a true effect of rhubarb, or due merely to chance. Therefore, larger clinical trials would be helpful to confirm this effect.

Rheum palmatum, Rheum officinale

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

Derived from the root of the plant. Rhubarb has been used for a variety of conditions including cancer ⁽⁷⁾, immunosuppression, constipation ⁽¹⁾, diarrhea, gastrointestinal ulcers, hypertension ⁽⁸⁾ and chronic renal failure ⁽⁹⁾. The anthraquinone and tannins are thought responsible for the laxative and constipating effects, respectively ⁽⁴⁾. Limited human clinical data are available for any claims made; most clinical trials have been conducted in China, often using herbal combinations. Animal data show antitumor effects in mice ⁽⁷⁾, but this has not been studied in humans. Adverse effects are primarily gastrointestinal in nature. Chronic consumption can cause hypokalemia due to diarrhea, possible renal and hepatic damage from oxalates ⁽³⁾, theoretical hypokalemia when combined with diuretics, and altered response to digoxin ⁽⁶⁾. Rhubarb should only be used under medical supervision.

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. Anthraquinone extracts have been shown to induce tumor necrosis in mice (sarcoma 37, mammary, and Ehrlich) ⁽⁷⁾, although this has not been demonstrated in humans. Lindeyin, a phenolic gallylglucoside exhibits analgesic and antiinflammatory activity in animal models. Catechin, epicatechin, procyanidins, and gallylglucose inhibit hyaluronidase in vitro.
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Stimulant laxative products such as rhubarb should not be used for prolonged periods (i.e. greater than 7 days) without medical supervision.
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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.

Reported: Abdominal cramps, nausea, vomiting, diarrhea leading to possible hypokalemia, anaphylaxis, renal and hepatic damage
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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.
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Anthraquinones can cause discoloration of the urine interfering with urinalysis.

Zhang JH, Li LS, Zhang M. Clinical effects of rheum and captopril on preventing progression of chronic renal failure. Chin Med J 1990;103:788-93.
A prospective evaluation of 30 patients receiving either rheum (rhubarb) (n = 11), rheum and captopril (n = 9), or captopril alone (n = 10) compared to historical controls (n = 12). Patients receiving rheum were started on 1 gram/day and titrated up to 6 - 9 grams/day as tolerated; no information describing final doses achieved was provided. Anecdotal quality of life information stated that uremic symptoms disappeared and patients had more active lifestyle regardless of intervention. Rheum with or without captopril appeared to slow the progression of disease as compared to controls over a 10 month period. Two thirds of patients receiving rheum reported diarrhea, but no other adverse reactions were noted. Additional randomized studies are need to confirm the results found in this study.