Rhubarb acts as a stimulant laxative, but is not safe to use over 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, immunosuppression, and cancer in Chinese medicine. In laboratory experiments, rhubard showed biological effects, but scientists are still unsure of 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 study suggested that a rhubarb extract may reduce side effects associated with radiation therapy in lung cancer patients, but further studies are needed to confirm such effects.
To relieve constipation
Rhubarb acts as a laxative, although clinical trials have not tested this use.
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.
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 clinical trials have not been done.
Patient Warnings
Rhubarb is considered to be a stimulant laxative, and therefore should not be used for more than 7 days without medical supervision.
Do Not Take If
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 Cytochrome P450 substrate drugs: Rhubarb may reduce the effectiveness of these drugs.
Side Effects
A case of acute crystal-induced kidney failure has been reported in a type-1 diabetic patient (with normal excretory renal function) following excessive ingestion of rhubarb.
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 Chinese medicine for a variety of conditions including cancer, immunosuppression, 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), but human data are limited.
Cytotoxic (5), cytostatic (6)(14) and antitumor effects have been reported in cancer cells in vitro and in mice (1).
A rhubarb extract reduced radiation-induced lung toxicity and increased pulmonary function in lung cancer patients (7).
Purported Uses
Cancer treatment
Constipation
Fever
Hypertension
Immunosuppression
Inflammation
Microbial infection
Peptic ulcers
Mechanism of Action
When used in very 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); in vitro tests show suppression of TNF, IL-1, and IL-6 production. The actions of anthraquinones on rheinanthrone that 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 activity in animal models. Catechin, epicatechin, procyanidins, and gallylglucose inhibit hyaluronidase in vitro (10)(12).
Aloe-emodin also possesses 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 necrosis in mice (sarcoma 37, mammary, and Ehrlich) (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).
Warnings
Stimulant laxative products such as rhubarb should not be used for more than 1 week without medical supervision.
Contraindications
Patients with hormone-sensitive cancers should avoid rhubarb because estrogenic activity has been reported (13).
Adverse Reactions
A case of acute crystal-induced renal failure has been reported in a type-1 diabetic patient (with normal excretory renal function) following excessive ingestion of rhubarb (18).
Herb-Drug Interactions
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)(19).
