What is rhubarb as a dietary supplement?

Overview

The stalk of the intensely flavored rhubarb plant has been used in European cooking since the seventeenth century. Before this time, rhubarb species were utilized medicinally in traditional Chinese herbal medicine. Traditional uses include treatment of constipation, diarrhea, fever, menstrual problems, jaundice, sores (when applied topically), ulcers, and burns. Although there are many species of rhubarb, the one most studied is Rheum rhaponticum.

Uses and Applications

Rhubarb root contains lindleyin, a substance with estrogen-like properties. On this basis, extracts of rhubarb have been tried for the control of menopausal symptoms. In a twelve-week, double-blind, placebo-controlled trial of 109 women with menopause-related symptoms, the use of a standardized R. rhaponticum extract significantly improved symptoms compared with placebo. Improvements were particularly seen in rate and severity of hot flashes. While this is meaningful supporting evidence, additional independent trials are necessary to establish that this rhubarb extract is a safe and effective treatment for menopause.

Other potential uses of rhubarb lack reliable supporting evidence. One human trial purportedly found evidence that rhubarb could reduce the impairment of lung function that may occur when people with lung cancer receive radiation therapy. However, this study had a number of significant flaws, and its results cannot be regarded as reliable.

In another human trial, this one using a cream containing sage and rhubarb, researchers failed to find more than modest benefits for the treatment of herpes. Additional proposed uses of rhubarb are supported only by test-tube studies. For example, various rhubarb species have shown hints of potential value for the treatment of diabetes, kidney disease, liver disease, allergies, and pancreatitis. However, the vast majority of effects seen in test-tube studies do not recur in human trials.

Dosage

A typical dosage of rhubarb root is one-half to one teaspoonful of the root boiled for ten minutes in a cup of water, three times daily. In the foregoing menopause study, a standardized extract was used. Such extracts should be used according to label instructions.

Safety Issues

As a widely consumed food, rhubarb is thought to be relatively safe if consumed in moderation. However, the plant contains high levels of oxalic acid, and rhubarb consumption can markedly increase oxalic acid levels in the urine. This could lead to increased risk of kidney stones and other problems. Rhubarb leaf contains the highest oxalic acid content. The roots and stems contain less oxalic acid but higher levels of anthraquinones, laxative substances similar to those found in senna or cascara. It is safest to use rhubarb standardized extracts that have been processed to remove oxalic acid.

Contrary to some reports, consumption of rhubarb probably does not impair calcium absorption. Weak evidence hints that excessive consumption of rhubarb could increase the risk of stomach or colon cancer. Maximum safe doses in pregnant or nursing women, young children, and people with severe liver or kidney disease have not been established.

Bibliography

Choi, S. Z., et al. “Antidiabetic Stilbene and Anthraquinone Derivatives from Rheum undulatum.” Archives of Pharmacy Research 28 (2005): 1027-1030.

Heger, M., et al. “Efficacy and Safety of a Special Extract of Rheum rhaponticum (ERr 731) in Perimenopausal Women with Climacteric Complaints.” Menopause 13 (2006): 744-759.

Vollmer, G., A. Papke, and O. Zierau. “Treatment of Menopausal Symptoms by an Extract from the Roots of Rhapontic Rhubarb: The Role of Estrogen Receptors.” Chinese Medicine 5 (2010): 7.

Yu, H. M., 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 59 (2008): 219-226.

Zhao, Y. Q., et al. “Protective Effects of Rhubarb on Experimental Severe Acute Pancreatitis.” World Journal of Gastroenterology 10 (2004): 1005-1009.