Ordinary garden rhubarb carries the botanical name of Rheum rhaponticum, though there are other members of this botanical group that are also used for medicinal purposes.
Chinese rhubarb, which is called da huang in traditional Chinese medicine, has the botanical name Rheum palmatum. Chinese rhubarb has a much stronger taste and properties than the common American variety.
Rhubarb is a member of the same family as buckwheat, the Polygonaceae family. It originally came from Mongolia in northern Asia, but was long ago introduced to both India and Turkey. It was formerly called India or Turkey rhubarb.
In the 1760s, in England, an Oxfordshire pharmacist named Hayward began developing and growing the type of rhubarb most commonly grown today.
Records indicate that rhubarb was first grown as a market crop in England in 1810. But because it was unknown, few people purchased it. In the next one hundred years, its popularity grew tremendously.
The average life expectancy of rhubarb plants is five to eight years. Although rhubarb produces seeds, they can give birth to plants remarkably different from the parent plant. For this reason, rhubarb cultivation is usually done by cutting and replanting pieces of its large storage root.
Rhubarb is an early plant that is extremely hardy. It is relatively immune to attack by insects or disease. It puts out smaller feeder roots in early spring; even in colder regions, reddish bud-like projections appear in early April.
These develop rapidly into long thick succulent stalks that can grow from 1–3 ft (approximately 30–90 cm) in length. Rhubarb stalks are generally ready for harvesting by late May.
One very large spade-shaped leaf with curled edges grows at the tip of each stalk. There is considerable evidence that these leaves should be considered poisonous due to their high content of salts of oxalic acid. Oxalic acid is a powerful but toxic cleaning agent.
Although M. Grieve reports that people have eaten both the leaves and the newly formed rhubarb buds without any problem, she also mentions several sources that listed several cases of death by rhubarb leaf poisoning around 1910.
Rhubarb stalks have a tangy, sweet-sour taste much prized for the making of desserts, especially pies. Rhubarb stalks are a good source of ascorbic acid (vitamin C).
Chinese rhubarb produces a yellowish root with a distinctive network of white lines running along the outer surface. Chinese rhubarb root is much larger and more firmly textured than its Western relatives, and has much stronger laxative qualities, but it is also less astringent.
The root of Western garden rhubarb is smaller, spongier, and is usually pinkish in color. It has sporadic star-shaped spots evident along its transverse sections.
General use
Rhubarb root has properties that make it a highly effective laxative. Its astringent qualities help to improve bowel tone after it has purged the intestines, making it an excellent agent for improving the tone and health of the digestive tract. Its laxative effects make it a valuable aid in the treatment of chronic constipation, hemorrhoids, and gastroenteritis.
Skin eruptions caused by problems in elimination are also treated with rhubarb root. The Western rhubarb root, being milder, is used in treating infant digestive problems, constipation, or diarrhea.
Traditional Chinese medicine
Da huang, or Chinese rhubarb, is one of the most ancient and best known plants used in Chinese herbal medicine. Rhubarb and its wide range of uses were first documented in the Divine Husbandman’s Classic of Materia Medica, which was written during the later Han Dynasty, around 200 A.D. The Chinese also used rhubarb root as a laxative and purgative for the treatment of both constipation and diarrhea, depending upon the dosage used.
Larger doses cause purging that removes toxins from the intestinal tract, while smaller doses are believed to moisten the mucous membranes of the intestines and improve their tone.
The tannins that are also found in the root may eventually cause binding of the bowel. Chinese rhubarb’s laxative component normally works within eight hours.
Rhubarb root has been found useful in controlling gastrointestinal hemorrhage by promoting the formation of blood platelets. This increase in the number of platelets shortens blood clotting time and is helpful in treating jaundice. Recent studies in China and Japan demonstrated that rhubarb root can delay or stop the progression of chronic renal failure.
One of the tannin components of rhubarb root, lindleyin, has been shown to act as an anti-inflammatory agent with fever-reducing properties similar to those of aspirin. Lindleyin is used in treating endometriosis and some menstrual problems.
Emodin, another component of Chinese rhubarb root, has been found to inhibit the growth of cancer cells. Chinese herbalists have found rhubarb root helpful in external applications for burns, suppurative sores and ulcers, conjunctivitis, and traumatic injuries.
There is some empirical evidence that da huang can reduce high blood pressure during pregnancy, although it should be used very cautiously in pregnancy. It has the ability to fight such anaerobic infectious agents as Candida albicans.
Chinese herbalists also use rhubarb root for diseases and disorders in the upper body, including sinus and lung infections, nosebleeds, and eye infections. According to the principles of traditional Chinese medicine, rhubarb root makes the heat in the upper body discharge through the bowel.
More recently, Japanese researchers have suggested that rhubarb root is effective in treating the severe diarrhea associated with cholera. One of the tannins isolated from rhubarb root, galloyl-tannin, appears to counteract the toxin secreted by the bacterium that causes cholera.
Although some of the individual chemical compounds that can be isolated from rhubarb have been reported to cause cancer, there is no evidence as of 2002 that rhubarb by itself or herbal preparations containing it cause cancer in humans.
Preparations
Rhubarb root is usually taken from plants four or more years of age. It is dug up in the autumn, usually October, washed thoroughly, external fibers removed, and dried completely. The root is then pulverized and stored in a tightly closed container.
Chinese rhubarb root usually comes from either China or Turkey. It can be purchased either in a powdered form or as a tincture. Putting 1.5–1 tsp (2.5–5 cc) of pulverized rhubarb root in 1 cup (240 cc) of water can make a decoction, or tea.
This mixture is brought to a boil and then simmered at reduced heat for 10 minutes. Rhubarb tea can be taken twice a day. The tincture can be taken in a dose of 1–2 ml three times a day. Chinese herbal preparations of rhubarb root are individually compounded for each patient. Rhubarb root may be combined with other herbs.
Precautions
Chinese rhubarb should be prescribed only by a trained herbalist. It should not be taken by children under twelve years of age, or by pregnant or nursing women. It should also not be used by persons with acute and chronic inflam- matory diseases of the intestine, including Crohn’s disease, appendicitis, and intestinal obstruction.
When rhubarb is used for its laxative-purgative qualities, the patient should be reminded that constipation is often caused by poor diet and lack of proper exercise.
Correcting these patterns can improve bowel function without the use of any other therapy. People who use rhubarb root long-term for bowel problems may find that its effectiveness is decreased by extended use, and can also cause excessive loss of electrolytes from the intestinal tract.
Loss of electrolytes, especially potassium, can lead to muscle weakness, and in extreme cases, cardiac arrhythmias. It should be noted that rhubarb root can color the urine either a deep yellow or even red.
It is possible to become intoxicated from an overdose of rhubarb, though the plant is generally safe to take in the recommended doses and manner. Signs of overdosage include vertigo, nausea and vomiting, and severe abdominal cramps. Long-term use can lead to hypokalemia and cirrhosis of the liver.
Some specialists in internal medicine maintain that rhubarb should not be taken by people who are susceptible to gallstones or kidney stones.
Side effects
Severe abdominal cramping is a common side effect of rhubarb root. This problem can often be alleviated by reducing the dose.
Interactions
Due to the possible loss of potassium, rhubarb root should not be taken in combination with cardiac medications, diuretics, other laxatives or cathartics, or steroids. Loss of potassium from the system can be decreased by combining the rhubarb root with licorice root.
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