rhubarb
Meaning of rhubarb: A garden plant whose edible stalk and toxic leaf sit on the same stem, and whose dried root is a traditional laxative.
Definition of rhubarb
Rhubarb is a plant of the genus Rheum, grown both as a food and used medicinally. The thick red stalks are eaten cooked, while the leaves contain enough oxalic acid to be poisonous. The dried root of Rheum palmatum and Rheum officinale has a long history in traditional Chinese medicine, mainly as a laxative, and it contains compounds called anthraquinones.
Which part is which?
| Part | Use | Notes |
|---|---|---|
| Stalk | Eaten, cooked with sugar | Very sour, safe in normal amounts |
| Leaf | Not eaten | High in oxalic acid, poisoning reported |
| Root | Dried for traditional preparations | Contains anthraquinone laxative compounds |
The plant sold as a vegetable and the plant used as a herbal remedy are related but usually different species. Garden rhubarb is normally Rheum rhabarbarum, while the medicinal root comes from Chinese rhubarb and its close relatives.
How does the root act as a laxative?
Anthraquinones pass through the small intestine largely unchanged. Bacteria in the colon then convert them into active forms that irritate the bowel lining, increase the fluid held in the stool and stimulate the muscle to contract. Senna and cascara work by the same mechanism. Effects of this class include cramping, loss of potassium with prolonged use, and a harmless darkening of the bowel lining seen at colonoscopy. The same compounds explain why the root has been used as a dye.
What is known about its other claimed effects?
Laboratory work has examined rhubarb extracts for anti-inflammatory and antitumor activity, and individual compounds such as emodin and rhein have been studied in cells and animals. These findings have not established a treatment use in people, and results in a dish do not carry over to a person taking a preparation of uncertain composition. Oxalate content is a separate consideration, since oxalate is a component of the commonest kind of kidney stone. Traditional systems also use the root in small amounts for the opposite purpose, to firm rather than loosen the stool, because its tannins act differently at low dose.
Also known as
Used in a sentence
The supplement history included a traditional preparation containing rhubarb root.
Good to know
Rhubarb leaves contain oxalic acid at levels that have caused poisoning, and the anthraquinones in the root act as a stimulant laxative rather than as an established treatment for inflammation.
Word origin
Where “rhubarb” comes from
From the Latin rha barbarum, meaning foreign rhubarb, where rha was an old name for the Volga river along which it was traded.