Rhubarb is a common garden plant, widely appreciated for its tart, fleshy stalks often used in pies and desserts. Despite the popularity of its edible stems, the large, green leaves of the rhubarb plant are toxic and should never be consumed. It is important to understand the potential dangers associated with rhubarb leaves.
The Source of Toxicity
The primary toxic compound found in rhubarb leaves is oxalic acid, along with its salts, calcium and potassium oxalates. Oxalic acid is an organic acid that occurs naturally in various plants, though its concentration is particularly high in rhubarb leaves. When ingested, oxalic acid binds with calcium ions in the body, forming insoluble calcium oxalate crystals. This binding removes calcium from the bloodstream, which can disrupt normal bodily functions. These calcium oxalate crystals can accumulate in the kidneys, potentially causing kidney stone formation and kidney damage.
Some research suggests that other unidentified chemical components, such as anthraquinone glycosides, may also contribute to the leaves’ toxicity. While oxalic acid is a known concern, some reports indicate that fatalities attributed to rhubarb leaf consumption might involve these additional compounds, as oxalate crystals have not always been found in post-mortem examinations.
Signs of Ingestion
Consuming rhubarb leaves can lead to a variety of symptoms. Initial signs of mild poisoning often include irritation, such as a burning sensation in the mouth and throat, increased saliva production, nausea, vomiting, abdominal pain, and diarrhea. These gastrointestinal disturbances typically resolve within a few hours.
More significant exposures can result in more serious issues, including difficulty swallowing, a sore throat, and persistent vomiting, which may sometimes contain blood. The accumulation of calcium oxalate crystals can lead to kidney damage, manifesting as flank and back pain from kidney stones, and in severe cases, kidney failure. In rare but severe instances, individuals might experience muscle weakness, numbness, muscle twitching, seizures, breathing difficulties, or even fall into a coma. Blistering and swelling in the mouth can become so pronounced that they hinder normal speech and swallowing. Symptoms can persist for one to three days and may necessitate hospitalization.
What to Do After Exposure
If someone has ingested rhubarb leaves, immediate medical attention is necessary. Contact a local emergency number or the national toll-free Poison Help hotline at 1-800-222-1222 in the United States. Do not induce vomiting unless specifically instructed to do so by a medical professional or poison control expert.
If the plant material has come into contact with the skin or eyes, thoroughly flush the affected areas with plenty of water. When seeking medical help, providing details such as the person’s age, weight, condition, and the approximate time and amount of leaves swallowed, can assist healthcare providers. Medical staff will monitor vital signs and kidney function, providing supportive care and managing symptoms as needed.
Rhubarb: Leaves vs. Stalks
The distinction between edible rhubarb stalks and toxic leaves is important. While both parts of the rhubarb plant contain oxalic acid, the concentration in the leaves is significantly higher, rendering them unsafe for consumption. Rhubarb stalks, or petioles, contain much lower levels of oxalic acid, which is not enough to pose a health risk.
The stalks derive much of their acidity from malic acid, contributing to their distinctive tart flavor. Cooking the stalks can further reduce their oxalic acid content. Always remove and discard the leaves entirely before preparing or consuming rhubarb stalks. If rhubarb plants experience severe freezing, the oxalic acid can potentially migrate from the leaves into the stalks, making it prudent to discard any stalks that appear damaged or mushy after a hard frost.