Rhubarb is a common garden plant, prized by cooks and bakers for its pleasantly tart stalks. While the firm, reddish-green stems are a popular ingredient, the large, fan-shaped leaves must never be consumed. Ingestion of rhubarb leaves introduces powerful toxic compounds into the body, which can lead to a severe and potentially life-threatening reaction.
The Toxic Compound in Rhubarb Leaves
The primary source of toxicity in rhubarb leaves is a naturally occurring substance called oxalic acid. This chemical compound is present in many common vegetables but exists in significantly higher concentrations within the rhubarb foliage. When ingested, oxalic acid causes harm primarily through a process known as calcium chelation. The acid rapidly binds with free calcium ions in the bloodstream and digestive tract, forming insoluble calcium oxalate crystals. These microscopic, sharp crystals immediately begin irritating and damaging the delicate mucous membranes lining the mouth, throat, and gastrointestinal system. The systemic binding of calcium depletes the body’s store of this mineral, which is necessary for nerve and muscle function.
Immediate Effects and Symptoms of Ingestion
The initial symptoms of consuming rhubarb leaves are often immediate and centered in the mouth and digestive tract. A person will typically experience a burning sensation in the mouth and throat, followed quickly by intense nausea and vomiting. Abdominal cramps and diarrhea are common as the sharp calcium oxalate crystals irritate the stomach and intestines.
As the toxins are absorbed, the effects become systemic, with the most serious consequences targeting the kidneys. The insoluble calcium oxalate crystals that form in the blood are filtered by the kidneys, where they accumulate in the renal tubules. This accumulation can physically obstruct and damage the kidney tissue, leading to acute kidney injury or renal failure.
Systemic Effects
The depletion of systemic calcium due to chelation can also lead to neuromuscular symptoms. Severe poisoning may cause muscle weakness, difficulty breathing, and seizures. Significant ingestion can result in a drop in blood calcium that affects cardiac function, potentially leading to coma. Recovery typically takes one to three days, but serious cases may require extensive hospitalization.
Emergency Protocol Following Consumption
If rhubarb leaves have been ingested, the immediate first step is to contact a regional Poison Control Center (1-800-222-1222). These experts provide tailored instructions based on the person’s age, weight, and the estimated amount consumed. It is important to rinse the mouth thoroughly to remove any remaining plant pieces or irritating residue.
Administering a small amount of milk or other calcium-rich liquid may be advised as a preliminary measure. The calcium in the liquid can help bind the oxalic acid in the stomach, neutralizing it before absorption. Vomiting should not be induced unless a medical professional or Poison Control explicitly instructs it.
Professional medical attention is necessary to monitor kidney function and electrolyte levels following any ingestion. Treatment typically involves monitoring vital signs and providing intravenous fluids to ensure proper hydration and assist the kidneys in flushing toxins. Blood tests will be performed to check calcium levels and assess the extent of potential renal damage.
Distinguishing Edible Stalks from Toxic Leaves
The difference in toxicity between the rhubarb stalks and the leaves is purely a matter of concentration. While the large, green leaves contain high levels of oxalic acid, the firm, typically pink or red stalks contain a significantly lower, non-toxic amount. Stalks generally contain between 0.39 and 0.54 grams of oxalic acid per 100 grams, whereas the leaves can contain up to 1.5 grams per 100 grams. When preparing rhubarb, the entire leaf blade must be trimmed away and discarded completely. The edible part is only the stalk, or petiole, which is visually distinct, being long, slender, and firm. This separation ensures that only the part of the plant with safe levels of the compound is used for culinary purposes.