The Toxic Danger of Rhubarb Leaves
One of the most significant and well-documented negatives of rhubarb is the toxicity of its leaves. Rhubarb leaves are poisonous to both humans and animals due to their extremely high concentration of oxalic acid, a naturally occurring chemical compound. Consuming these leaves, even in relatively small quantities, can lead to severe poisoning. During World War I, some people mistook the leaves for a vegetable substitute, leading to documented cases of poisoning and fatalities. Symptoms of rhubarb leaf poisoning include:
- Burning sensation in the mouth and throat
- Nausea and vomiting, which can sometimes contain blood
- Diarrhea and abdominal pain
- Difficulty breathing
- Severe cases may lead to seizures, kidney failure, and even death
It is imperative to always discard the leaves entirely and only consume the stalks. Even a small amount of leaf residue could cause adverse effects, especially in children or small pets, who are more susceptible to poisoning.
Oxalate Content and Risk of Kidney Stones
While the stalks are safe, they also contain oxalates, though in much lower concentrations than the leaves. For most healthy individuals, consuming rhubarb in moderation is not an issue, especially when cooked, as this process can reduce oxalate levels significantly. However, people who are prone to developing kidney stones should be cautious or avoid rhubarb altogether. The most common type of kidney stone is calcium oxalate, and a high intake of dietary oxalates can increase the risk of their formation. In the kidneys, a buildup of calcium oxalate crystals can form these painful stones and, if left untreated, potentially lead to kidney failure in rare instances. Individuals with pre-existing kidney disease should also avoid rhubarb, as the compounds can exacerbate their condition.
Laxative Effects and Digestive Discomfort
Rhubarb is known for its strong laxative properties, which are attributed to compounds called anthraquinone glycosides. While this can be beneficial for those with occasional constipation, excessive or long-term use can lead to several negative side effects.
- Stomach pain and cramps: Overconsumption can cause significant gastrointestinal discomfort.
- Diarrhea: Its potent laxative effect can lead to watery diarrhea.
- Electrolyte imbalance: Long-term use or heavy consumption can cause a loss of potassium and other electrolytes, leading to dehydration and potentially irregular heart rhythms.
- Laxative dependence: Chronic use can cause the bowels to become dependent on laxatives, weakening the natural function of the digestive system.
People with inflammatory bowel diseases, such as Crohn's disease or ulcerative colitis, should avoid rhubarb.
Impact on Mineral Absorption and Nutrient Deficiencies
Oxalic acid is considered an "antinutrient" because it binds to minerals in the digestive tract, primarily calcium, and prevents their absorption. While this is usually not a concern with moderate intake for most people, those consuming large quantities of rhubarb, or those with existing mineral deficiencies, could see an impact. The unabsorbed calcium can also contribute to the formation of kidney stones. Similarly, the long-term depletion of calcium can potentially contribute to bone loss.
Drug Interactions and Medical Contraindications
Rhubarb's components can interact with various medications, making it unsafe for certain individuals. It is crucial to consult a doctor before consuming rhubarb, particularly in medicinal amounts or supplemental form, if you are on any of the following medications:
- Warfarin (Coumadin): Rhubarb's laxative effect can increase the risk of bleeding.
- Digoxin (Lanoxin): Lowered potassium levels from laxative use can increase the risk of digoxin toxicity.
- Corticosteroids and diuretics: These medications can also cause potassium loss, and combining them with rhubarb can lead to dangerously low potassium levels.
- Nephrotoxic drugs: As rhubarb can harm the kidneys, combining it with other drugs that affect kidney function can increase the risk of kidney damage.
Comparison Table: Rhubarb Risks vs. Benefits
| Aspect | Potential Negatives | Potential Positives |
|---|---|---|
| Leaves | Highly toxic and poisonous due to high oxalic acid levels; can cause severe symptoms or death. | None. Inedible and should be discarded. |
| Stalks (General) | Can cause digestive issues and cramps, especially if consumed in large quantities. | Good source of fiber, vitamin K, and antioxidants. |
| Oxalate Content | Increases risk of calcium oxalate kidney stones, especially for susceptible individuals. | Negligible benefit, and can be an antinutrient. |
| Digestive Effect | Stimulant laxative can cause dependency and dehydration with long-term use. | Promotes bowel regularity when used in moderation for occasional constipation. |
| Mineral Absorption | Oxalates can bind to and prevent absorption of minerals like calcium and iron. | None; this is a negative effect. |
| Health Conditions | Unsuitable for individuals with kidney disease, gout, IBS, and certain other conditions. | Contains antioxidant and anti-inflammatory compounds. |
Who Should Avoid Rhubarb?
Certain groups should avoid consuming rhubarb to prevent adverse health effects:
- Individuals with a history of kidney stones or kidney disease.
- People with inflammatory bowel diseases (Crohn's, colitis), bowel obstruction, or appendicitis.
- Pregnant and breastfeeding women.
- Toddlers and small children.
- People with liver problems.
- Individuals taking medications that can interact with rhubarb, including blood thinners and certain diuretics.
Conclusion
While the crisp, tart stalks of rhubarb are a popular ingredient for pies and crumbles, a clear understanding of what are the negatives of rhubarb is essential for health and safety. The leaves are highly toxic and must be avoided at all costs. The stalks, though safe for most people in moderation, contain oxalates that pose a risk for individuals with a history of kidney stones or existing kidney disease. Additionally, the laxative effect of rhubarb means it should be used cautiously, especially by those with gastrointestinal conditions or those on interacting medications. By consuming only the stalks, preparing them correctly (peeling and cooking), and being mindful of personal health conditions, one can enjoy rhubarb safely. For anyone with underlying health concerns, particularly those related to kidney, liver, or gastrointestinal function, consulting a healthcare provider before consuming rhubarb is the safest approach.
