Rhubarb is a perennial vegetable that’s a staple of many desserts, often finding its way into pies and crumbles. While the vegetable provides numerous health benefits, the key is to only eat the stalks. The plant’s leaves contain a chemical called oxalic acid, which can be poisonous.
“Rhubarb leaves poisoning occurs when someone eats pieces of leaves from the rhubarb plant,” warns the U.S. National Library of Medicine.
The leaves also contain anthraquinone glycosides, which are suspected to be toxic, warns the health body.
Oxalic acid can also be found in spinach, Brussels sprouts, cauliflower, and broccoli but in lower concentrations.
According to the Ohio State University, oxalic acid is found in rhubarb leaves with a high content of around 0.5 grams per 100 grams of leaves.
Although, the health body notes that “the suggested lethal dose of oxalic acid is in the region of 15-30 grams, meaning you’d have to eat a fair few kilograms of the leaves to reach this dose, but lower doses can still cause nausea and vomiting”.
Symptoms (of oxalic poisoning):
- Burning in the mouth
- Death from cardiovascular collapse
- Difficulty breathing
- Burning in the throat/mouth
- Abdominal pain
- Kidney stones
- Red-coloured urine
- Eye pain.
Symptoms of anthraquinone poisoning include skin irritation, eye irritation and discolouration of urine.
Anecdotal reports of poisoning from rhubarb leaves makes for harrowing reading.
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In 1919, a doctor in Helena, Montana, wrote to the Journal of the American Medical Association concerning the disturbing case of a young wife who was pale, exhausted, and vomiting when he arrived.
She had apparently been pregnant – he found “the complete products of conception of about six weeks’ development, discharged into the bed clothes” – but the placenta was bloodless, and what blood there was would not coagulate.
She died a few hours later, bleeding from the nose.
The night before, she’d made rhubarb stems and leaves for supper, and had eaten most of the leaves herself, while her husband had only a little.
He was weak and dizzy, but did not die. The journal editors wrote back that the doctor’s hunch – that she had been poisoned by the rhubarb leaves, probably by oxalic acid – was likely correct.
A number of deaths from the use of the leaves have been reported,” they wrote.
“During the war the use of the leaves as a food substitute was recommended in England; when the danger of fatal poisoning became apparent (owing to several deaths) warnings against the use of the leaves were issued.”
While steering clear of the leaves is crucial, the stalks can provide a host of health benefits.
Rhubarb is jam-packed full of healthy nutrients, minerals, and vitamins.
Studies on the health benefits of rhubarb are limited, but there are some promising results.
For example, rhubarb contains high levels of fibre, which is linked to the lowering of cholesterol levels within the body.
A recent controlled study found that men who ate 27 grams of rhubarb-stalk fibre every day for a month experienced a drop in their cholesterol levels by eight percent as well as a drop in their LDL (bad) cholesterol of nine percent.
High cholesterol is a precursor to heart disease.