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I've heard that rhubarb leaves are poisonous, and that you can even die from rhubarb poisoning. Is that true?

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The dosage makes the poison. Maybe you want to add your question to specify the amount? For example: "Can eating a single leave of rhubarb kill a man?" – Lagerbaer Apr 9 '11 at 15:32
I've edited out the single leave part again, I think the general question about toxicity is fine, we don't need to be overly specific about amounts. – Fabian♦ Apr 9 '11 at 16:00
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2 Answers

up vote 12 down vote accepted

The green leaves of the rhubarb contain large amount of oxalic acid and probably toxic anthraquinone glycosides. Eating the leaves can lead to acute poisoning and also death. The anthraquinone glycosides are thought to be the main cause for rhubarb leave poisoning.

On the website of the Canadian Poisonous Plants Information System you find the following about rhubarb:

The stalks are widely used as preserves and are also eaten raw, without problems. The toxic content is much lower in the stalks. Humans have been poisoned after ingesting the leaves. Human poisoning was a particular problem in World War I, when the leaves were recommended as a food source in Britain.

To summarize, the rhubarb stalks are safe, but you should never eat the rhubarb leaves.

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Mmmm, rhubarb pie! :) – Larian LeQuella♦ Apr 9 '11 at 16:52
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Great answer.Just to kick in some boring details, the estimated lethal dose of oxalic acid is about 375mg/kg.Rhubarb leaves contain on average 0.5% oxalic acid, which means to cause death, a 70kg (150lbs) person would have to eat about 5kg (11lbs) of leaves in order to die.However,sickness occurs at much lower doses.It is usually fairly rapid in onset and unpleasant enough (abdominal pain, vomiting, etc) to keep the average person from continuing to eat the leaves.The oxalic acid may also have some effect on formation of kidney stones if enough is consumed.So, stick to the pie – Monkey Tuesday Apr 11 '11 at 0:34
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up vote 3 down vote

According to Rhubarb Info, the leaves are toxic, but on average require a large amount to actually poison you, though it doesn't take nearly as much to make you sick.

Oxalates are contained in all parts of rhubarb plants, especially in the green leaves. There is some evidence that anthraquinone glycosides are also present and may be partly responsible. It is not clear as to the exact source of poisoning from rhubarb, possibly a result of both compounds. The stalks contain low levels of oxalates, so this does not cause problems.

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