Rhubarb and Oxalic Acid

The oxalic acid in rhubarb leaves makes them inedible, and even poisonous. According to Wikipedia, "The long term consumption of oxalic acid leads to kidney stone formation in humans. Humans have been poisoned after ingesting the leaves, a particular problem during World War I when the leaves were mistakenly recommended as a food source in Britain."

Wikipedia also advises that rhubarb [stalks] should not be eaten if the plant has been damaged by severe cold, as the oxalic acid migrates from the leaves under these conditions.

Oxalic acid is also known as ethanedioic acid.

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