Oxalic Acid is present in very small amounts in chives, oca, parsley, rhubarb, sorrel, spinach and taro, and in even smaller amounts in a zillion other types of produce from asparagus to sweet corn.
It can make something taste tart, as it does in sorrel.
Oxalic Acid is poisonous in very large amounts.
It hinders the body from absorbing calcium and iron because it combines with them to form compounds called “oxalates” that our bodies can’t absorb very well. But in small amounts, it is nothing to worry about it: our own bodies actually even make it, while processing Vitamin C.
The two main Oxalic Acid caveats regarding foods that you might possibly eat are:
- If you ever cook taro, always cook it properly;
- When using rhubarb, never, ever be tempted to eat or use the leaves. The Oxalic Acid in rhubarb leaves is so high that it is fatal to many people.
Oxalic Acid was discovered in 1776.
During WW1, Americans were encouraged to eat rhubarb leaves as a supplement to fresh vegetables, which added a few homefront casualties to the overall toll of the war.