I had quite some customers who were concerned about eating sorrel, because of the oxalic acid it contains. I wanted to check out if it is true that sorrel or other oxalic acid foods are bad for you and should only be eaten in moderation. This is what I found out:
You cannot prevent to eat oxalic acid:
First there are a lot of foods containing oxalic acids and some of them don’t even taste sour, like chocolate, buckwheat, almonds, spinach, parsley or chives and more. The levels of oxalic acid vary a lot, depening on the growing conditions.
What's wrong with oxalic acids?
There are two concerns about oxalic acid: First, that too much oxalic acids leads to an increased risk of kidney stones. Second, that oxalic acid prevents the absorption of calcium. Both assumptions are rather oversimplified.
Why eating oxalic acids is not all that bad:
First, most of the oxalic acid in our body does not come from food, our body synthesises oxalic acid itself. Second, it seems that healthy people can dispose oxalic acid quite easily. Third it seems that there is not much difference in the uptake of calcium with or without oxalic acid in the food.
Who should be concerned?
However, for some people oxalic acid is not good. If you suffer from a kidney disorder, gout, rheumatoid arthritis, or chronic vulvar pain or hypercalcinuria (elevated levels of calcium in the urine) then you have to be careful how much oxalic acid you eat. For healthy people oxalic acid is not a problem unless you eat a lot of it and over a long time but you probably would have enough of it long before.
There are different opinions on whether or not blanching reduces the oxalic acid content but experts agree, that cooking does not help.
The good news:
Oxalic acid is not only bad for you, it is important for your colon health. Some of the healthiest foods contain oxalic acid and all food rich in antioxidants contain oxalic acids.
Last but not least, oxalic acid fights cancer.
Sorrel is a great perennial which is easy to grow in the shade. The variety of sorrel I offer is a garden sorrel with nice big leaves. I was told by an Indian customer that Indian recipes calling for spinach were traditionally made with spinach and sorrel.