Kale and Chard: A Burning Sensation

Someone once said that the definition of insanity is doing the same stupid thing over and over again with the same results — not learning the lesson — and I must confess that applies to me here!

I grow a lot of chard and spinach and lettuce and kale. They all seem to thrive at Casa de Enchanted Seashells. I cook some, freeze some, annoy everyone by putting it in every baked good from brownies to cookies, and I love to eat it raw.

That’s where this started. For a while, I’ve been picking chard and kale while I’m outside gardening, just to enjoy being Mother Earth in action.

For a similarly long time, I’ve noticed that after I eat raw kale and chard and sometimes spinach, my throat starts to burn, not like I ate something spicy, but like I mixed bleach and ammonia and inhaled it (yes, I’ve done that, too, accidentally of course).

After several experiences of this painful throat, I finally did what I should have done the first time, I GOOGLED the symptoms.

Lo and behold, it’s a THING.

Maria Hepler, RDN, CLT: Calcium, which is an essential nutrient for strong bones, can be found in many green leafy vegetables, such as collard greens, spinach, mustard greens, kale, and Swiss chard.

However, oxalic acid, an organic acid found in spinach, chard, and beet greens, and moderately in kale, among other plants, binds with the calcium they supply and reduces its absorption, so in their raw form these should not be considered a good source of calcium.

What are the symptoms that one has eaten too much oxalic acid?  These include burning in the mouth and throat, difficulty breathing, weakness, stomach pain, nausea, vomiting, and diarrhea.

Spinach contains phytic acid and oxalic acid. It may be better to steam the spinach and not to eat it raw.

For sensitive individuals, even small quantities of oxalic acid  eaten regularly can lead to kidney stones or bladder crystals, along with the problem of calcium depletion. 

Does this mean we shouldn’t add kale or other greens that contain oxalic acid to our smoothies? Not necessarily. Cooking or steaming these vegetables can significantly reduce the amount of oxalic acid present, which will help with calcium absorption (make sure to drain your greens thoroughly as the oxalates go in the water).

If this is a concern, it’s best to precook leafy greens and store them in the freezer (in individual portions) for quick access.

I never used to notice this reaction to acidity in raw greens but now that I know, I will definitely stick to picking lettuce for my garden treats.