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Why You Shouldn't Eat Raw Kale

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Why You Shouldn't Eat Raw Kale

Cary Berkley

I recently had a friend ask me if it was OK to put raw kale in her smoothies every day. "No, don't do that!" I told her. Kale is a vegetable high in goitrogens and oxalic acid. It dawned on me that not everybody knows about these two obscure things. But of course, why would they?

First, goitrogens - These are substances that spur the thryroid by interfering with iodine uptake, which can result in enlargement of the thyroid. Here are some examples of goitrogenic foods:

  • Kale
  • Broccoli
  • Cauliflower
  • Brussels Sprouts
  • Mustard Greens
  • Radishes

These foods should be cooked, or consumed only in very small amounts if eaten raw. Being careful with your intake of goitrogenic foods is particularly important if you have a thyroid issue.  If you don't, it's still recommended that you primarily eat these foods cooked.

Second, oxalic acid - This acid found in fruits and vegetables binds with important minerals and causes them to crystallize, which can damage tissues and cause inflammation. Oxalic acid also contributes to kidney stones, so if you have been diagnosed with a kidney stone, you should definitely limit your intake of foods that are high in oxalic acid. Some examples of vegetables high in oxalic acid include:

  • Kale
  • Beet greens
  • Spinach
  • Rhubarb

One way to reduce oxalic acid uptake is to eat oxalic acid-containing foods with a calcium source such as yogurt or cheese which may reduce the formation of kidney stones, according to the University of Maryland Medical Center.  Another way is by boiling or steaming foods high in oxalic acid, which greatly reduces the oxalic acid content according to a study in 2005 in the Journal of Agricultural Food Chemistry. The study found that boiling spinach reduced the oxalic acid content by 87 percent. 

So, the next time you go for the green smoothie, try this recipe and modify it to suit your taste: 

  • 1 cup water
  • 1/2 cup full-fat coconut milk
  • 1 cup frozen mango
  • 1/2 sliced cucumber
  • 1 stalked celery, rinsed and coarsely chopped
  • 1 small handful of cilantro, rinsed
  • juice of 1/2 of a lemon
  • 1 tablespoon chia seeds
  • 1 cup frozen, organic strawberries
  • 1 bunch of kale, boiled for 5 minutes then squeeze excess water out
  • 1 scoop of Plant Fusion protein powder, grass-fed gelatin, or grass-fed whey protein powder

Play with the ingredients and see what works for you and your unique biochemistry. Some individuals may require more or less fat, or specific types of proteins depending on your situation. I will often make a whole pitcher and drink throughout the day. 

Let me know what combination works best for you!