how to eat kale (and its cousins) safely

There was a period of time when kale was everyone’s favorite health food (whether or not they personally enjoyed it.) Then came the backlash, with dozens of articles and YouTube videos sharing titles like “the dark side of kale.”

Obviously, anything eaten in excess can be harmful. And if it’s grown in soils with heavy metals, or loaded with toxic pesticides, that’s not going to be good for you.

But the main issue I have with kale and its Brassicaceae family cousins is that people don’t know one basic thing about it: If you don’t cook them, these plants can impair your thyroid function.

But see, it’s really just that simple. Cook these veggies and you’re fine. If you have a thyroid problem — low levels, autoimmune disease, history of thyroid cancer — you may need to minimize or avoid the members of this family that you don’t cook.

What’s missing, though, is a comprehensive list of Brassicaceae (or mustard) family veggies. So to help the cause, I’ve created one here.

Again, these are generally healthy foods for most people. You just need to avoid extremes and remember to keep the majority cooked.

most common brassicas

  • Cabbage
  • Kale
  • Broccoli
  • Cauliflower
  • Brussels sprouts
  • Mustard greens or seeds
  • Radishes (all kinds)
  • Arugula

less common cousins

  • Collard greens
  • Kohlrabi
  • Napa cabbage
  • Daikon radish
  • Rapini (a.k.a. broccoli rabe)
  • Turnips (including greens)
  • Bok choi

brassica spices

  • Watercress
  • Horseradish
  • Wasabi

I worry least about this last category since doses are likely to be small. Even if you really, really love wasabi peas.

what about fermentation?

I’m generally a big fan of fermented veggies, especially things like sauerkraut and kimchi that are so easy to make at home. But does fermentation address the compounds in brassicas that can impair your thyroid?

The answer is a confusing probably not. In the case of millet (not a brassica) fermentation can actually increase the levels of thyroid-suppressing compounds.

how to eat brassicas safely

The best and safest way to eat these foods is the most basic: Rotate what you eat, try to mix up foods from different plant families, and lean toward cooking these plants when you eat them. (Here’s how I make kale chips.)

There’s also increasing evidence that adding iodine to you meals can reduce the anti-thyroid effects of brassica family foods. So toss on some gomasio or sprinkle your food with seaweed flakes and you’ll be better equipped to handle the less-healthy aspects of these otherwise rockstar veggies.


Read more about foods that affect the thyroid here.

Want help dialing in your diet? Book your personal appointment here.