Myth About Thyroid Health: "I Can't Eat Kale, Broccoli, Cabbage and Other Cruciferous Veggies"

food as medicine thyroid health Jan 03, 2020

This is one topic I love talking about because I’ll rarely tell someone to NOT eat their veggies! And when it comes to supporting optimal thyroid health, I’m not going to deny you your plate of greens! Let’s redeem those cruciferous vegetables and give them a place back at your table.

Delicious and nourishing vegetables like cabbage, broccoli, kale, Brussels sprouts, and cauliflower have been shunned from too many meals due to outdated misunderstandings and beliefs about thyroid disease.

What caused them to be dismissed?


It’s a funny-sounding word that can have a big impact on your thyroid health. Goitrogens are anti-nutrients. That means exactly what it sounds like. Whereas a nutrient helps and adds value to your health, an anti-nutrient hinders or takes away from health.


What Exactly Does a Goitrogen do to Your Thyroid? 

Goitrogens are compounds that impact your thyroid gland by interfering with or suppressing thyroid hormone production. They can also prevent your thyroid gland from absorbing adequate iodine, a mineral needed to make your thyroid hormones. To compensate, your thyroid enlarges to counteract the reduced hormone production and to try to grab more of your circulating iodine. This enlargement is what’s known as a goiter. Some refer to it now as a more delicate-sounding thyroid nodule.

You may have heard that you should avoid goitrogenic foods if you have a thyroid condition. This is only partially true, as all goitrogens are not equal. Different foods have different goitrogenic substances and properties. Let’s talk first about the big one.


Cruciferous veggies

Cruciferous vegetables such as cabbage, broccoli, kale, and cauliflower contain glucosinolates, compounds that can prevent the absorption of iodine into your thyroid gland. Eating too many of these foods in their raw state can cause symptoms of hypothyroidism in someone with otherwise well-controlled symptoms.

This was more of a problem decades ago when a primary cause for hypothyroidism was iodine deficiency. Since then, most industrialized countries have added iodine to their salt supplies, and iodine deficiency is rarely the main cause of hypothyroid conditions. The autoimmune condition, Hashimoto’s thyroiditis, is now the primary reason behind over 90 percent of hypothyroidism diagnoses in the United States. Remember, Hashimoto’s isn’t really a thyroid problem; it’s a problem with your immune system. Your thyroid gland just becomes the unfortunate victim of the attack.

Iodine deficiency is no longer a major concern in people with Hashimoto’s, and most cruciferous vegetables don’t even contain enough glucosinolates to cause an iodine deficiency.

Luckily, cruciferous vegetables are only goitrogenic when they’re consumed raw. Cooking or lightly steaming will deactivate the glucosinolates, and so will fermenting the vegetables (like when cabbage becomes sauerkraut). What was once a potential threat to your thyroid is now an inactive harmless substance.

While consuming fermented and cooked cruciferous vegetables is preferred, occasionally eating small amounts of these foods in the raw states should not aggravate autoimmune thyroid conditions. But, no more kale smoothies every morning!

So, have your crucifers and eat them too! Unless you have an overt or diagnosed sensitivity to this family of foods, it’s perfectly healthy for you to include (mostly cooked) cruciferous veggies to your meals. Most should be well-tolerated even if you have a diagnosed thyroid condition, and they offer health benefits like enhanced detoxification that you don’t want to miss out on.



Now here’s a food that should remain on the avoid list. Soy is one particular goitrogen-containing food that can be harmful to people with hypothyroidism and especially for those with Hashimoto’s disease. Soy contains a family of powerful phytochemicals called isoflavones. Three of these isoflavones, daidzein, genistein, and glycitein, block the activity of your thyroid peroxidase enzyme (TPO). TPO is essential for your thyroid gland to make your thyroid hormones. When it’s blocked, your thyroid can’t make all the T4 and T3 hormones that your body requires.

Isoflavones can be very beneficial to women, helping them reduce hot flashes and other bothersome symptoms associated with menopause. Genistein has even been shown to help reduce the risk and recurrence of hormonal cancers! When it comes to thyroid conditions, however, soy doesn’t have a place at the table.

Unlike cruciferous vegetables, the goitrogens in soy aren’t deactivated when they’re heated. So whether you’re drinking soy milk or gobbling up your tofu scramble, the goitrogen effect is the same.

Additionally, soy is a very common food allergen, is almost always genetically modified, and is rarely organic. Soybean crops just aren’t what they used to be.

If you have a diagnosed or suspected underactive thyroid condition, you should avoid soy and it’s goitrogenic compounds completely. If you currently include soy regularly, try removing it from your diet and stay attentive to how you feel or if you notice changes in your lab values. Of course, let your doctor know about the changes you’re making with this or any other major food category.


A few lesser-known goitrogenic foods:

Millet is a gluten-free grain that is frequently used in gluten-free breads and baked goods. Like soy, millet contains isoflavones that inhibit your TPO enzyme and should be avoided by people with thyroid disorders. 

Canola oil (made from the rapeseed plant) and nitrates can have toxic effects on your thyroid gland, inhibiting iodine uptake in a similar way to the glucosinolate-containing crucifers. Both of these are commonly found in processed and packaged foods, so focusing your intake as much as possible on whole, real foods will reduce both.


So let’s review!

  • Goitrogens are compounds found in cruciferous vegetables and other foods that prevent your thyroid gland from absorbing all the iodine it needs to make your thyroid hormones.
  • Many goitrogens, especially those in cruciferous vegetables, are deactivated when you heat, cook, steam, or ferment them. These foods can be eaten in moderation without causing impairment to your thyroid gland.
  • Raw kale is very high in goitrogenic compounds and should be eaten rarely, if at all, by those with hypothyroid conditions.
  • Goitrogens in soy foods remain active after heating and cooking. Soy foods should be avoided by those who have hypothyroidism or Hashimoto’s.
  • Other foods like millet, canola oil, and nitrates can impact thyroid health and should be avoided if you have an active thyroid condition.

I hope this gives you a greater understanding of why these colorful vegetables can safely find a spot on your plate.


Have you avoided any of these foods because of a thyroid condition? Let me know!





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