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Emilia A asks: Should I avoid foods like broccoli and kale if I have a thyroid issue?

cruciferous vegetables and thyroid, goitrogens, hypothyroidism

Dear Emilia:


One of the top most misdiagnosed conditions people come to me for help with is their thyroid function, or lack thereof.  Unfortunately, many patients miss receiving proper diagnosis and care for their thyroid because the appropriate labs were never ordered.  Even more problematic, your symptoms plaguing your daily life as a thyroid patient may have been shrugged off as “normal.”  But when did unrelenting fatigue, stubborn weight loss, or depression become tolerable or normal?

When I hear patients complain of stubborn weight loss, cravings, dry skin, acne or eczema, unexplainable fatigue, inability to focus or concentrate, problems with menstruation or fertility, or even abnormal metabolic lab results for cholesterol, iron, or blood sugar, I immediately question if their thyroid is properly functioning.

There are many reasons why a large percentage of our population is suffering from a low functioning thyroid and Hypothydroidism. These reasons range from environmental toxins like mercury, which block active thyroid hormone from entering the cells through the receptor site, to low nutrient status, which inhibits the conversion of the inactive thyroid hormone T4 to its active form T3. Because everyone is different I use lengthy checklists and labs to assess an individual’s unique root cause of low thyroid.


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What I do not look for in these assessments, however, is if a person eats cruciferous vegetables and whether or not foods like broccoli, kale, collards, Brussels sprouts, radish or cabbage are the trigger for their hypothyroid or an autoimmune Hashimoto’s condition.

Hypothroidism and Why I Don’t Look at Cruciferous Vegetables

What are Goitrogens?

There is a lot of chatter in the pop-nutrition culture saying that these vegetables have an ill effect on the thyroid because they contain goitrogens.  Goitrogens can block iodine from entering the thyroid and eventually cause a swollen thyroid or goiter.  Because iodine is critical for normal thyroid function, some believe that if you consume too many goitrogens, then your thyroid will not function properly, leading to an underactive thyroid.

The active form of your thyroid hormone is called triiodothyronine – the “iodo” part of the word highlighting the significance of iodine in proper hormone function.  So you can see why people would be curious to know if foods containing substances (goitrogens) would block iodine from the thyroid and question if they should eliminate or at least eat them with caution.

The truth is, you would need to consume a large amount of these vegetables for their goitrogenic constituents to have an impact on your thyroid.  Even more important is that you would have to consume them raw.  When was the last time you ate 10 cups of raw Brussels sprouts or blended up 5 cups of raw kale in your Dr. Hyman’s Whole Foods Protein Smoothie and consumed it every day?



Because most of us steam, lightly boil, roast, sauté or bake our cruciferous vegetables, the amount of goitrogens our body actually receives is that much less due to the effect cooking these foods has on active goitrogenic level.  So, my advice is not to worry about eating moderate servings of raw or cooked cruciferous veggies and to actually make a point of consuming 1 to 2 servings of them daily because they are so fundamentally crucial to disease prevention (especially cancer), as well as normal metabolic function (such as detoxification).

If you are still concerned about how eating these vegetables affects your thyroid then follow some of these guidelines:

  1. Know the whole story. Cruciferous vegetables are not the only foods that contain goitrogenic substances.  Cassava (yuka), sweet potato, millet, soy, and even certain medications (such as Lithium) contain goitrogens.  The goal is not to demonize individual foods, but to eat a variety of foods in moderation.  Especially when studies repeatedly show that the goitrogenic substances in food are nothing to fear in terms of how they affect your thyroid function.
  1. Focus on the proven triggers for thyroid dysfunction. If we are to single out foods that specifically do impact your thyroid function then let’s spend time examining foods like sugar, gluten, conventional dairy foods, and processed soy.  All four have been researched and shown to negatively impact your thyroid.  One of the first suggestions I give newly diagnosed thyroid patients is to go 100% gluten free.  For more on the impact of gluten on thyroid function, read this article.
  1. Concentrate on what we can have! The best way to prevent your thyroid from crashing is not to eliminate healthy foods that are sensible parts of your whole foods diet (broccoli or kale), but to abundantly consume real, whole, nutrient-dense foods that contain copious amounts of thyroid-friendly nutrients (vitamins A and D, omega-3 fatty acids, B vitamins, selenium, tyrosine, and iodine).

Consume more of these:

Vitamin A: orange and yellow vegetables or dark leafy greens

Vitamin D: look for a high-quality D3 supplement


Omega-3 Fats: fatty fish like sardines and wild salmon; walnuts; and flax, chia, or hemp seeds

B Vitamins: wild meat, poultry, eggs, green leafy vegetables, legumes

Selenium: seafood, eggs, Brazil nuts

Tyrosine: poultry, grass-fed dairy, avocado

Iodine: sea vegetables (nori, wakame, etc.), seafood, grass-fed dairy


Steam or cook your cruciferous veggies to decrease the amount of goitrogenic properties. Remember, however, that the longer vegetables are cooked, the more water-soluble nutrients (including disease-fighting phytonutrients) are lost in the cooking process.  Clearly, you want to steam or cook lightly and not for too long or at too high temperatures.  The ultimate goal is a mixture of raw and cooked vegetables.

Bottom Line: 

There are just too many important health benefits from eating cruciferous vegetables to think that tossing them from your healthy, whole foods diet makes sense.  The only time I would suggest monitoring your intake of them is if you have a known iodine deficiency coupled with advanced, uncontrolled hypothyroidism.  In that extremely rare case, please work with your local Functional Medicine provider to discuss the best supplement and diet to replenish your iodine levels and replete your overall nutrition and health status.

Wishing you health and happiness,
Mark Hyman, MD.


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Mark Hyman
Mark Hyman, MD, believes that we all deserve a life of vitality—and that we have the potential to create it for ourselves. That’s why he is dedicated to tackling the root causes of chronic disease by harnessing the power of Functional Medicine to transform healthcare. Dr. Hyman is a practicing family physician, a nine-time #1 New York Times bestselling author, and an internationally recognized leader, speaker, educator, and advocate in his field.