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Does Kale Destroy Your Thyroid?

This is a guest post written by Christa Orecchio, C.N., a clinical and holistic nutritionist and a member of my Advisory Council. As the founder of The Whole Journey, she uses food as medicine wherever possible to help others heal and thrive and takes a mind, body, spirit approach in order to address the whole person. I reached out to Christa to write a post about the consumption of kale because it’s one of my favorite foods and one that I get asked about often. I want to provide you with the most cutting-edge health information backed by nutrition research. Here’s what Christa has to say about how cruciferous vegetables – like kale – can affect the thyroid:

As a nutritionist, I often get asked if cruciferous vegetables can cause or worsen thyroid issues. As is the answer to most controversial and confusing nutrition topics, it depends on a myriad of factors such as your current state of thyroid, digestive, and brain health, how much energy you are able to produce (mitochondrial production), the quality of the vegetable (soil it was grown in and whether pesticides were used), your cooking method, and how often you consume these foods.

Kale Thyroid

Cruciferous vegetables are vegetables that belong to the Brassica family. Examples include:

  • Arugula
  • Bok Choy
  • Broccoli
  • Broccoli Rabe
  • Brussels Sprouts
  • Cabbage (all kinds)
  • Collard Greens
  • Kale
  • Radish (includes Daikon)
  • Maca
  • Romanesco
  • Rutabaga
  • Turnip
  • Wasabi
  • Watercress

Being high in powerful antioxidants like sulforaphane and vitamin C, fiber, carotenoids, vitamin E and K, and folate, there is quite a case for consumption of these foods as a big contribution to enjoying greater health.

They have long since been touted as supportive medicinal foods that help prevent cancer, support the liver, and contribute to improved immune and neurological health.

However, cruciferous vegetables offer a unique dichotomy because they also contain compounds called glucosinolates which are connected to exacerbating iodine-deficiency related hypothyroidism that can lead to thyroid swelling called a goiter. Hence these foods are referred to as goitrogenic foods.

They can do this by blocking the body’s ability to uptake iodine, which every cell of the body needs, but especially the thyroid, which contains the highest concentration of iodine in the human body. Those with pre-existing hypothyroidism may find that excessive consumption of raw cruciferous vegetables, could further suppress thyroid activity.

However, you may have heard the saying “the dose makes the poison” and it takes a lot of brassica to be clinically significant.

Many clinicians believe that one would have to eat a ton of raw cruciferous vegetables, in excess of 1-2 pounds daily to have an adverse effect on the thyroid.

You can start off with a smaller amount and work up from there. According to a study in Human Toxicology, no effect on thyroid function was observed in people who ate almost 1 cup of cooked Brussels sprouts daily for 4 weeks.

How Cooking and Fermentation Help:

Steaming your veggies until they are fully cooked reduces the goitrogens to one-third of the original content while boiling for thirty minutes is known to be a reliable way to destroy 90% of the goitrogens (which are released into the water and discarded).

Cooking also reduces other goitrogenic compounds in foods called nitriles.

Fermentation is another way to make them healthier for you. When you ferment something like cabbage, it actually increases the goitrogen content but truly reduces the nitriles by 50% or more, making the benefits of fermented vegetables far outweigh the goitrogenic risk to the thyroid that raw cabbage could potentially propose in large amounts.

What About Green Smoothies?

If you are worried about goitrogens or have been diagnosed with hypothyroidism, then add steamed greens (instead of raw) like kale and Collards to your morning green smoothie or only add raw kale to your green juice once or twice a week versus daily.

You may have seen the recent article in Mother Jones entitled “Sorry Foodies: We’re About to Ruin Kale” where they discussed how kale can uptake thallium, a toxic heavy metal from the soil. They also included other cruciferous vegetables in the article like cabbage, watercress, radishes, and turnips.

Again, there are many factors involved here and this doesn’t mean that you should not eat these foods. The quality of the soil is the key. The majority of organic farms (which test their soil) likely do not have dangerous levels of thallium. Because thallium contamination comes from nearby oil drilling, cement plants, and coal burning, it’s good to find out if the farm you purchase your kale from has exposure to these things. Or better yet, grow your own organic veggies in clean, nutrient rich soil.

The Bottom Line

It’s worth repeating not to go overboard with any one food so don’t eat a diet of just kale or any other vegetable for that matter.

If you are concerned about this and have hypothyroidism, then steam or boil your cruciferous vegetables and limit them to 1.5 – 2 cups/day.

This way you can still benefit from their high micronutrient profile and their anticancer benefits while supporting your immune function and brain health. These health benefits will support cellular energy and mitochondrial health, which is highly supportive to the thyroid gland.

I often operate by the mantra, “don’t guess at it, test it” so be sure to ask your doctor about testing your iodine levels and get adequate iodine from your diet.

Getting Iodine From Your Diet

Being in the nutrition field I am not a fan of iodized salt because it contains 2.5% chemicals in the form of anticaking agents and is exposed to extremely high heat during processing. This process removes much of the minerals, which in turn can create a mineral deficiency and therefore more salt cravings (because a craving for salt is a craving for minerals) as the body intelligently seeks to fill in its nutritional gaps.

I prefer to use Himalayan or Celtic sea salt, which does not contain added iodine like traditional salt but it does contain all 84 essential trace minerals to support the nervous system.

You can obtain adequate iodine from foods such as kelp, wild cod, wild shrimp and other shellfish, pasture-raised eggs, free-range turkey and organic raw milk.

Thyroid Testing

If you have symptoms of hypothyroidism like constipation, cold hands and feet, hair loss, exhaustion, or dry skin, it’s always a good idea to get tested because this knowledge gives you great power to create balance and choose your food and supplement intake wisely.

I always test four thyroid markers to get a complete understanding of what is going on with a person’s thyroid. The four markers are TSH (thyroid stimulating hormone), T4 (inactive thyroid hormone) T3 which is the active thyroid hormone that truly translates to how well you are able to convert oxygen and calories to energy, and TPO or thyroid peroxidase which will tell you if you are building up antibodies and forming an autoimmune thyroid condition called Hashimoto’s Disease.

And lastly, let’s not forget to support the thyroid in other ways by minimizing or eliminating all of the truly thyroid destructive foods like canola, unfermented soy, an excess of polyunsaturated fats, gluten, and processed and refined sugar and flour. This alone will have a more positive impact on your thyroid health than whether or not you eat cruciferous vegetables.


Note from Vani:

What do you think about Christa’s post? Please share your thoughts in the comments below. Are there other topics you’d like to see her address? For more information on thyroid health from Christa, you may want to read her blog called The Thyroid Uncovered which gets deeper into the science and lab work of thyroid testing and balancing or watch her TV episode on How To Optimize Thyroid Function.

I’m now on Periscope!!! 

Sorry my recent playback to the grocery store is no longer available – but be sure to follow me on Periscope for future broadcasts! I’m “thefoodbabe”. See you on the flip side.



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44 responses to “Does Kale Destroy Your Thyroid?

  1. I’ve managed the wellness department of a Whole Foods-type store for the past 7 years, and I’ve seen many people—men and women—- complaining of tiredness, dry skin, hair loss, etc. When I quiz them on what changes they’ve made in their diets over the past few months, 90% admit to eating and juicing tons of raw kale every day. When they switch to cooking it, their symptoms go away, and their hair starts coming back. I suspect it’s a much more common problem than the article suggests. Everything in moderation, after all;)

    1. Hair loss has been a huge issue for me lately! I blamed it on fertility drugs that I feel like I have to take, but now I’m wondering if it could be the amount of raw cruciferous vegetables I’ve been eating everyday. I would saw I do eat an excess of 1-2 pounds of veggies per day and now I’m concerned that this is causing my hair loss. Due to the fertility drugs though, I get my thyroid check out constantly and they say it’s perfect. But why then the dry skin and falling out hair? I used to have the thickest hair on the planet (no lie) and now, it’s normal but I would say 70% is gone, I still have a ton but don’t see how this isn’t related to my thyroid. I’m glad you posted this as I go to my dr. tomorrow.

      1. The problem with those thyroid tests is that the ‘normal’ range is HUGE. You can have nearly every symptom of low-functioning thyroid and still fall within the normal numbers. For example, most doctors would like your TSH levels to be around 2, but studies have found that most women feel better—-and decrease their cardiovascular risks dramatically—if that number is between .8 and 1. I’d cut back on the raw cruciferous veggies, and if that doesn’t improve the situation, then push to have them treat you based on your symptoms, not your numbers. Make sure they’re testing T-3 levels as well as T-4 and TSH. Low-functioning thyroid can definitely influence fertility levels.

  2. I had thyroid cancer five years ago and had my thyroid removed…Is there certain foods that are better for me? All I ever see is foods that is good for your thyroid…but, what if you don’t have a thyroid? Right now I’m hypothyroidism..My TSH is high..7.5..My dr. changed my dosage…hopefully it will soon Help. Are there any foods that I should eat more of or try? Thank You.

      1. Sadly, Medical doctors are highly educated in Medicine, but they lack education in all aspects regarding nutrition.

      2. Come on, my cholesterol was a bit high, the first thing the medical doctor said “we need to get you on medication”.

    1. I suggest you look at the Functional Medicine Institute online and find a doctor they’ve trained. You can also look at Dr. D. Kalish. His website should have a list of doctors he trained in Functional Medicine. It’s your best bet!

  3. What about spinach? I usually use spinach in my green smoothies, but I am hypothyroid. Should I reduce spinach consumption as well?

    1. Spinach is not a cruciferous vegetable so it is considered safe to eat raw, in terms of thyroid health if you have an iodine deficiency. However, spinach is high in oxalates, which is fine if you can tolerate oxalates. A general rule for health is to eat foods in moderation, and eat a large variety of foods each day.

    2. Spinach contains goitrogenic compounds in small amounts. Probably not enough to do harm unless you’re ingesting large quantities every day.

  4. Loved the Periscope, but hate I can’t rewind and hear what you say when I miss it. On the desk top computer, but I could not find a rewind, but instead only pause. Fun trip to the store!! thanks!

    1. I don’t like that you can’t do that either! Feel free to ask me about anything you might have missed 🙂

  5. Will you please ask your Web designer to enable printing your articles without all the ads? Sorry I missed the deadline for the Whole Foods trip. Thank you for offering these outings on Periscope.

  6. I’ve been steaming my kale for my smoothies because I have a tendency to low thyroid. I guess i should throw out the steaming water instead of drinking it, right??

    I have a package of dry kelp. i put some dry kelp and some dry mushroom into a small glass jar with water & store it in my ‘fridge. Then when I’m making a soup or stir fry, I take some out, chop it small and add it. This is an easy, palatable way to add kelp to my diet.

  7. i’m a wild food enthusiast. I love that Lambsquarters grow so freely and abundantly.
    I wonder how important where they grow is. I find them on roadsides and sidewalks
    should I be wary of eating them? Of course, I wash them well.
    Same question applies to purselane. ??

  8. What about iodine supplements in relation to this blog topic?
    I take a liquid iodine.
    Thank you

    1. If you are supplementing with high levels of iodine, just be sure to obtain enough selenium (100 mcg to 200 mcg a day). Much above 400 mcg of selenium a day can be toxic.) Brazil nuts are good sources for selenium. However, eat only 1 or 2, since Brazil nuts can have enough selenium to be toxic if more than two or three of these nuts are consumed in a single day, depending on exactly where the nuts were grown.

  9. I like to make kale chips to dry crispy in my dehydrator. If this is a good source, how many can I consume that would not affect my thyroid?

  10. The article implies that Himalayan and Celtic salts do not contain sufficient iodine to satisfy daily needs, hence it suggests a list of foods to obtain adequate levels of iodine. The only vegan entry on that list is kelp. However, kelp can readily provide dangerously high levels of iodine. A two ounce package contains sufficient iodine for five years, making a quarter gram a day too much. Ref: Dr Michael Greger at, more specifically at this link:
    More generally, sea vegetables provide iodine, and seaweed provides dosage levels that are more reasonable and safe for humans. Nori provides the most moderate dosage – a week’s worth in a 2 ounce package. Dulse and wakame provide 1 and 2 month doses, respectively, in a 2 ounce bag. Haziki (or Hajiki) should not be consumed due to it’s ability to capture and concentrate arsenic from the seawater. (Same source as cited above.)

    1. I think that you may be relying on old data and outdated information and beliefs about the safety of iodine levels, including how high the levels actually should be. Some people require very high levels, others can thrive on lower levels. However, the RDA levels appear to be too low to support optimal health. However, sufficient selenium needs to be included in one’s diet if high levels of iodine are to be safely ingested. With sufficient selenium intake, kelp is does not supply too much iodine.

      Read, Lynn Farrow’s book “The Iodine Crisis: What You Don’t Know About Iodine Can Wreck Your Life”, with a forward by David Brownstein, M.D.

      1. The Dr, Greger reference is dated 2007, while Farrow’s book was published in 2013. However the body of knowledge on the health effects of iodine goes back to 1820, with massive trials and studies in the 20th Century.

        My examination of present day websites indicates that mainstream, independent health organizations (NIH, CDC, American Thyroid Association, National Academies Press Institute of Medicine (DRI)) continue to recommend a maximum of 1100 mcg of iodine. That is the same as the basis for Dr. Greger’s article. Even Dr. Mercola, who on his website provides a video by Dr. Jorge Flechas discussing intake of higher levels of iodine, backs away from recommending such high levels.

        Looking at the Lynn Farrow’s website, and the links provided there (e.g. I can’t find study results published in mainstream, peer-reviewed, medical journals supporting the very much higher levels of iodine intake. Ideally they would be double blind, placebo controlled, cohort studies, but one website I visited said such studies do not exist. Perhaps you can provide such references to published studies supporting the contention that such high levels are safe, and perhaps optimal.

        Unfortunately, Farrow’s book is not cataloged in any of the libraries to which I have access. I don’t expect to be reading it until it is.

      2. To John Sirutis: Try reading Dr. David Brownstein’s books on thyroid and iodine and also look up and read Dr. Sircus’ writings on actual therapeutic levels of iodine. Lynn Farrow’s book discusses how people have been successfully utilizing iodine at varying levels, usually in the mg range and provides a historical account of how iodine levels were set much too low for therapeutic utilization for most conditions not associated with goiter. There was a lot of politics involved with very little actual applicable research, even though many of the researchers had good credentials. It has to do with recognizing the degree to which the protocol parameters restrict the general applicability of the study. Double blind does not mean viable.

        However, if you were to personally consider utilizing iodine therapeutically, I would suggest that you work with a doctor who is trained and specializes in functional medicine. Your iodine levels would be tested and an appropriate level would be prescribed for you. It might be low, but typically it would ofen be quite a bit higher than the reports that you are quoting would suggest. This is because you are an individual with specific needs and not a statistic. Individual iodine requirements vary all over the place, sometimes into the 100 mg. range. Sometimes iodine is contraindicated.

        The key to therapeutically utilizing high dosages of iodine appears to involve guaranteeing that sufficient selenium supplementation is being taken with the iodine and that iodine utilization is slowly increased and monitored under the guidance of a doctor who is suitably trained in functional medicine, with experience with iodine supplementation.

        One of the problems associated with the early studies of iodine was that selenium intake was not considered. Another was that goiter was often the condition being studied and that very low iodine levels are sufficient for this purpose. However, other tissues in the body often require much higher levels of iodine intake. This is not addressed in the double blind studies that you appear to be referring to, and confounding conditions that needed to be considered were ignored, often because their connection to the problems being studies was not well understood.

        Please don’t be misled. Double blind studies are appropriate only under restricted conditions. They provide guidance under restricted conditions, and may or may not provide the appropriate guidance for specific individuals with specific conditions. I know that this sounds like heresy but it’s the truth. So don’t shoot the messenger. If appropriate confounding conditions are not considered because they were not included in a study’s protocol when the study was designed, then the study may be a model for a perfect study, and still provide meaningless information when applied to an individual with a confounding condition that was was not included in the study’s protocol. Just because it is a double blind study does not make it a meaningful study.

  11. Will a Brazil nit and slice of Nori a day solve the selenium and iodine requirements and be the new ‘apple a day’

  12. The answer to your question “Will a Brazil nut and a slice of Nori a day solve the selenium and iodine requirements and be the new ‘apple a day”, the answer is: It depends on a number of factors. Not all Brazil nuts contain the same amount of selenium. I would recommend considering eating 2 Brazil nuts a day, just to be safe. In addition, the amount of iodine that an individual needs varies from individual to individual by such a large amount that it would be best to consult with a functional medicine doctor and get yourself tested.

    1. Thank you for education doc. I have an unrelated question about acid reflux. I have been trying a lot of different avenues as a means to cure it and none are too effective as the problem persists. I eat an organic based diet for the most part; breakfast consist of organic fruit oats and almond milk, lunch entails salmon with quinoa and raisins, dinner is usually a banana and I drink 3 to 4 btls of water per day. I was recently told by my PCP to take an acid reducer (Omeprazole 20 mg) as I am experiencing high levels of stress at my workplace which is supposedly producing acid. I can feel a burn in my stomach from time to time and I constantly burp a lot. Would love to get your feedback on this if i can…

  13. The article was most professional & informative. I perceive that including professionals articles can only help educate your followers & detract from your critics, who fire negative comments about you (Vani), not being a nutritionist or doctor. Well researched & written Christa !

  14. Very informative post. I have thyroid problems myself, so I have to always pay attention what I eat. I printed out this post so I would have the information available all the time. I have noticed that even small portion of a product I shouldn’t eat, makes a huge difference in my well-being. Thanks for the post and tips!

  15. It’s been a while since I’ve eaten kale so honestly I wouldn’t really know, but it’s great to be aware! I’ll definitely check in with my doctor about hypothyroidism because what you listed are things I deal with somewhat regularly. Thank you!


  17. What if you do not have a thyroid, as it was surgically removed because they said I had cancer and then after removed said I did’t have cancer? I am now considered as hypothyroidism. What should my diet consist of? I take Armour Thyroid everyday now and will have to for the rest of my life. I totally wish I knew then what I am learning now about reversing my health by the foods I eat.

    I look forward to your reply.

  18. Great article! I found this very informative and although I do not have a thyroid issue, I found this information very helpful. I would love to see more articles that talk about food’s medicinal value and how they can help our bodies in ways that traditional nutritional info seems to leave out.

    Thanks again!

  19. I enjoyed the article very much. However, if I were to bring this article to my Endo, it would be dismissed as are my comments about the way I feel on my current thyroid meds. I was diagnosed with hypothyroidism when I was 11. Until I had my children, everything was great. The medicine worked, I had energy and focus. After the birth of my 2nd child, everything went haywire. 12 years later, my test results still continue to tell my doctor that my levels are too high, but I feel exhausted all the time, fuzzy headed and in a fog, unable to focus and accomplish much at all during the day. When my dose was 2x what I currently take, I felt like I could conquer the world. I had unlimited energy and enthusiasm for everything. Not so now. Just because there is an “acceptable and normal range” for my age group, does not mean that it is my “norm”. I have seen 3 different endocrinologists in the past 12 years and none of them listen to ME and my issues. They all pretty much tell me to eat less and move more and everything will be fine. Is this what I have to look forward to for the rest of my life, because this bites!

  20. Do dandelion greens and parsley fall into this category? I juice with them several mornings a week, but since I have been diagnosed with Hashimotos, want to be sure it’s okay.

  21. As someone with diagnosed hypothyroidism, I really appreciate your bringing awareness to this topic. I will bring new attention to my cruciferous vegitable intake. Thanks!

  22. Anyone here (specifically from the scientific community and advisory board) can enlighten the limitations of this ‘generalized’ prescriptive approach we as a community are forced to take? Any Guru from the field of nutrigenomics would like to offer the insight? What works for me does not mean that it will work for you, or for that matter even for my kids. Its time to ask for personalized nutritional service(s) and guidance! My call is not limited to just thyroid here.

    Keep up the great work meanwhile…

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