Is Kale Really Bad For You?

I’ve noticed a few opinion pieces (like this one in The New York Times) floating around out there suggesting that kale may not be as good for you as previously thought.

In fact, they say, it could actually be unhealthy for you and cause problems for your thyroid.

I can completely understand why there’s concern, but rest assured that there’s no need to panic and swear off kale or any other leafy greens.

Everyone Is Different

Picture of four pieces of kale on top of a wooden table

I’ve eaten kale for almost a decade now with no adverse effects. My thyroid is healthy, my skin is glowing, my hair is healthier than ever, and I feel amazing.

Just because I’ve had no issues doesn’t mean that the anecdotes about how kale has had negative effects on peoples’ thyroids are not true or meaningful, but they’re just that—anecdotes.

Plenty of people have been eating kale for years, just like I have, without any trouble at all. In fact, their health has improved because of it (it hasn’t been called a superfood in the past for nothing!).

Taking the Whole Story into Consideration

Picture of kale in a white bowl and on wooden table

In many cases, the “kale is bad” stories involve excessive amounts, and the greens haven’t been rotated.

For example, there is the case of an 88-year-old Chinese woman who ate 1 to 1.5 kg (about 15 cups!) of raw bok choy (a type of cabbage, like kale), daily for months in an attempt to control her diabetes. She then developed severe hypothyroidism and fell into a coma.

The theory behind why this happened is a little complicated. First, there was too much goitrin in her system (a result of all that bok choy being broken down), and it hindered the synthesis of the thyroid hormone.

Another issue came from thiocyanate ions (also a result of the bok choy being broken down), which compete with iodine in the body. When the thiocyanate ions interfere with the thyroid gland’s uptake of iodine, that could contribute to hypothyroidism.

However, that is usually only an issue if you already have an iodine deficiency, as mentioned above, something that’s rare in the United States.

One final thing that wasn’t mentioned in the study was what else she ate during those months.

Was she sacrificing other nutrients from other foods in order to consume all that bok choy? Not everyone who really enjoys eating kale eats these amounts of it, so it’s important to dig for the whole story and take the differences between individuals into account when you hear something like, “Kale (or other whole food) causes [insert health condition here].”

It’s often not as clear-cut as it seems.

Cycle, Cycle, Cycle

Picture of fresh herbs and lettuces

No, I’m not telling you to get your buns to a spin class! I always recommend rotating your greens—and all vegetables, really—because there’s always a possibility of “too much of a good thing” even where healthy foods are concerned.

Anything can be unhealthy when consumed in excess—even water!

Don’t put kale or any specific green in your Glowing Green Smoothie every single time. It’s fun to mix it up and experiment with flavor combinations anyway. See what’s available locally and play around with your greens and fruit.

Other Imbalances Could Be Contributing

Just as I mentioned above that everyone is different, there’s a chance that an imbalance or health concern in one person could lead to problems from consuming too much kale. Someone without the same or a similar issue may be able to eat the same amount of kale with no problems whatsoever.

If you’ve ever experienced candida, you know that fruit can act like your nemesis. Once candida is no longer a concern, however, fruit no longer comes with a host of nasty side effects when consumed.

When you have candida, is the fruit the problem?

Not really. Sure, the fruit could be a contributing factor to your discomfort, but in reality, there’s more going on. An excess of fat, blood toxicity, or heavy metals could be contributing to the candida, too, and the fruit just makes the issue more obvious.

You can think of kale in a similar way. If you’ve already got a condition that kale could have a little influence over when you eat it, other things in your system could be contributing to the problem.

It’s not that kale is unhealthy.

The Difference Between Juicing Kale and Smoothies

Picture of green juice in a glass

Juicing is one common thread between a lot of the cases where kale consumption has been deemed the cause of or contributor to health issues. Juicing is a fantastic way to quickly deliver nutrients to the body, but only in moderation.

There are some cold-pressed organic juices in our Glow Bio cleanses, and I do believe juice can be a good supplement to your diet.

Once you start juicing pounds and pounds of produce and drinking it on a regular basis, you could run into problems. The nutrients are so concentrated and so much juice is usually consumed at one time, you could end up with excess in some areas that may exacerbate pre-existing health conditions.

Think about how much kale and other produce it takes to get a whole glass of juice. Would you eat all that produce at one time?

I encourage the use of kale and other greens in smoothie form, like in the Glowing Green Smoothie, over juices because they’re not as concentrated and you’re still consuming the whole plant this way, fiber included.

When you eat (or drink), the whole food, you’re less likely to consume so much, and you’re less likely to see negative results. The fiber slows you down and prevents you from overdoing it.

Kale May Not Be the Culprit at All: Causes of Thyroid Dysfunction

Kale is getting a bad rap as if it’s single-handedly the cause of decreased thyroid function when in reality, excess (and I’m talking about tons and tons of excess here!), kale is just bringing an underlying issue to light.

There are other proven causes of thyroid dysfunction, like iodine deficiency.

To add extra iodine to your diet, don’t turn to a shaker of iodized table salt. Instead, try getting more dulse, kelp, chlorella, spirulina, and other sea vegetables.

Picture of sea vegetables on a plate

Fluoride intake can also play a role in the efficiency of thyroid function. In a study concerning the effects of fluorine and iodine on thyroid function in rats, the amounts of each interacted in different ways over the course of 150 days.

Sometimes the fluorine stimulated the thyroid and sometimes it decreased its function.

Fluoride used to be used as a treatment for hyperthyroidism. Even tiny amounts of fluoride can affect your thyroid function.

Lastly, there common chemicals many of us are exposed to every single day that could influence thyroid function as well. For example, one study found that a chemical used in carpets and other household products, called perfluorinated chemicals (PFCs) has been linked to adverse changes in thyroid levels in both men and women.

At the root of thyroid challenges, there is still debate over what percentage of the disease is hereditary/genetic versus environment. Either way, it’s clear that are many factors other than kale consumption that could be contributing to and causing hypothyroidism.

I don’t really think kale should be a target, and it definitely shouldn’t be under fire the way it has been or considered unsafe or unhealthy.

Should You Worry?

Picture of kale pieces on a baking sheet

So should you be worried about your kale consumption? Probably not. Unless you already have a health issue that can be exacerbated by green cruciferous veggies or you’re juicing large amounts of kale on a regular basis, you’re most likely fine.

Rotate your greens when blending your Glowing Green Smoothie and the types of salads you make, but adding some kale to your GGS and enjoying kale salad a few times per week should be okay.

Overall, I hope the recent scare over kale will serve to educate people and bring greater awareness to the complexity of health challenges and how dangerous (and unfair), it can be to oversimplify our approach too much.

Especially when it comes to our good and unfairly maligned friend kale, who has been so good to me and others in this community!





Last updated: Monday, December 21, 2015
  • Shelby Cohn

    Hi Kim!
    Thank you for addressing this topic! lately on the beauty detox group on Facebook everyone’s been arguing about this and for some reason noBody ever knew that in your book it specifically says to rotate your greens and fruit as well!
    if I could put in a request for the next topic you talk about could it possibly be food pairing because everyone is very confused on which items get paired as which like what is a protein or fat ! A list of what falls in what category would benefit the BDS community :)


  • Colleen Daiger

    Thank you so much for this post. I have been diagnosed with Hashimotos Thyroiditis. I am not on any medications and hope to control my Hashimotos with diet. I do not eat dairy, gluten and soy. I am also trying to stay away from goitrogenic foods. Trying to find information on line about goitrogenic foods can be frustrating at times. There is a lot of conflicting information . I would love to hear your thoughts on this. I have been making my GGS with cucumber, celery, romaine and leaf lettuce. I would love more guidance. Thank you!!

  • Elizabeth

    Very eloquently written. I enjoy your responses to these types of concerns as you do it with class, information, and education. I save my vitamix for my green drinks, including my kale, and I chose a slow juicer so that I can keep the fiber in what I do choose to juice. But I juice in moderation, as the sugar can be an overload if too much. Here’s a great recipe for juicing.. Beets, apple, carrot, celery, parsley, ginger, and lemon. Thank you Kim for all that you do. Wishing you all much health, happiness and many blessings!

  • robert simard

    Thanks for putting this concern about kale into perspective.

  • Paulette

    Since kale contains goitrogens, which are known to affect thyroid medicine and slow down thyroid functions, I choose to limit my consumption to a few times a week. When not using raw in smoothies, I choose to lightly steam to cut back on the effects.

  • Ashley

    I recently was diagnosed with hypothyroidism after loosely following Kimberly’s diet for 2 years. I have been a huge advocate of the GGS. It has really changed my life for the better. Unfortunately, most greens you would want to put in your GGS contain goitrogens which can severely disrupt thyroid function. I’m not sure why Kimberly would reference iodine deficiency as a cause for thyroid dysfunction. The reason why kale is “bad” is because it is a goitrogenic food. Goitrogens are able to disrupt normal thyroid function by inhibiting the body’s ability to use iodine, block the process by which iodine becomes the thyroid hormones thyroxine (T4) and triiodothyronine (T3), inhibit the actual secretion of thyroid hormone, and disrupt the peripheral conversion of T4 to T3. Anyway, I’m not trying to discredit everything Kimberly says because I have been following her for years and she has changed my life for the better. If you have hypothyroidism or if thyroid problems run in your family, PLEASE do your own research! Kale, spinach, Brussels sprouts, pears and many other foods you have probably come to love through Kimberly’s Beauty Detox can have detrimental effects on your thyroid.

    • Lori

      There are many reasons why Kimberly would reference iodine deficiency as a thyroid disruptor. Many doctors who specialize in thyroid disease believe that low iodine levels play a huge role. Check out “Overcoming Thyroid Disorders” by Dr. David Brownstein as just one reference or many if you do some research.

  • samira

    I loved reading the article.but what if it is hyperthyroidism. I have graves disease and I am confused whether to consume green leafs or not. I usually switch between spinach and kale in my smoothies . I have been having smoothies only recently because I heard of the benefits. I was diagnosed with graves disease 4 years ago.i would love to hear your opinion on this.
    Thank you

  • Marianna

    Thank you Kimberly for going in to bat for kale. Such reports have been making the rounds on Australian shores as well much to my chagrin. I like your inquiry about the poor 88 year old’s overall eating regime. Thanks so much for this post.

  • Heather

    I love this!!! I needed to hear it, because my two go-to greens are spinach & kale for the GGS. I need to mix it up because I DO have hypothyroidism (since before veganism). I always have spinach, kale, broccoli, zucchini, & green onions every day, but am going to mix it up.
    I’m writing because I recently heard if you do have a low thyroid, to consume very few green veggies… And freaked out bc that’s most of my diet! Anyone (or Kim) have knowledge of this?

    BTW Kim, you’re so inspiring! Thanks for introducing me to nutritional yeast, it’s addicting! Please listen to my music and visit my website!

    -XX, Heather Graham

  • jennifer lahr

    Great article. I really appreciated the comparison of juicing vs smoothies. Very good points that I never really though about.
    Thank you

  • Kathy

    I have been having problems with diarrhea since I started smoothies. I recently stopped for a month but as soon as I made a smoothie it started again. Has anyone else had this problem? Any solutions? I don’t know if it’s the fruit or greens or combination. Help.

  • Sara Adam

    Hi kimberly, I believe I have been juicing and eating excessive kale as I wish you would give more varieties in different leaves and greens we could rotate, after 4 months I have noticed my skin is patchy in tone and I have tiny amount of eczema on my eyelid and tip of elbow, I have low energy and feel lack of enthusiasm where it was opposite and now I feel weight sliding on me where I never needed to worry as my tummy always stayed flat , please advise ..
    Thanks sara

  • Beckie

    I think it is worth noting that if Kale is cooked the goitregens are greatly reduced making it probably the safest way to eat this nutrient green

  • Wendy

    Kale and spinach both cause me to have extremely sore breast with cysts. Iodine is very important for breast health too. If you read more about iodine you will find that many people do not get enough iodine in their diet. I’ve cut out all iodine reducing foods and I no longer have breast cysts.

  • Heather McKissick

    Thank you so much for addressing this! I had seen some of these claims and wasn’t sure what to think.

  • NOB

    This is so idiotic. Hypocritical too. If small amounts of kale don’t harm you, neither does chemicals. It’s true, if you read the proper information and actually educated yourself. And sorry you have use table salt to get iodine, not kelp.

    • Truthnut

      Agreed and kelp, seaweed, dulse and nori are full of toxic chemicals- but notice only fish is mentioned with respect to the sea to try and force the non meat thing- really am not a fan of people trying to force one food over another without the actual data…

  • Juan Johnson

    I think what happens in the media is they run out of articles to write and have other motives behind them. What’s the economic reason they’re bashing Kale when they never did before. What’s funny is how people look at the negative first before the positive,just like the 5 o clock news. Thanks for always being honest through your work.

    • Truthnut

      Same thing with people who bash dairy, meat, eggs, fish, soy and gluten. There’s a reason it’s called a balanced diet…

  • regina

    Regarding kale,it is very suitable for ruminants, but I’m not sure about it’s suitability for humans. It is used, cooked in small amounts, and added to potatoes/onions/butter to make a tasty dish of “colcannon” in Ireland.

    Regarding “glowing green smoothies”,it’s important to note that raw spinach inhibits the absorption of magnesium in the body.

    Also regarding juiced vegetables and fruits, drinking rather than eating same bypasses the digestive enzyme amylase, which is released in the mouth by the action of chewing.


  • Corinne

    Thank you for that great article. You taught me to look deeper into health claims and not just take them at face value. What you say makes so much sense and clears up my confusion on this issue.

  • Devi

    I have a question for you Kimberly. I juice 4 bunches of Kale ‘each week’ in an high-end slow juicer along with beets, celery, dandelion, carrots and 1 or 2 other chlorophyll based leafs – and drink the combination 4 times a week about 1 glass (500 ml) per day. That makes it 2 litres of the combination for me per week. Do you consider this to be too much of Kale ? I must admit that I was diagnosed with hypothyroidism 2 years ago, was given synthroid to administer. But I got rid of my synthroid medication for the past 1 and half year and got into Kale/chlorophyll juicing since then and I am so far good with thyroid health as per lab test results. Thank you.

  • lisa hreha

    This is a great article but what if you already have thyroid disease and have that condition where you not supposed to eat the cruciferous uncooked veggies. I love your green glowing smoothe but stopped doing it cause of the whole spinich/kale issue. What can I do to still enjoy your smoothie? I have hashimoto’s disease. Thanks, Lisa

  • SP

    Hello Kim,

    What health issues can be exacerbated by green cruciferous veggies? Do you already have a blog on this subject? If so, would you please direct me to the blog? Thank you.

  • shelley heaslip

    Thank you to you and your team for addressing issues as they crop up in the media. In my quest for a balanced diet, I have in the past incorporated seaweed products in my diet. However, I am reluctant to continue because it seems most of these products come from Asia. In addition to the fact that we know that land pollution runs off into the ocean there is the continued problem with nuclear leakage coming from Japan. Do you have any information regarding just how ‘clean’ the seaweed products are?

  • Ashley

    The goitrogenic effects of the compounds in kale that impair thyroid function can be reduced or eliminated simply by cooking them. While it is of course better overall to consume kale raw, wary hypothyroidism sufferers can still enjoy kale once it has been cooked.

  • Shelly

    hmm. I drink a kale drink every morning on an empty stomach. I drink roughly 85 grams. Is that overkill? It’s much more cost efficient being organic, when I buy it in bulk – so drinking it daily ensures it will not ruin.

  • Shelly

    *I did mean to mention that i do not juice the kale. I blend it in my vitamix with an organic apple.