“Variety and moderation.” That’s become my food mantra since my shockingly low thyroid result in September. I asked the question “Can you overdose on kale?” and now, 5 months later, I am more convinced than ever that YES, you can overdose on kale.
Too much of any food – even healthy ones – can be harmful.
But I am so happy to report that after 5 months of healthy eating, de-stressing and cutting back on kale has my thyroid almost completely back to normal (woohoo!).
So what does this mean for you? How do you know if you’re eating “too much” kale? Should you eat it at all? Are there other foods that can suppress your thyroid function too? In the past 5 months I’ve done a ton of research about the kale-thyroid connection, and there’s a lot to learn. Let’s dig in.
Why does kale suppress thyroid function?
Stick with me through 30 seconds of sciency talk, and then we’ll get back to the practical information.
Kale is a cruciferous vegetable (also known as brassicas). Cruciferous veggies include cabbage, kale, broccoli, cauliflower, bok choi, arugula (rocket), turnips and watercress (get a longer list of cruciferous vegetables here). There are a lot of healthy veggies in the list!
The connection with the thyroid is that in addition to their healthy compounds, cruciferous vegetables also include isothyocyanates which can inhibit the uptake of iodine by your thyroid – which decreases the amount of thyroid hormone produced and results in ‘underactive thyroid’ or hypothyroidism. (Check out this link for more techincal information on how cruciferous vegetables affect thyroid)
Rather than remembering all of this, it’s probably easier to remember that cruciferous veggies like kale contain contain goitrogens. (From Wikipedia: “Goitrogens are substances that suppress the function of the thyroid gland by interfering with iodine uptake, which can, as a result, cause an enlargement of the thyroid, i.e., a goiter.)
And it looks like goitrogens can suppress thyroid function in susceptible individuals (who are predisposed to low thyroid, or have low iodine intake, etc.)
Apparently I was susceptible!
Can I ever eat kale again?
YES! Yes, yes yes. Please do eat kale. It’s tasty and packed with nutrients!
You probably just don’t want to eat it raw in smoothies, every day, for a long period of time.
Mix up your greens! Try different greens from different families (for example, add in some romaine lettuce to your green smoothies). And if you’re eating cruciferous veggies, try cooking them first, at least some of the time. If you are a green smoothie drinker, here are some guidelines for rotating your greens.
What’s a ‘normal’ amount of kale to eat?
If you’re a bit of a greens addict, like me, it can be hard to remember what a ‘normal’ serving is.
This study from 1986 showed that people who ate 5 ounces (2/3 cups) of cooked Brussels Sprouts daily for 4 weeks, had no adverse impact on thyroid. Of course, that’s cooked brussels sprouts, where the goitrogens are mostly deactivated.
I couldn’t find any research or firm guidelines on what is safe to eat for thyroid function. So I think this is where you use common sense and listen to your body. If you have any thyroid issues or a family history of them, really limit your intake of raw cruciferous veggies and instead, eat them cooked.
Personally at this point, I’m only eating raw cruciferous veggies as a small amount of homemade sauerkraut. Other than that, it’s all cooked.
But that’s just me. I’d love to hear what you’re doing if you’ve also cut back on kale and cruciferous veg – let’s discuss in the comments!
What other foods can suppress thyroid function?
It’s not just kale. It’s all of the cruciferous veggies I mentioned above, and a few other sneaky additions:
- Soybeans (this is one of the hardest to avoid because many processed foods include soy! Even more reason to cook your own.)
- Pine Nuts
- Sweet Potatoes
There are also a few lesser known cruciferous vegetables:
- maca (are you putting this in your smoothies too?)
- canola / rapeseed
- arugula (rocket)
Again, it doesn’t mean to not eat these foods – just to be aware of them if you’re dealing with a low thyroid issue.
And it’s not just foods – what about chemical exposure?
Not surprisingly, thyroid function (like most other things in our bodies) is affected by environmental toxins as well. Even more reason to DIY your beauty products!
- Bromine – in processed baked goods, some hard plastics, citrus flavored sodas etc.
- Flouride – in toothpastes, urban drinking water
- Triclosan – in antibacterial hand wash and soaps
This is an area I’m just starting to look into – stay tuned for more information on this and healthy DIY alternatives to these products!
Where can I find more information?
Over the past 5 months I’ve done a ton of research, and here are some of my favorite resources for learning more about the kale-thyroid connection (and how to nourish your thyroid back to health – naturally!)
- Listen to this awesome podcast about thyroid health with health coaches Sarah Wilson and Andrea Beaman.
- Read Aviva Romm’s book: The Adrenal Thyroid Revolution
- The super comprehensive About.com thyroid site – highly recommended.
- Love him or hate him, Dr. Mercola is always an interesting source for alternative health information – here’s his thyroid article.
- Traditional methods of eating cruciferous veg and a deep look into the dark side of these vegetables. Weston A Price Foundation.
Let's Trace the Roots of You
(Re)discover the foods, places, traditions, and rituals that make you, YOU.
Sign up for weekly insights to get unstuck + create a life of meaning!