Carnivore diet

Goitrogenic Foods That Destroy Your Thyroid

Goitrogenic Food That Affects Your Thyroid

If you’re like most people, you think that drinking a veggie smoothie is the healthiest thing you can do. You think that you’d have to be crazy to not eat vegetables.

Well I’m here to tell you that you’ve been lied to. Not only are vegetables not the healthiest food in the world. They may be bad for you.


Yes. You read that correctly. Some vegetables are goitrogenic. No, goitrogenic doesn’t mean overpriced and bland.

It means they may be bad for your thyroid.

And it means that they can cause

  • Weight gain
  • Dry skin
  • Depression
  • Cold sensitivity

Yes this is shocking. But you should be thrilled. Face it. You’ve never liked vegetables since the first time your mom put microwaved broccoli in front of you.

You’ve been brainwashed into joining the church of superfoods. But it’s come at a high price...and it’s not just the taste of kale.

In this post I’m going to tell you what goitrogens are, what the biggest culprits are and why they may be bad for you and your thyroid.

Thyroid Overview: What is the Thyroid?

What is the thyroid? It is in the base of the neck and ~2.5 inches wide. It produces three important metabolic hormones -- Thryoxine, Tri-Iodothyronine and Calcitronin. TSH controls the production of these hormones <*>.

The gland is small, but packs a big punch. It’s like the yapping chihuahua of glands.

It’s responsible for almost all of metabolism. Metabolism isn’t just that thing that “slows down as you age” or “makes you fat”. It’s the entirety of chemical reactions in your body.

Therefore the thyroid affects everything from the brain to the cardiovascular system to gallbladder and liver function. T3 and T4 regulate the speed of your cells and metabolism.

If they’re low, for example, you’ll get constipated and gain weight. If they’re too high, you’ll have a rapid heart rate and diarrhea. Think about that next time you see someone running to the bathroom...

Thyroid issues are on the rise. Almost 20 million Americans suffer from thyroid disease. And up to 60% of those may not even be aware of it. Can you imagine this?

People are just walking around cold, depressed and overweight and they have NO idea why. It’s like there’s a monkey hanging from their neck and they’ve never noticed it.

One culprit: the vegetarian and vegan health craze. People are practically hooking themselves up to an IV drip of Kale to get healthy. Trust me, if this really made you healthy I’d be the first one in line. But it doesn’t work. They may as well rip their thyroid out and throw it in the trash.

Kale smoothies. Green tea extracts. Broccoli sprout powder to wash it down. This is insanity.

The saddest part is that people think that it’s healthy. But it’s making problems worse. I’m here to help.

Goitrogens 101

Goitrogens are foods that cause goiter -- or swelling of the thyroid.

For some muscularly inclined Neanderthals -- i.e. bros -- a swollen neck means CrossFit is working. However, for most of us, it’s not a good thing.

Goitrogens do this by interfering with iodine absorption in the thyroid. Iodine is required for thyroid hormone production. Without it, the thyroid cannot produce the T4 and T3 hormones.

TSH is like a 5am wake up call for your thyroid, and iodine is its coffee. Without it your thyroid is like a hibernating bear.

In response to deficient T4 and T3 levels, your pituitary gland produces more TSH to signal to your thyroid to produce more T4. The excess TSH causes swelling.

Symptoms of Thyroid Issues: Side Effects Include

The thyroid plays an indispensable role in all metabolism. Thus when you have hormone production issues, it wreaks havoc throughout your body.

Some issues include:

  • Increased dementia risk <*>
  • Weight gain <*>
  • Constipation
  • Increased heart disease risk <*>
  • Bone fractures <*>
  • Trouble sleeping <*>
  • Dry skin <*>
  • Sensitivity to the cold <*>
  • Depression <*>

Where do these evil goitrogens come from? Hell? Florida? Your scary Aunt’s attic?

What if I told you that some of the worst offenders were hiding in the “healthy” grocery section aisle.

Goitrogenic Plant Toxins

People think plants are these perfect vessels placed here to protect us. They’re going to stop climate change and save the rainforest. If we eat enough spinach we will have muscles like popeye...this is just hippie propaganda.

The worst turns out they may even be bad for you. It’s almost like finding out your doctor is an axe murderer in his free time…

Plants look so innocent, but turns out they’re loaded with booby traps to kill predators. Almost like Kevin McCallister in Home Alone.

In an arms race over millions of years of co-evolution with animals, plants developed toxins to fend off predators. Goitrogens are one mechanism.

All goitrogens are derived from naturally occurring plant pesticides called glucosinolates.

These goitrogenic chemicals are even too toxic for the plant to store. So they store them in an inactive glucosinolate form. But when the plant is cut, chewed or digested, BOOM, it combines with the myronase enzyme. A nuclear bomb of plant pesticides explodes, turning your gut into a wasteland.

Glucosinolates are mainly in the brassica family of vegetables. There are over 120 known glucosinolates <*>.

The chemical Broccoli produces, for instance, is called sulforaphane.

Think of this like coke and mentos mixing together. It serves a impressing someone at a middle school party. But it’s pretty much unacceptable and damaging at all other times.

Well the same goes for these plant toxins.

Glucosinolates severely damage vertebrates and insects who eat them. They cause everything from liver lesions to growth issues <*>.If you are a vertebrate, watch out. If you are not a vertebrate and you are here, please send pictures.

In fact, they are so effective that plant breeders increase their concentration to deter predators <*>.

How Goitrogens Cause Damage: Thyroid Hormone Factory Shutdown

Goitrogens cause damage by three main mechanisms

  1. Iodine competition: Goitrogens can prevent iodine from entering the thyroid.
  2. Interfering with TPO: Thyroid Peroxidase (TPO) enzyme is like the assembly line that constructs Thyroid hormones. If it’s damaged, thyroid hormone production is impaired.
  3. Reducing TSH: TSH signals to the thyroid to produce T3 and T4.

There are a number of different types of goitrogens. Let’s dive in.

Types of Plant Goitrogens

There are three main sources of plant goitrogens.

  1. Goitrins: Labor union on strike.
  2. Thiocyanates: Bully who steals lunch money
  3. Flavonoids: Two headed hydra of Muhammad Ali and Mike Tyson


Goitrin is the most insidious plant goitrogen. It can cause goiter, even if you eat plenty of iodine. Why?

(Because its a S.O.B!). It targets thyroid peroxidase, which is necessary to create thyroid hormones. Instead of attacking the building blocks, it attacks the builder.

Goitrin isn’t naturally occuring in plants. It’s the result of the enzymatic breakdown process of the glucosinolate called progoitrin.

How much is needed to be damaging?

One study found that when a diet of 154 μmol of progroitrin per 100g was fed to rats, they developed hypothyroidism. They found that in pigs it took a higher concentration to induce liver damage -- a diet of 383 umol / 100g <*>.

According to another study, 70 μmol / 100g of progoitrin was not associated with thyroid issues, whereas 194 μmol was. Based on his study, three foods were highest in progoitrin compounds with over 100 μmol per 100g of weight <*>:

  1. Siberian russian kales
  2. One collard green
  3. One brussels sprout

Russian Kales are very high in progoitrin. Like with Russian Olympic athletes, they pack a bigger punch than their American counterparts. They have almost 30x more progoitrin than Broccoli.

Chinese cabbages and other brussels sprouts had between 10 and 100 μmol. Commercial Brocolli rabe and Brocolli have less than 10 umol per 100g.

Below are the four foods highest in goitrin producing glucosinolates.

Cooking can minimize concerns. For instance, one study showed that 150g of Brussels Sprouts daily for 4 weeks had no effect on thyroid function <*>.

However, this doesn’t mean you’re in the clear. This is something I’ll continuously harp on. If you already have thyroid issues, high doses of these vegetables are not a good idea. It’s like playing basketball on a broken ankle.

Even if you’re in optimal health, I’d still advise against megadosing them. But if you’re just eating small amounts of whole food versions, you’ll probably be okay.


Other glucosinolates break down into thiocyanates. Try saying that sentence 4 times fast…

Thiocyanates are positively charged ions that compete for iodine uptake in the thyroid. Unlike Goitrins, thiocyanates attack the building blocks of thyroid hormones. They’re like thyroid bullies who steal their lunch money.

Sulforaphane, a metabolite produced from Broccoli ingestion, is a thiocyanate.

What is its function? Sulforaphane is a powerful insecticide...and it can do the very same thing to your cells. How does it kill insects? Does it smash them with a shoe? No.

Sulforaphane <*> <*>:

  • Poisons mitochondria
  • Generates free radicals
  • Damages thyroid functions
  • Depletes glutathione
  • Damages epithelial layer

Some researchers suggest that normal broccoli consumption shouldn’t be a concern <*>. Going back to my point above, if you have a healthy thyroid it’s unlikely that thiocyanate consumption is going to hurt you.

However, the problem arises from megadosing raw amounts.

Sulforaphane is the most recent health craze because it may upregulate antioxidant pathways <*>.

Similar to an alchemist trying to turn lead into gold, people came up with the brilliant idea to mega dose sulforaphane to increase their superfood potential. But the only thing super about megadosing these “super”foods is the damage to your thyroid levels.

There’s a common theme here...Trying to manipulate foods for your advantage will almost always backfire.

Sam dancing, a bodybuilder, developed hypothyroidism from excessive broccoli sprout consumption.

Another case: an elderly woman in New York developed myxedema coma, the most life threatening form of hypothyroidism, after eating 1.6kg of raw bok choy daily for several months <*>. Now, that is a Joey Chestnut like amount of Bok Choy. However, there are a number of carnivores eating that amount of beef daily and they’re thriving.

My verdict...if you’re not at optimal health, be wary of these foods --especially raw. For most people who feel perfect, they’re probably okay to be eaten in their whole form.


The last stop on the tour of unfriendly plant goitrogens is Flavonoids.

What are they?

Flavonoids are naturally occurring plant pesticides and pigments. They are debatably the most potent thyroid affecting compounds. They are present in a wide array of foods, from wine to tea to soy.

Flavonoids exert their effects via both mechanisms discussed above. Some inhibit iodine absorption and others damage TPO. They’re like a double headed hydra between Goitrins and Thiocyanates. They’ll steal your lunch money. Then they’ll make you cook lunch for them after.

You don’t want to mess with them.

The most common flavonoids are called flavonols. Some of the foods highest in flavonoids are below <*>

Studies on rats show that quercitin -- one of the most abundant flavonoids in fruits and vegetables -- inhibited iodine uptake at their thyroid. <*>.

I’m most concerned about Soy. Soy contains isoflavonoids...which translates to PLEASE STOP EATING THEM.

Soy has the most compelling goitrogenic evidence and is one of the most detrimental aspects of the vegan diet.

When Americans were told to avoid the healthiest fats and proteins in the world, soy was elevated to a dietary staple. It was touted as a perfect protein to replace meat and a versatile cooking oil that wouldn’t increase your cholesterol.

So it began. The soyification of the world. Cheap soy flooded the market. And now you can find soy playing dress up as almost any meat in the market. Now that would actually be a scary Halloween costume...

The damage starts from day 1 out of the womb. Studies show that babies who consume soy based formulas have increased risk for autoimmune disorders <*>.

Two flavonoids found in soy products, genistein and daidzein, inhibit TPO function <*>. A study in 1991 showed that 50% of subjects eating 30g of soy beans every day for 3 months developed hypothyroid symptoms <*>.

And if you already have thyroid issues, soy is one of the worst things you can eat. A study of 60 patients with borderline hypothyroidism were 3x more likely to develop clinical hypothyroidism when consuming 16mg of soy isoflavones (typical amount in a vegetarian’s diet) <*>

One of the biggest problems is that cooking does not destroy the goitrogenic activity of soy isoflavones.

Goitrogens Are a Double Edged Sword

Why are people eating them in such high doses?

Several studies have elevated the most goitrogenic foods to life saving white knights. Sulforaphane, for instance, has been shown to activate the NRF2 pathway, which has anti-carcinogenic effects <*>. Another study showed that Sulforaphane was the reason why Bruce Willis always saves people in Die Hard...Okay, maybe that's an exaggeration.

According to this study, however, you’d have to consume 1,000,000g of Broccoli sprouts a day to achieve sufficient sulforaphane intake <*>. That sounds like a full time job….


Supplement companies have jumped on this gold mine and produced concentrated broccoli sprout supplements to achieve these levels.

But like other nutritional guidance, the studies do not hold up when scrutinized. Tests in petri dishes don’t always translate to the real world.

Dr. Georgia Ede looked at all 726 studies regarding vegetables on PubMed and none have shown conclusively positive benefits on health <*>, independent of other lifestyle and carbohydrate factors.

Even if they do work, these astronomical doses of broccoli sprouts are a double edged sword. Yes, they may up-regulate antioxidant pathways, but they also destroy your thyroid. So maybe you reduce your cancer risk, but say sayonara to your thyroid.

Telling someone to take 1 million grams of Broccoli sprouts to reduce cancer risk is like taking cocaine for a headache.

Meanwhile, the ketogenic diet upregulates the same exact pathways -- without all the negative side effects <*>.

The story is similar with flavonoids. They’ve shown antioxidant potential by scavenging free radicals <*>. Other studies have showed antiinflammatory benefits <*>.

But once again, at high doses, flavonoids can have the opposite effect.

This study pictured below shows that they can induce free radical damage and inhibit hormone metabolism.

Green tea extracts also impair thyroid function. This study showed that catechins, the flavonoids in green tea, decreased levels of t3 and t4 and increased TSH <*>

I get it. The word antioxidant lulls me to sleep too. But this madness needs to stop.

Other Goitrogens to Watch Out For

Plants aren’t the only source of goitrogens. There are a number of other goitrogenic foods in your diet and environment:

  • Heavy metals like lead and mercury
  • Antibiotics
  • Bromides
  • Dioxins
  • Pesticides like glyphosate
  • NSAIDs
  • Fluoride
  • Perchlorate

How to Reduce Goitrogenic Content in Foods...and Put the Bullies in Their Place

It’s time these plant compounds stop shoving you in a locker. It’s time to fight back.

The easiest way to shutup a bully: ignore it. This is why I follow the carnivore diet. Cutting out vegetables and plant foods was the best thing I’ve ever done for my health.

If you insist on still eating some of the foods high in goitrogens above, there are ways to counter their defense mechanisms.

Boiling cruciferous vegetables can reduce their glucosinolate content, more than steaming or microwaving. Nonetheless, bacteria in your colon will still break down glucosinolate into toxins <*>.

Freezing or boiling them for 10 minutes will reduce glucosinolate by ~50% <*>. Please don’t try this with real life bullies.

The Verdict

If you already have thyroid issues, the research shows you may want to avoid goitrogens.

If you’re healthy, it’s probably fine to eat small amounts of cruciferous vegetables.

However, based on the research above, I’d recommend everybody avoids soy and mega dose of goitrogens in the form of raw juices and supplements.

Ultimately, megadosing leads to major unintended consequences. Just because 100mg is good, doesn’t mean 10kg is good…The only thing you should megadose is your steak.

Anecdotally, many carnivores have benefited from wholesale elimination of these foods. The evidence is now too strong to ignore.

Like with anything, experimentation is warranted.

It’s time to topple the church of vegetables.


To learn, you first need to unlearn.

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