Health Dangers of Cruciferous Vegetables

Health Dangers of Cruciferous Vegetables

Health Dangers of Cruciferous Vegetables

Health Dangers of Cruciferous VegetablesIn our look at the Health Dangers of a Plant-based Diet we turn to the cruciferous vegetables. You might be surprised to learn that broccoli and brussel sprouts have a dark side. I mean these are the vegetables that kill cancer, right? How can there possibly be health dangers of cruciferous vegetables?

Well just like other plants, these vegetables place a high priority on survival. And this means protecting themselves with phytochemicals. The cruciferous vegetables use a special chemical called glucosinolate to deter pests. [r, r] Here we’ll look at glucosinolates and their role in the health dangers of cruciferous vegetables.

Health Dangers of Cruciferous Vegetables – What are they?

Last week as I was walking to perimeter of the grocery store (headed to the butcher) I realized how many vegetables are from the cruciferous family. It’s not just broccoli and brussel sprouts. But it also includes cabbage and cauliflower, kale and collards, radishes and arugula, mustard greens and mustard seeds, and the list goes on.

The crucifers are just like every single plant specie commonly eaten today; it’s vastly different from its pre-agriculture predecessor. We transformed these plants through artificial selection to get the biggest, most pest-resistant breeds possible.

Cabbage, broccoli, cauliflower, brussels sprouts and kale are all different cultivars of a single species, Brassica oleracea. But generation by generation, we engineered this one plant’s leaves, stems and flowers into new “foods.”

You may be familiar with these crucifers because of their pungent smell. It’s the sulfur. And it’s a part of their defense.

Health Dangers of Cruciferous Vegetables – “Broccoli Bomb”

sulforaphaneThe crucifers like broccoli have this chemical called glucosinolate. I like to think of this chemical as the main ingredient of the “bomb.” They also have another chemical called myrosinase. I think of this as the “matchstick” that lights the bomb.

While growing out in a field the bomb and the matchstick sit in separate compartments so that the broccoli doesn’t blow itself up.

But when a little hungry animal comes looking for a snack and bites into the broccoli the bomb gets lit by the match. The explosion that results are bioactive chemicals call isothiocyanates. [r, r] One of the most well-studied isothiocyanate is call sulforaphane.


Sulforaphane is a pungent molecule (perhaps you’ve cooked broccoli and smelled it…) that can deter and kill insects, bacteria, and fungi. It causes cellular apoptosis (cell death). This happens in the cells of these small predators as well as human cells.

If you eat broccoli about 75% of the sulforaphane will be absorbed into the bloodstream and taken up by cells.

Once inside sulforaphane can damage important intracellular structures like mitochondria and enzymes.

The damage increases reactive oxygen species (ROS). And in an attempt to limit the damage, glutathione, our powerful endogenous antioxidant, binds with sulforaphane to get rid of it as quickly as possible (~2-3 hours after eating it). [r] This depletes our glutathione (our most potent human antioxidant) leaving cells vulnerable to further oxidative damage.

Sulforaphane can even disrupt epithelial barriers providing yet another plant chemical that can contribute to “leaky gut.” [rr]

Sulforaphane and Cancer

It’s not surprising that this cell killer has been recognized as an anticancer chemical. It kills cells. Cancer cells and healthy cells. [r, r, r]

Isothiocyanates like sulforaphane trigger the activation of Phase II enzymes. [r] This is like turning up the dial on the human immune system.

For some reason, research paints this in a positive light. Sulforaphane is a hero. Isothiocyanates increase our natural antioxidants. They say it’s a hormetic response. [r] If it doesn’t kill you, it makes you stronger.

I see it through another lense though.

When the body encounters something that is damaging, it wants to get rid of it. To do this it will upregulate an army to fight it. Some of these troops are antioxidants like our friend glutathione. While this is good in the context of fighting a cancerous cell or ridding the body of sulforaphane, I don’t think sending the troops to battle on a constant basis should be seen as a good thing.

The fact that the body puts such a vast importance on getting rid of sulforaphane as quickly as possible suggest to me that it’s more of a danger than a cancer-killing sidekick.

For me, a helpful analogy is to relate to chemotherapy treatment. It is very effective at killing cells. And while the intent is to kill cancerous cells, there is often a significant amount of “friendly fire” and the death of healthy cells as well.

Most people don’t take low dose chemotherapy as a cancer prevention strategy. There’s a reason for this.

Health Dangers of Cruciferous Vegetables – Thyroid Health

goiterThe isothiocyanates created by chewing up broccoli can have potent antithyroid effects and interfere with thyroid hormone production. They compete with iodine and thereby block its uptake by the thyroid. With inadequate iodine there is decreased production of thyroxine and potential for hypothyroidism. [r]

The abnormal absorption of iodine also provokes hypertrophy of the thyroid and goiter. [r]

And it’s not just humans, but animals too.

Oil meals, like rapeseed meal for example, are important protein supplements for livestock. And they are high in glucosinolates. Animals can tolerate up to 5-10% rapeseed meal in their diets before suffering from goiters, depressed growth, gastrointestinal irritation, anemia, perosis, poor egg production, and liver and kidney lesions. [rr]

The high sulfur diet can result in trace mineral deficiencies and polioencephalomalacia, a neurologic disease in ruminants.

Health Dangers of Cruciferous Vegetables – What to do

If you decide to eat cruciferous vegetables, it’s a good idea to take some protective measures.

  • Adding extra iodine to counteract the thiocyanates is helpful. However, additional iodine consumption cannot counteract other glucosinolate byproducts like oxazolidine-2-thiones which also blocks iodine preventing thyroxine production. [r]
  • Avoid sprouts and seeds as they can have orders of magnitude more glucosinolate than matured plants. Plants protect their babies. Eat them with caution.
  • Freezing as well as boiling them can help reduce the glucosinolate concentration (~50%).

Heat actually destroys the myrosinase (the matchstick that lights the bomb); however, the bacteria in our gut can act as the lighter, so sulforaphane will still be produced. [r]

As with other plant chemicals, the poison is in the dose, and an individual’s ability (or lack thereof) to disarm the plant poisons.

An elimination diet (like “Level 3” in the 30 Day Guide to Going Full Carnivore) is a very effective way to determine your ability to handle certain plant foods, which (if any…) are ok, and in what quantity.

[NOTE: You can now access the complete “Health Dangers of a Plant-Based Diet” series here]:

85 Replies to “Health Dangers of Cruciferous Vegetables”

  1. I’ve been “allergic” to cruciferous vegetables. I will develop “explosive” cramps and diarrhea WHILE I AM SITTING THERE EATING. Half way through my meal, I will jump up and run to be sick. I also have an allergy to sulfa drugs. Related? Are there other foods that contain these chemicals in smaller amounts, or are cruciferous veggies totally unique?

    1. Very interesting – thanks for sharing your experience!

      I’d recommend checking out the full pdf download of “Health Dangers of a Plant-based Diet” for a deeper dive into your question.

    2. No connection. Sulfur is in cruciferous vegetables, not Sulpha medications. Common misnomer,

  2. Hi Kevin, I’d also look into mercury poisoning if you’re doing better by staying away from cruciferous veggies. They are full of sulfur and this is one of the pathways that gets damaged by mercury, IT’s the reason for the many food intolerances and allergies of our time, mainly gluten, casein, salicylates and sulfur. Mercury damages methylation which is responsible for DNA formation, and thousands of enzyme processes are at risk. It’s most insidious action is DNA formation of T cells get damaged, this is when B cells are left unregulated and auto immunity begins. People are healing all types of neurological and autoimmune disorders using ACC frequent low dose chelation, the only safe way to move mercury out of the body. Amalgams, vaccines and CFL bulbs are the biggest culprits, many people have no idea how they were exposed.

  3. We have to consume everything in moderation. Every substance is toxic it is just the matter of amount. Plus everybody is different one may have allergy or intolerance to the ingredients of broccoli or any plant and animal product. Nothing is 100% true or wrong. Therefore test everything before drown yourself in smoothies or totally giving up on them.

    My kids loved the idea of dangerous broccoli.

  4. Thanks Kevin for eye opening info that will receive scrutiny from a society that’s been lied to for so long, it somehow becomes the (Ugly) truth. Coming from Keto to Carnivore, my digestive system has never felt better in all of my 59 years. My clarity of mind, especially getting up in the morning (it’s like instantanious!) instead of feeling like I’m trying to crawl out of a 12′ hole. Adios veggies, grains and nuts, I’ve got a Tomahawk steak to cook!

    1. I just came across this article. It certainly is thought provoking. I am also eating Keto right now. Jim, how are you feeling at this point on the carnivore diet? Also, how do we get the RDA of vitamins and minerals not found in meat? I am considering giving it a try.

  5. I just made a recipe that had broccoli cauliflower kale and brussels sprouts. They were sautéed. As soon as I ate them I felt like I had been poisoned. So I googled toxicity in those foods. And came across your article. I am never eating that stuff again. It is poison to me.

  6. Where is the research to back what you are stating about the dangers of eating plants? This is hard to believe and I do not see anything sited here. Man was created by God and all the fruits and vegetables were food for man. Until the fall of man, meats were not eaten. If I talk with a nutritionist, would they be in agreement with you deterring eating vegetables? Seems odd they would be in the dark if this research is legitiment.

    1. Hi Marsha please see the (R) references throughout the posts.

      And no I’m not in agreement with most nutritionists as their recommendations have resulted in unprecedented chronic disease.

      But of course, and by all means, you can believe and eat exactly as you wish 🙂 I’m just offering another perspective.

    2. You discredit your (valid) argument by bringing religion into a conversation about science. Also, lets leave it to the PHDs and qualified scientists to present reseach .

      1. Well, since you can’t do science without the one true and living God that created it; it’s right to bring His word into every discussion on science.

    3. I am getting tired of people using the “Where is the research” line to avoid obvious truths. Practically all of the “research” is funded by the same companies that provide the product being researched. So of course it is biased and has been for over a hundred years. You can talk about the complex science all day.(it is rather fascinating) However, all you need to know is this. Almost everything we eat today in modern society we could not have eaten, would not have eaten, and simply didn’t exist. In regard to fruits and vegetables, of course they can be used as food. The truth is, the fruits and veggies of today are not even close to the same quality or even species. Perhaps you could source high quality fruits or even grow your own, but the energy required to do so would exceed the caloric and nutritional gain in my opinion. Now when it comes to the “fall of man” causing the consumption of meat I am unsure what that proves. I’m not sure if you have read the Bible but milk, meat and other animal products are mentioned far more often than vegetables and in a more positive view. I recommend “Nutrition and Physical Degeneration” as well as “The untold story of Milk”. The former will help you understand what we have always eaten and the effects of modern diet and the latter sheds light on the corruption of medical institutions following the early 1900’s.

      1. Brendon, that was a very thorough and throughtful reply. Thank you! I have been a Carnivore for 2 months, and acting as my own free will Guinea Pig, the results so far have been amazing…how is it even possible to gain muscle size and strength while losing fat at the same time?? How by eating these huge quantities of protein cause such mental clarity? How is it possible to reduce high blood pressure, have an excellent blood profile and beat every PR in the gym I had when I was 30, at the age of 59? It’s a simple equation…I’m made of meat and that’s what I will feed it.

        1. How are you now, are you still on the Carni diet, I did it for 3 weeks and stopped due to worrying about Cancer and Heart disease.

      2. How can you be tired of “where is the research?” It protects us from people stating whatever they want to believe is the truth. There is no “obvious truths” – for example most people would consider cruciferous vegeatbles as being healthy. Most people would consider that obvious. Yet in this article it says otherwise. How is anyone to know the real truth unless research is conducted? Yes, some research is tainted if conducted for a reason. But that is why whoever reads the studies needs to know who did the research and were the methods used correct and impartial.

  7. I have a question, I understand that plants have toxins and see where you are coming from, but how come animals don’t have similar toxins? Obviously they don’t want to die either. Arguably even more so than plants. My hypothesis is that our body has adapted to eating meat for so long that we can tolerate whatever toxins are in meat. However, it is just a guess. Is there any evidence to either support or counter my claim?

    1. That’s exactly right. We’ve become ill-equipped to handle these toxins over millions of years of human evolution (https://www.kevinstock.io/health/what-did-humans-evolve-to-eat/)

      That said, a natural diet for a cow is grass. Though many are grain-finished today – and we do see an impact from this. Grain-finished meat, for example, has a higher ratio of omega 6:3 fatty acids, it’s lower in CLA, and the fat is more likely to store plant-based toxins (which cows are far better equipped to deal with than humans).

      1. So when i eat pork ribs then the fat do contain lots of grain toxins or plant toxins?

        I feel better with lean meat due to the histamine… so what do YOu think.

        Is there more plant toxins if the animals are grain finnished? in liver or tenderloin or ribs are the most? I dont have acces to good quality meat so i want to know and i also have good quality potatoes (home grown)

        You will say that potatoes are bad if free from fertilizers? What will be better, carrots or potatoes for meal?

        Best Wishes


          1. Thank You, tell me why i dont tolerate sardines from cans and i m really allergic to fish.

            I think fish is not for me… i will have raw goat milk. I hope i will tolerate this milk but the goats what eat i dont know but it is form nice person. A women which have 3 goats and sell buckwheat and vegetables. May the milk cause die off reaction or will be allergic reaction how to recognize die off reaction due to the yeast die off and allergic to raw goat milk from this women?

      2. Kevin. This is by FAR the best article I have ever read about the toxins in the vegetables that were at one time good for us. Gotta say I am in complete agreement with you. Everything we once ate before the crops were destroyed by all that you have mentioned, I find myself lost. I have had five bouts of cancer. Two primary cancers LATE stages three AND four, and three recurrences. I am throwing in the sugar component here because I don’t even eat my “allotted” amount of sugar. Please, 10 teaspoons of sugar in one can of coke! FOOD FRAUD. It is exactly like the tobacco industry, who little by little by little were forced to write the hazardous warnings on the side of the pack. Now, we live in a nearly smoke free society. I NEVER thought I would see that day. The same is correct with the FOOD FRAUD we are fed. I love your knowledge and the sharing of it Kevin. And you know something, most of my doctors and every nurse I have are WAY over weight. I remember doctors taking a “smoke break,” back in the day. Doctors will never tell a patient that cancer cells thrive on sugar. You know why? They do absolutely no research. They see patients all day, they perform day long surgeries. When would they have the time or the desire to EVER do any research. They don’t even know what is in the medications they prescribe. Or the side effects. My God! I got my first cancer in 2001 because my doctor had me on hormone replacement for seven years. She never asked me “So. What are your symptoms for menopause?” Had she asked that ONE question, I would have said, “What do you mean. She would have said, “Well you know, hot flashes, night sweats, low libido. I would have told her that I didn’t have any symptoms. Then she might have said, “then why do you think you need hormone replacement.” And I would have said, “Well I thought women just automatically went on it during menopause.” WRONG! And now they never keep women on it longer than two years because of the high percentage of women who were getting breast cancer which was highly correlated to the long use of HRT. Research is NOT a doctor’s thing. And patients for the most part see their doctors as some kind of God.

        I cannot tell you how frustrated I am to read this piece you wrote and to have comments from idiots who challenge you “just because.” I want you to know how much you wrote has only confirmed what I seemed to have inherently believed about those vegetables. The best I can do at this point is buy frozen only.

        Anyway. I would love to follow you. How do I make sure to link up to you. I have zero computer skills. I can read and I can write. I feel like I was supposed to have found you, and I am not one of those mystical souls. I believe in science, and if science can find parts of the Creator it agrees with, then I am on board. I believe in something. But the God others believe in is not the God I believe in. It’s more like an Unknowable Essence. There must be the harmony between Science and Religion. Not Churchianity. But rather all world religions, which really say the same thing. The truth is one point. And the ignorant have multiplied it.

    2. I beieve if you search why broccoli is bad for you there is all sprts of studies on this subject that you can find out your self but because of all the build up toxins that is why there are so many disease today because of these toxins

    3. Because animals have locomotion and limbs. Animals’ main defenses are to run away, or to use violence. Fight or flight.

      Plants are stationary and have neither the option of fight nor flight, so they use chemical warfare instead.

    4. Animals run away, jump, climb, or attack with claws, spines, teeth, muscles, or
      venom. Once you get past those defenses, most animals are non-toxic. A rule of thumb could be that the easier it is for an animal to kill you while it is alive, the less it can kill you once it is dead. For example; elephant compared to toad.
      Plants cannot escape or bite, so they poison.

    5. Animals defense mechanisms are the fact that that are conscious enough to be able to fight for their life with their own muscle/body. They dont need to create internal chemicals that cause damage. The damage they cause is done through the material/outer world unlike plants and “non conscious” beings which are still technically conscious though

  8. Very interesting. I’ve been religiously eating cruciferous vegetables for decades, but I have some autoimmune issues. Perhaps this has been part of the cause.

    1. I’m doing the AIP diet now for psoriasis and it’s not getting better. I looked at what I’m eating plenty of….Brussels sprouts, cauliflower and cabbage. I will be taking these out for a while to see if I heal better. Thank you for this article!

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