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. A balanced diet, one in which you don’t consume a significantly larger quantity of one food source over another seems to me to be the most logical approach. I don’t believe I have ever read of any one food source not having some danger associated if not consumed in moderation. It’s not difficult to find a contradiction for any food source if you run a Web search. I am borderline hypothyroid and I do eat cooked broccoli every couple of weeks. I try not to overthink everything I put in my grocery cart, unless it’s processed food and then there is much higher scrutiny. I eat greens with almost every lunch and dinner which I contribute to help keeping me lean. Let’s not leave out the importance of movement. Stretching and exercise need to be part of your daily routine. The article was interesting and I will surely considering adding it to my mental diet map. Thank you.

  2. I ate a small handful of broccoli sprouts last night for the first time and within 10 minutes I had heart palpitations, tingling in upper extremities, hot head, and heavy breathing. I could not sleep and as of this morning I’m still off balance and jittery. I have estrogen dominance, and I went looking for ways to balance my hormones naturally. One thing I frequently found in many articles, and touted as the top remedy For estrogen dominance, next to flax seeds, was to eat broccoli sprouts. Well, I guess I’m the exception.

  3. HI Dr. Stock, this is so interesting and alarming…my functional doc has me taking a dose of a sulphurophane supplement daily, to help protect my liver. I take Methotrexate for RA (still, even after 8 years of trying to heal my gut, I can’t go without it yet.). So, which is more dangerous, the effects of the sulphurophane, or not having the extra liver protection? I am complete befuddled. Your example above of taking a chemo agent to protect against cancer….well I DO take a chemo agent. Any thoughts on this topic?

    1. Hi Sarah, you bring up an excellent point. There is a cost-benefit analysis of any kind of treatment / supplement.
      When doctors prescribe medicine, they know this, and prescribe based on the fact they believe in that situation for that particular patient the benefit is greater than the costs/risks.

      As I say in many articles: The “poison” is in the dose and frequency.
      For some people even a little “poison” is dangerous, for others, they handle it better. And for others, some “poison” is the “greater good” (potential benefits outweighting costs/risks).
      These are decisions you have to make, and ideally with your doctor who knows your situation in detail, and knows the costs/benefits/alternatives and can discuss these with you.

      1. Hello Kevin, Are you still doing Carni? Dr Saladino mentions that activating Nrf2 pathways via hormetic activities such as cold exposure is superior to Sulforaphane ingestion as it may have negatives like affecting dna and damaging it and so it being problematic, but activating the NRf2 pathway can be problematic either way right? On the other hand you want it to reduce oxidative stress and yet it has been linked to cancer growth and proliferation. Id it a case of choosing between accelerated aging or higher cancer risk? How can one balance these two?

  4. Hi Kevin. I have CRPS/RSD Complex Regional Pain Syndrome. My immune system is bad, horrific pain with my nerve and muscles. It is very rare, around 200,000 people in the world have it. I have it in my right foot, going up past my ankle. Drs. aren’t 100% sure that is causing my right scapula, shoulder, arm, ribs, hand, plus starting to feel in my left scapula and down my arm into my hand, (not as bad as right). I also have pudendal neuralgia. I go for CRPS PT, to try to retrain my brain and Pelvic Floor PT.
    I have cut out so many things from my diet. I absolutely don’t need to lose weight, but gain. I also need to strengthen my muscles, very weak from so much downtime, due to this.
    Nobody can tell me what I should be eating to help with my issues. The nutritionist and Drs. all differ.
    Would you be willing to check into this, and help me out, please. I’m in bed most of the time, and I’m scared of getting atrophy. I do my walking that’s allowed, my limited exercise, and my brain exercises.
    Please can you check, and help me. Very concerned. Help, please!

    1. Hi Lisa, sorry to hear about your struggles. I would recommend downloading the guides on this website, they are all free, and really going through them.

    2. Hi Lisa. I just happened to be reading this article and could hardly believe when I saw that you suffer from RSD/CRPS! Ive also suffered from this for the past 18years and its awful! No one I talk to has ever heard of it because it’s so rare. I’ve never met another person who had it. I was just so surprised to see you comment on it here and just had a need to reach out to you. This terrible chronic pain from this is so hard to describe to my friends and family. Pain is hard to see but it really makes for a poor quality of life doesn’t it!

  5. Very interesting. I am going to read Health Dangers of a Plant-based Diet. Also, I would like to see some of the research or studies done to support these “findings”,

  6. why are we told to never eat there foods by some & others say eat these foods;
    all so confusing ——– nightshade vegetables, such as tomatoes, potatoes, goji berries, peppers, and eggplant
    all legumes, such as lentils, beans, peanuts, and chickpeas
    peanut-based products, such as peanut butter and peanut oil
    all grains and products made with grain or flour, including cakes, crackers, and bread
    many dairy products, such as milk

    1. Too much broccoli was causing me to have burning tears, waking up with my eyelids glued together by crud. I quit the broccoli, brussels sprouts and mustard and problem went away.

      From your article: “As with other plant chemicals, the poison is in the dose”. Time to reintroduce a small amount and see what happens.

  7. Every child who hates to eat broccoli, will do a Google search and thank you for giving them the ammunition to combat the mandatory consumption of broccoli. From the reason for the putrid smell to the taste, you may have saved our lives.

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