"Carnivore doctors” are misrepresenting the goitrogenic activity of sulforaphane | Jed Fahey
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Broccoli sprouts are concentrated sources of sulforaphane, a type of isothiocyanate. Damaging broccoli sprouts – when chewing, chopping, or freezing – triggers an enzymatic reaction in the tiny plants that produces sulforaphane.
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The carnivore community is in error. Despite the overwhelming evidence demonstrating the beneficial health effects of isothiocyanates, some anti-nutritional effects of isothiocyanates have been reported. One example is seen in goitrin, an isothiocyanate compound derived from cabbage, rapeseed, and kale, that inhibits thyroid hormone formation. But long-term studies in humans and rodents have shown that broccoli sprouts carry little risk of goitrogenic effects. In this clip, Dr. Jed Fahey disputes claims that sulforaphane causes goiters.
[Dr. Fahey]: You mentioned... And certainly in this clip they talked about the carnivore lifestyle. I actually made notes of a number of things I'd like to rebut or comment on in terms of that part of the little clip I watched. If we have time for me to say a few things about it, I'll...
[Dr. Patrick]: Let's talk a little bit about the effects that were...that have been said by Saladino and others about sulforaphane being goitrogenic, in other words having a negative effect on the thyroid. I have some comments there, but can you go ahead and speak to that, is sulforaphane a goitrogen?
[Dr. Fahey]: No, it's not.
[Dr. Patrick]: Maybe not sulforaphane itself, but, yeah, a certain isothiocyanate.
[Dr. Fahey]: Yeah. So it's not, and nor are broccoli sprouts when eaten in moderation, nor are glucoraphanin-rich supplements. Mature broccoli... I mean this is a long story. But mature broccoli...broccoli produces different glucosinolates in different phases of its lifestyle. And market-stage broccoli, or heads of broccoli, florets, do have things called indole glucosinolates. And when they are acted on by myrosinase, they can form...they form unstable intermediates and they can form compounds which can be toxic or goitrogenic, and maybe even promote certain cancers, depending upon if they're administered before or after a person gets exposed to the carcinogen. There's a lot of literature on cancers...on...based on animal studies on that and I think the jury is still out on the beneficial effects of eating...of those compounds. But the byproducts of indole glucosinolate metabolism are, among others, are things called indole-3-carbinol and diindolylmethane. It's really the subject, I think, for another discussion, but I want to bring it back to broccoli sprouts and sulforaphane.
And so we did this 12-week study in China that I told you about. Well, collaborators... I'm not an author of this...coauthor of this most recent study. But they took some of the...they took the blood samples from this 12-week study where we gave them sulforaphane from broccoli sprouts and looked at indicators of thyroid status, hormone status, and autoimmune status and found absolutely no negative effects on thyroid function. So that's three months of continuous ingestion of sulforaphane, that's definitely the longest effect that's...study that's looked at thyroid-specific potential side effects. But this is...the first author's name is Chartoumpekis and it was 2019. And, you know, this is someone whose specialty is thyroid function who's published quite widely on it and there was no effect. So yeah.
[Dr. Patrick]: Yeah. That was a great study. I mean three months is a long time. And you certainly would think that after three months of taking continuous broccoli sprout extract every day, if there was going to be a negative effect on the thyroid you would see it after three months.
[Dr. Fahey]: Yeah.
[Dr. Patrick]: Moreover, in 2018 there was a very long-term animal study in rats where there were two groups of rats. There were some rats that were...that had hypothyroidism, drug-induced hypothyroidism, and then there was an iodine-deficient group of rats. And they were given broccoli sprouts, freeze-dried or whatever, you know, broccoli sprout extract. And not only was there no harmful effect on the thyroid even in iodine-deficient animals in terms of their thyroid homeostasis, so their thyroid stimulating hormone.
[Dr. Fahey]: TSH.
[Dr. Patrick]: Their T3, T4 were all the same. In the animals, in the rats, that had hypothyroidism there was a beneficial effect from the broccoli sprouts in the thyroid gland, an antioxidant effect that was beneficial.
So to say that it's a goitrogen and going to have negative effects on the thyroid, it's quite funny because you see this sort of echo chamber meme going around, particularly in groups that are anti-plant, and they just have it all wrong, a complete lack of understanding and not even looking at actual good data.
- [Dr. Fahey]: Yeah. Well, you know, interestingly this persists in the medical community, too. So in one of our studies, the autism study that we published in 2014, there were questions from the IRB, which is made up of, among other things, physicians, about potential for thyroid issues and were we going to monitor thyroid chemistry. And we did and we went through the same explanation sort of that I just did with you.
And so in that study, the 12-week study with a follow-up... Or 16-week, I guess. I'll have to review my own papers. But daily consumption... This was with autistic kids, not perfectly healthy subjects. But there were... We followed thyroid chemistry. And as I recall, there were a couple of times when thyroid function was flagged and they wound up being in placebos, those that are getting a placebo.
So yeah, I mean it's a concern that keeps on coming up. But with market-stage broccoli it's a valid question to ask, "Can you get too much market-stage broccoli?" Perhaps, yeah, yeah. But, and there are areas where goiter is endemic and those people eat a hell of a lot of cabbage.
[Dr. Patrick]: Right.
[Dr. Fahey]: But there also are certain things like arsenic in the soils there.
[Dr. Patrick]: The cabbage... Right, exactly. I mean there's a lot of confounding factors, and cabbage is not broccoli sprouts.
[Dr. Fahey]: Exactly.
[Dr. Patrick]: As we mentioned, there's hardly any glucoraphanin in cabbage.
[Dr. Fahey]: Exactly, yeah.
[Dr. Patrick]: So the other question also was related to Saladino and the question was, "How do you respond to Paul Saladino's claims on Joe Rogan's podcast, that the risks of sulforaphane outweigh the benefits?"
[Dr. Fahey]: Okay. Are we... Do we have from now until close?
[Dr. Patrick]: Until 11:30. Yeah, we've got 14 minutes.
[Dr. Fahey]: Okay. So I have...I made just a short little list of nine points. I don't want to go through them in detail, but let me just sort of tick them off, I guess. So I think on multiple levels it's bad advice, the carnivore lifestyle is bad advice. Human beings didn't evolve as carnivores, we're omnivores, that means we eat a variety, vegetable and meat. And, you know, this is a product of evolution. And you can look at tooth and mouth and jaw structure and all sorts of other anatomical things, it's clear we didn't evolve to be carnivores. And I think a self-anointed fitness and/or nutrition guru is not going to change the course of human evolution in a generation. And, you know, call them sensationalist claims or not, but the bottom line is there is certain dogma, scientific dogma, and evolution as human beings is something that they're not going to be able to rewrite.
So anyway, there's an abundance of... So this is... You and I agreed we weren't going to talk politics on this, but this is...I feel like a politician. That was the first point. Second point, there's...or number two, there's an abundance of peer-reviewed scientific literature showing diets rich in fruits and vegetables, and especially cruciferous vegetables, are good. I'm not aware of credible long-term studies supporting a carnivorous lifestyle, or the carnivore approach for humans.
Three, the risks to eating everything. And certainly for...you know, variety is the spice of life. Certainly eating broccoli sprouts only to the exclusion of everything else would be terrible for you. And so...but that's not what anybody is advocating.
Point four, studies of phytochemicals in isolation and in food matrices and in limited combinations with other phytochemicals, vitamins, minerals, etc., show almost without exception that, yes, some things are frank toxins. Think about nicotine, they're toxic at pretty much any level and the toxicity goes up. Most...many phytochemicals, not most, but many phytochemicals have a U-shaped effect curve, hormesis, or a hormetic effect. So spanning from no effect at very low concentrations to perhaps benefit or satisfy your requirement, to harm or toxicity at the highest level. You know, everything is toxic at some level. Water is, sugar is, salt is, and sulforaphane is. So I think the evidence is overwhelming though that eating a lot of broccoli or broccoli sprouts is not harmful for you.
We talked about the extensive evidence of all sorts of pathways that are upregulated, protective pathways. It's thoroughly documented in the literature and the subject of many clinical studies now, good clinical studies, and some bad ones.
A molecule that inhibits oxidative damage to DNA, proteins, and lipids in cells. Oxidative damage plays a role in the aging process, cancer, and neurodegeneration. Many vitamins and plant-based compounds are antioxidants.
A naturally-occurring element found in soil, water, food, and air. Chronic arsenic exposure is associated with the development of several diseases, including cancer, cardiovascular disease, and diabetes. In utero and early childhood exposure to arsenic is associated with poor cognitive development and increased deaths in young adults.
A developmental disorder characterized by impaired social interaction, behavioral problems, and poor communication. Autism typically manifests in early childhood and is slightly more common among boys than girls. In clinical trials, sulforaphane, a compound derived from broccoli and broccoli sprouts, reduces the characteristic behaviors associated with autism.
In statistics, a confounder (also confounding variable or confounding factor) is a variable that is correlated (directly or inversely) to both the dependent variable and independent variable.
A variable that is related to one or more of the other variables in a study. A confounding factor can mask an association that exists between variables or demonstrate an association that does not exist. If confounding factors are not measured and considered, the findings of the study may be biased.
An organic compound produced during the refining of petroleum products. Ethane is also produced in humans during the peroxidation of lipids. It is measurable in exhaled air and is a marker of oxidative stress.
A glucosinolate (see definition) found in certain cruciferous vegetables, including broccoli, Brussels sprouts, and mustard. Glucoraphanin is hydrolyzed by the enzyme myrosinase to produce sulforaphane, an isothiocyanate compound that has many beneficial health effects in humans.
Plant secondary metabolites found primarily in cruciferous vegetables. Glucosinolates give rise to a variety of compounds that have been identified as potent chemoprotective agents in humans against the pathogenesis of many chronic diseases such as cancer, cardiovascular disease, and neurodegenerative disease, among others. These products are responsible for the pungent aroma, sharp flavor, and the “heat” commonly associated with some cruciferous vegetables such as wasabi and horseradish.
An organism’s ability to maintain its internal environment within defined limits that allow it to survive. Homeostasis involves self-regulating processes that return critical bodily systems to a particular “set point” within a narrow range of operation, consistent with the organism’s survival.
Biological responses to low-dose exposures to toxins or other stressors such as exercise, heat, cold, fasting, and xenohormetics. Hormetic responses are generally favorable and elicit a wide array of protective mechanisms. Examples of xenohormetic substances include plant polyphenols – molecules that plants produce in response to stress. Some evidence suggests plant polyphenols may have longevity-conferring effects when consumed in the diet.
A trace mineral that is essential for human health. Iodine is necessary for normal thyroid and immune function.
An essential mineral present in many foods. Iron participates in many physiological functions and is a critical component of hemoglobin. Iron deficiency can cause anemia, fatigue, shortness of breath, and heart arrhythmias.
Byproduct of a reaction between two compounds (glucosinolates and myrosinase) that are found in cruciferous vegetables. Isothiocyanates inhibit phase I biotransformation enzymes, a class of enzymes that transform procarcinogens into their active carcinogenic state. Isothiocyanates activate phase II detoxification enzymes, a class of enzymes that play a protective role against DNA damage caused by reactive oxygen species and carcinogens. Examples of phase II enzymes include UDP-glucuronosyltransferases, sulfotransferases, N-acetyltransferases, glutathione S-transferases, and methyltransferases.
The thousands of biochemical processes that run all of the various cellular processes that produce energy. Since energy generation is so fundamental to all other processes, in some cases the word metabolism may refer more broadly to the sum of all chemical reactions in the cell.
A chemical that causes Parkinson's disease-like symptoms. MPTP undergoes enzymatic modification in the brain to form MPP+, a neurotoxic compound that interrupts the electron transport system of dopaminergic neurons. MPTP is chemically related to rotenone and paraquat, pesticides that can produce parkinsonian features in animals.
A family of enzymes whose sole known substrates are glucosinolates. Myrosinase is located in specialized cells within the leaves, stems, and flowers of cruciferous plants. When the plant is damaged by insects or eaten by humans, the myrosinase is released and subsequently hydrolyzes nearby glucosinolate compounds to form isothiocyanates (see definition), which demonstrate many beneficial health effects in humans. Microbes in the human gut also produce myrosinase and can convert non-hydrolyzed glucosinolates to isothiocyanates.
A highly toxic, addictive substance present in the tobacco plant. Nicotine is an alkaloid compound that stimulates the central nervous system by acting an agonist at the nicotinic cholinergic receptors in various regions of the brain. It promotes the release of several neurotransmitters, including acetylcholine, beta-endorphin, dopamine, norepinephrine, serotonin, and ACTH. Nicotine intake can cause peripheral vasoconstriction, tachycardia, and elevated blood pressure. Nicotine in breast milk can interfere with an infant's sleep patterns.
Highly reactive molecules that have the ability to oxidize other molecules and cause them to lose electrons. Common oxidants are oxygen, hydrogen peroxide, and superoxide anion.
An isothiocyanate compound derived from cruciferous vegetables such as broccoli, cauliflower, and mustard. Sulforaphane is produced when the plant is damaged when attacked by insects or eaten by humans. It activates cytoprotective mechanisms within cells in a hormetic-type response. Sulforaphane has demonstrated beneficial effects against several chronic health conditions, including autism, cancer, cardiovascular disease, diabetes, and others.
Volatile organic compound. An organic chemical that has a high vapor pressure at ordinary room temperature.
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Sulforaphane News
- Sulforaphane extends lifespan and healthspan in worms via insulin and insulin-like growth factor-1 signaling.
- Paul Saladino, MD explains how we may have overstated the health benefits of plants and especially sulforaphane
- NRF2 much of a good thing (December 2017)
- A pilot trial finds sulforaphane treatment increased glutathione levels in the blood & hippocampus region of the brain in healthy people.
- A new study found sulforaphane (found in broccoli sprouts) improved behavior & social responsiveness in children with autism.
