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.
In our Sprouting Guide PDF, you'll learn the basics of sprouting, read the science of sulforaphane, and gain insights from one of the in the field of chemoprotection.
The conversion of glucosinolates to their cognate isothiocyanates via myrosinase-driven hydrolysis is not a direct path; rather, it occurs in a stepwise fashion, yielding a variety of intermediate bioactive compounds that can rearrange to form the final product. Several factors – such as gut pH and temperature, or the presence of iron – can influence whether the conversion process stops at the intermediate stage or continues to form the isothiocyanate. The myrosinase in daikon radish and mustard seeds are particularly effective at driving the formation of isothiocyanates, however, providing a culinary "hack" that favors isothiocyanate production. In this clip, Dr. Jed Fahey describes factors that influence isothiocyanate production.
Rhonda: It's very interesting and it kind of brings me to just another quick question because you mentioned daikon and that's something that I've seen in several studies where there seems to be some particularly stable form of myrosinase in daikon. Is that true?
Rhonda: You know where I'm going with this? Can you eat daikon or add some... Is it found in mustard powder? Is that...
Jed: It is. It is.
Rhonda: Okay. Can you sprinkle mustard powder on your broccoli and increase the bioavailability? That's what I was getting at.
Jed: I think so. And so where you're, I think you're trying to draw me out on the issue of myrosinase and where it is, and how it is, and what the complications are. So myrosinase is a simple enzyme. It's a protein. It turns out that there are companion proteins that have slightly different activities or that modify the products of myrosinase. To make a complicated story even more complicated, the glucosinolate gets converted by myrosinase, not directly to an isothiocyanate, but to an unstable intermediate that then rearranges and forms the isothiocyanate.
So there's an opportunity for other enzymes to come in and sort of re-direct the pathway. And one of those enzymes is actually present in broccoli and at normal physiologic gut pH, temperature and without an excess of iron ions and so on and so forth. There's not a lot of diversion from isothiocyanate to these other compounds, but most of the other compounds are not necessarily bad for you, but they don't have the same phase II enzyme-inducing activity so you're essentially wasting or losing some of the precursor.
Rhonda: Are we talking about sulforaphane nitriles?
Jed: Sulforaphane nitriles...
Rhonda: So they're not bad. They're just not...
Jed: They're not effective, right.
Rhonda: Okay, because that was another question I had.
Jed: Well, there are some other compounds called indoles that we can talk about in a minute and they're present in the broccoli heads. They're not present to any large degree in broccoli sprouts. So indoles from broccoli form, we're going all over the map here, but I'll come back. I'll come back. So indoles from broccoli form something called indole-3-carbinol or I3C, which is omnipresent in health food stores or supplement sites, or DIM, D-I-M, diindolylmethane.
These compounds have gotten sort of a mixed review from a health perspective because it's been shown they can polymerize or form dimers or tetramers that actually resemble dioxin, the potent toxin. And so in animal studies, now I haven't updated my brain on this for a number of years, but when I last did about four, five years ago, there were an equivalent number of animal studies showing a cancer-preventive effect of indole carbinol, I3C, to those which showed that it actually promoted cancer. And some of these were even in the same animal model and what it turned out was that the preventive effect depended on whether you gave I3C before or after you gave a carcinogen.
So as a lab animal, you're in a cage, you eat what you're given, and then the way these experiments are done is a carcinogen is administered usually for once or for maybe three or four days either before giving the protective compound or after giving the protective compound. And then you follow that animal out or those animals out for many, many weeks until cancers develop and you count tumors, and you determine that there was protection or not. It depended on when vis-à-vis the carcinogen, they got the protection. That's great for an animal...well, it's not so great for the animal, but it's great for an animal experiment, but you and I get our carcinogens continuously, one might imagine, right? Whether it's from sunlight or aflatoxins in our food...
Rhonda: Or benzene.
Jed: ...or benzene, yeah. So we get our carcinogens continuously and we do get to choose when we eat our protective compounds if you want to look at it that way, I suppose, or else, we're eating our protective compounds all along if we are eating a protective diet.
I think I'm going to be able to get back to what you originally asked me, but we were quite happy when we determined that in broccoli sprouts, there were essentially no indole glucosinolates, therefore, there was no indole-3-carbinol or diindolylmethane that we would have to worry about. We wouldn't have to do this sort of mental arithmetic and think "It's unbalanced, is this a good thing or not?" Now, the epidemiologic studies still say that eating more broccoli or more cruciferous vegetables is good for you from the perspective of a bunch of different cancers, etc., etc.
Rhonda: Across the board.
Jed: Across the board, yeah. So I don't think that I3C, indole-3-carbinol, is bad for you. A lot of women take it for menopausal problems, it's invoked in the estrogen cycle, and I can't remember off the top of my head exactly what the indication is, but I don't think it's bad for you. We don't worry about it with broccoli sprouts because it's just not a factor. So back to your...we got off track, but you asked about myrosinase. So all the cruciferous vegetables do have myrosinase. Many of them have these other accessory proteins or additional enzymes that will direct the conversion of glucosinolates not just to isothiocyanates, but to some other stuff.
And, interestingly, daikon or Japanese radish doesn't have... I'm not sure that I can say it doesn't have all of them, but it doesn't have the main enzymes, epithiospecifier proteins, they're called, that do some of this redirection to alternative products. So, in fact, if you were to eat cooked broccoli, so just, let's get hypothetical now in the kitchen. So if you were to eat cooked broccoli and you were to want to get as much of a sulforaphane benefit as you could from it, you might add grated daikon or ground up daikon seeds even at very low level to facilitate the conversion. In other words, add live enzyme to facilitate the conversion and you wouldn't have the complication of that other enzyme.
Actually, this has been published. My colleague Yuesheng Zhang who was one of the people who discovered sulforaphane originally, he was the one who actually pointed this out to us many, many years ago and it was subsequently published by others in Illinois. But the fact that broccoli has this epithiospecifier protein means that you're not getting complete conversion to sulforaphane if you use the broccoli enzyme. So for reasons that had nothing to do with knowledge of that fact when we first started making broccoli sprout extracts rich in sulforaphane, I was adding in a very small amount of seven-day-old daikon sprouts to the boiling kettles once they cooled down to catalyze the conversion. And the reason I was doing it is because once we boiled broccoli, we kill the native enzyme, and I wanted to add something that had the biggest bang for its buck of myrosinase and I had found that daikon sprouts had a hell of a lot of myrosinase activity. It was really just sort of a greedy...well, I was actually doing it because I wanted as little contamination of the taste and the other compounds present in daikon sprouts. So I was able to add 1% or 2% by weight daikon sprouts to the broccoli mix to get complete conversion. And as I say, Yuesheng Zhang, who's now at the Roswell Park Cancer Institute, then pointed out to me that, "Hey, did you know that we found the epithiospecifier protein isn't in daikon sprouts?" So, anyway, a long story, but...
Rhonda: So that's really a useful little hack for people including myself.
Jed: Yeah. But daikon sprouts are pretty harsh-tasting. I mean, if you don't...
Rhonda: You can just do a little bit, right?
Jed: But you can do a little bit, yeah.
Rhonda: And what about the mustard seed?
Jed: Mustard seed has isothiocyanates. It has glucosinolates, rather. Sinigrin is the name of the glucosinolate it's rich in. It produces a compound called allyl isothiocyanate and it has myrosinase. And so, yes, you can grind up mustard seed and use that, too.
Rhonda: Mustard powder and put it on your broccoli after you...
Jed: Yeah. I don't know. I suppose most mustard powder is okay, but it depends on how long it's been stored. I mean, as long as it develops a bite when you eat it, it should have active myrosinase.
Rhonda: Okay, yeah. I guess the other thing would be taking some of these supplements like glucoraphanin, taking it, eating it with your cruciferous may even enhance because the cruciferous, the raw cruciferous theoretically would have myrosinase. So if you're taking your supplement with the cruciferous, you may also be getting the biggest bang for your buck, as well.
Jed: Yeah, yeah. Well, that's what this...Nutramax, the supplement company, was trying to do, I think, is to develop to co-deliver myrosinase from a known source, known purity and potency with glucoraphanin. But it's a supplement, not a food.
A family of carcinogenic toxins produced by certain fungi endemic to areas with hot and humid climates. Aflatoxins are commonly found in agricultural crops such as maize (corn), peanuts, cottonseed, and tree nuts. In people who are infected with hepatitis B, aflatoxin markedly increases the risk for liver cancer.
Poisonous and cancer-causing chemicals that are produced by certain molds which grow in soil, decaying vegetation, hay, and grains. They are regularly found in improperly stored staple commodities such as cassava, chili peppers, corn, cotton seed, millet, peanuts, rice, sesame seeds, sorghum, sunflower seeds, tree nuts, wheat, and a variety of spices.
An aromatic hydrocarbon compound produced during the distillation and burning of fossil fuels, such as gasoline. It is also present in the smoke from forest fires, volcanoes, and cigarettes. Benzene is a carcinogen that targets the liver, kidney, lung, heart, and brain and can cause DNA strand breaks, chromosomal damage, and genetic instability.
The extent and rate at which drugs or other substances, such as plant-based dietary compounds, enter the body’s circulation. Bioavailability is influenced by a variety of factors, including dose, the presence of other foods or substances, and interindividual differences in metabolism due to gut absorptive surface and commensal microbial populations.
A class of edible plants from the Brassicaceae, Capparaceae, and Caricaceae families, so named for their cross-shaped flowers. Crucifers contain glucosinolates and myrosinase, which react to form isothiocyanates, a class of compounds with known beneficial health effects in humans. Cruciferous vegetables include arugula, broccoli, bok choy, Brussels sprouts, cabbage, capers, cauliflower, cress, collards, kale, kohlrabi, moringa, mustard, papaya, radish, rutabaga, turnips, wasabi, and watercress.
Any of a group of complex proteins or conjugated proteins that are produced by living cells and act as catalyst in specific biochemical reactions.
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.
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.
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.
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.
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