Best Sulforaphane Supplement: Myrosinase Is the Whole Decision

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Sulforaphane
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Reader sentiment only. Not medical advice, not a recommendation, and not a measure of evidence quality.

Quick answer

Most sulforaphane supplements contain no sulforaphane. They contain glucoraphanin, an inert precursor that only becomes sulforaphane when the enzyme myrosinase acts on it, and heat-processed broccoli seed extracts have had that enzyme destroyed. This is the whole decision. In a randomized crossover trial, glucoraphanin taken with an active myrosinase source delivered 39.8% of the dose as absorbed sulforaphane, against 18.6% for glucoraphanin alone. So buy a product that states active myrosinase (from broccoli sprout material or mustard seed powder), discloses glucoraphanin in milligrams rather than burying it in a proprietary blend, and publishes a lot-matched third-party certificate of analysis covering assayed potency and heavy metals. Human trials have generally used 40 to 100 micromoles of sulforaphane per day, roughly 7 to 18 mg, which implies something like 80 to 250 mg of glucoraphanin taken with active enzyme. Watch the unit trap: milligrams of broccoli extract, milligrams of glucoraphanin, and milligrams of sulforaphane are three different numbers that labels routinely blur.

Key takeaways

The label almost never says sulforaphane because sulforaphane is unstable. It says glucoraphanin, which is stable, inert, and useless without the enzyme myrosinase.
Active myrosinase roughly doubles absorbed sulforaphane: 39.8% of dose versus 18.6% for glucoraphanin alone in a randomized crossover study. No other label feature moves the number this much.
Most broccoli seed extracts are heat-processed, which destroys myrosinase. Gut bacteria provide some backup conversion, but it varies widely between people and is a weak substitute.
Mustard seed powder is a legitimate added enzyme source rather than a filler. It is what produced the doubling in the bioavailability trial.
Do the arithmetic on tablet counts. The randomized phase II lung trial used eight tablets a day, about 120 mg glucoraphanin, calculated as roughly 95 micromoles of sulforaphane. Most retail bottles suggest one or two capsules.
Liposomal sulforaphane targets the wrong bottleneck. Free sulforaphane already absorbs well; the hard part is producing it from the precursor, and there is no published human head-to-head showing a liposomal advantage.
Third-party testing matters more here than in most categories, because enzyme activity degrades invisibly with heat and time and brassica plants take up heavy metals from soil readily.
Human trials cluster around 40 to 100 micromoles of sulforaphane per day. No dose-ranging trial has established an optimal intake for a healthy person.

The short answer

Almost every sulforaphane supplement on the shelf contains no sulforaphane. It contains glucoraphanin, an inert precursor, and glucoraphanin only becomes sulforaphane when an enzyme called myrosinase gets to it. Whether that enzyme is present, and still active, is the single decision that separates a product that works from a very expensive capsule of broccoli powder. In a randomized crossover trial, glucoraphanin taken with an active myrosinase source delivered 39.8% of its dose as absorbed sulforaphane. The same glucoraphanin without myrosinase delivered 18.6%. Everything else on the label matters less than that one factor.

So the buying rule is short: look for a product that states active myrosinase (usually as broccoli seed plus sprout extract, or with added mustard seed powder), check that the glucoraphanin amount is disclosed in milligrams rather than hidden in a blend, and insist on a lot-matched third-party certificate of analysis. If you want the mechanism behind why any of this is worth doing, start with what sulforaphane actually does through Nrf2.

Why the label almost never says “sulforaphane”

In an intact broccoli plant, glucoraphanin and myrosinase are stored in separate compartments. Damage the tissue by chewing, chopping, or crushing it, and the two meet, and the enzyme converts glucoraphanin into sulforaphane in seconds. That separation is the plant’s chemical defense system, and it is also the entire problem for supplement manufacturers.

Sulforaphane itself is unstable. It degrades with heat, moisture, and time, which makes it difficult to put a known quantity of it in a capsule and have that quantity still be there eighteen months later on a warehouse shelf. Glucoraphanin, by contrast, is stable and easy to standardize. So the industry sells glucoraphanin and quietly leaves the conversion step to you.

The catch is that the conversion step is where products diverge wildly. Most broccoli seed extracts are produced with heat, and heat destroys myrosinase. What you are left with is a stable precursor and no enzyme to activate it. Urinary tracing shows how little survives that route: in the Qidong crossover trial, a glucoraphanin-rich beverage was substantially outperformed by a sulforaphane-rich one, and unconverted glucoraphanin passed through largely unused, with urinary glucoraphanin accounting for under 3% of the administered dose.

⚠ CLAIM (wellness): Co-administering an active myrosinase source with glucoraphanin roughly doubles the proportion of the dose absorbed as sulforaphane, per a randomized crossover bioavailability study. This is a statement about absorption, not a claim that any product treats or prevents a disease. Lane: educational.

The three kinds of product, and what each one is really selling

1. Glucoraphanin only. Broccoli seed extract standardized to a percentage of glucoraphanin, no enzyme. This is the most common and the cheapest to make. It is not useless, because gut bacteria have some myrosinase-like activity, but that activity varies enormously between people and is a weak substitute. Expect the low end of the conversion range.

2. Glucoraphanin plus active myrosinase. Typically a blend of broccoli seed extract (for the glucoraphanin) with broccoli sprout powder processed to keep the enzyme alive, or with mustard seed powder as the enzyme source. Mustard seed is a legitimate shortcut here rather than a cheap filler, because it carries a robust myrosinase and it works: it is what produced the doubling of bioavailability described above. This is the category to buy from.

3. Preformed or “stabilized” sulforaphane. Actual sulforaphane, protected from degradation, usually by complexing it with alpha-cyclodextrin. The best-characterized example is the synthetic stabilized compound used in clinical research. This skips the conversion question entirely and is the most bioavailable route in principle. It is also the most expensive, the rarest on retail shelves, and the easiest to counterfeit in spirit: “stabilized sulforaphane” on a bottle is a marketing phrase, not a regulated term, and plenty of products using it are ordinary glucoraphanin extracts.

Avmacol, and what “used in the trials” is worth

If you read the clinical literature you will keep meeting one product, because researchers needed a supplement with reliable, verified myrosinase activity and there were not many options. Each tablet supplies roughly 15 mg of glucoraphanin alongside myrosinase from broccoli seed and sprout material, and the formula has been characterized as delivering something like 20% to 35% of its glucoraphanin content as sulforaphane in vivo. A randomized phase II trial in former smokers dosed eight tablets a day, about 120 mg of glucoraphanin, which the authors calculated as roughly 95 µmol of sulforaphane at a 35% conversion rate.

That is genuinely useful information, and not because you should go buy that specific brand. It is useful because it gives you the arithmetic to judge any product on a shelf. Note the number of tablets: eight. A single tablet at 15 mg of glucoraphanin yields on the order of 2 mg of sulforaphane. Most retail bottles suggest one or two capsules a day. Run the math on the bottle in your hand before you assume it lands anywhere near a studied intake.

The unit trap: µmol, mg of glucoraphanin, and mg of sulforaphane

This category has the messiest labeling in the supplement aisle, and the mess is doing work for the seller. Three different numbers get printed as if they were the same thing.

Glucoraphanin has a molecular weight near 436, sulforaphane near 177. So 100 mg of glucoraphanin is about 229 µmol of precursor, and even at a good 40% conversion that is roughly 92 µmol, or about 16 mg, of actual sulforaphane. A label boasting “500 mg broccoli extract” may mean 500 mg of plant powder containing a few milligrams of glucoraphanin, which is a different universe from 500 mg of glucoraphanin. Three questions cut through it:

How many milligrams of glucoraphanin, stated explicitly, not milligrams of extract or of “broccoli concentrate”?
Is there an active myrosinase source, and does the company say so in those words?
If the label claims a sulforaphane yield in mg or µmol, on what conversion rate, and can they show the data?

A company that cannot answer the first two on the label itself has told you what you need to know.

Liposomal and other delivery claims

Liposomal sulforaphane has appeared in the last few years with the usual absorption promises. Liposomal delivery is a real technology and it has published human data behind it for some compounds, but for sulforaphane specifically there is no published head-to-head human bioavailability trial showing a liposomal product beats glucoraphanin plus myrosinase. The absorption problem with sulforaphane was never that the molecule crosses membranes poorly. Free sulforaphane is small, fat-soluble, and absorbs well on its own. The problem is upstream: making the molecule in the first place. A delivery technology aimed at the wrong bottleneck is a solution to a problem this compound does not have.

Third-party testing, and why it bites harder here

Sulforaphane products fail quality checks in a way that is invisible to the buyer. You cannot taste, smell, or see whether the myrosinase in your capsule is still active, and enzyme activity is exactly the thing that degrades in a hot warehouse or a badly sealed bottle. This is a compound like astaxanthin, where freshness and handling are part of the product rather than an afterthought, and unlike a rugged commodity such as creatine where the main risk is simply being underdosed.

What to insist on:

A finished-product certificate of analysis from an independent lab, matched to the lot number on your bottle, confirming glucoraphanin content by assay rather than by calculation from the raw material.
Heavy-metal screening on that same document. Brassica plants take up metals from soil readily, so this is not a box-ticking exercise for this category.
Some statement of myrosinase activity, or at minimum an unambiguous claim that active enzyme is present. Very few companies test and publish this. The ones that do are telling you where their money went.
An expiry date and storage guidance. Enzyme activity is time-limited. A product with no expiry, or one sold from an unrefrigerated bulk bin, is not being handled as if the enzyme matters.
Certification from a real program (NSF, USP, Informed Choice) rather than a self-designed “lab tested” badge.

⚠ CLAIM (wellness): Independent, lot-matched potency and heavy-metal verification is the most useful quality signal available to a buyer in this category, because myrosinase activity cannot be assessed by the consumer and is not enforced pre-market in the United States. This is a purchasing-quality statement, not a health-effect claim. Lane: educational.

How much sulforaphane per day

Human trials have clustered in a fairly narrow band. Broccoli sprout beverage studies and the supplement trials that followed have mostly used intakes on the order of 40 to 100 µmol of sulforaphane per day, which is roughly 7 to 18 mg. Working backwards through a realistic 30% to 40% conversion, that implies something like 80 to 250 mg of glucoraphanin daily, taken with active myrosinase.

Two honest caveats. First, no dose-ranging trial has established an optimal intake for a healthy person; the doses above are the doses researchers chose for specific endpoints, not a validated target for general use. Second, conversion is genuinely individual. Gut microbiome composition, stomach acid, and whether you take the capsule with food all move the number, which is why published conversion figures come with wide error bars. This is educational information, not a dosing protocol.

Quick label check

What to check	Green flag	Red flag
Enzyme	“Active myrosinase” stated, from sprout or mustard seed	No mention of myrosinase anywhere
Precursor amount	Glucoraphanin in mg, stated explicitly	“500 mg broccoli extract” with no glucoraphanin figure
Yield claims	Sulforaphane yield given with the assumed conversion rate	A big sulforaphane number with no method behind it
Testing	Lot-matched independent COA with assay and heavy metals	Supplier COA only, or a badge with no document
Freshness	Expiry date, sealed opaque packaging, storage guidance	No expiry, clear bottle, bulk gummies
Blend structure	Every ingredient disclosed with its own amount	“Proprietary detox blend”
Claims	Plain description of the ingredient	Cancer, detox, or disease-treatment language

What a sensible purchase looks like

Broccoli seed extract with a stated glucoraphanin dose in the 100 mg range, combined with a named active myrosinase source, in sealed opaque packaging, with a lot-matched third-party COA and a real expiry date. No proprietary blend, no disease claims, no absorption technology solving a bottleneck that does not exist. If you find a genuine stabilized preformed sulforaphane product with published characterization behind it, that is the cleanest option available and you will pay for it.

It is also worth knowing what the food route can and cannot do before you commit to a monthly cost. Fresh broccoli sprouts carry their own live myrosinase, which is precisely the thing supplements struggle to preserve, and we work through the numbers in sulforaphane foods. Sulforaphane sits in the promising-but-unsettled tier of our evidence-graded supplement guide, alongside compounds where the mechanism is strong and the long-term human outcome data is still thin.

Educational information only, not medical advice, and not evaluated by the FDA. Sulforaphane is not a treatment for any disease, and nothing here is a dosing protocol. We do not sell supplements and this guide recommends no brands. Talk to a clinician before supplementing, particularly if you are pregnant or breastfeeding, take thyroid medication, or are undergoing cancer treatment.

Frequently asked questions

What is the best sulforaphane supplement?

The best one is whichever product combines a disclosed glucoraphanin dose with a genuinely active myrosinase source and can prove both with a lot-matched independent certificate of analysis. That combination is rarer than the shelf suggests. A supplement with 200 mg of glucoraphanin and no enzyme will deliver less absorbed sulforaphane than a smaller dose paired with active myrosinase, so headline milligrams are a poor way to compare products. Preformed stabilized sulforaphane, usually complexed with alpha-cyclodextrin, is the cleanest option in principle because it skips conversion entirely, but it is expensive and uncommon at retail. We name no brands.

Does sulforaphane need myrosinase to work?

Effectively, yes. Glucoraphanin is biologically inert until myrosinase converts it. Your gut bacteria have some myrosinase-like activity, so a glucoraphanin-only product is not completely wasted, but that bacterial conversion is highly variable between individuals and delivers substantially less. A randomized crossover study found 39.8% of the dose absorbed as sulforaphane when an active myrosinase source was co-administered, against 18.6% for glucoraphanin alone. If a product does not mention myrosinase, assume it does not have any active enzyme.

How much sulforaphane per day should you take?

Published human trials have mostly used 40 to 100 micromoles of sulforaphane per day, which is roughly 7 to 18 mg. Working backwards through a realistic 30% to 40% conversion rate, that implies something like 80 to 250 mg of glucoraphanin daily taken with active myrosinase. Two caveats matter. No dose-ranging trial has established an optimal intake for a healthy person, so these are the doses researchers picked for particular endpoints rather than a validated target. And individual conversion varies with gut microbiome, stomach acid, and whether you take it with food. This is educational information, not a dosing protocol.

What is stabilized sulforaphane?

It refers to actual preformed sulforaphane protected against degradation, most often by complexing it with alpha-cyclodextrin, which shields the unstable molecule from heat and moisture. The best-characterized version is a synthetic stabilized compound used in clinical research. In principle this is the most reliable route because it removes the conversion question entirely. The problem is that the phrase is unregulated marketing language, so plenty of products labeled stabilized sulforaphane are ordinary glucoraphanin extracts. Ask what the stabilization technology actually is and whether there is characterization data behind it.

Is liposomal sulforaphane better absorbed?

There is no published human head-to-head trial showing that it is. Liposomal delivery is a real technology, but it addresses a bottleneck sulforaphane does not have: free sulforaphane is small, fat-soluble, and absorbs well unaided. The rate-limiting step is generating sulforaphane from glucoraphanin in the first place, which is an enzyme problem, not a membrane problem. A liposomal product with no active myrosinase has spent money on the wrong end of the pathway.

Sulforaphane powder or capsules, which is better?

The format matters far less than what is inside it, but powders carry one specific risk in this category. Myrosinase is an enzyme, and enzyme activity degrades with exposure to heat, moisture, and air. A powder in a tub that gets opened daily in a warm kitchen is a harsher environment than a sealed capsule or a coated tablet. If you buy powder, buy from a company that publishes an expiry date and stores it properly, and keep it sealed and cool. Coated tablets exist in this category partly for that reason.

Can you just eat broccoli sprouts instead?

For many people, yes, and it sidesteps the central problem: fresh sprouts contain their own live myrosinase, which is exactly the ingredient supplements struggle to preserve. Three-day broccoli sprouts were found to carry 10 to 100 times the glucoraphanin of mature broccoli of the same variety. The practical downsides are consistency, taste, and food safety, since raw sprouts carry a real foodborne illness risk for anyone immunocompromised. We compare the food route with supplements in our sulforaphane foods guide.

Who should not take a sulforaphane supplement?

Anyone pregnant or breastfeeding should treat concentrated supplement doses as a no-data situation, which is a different question from eating cruciferous vegetables. People taking thyroid medication or with existing thyroid conditions should raise it with their clinician, since brassica compounds interact with iodine uptake at high intakes. Anyone undergoing chemotherapy or radiotherapy should ask their oncologist, as this applies to potent Nrf2 activators generally. And if you are on prescription medication, mention it to your prescriber rather than assuming a vegetable extract is inert.

References

1.Fahey JW, Zhang Y, Talalay P. Broccoli sprouts: an exceptionally rich source of inducers of enzymes that protect against chemical carcinogens. Proc Natl Acad Sci USA. 1997;94(19):10367-10372.
2.Fahey JW, Holtzclaw WD, Wehage SL, Wade KL, Stephenson KK, Talalay P. Sulforaphane bioavailability from glucoraphanin-rich broccoli: control by active endogenous myrosinase. PLoS One. 2015;10(11):e0140963.
3.Exogenous myrosinase from mustard seed increases bioavailability of sulforaphane from a glucoraphanin-rich broccoli seed extract in a randomized clinical study. Scientific Reports. 2026. (PMID 41692762)
4.Egner PA, Chen JG, Wang JB, et al. Bioavailability of sulforaphane from two broccoli sprout beverages: results of a short-term, cross-over clinical trial in Qidong, China. Cancer Prev Res. 2011;4(3):384-395.
5.Randomized phase II clinical trial of sulforaphane in former smokers at high risk for lung cancer. Cancer Prev Res. 2025;18(6):335.
6.Atwell LL, Hsu A, Wong CP, et al. Absorption and chemopreventive targets of sulforaphane-rich broccoli sprouts versus a myrosinase-treated broccoli sprout extract in humans. Mol Nutr Food Res. 2015;59(3):424-433.
7.Fahey JW, Wade KL, Wehage SL, et al. Bioavailability of sulforaphane following ingestion of glucoraphanin-rich broccoli sprout and seed extracts with active myrosinase: a pilot study of the effects of proton pump inhibitor administration. Mol Nutr Food Res. 2019;63(8):e1801012.
8.Ghawi SK, Methven L, Niranjan K. The potential to intensify sulforaphane formation in cooked broccoli (Brassica oleracea var. italica) using mustard seeds. Food Chem. 2013;138(2-3):1734-1741.
9.Linus Pauling Institute Micronutrient Information Center. Isothiocyanates. Oregon State University.
10.Connolly EL, Sim M, Travica N, et al. Glucosinolates from cruciferous vegetables and their potential role in chronic disease: investigating the preclinical and clinical evidence. Front Pharmacol. 2021;12:767975.