Data
Sulforaphane content by food
Published figures for every common source, each one carrying the method that produced it.
Quick answer
Measured glucoraphanin in mature broccoli ranges from 0.8 to 21.7 µmol per gram dry weight across 50 accessions grown side by side, a 27-fold spread within one vegetable. Broccoli sprouts hold 10 to 100 times the glucoraphanin of the mature plant. Published figures use different compounds, different weight bases and different assays, so every row below states all three.
Ask how much sulforaphane is in broccoli and you will get answers that differ by a factor of twenty. They are not all wrong. They are measuring different things.
Why this table exists
Sulforaphane figures circulate widely without the information needed to use them. The number depends on:
- Cultivar. Kushad and colleagues grew 50 broccoli accessions under uniform conditions and measured glucoraphanin from 0.8 µmol per gram dry weight in the accession EV6-1 to 21.7 in the cultivar Brigadier. That is a 27-fold spread with soil, climate and assay held constant.
- Plant age. Young sprouts concentrate glucoraphanin far more densely than the mature vegetable. Fahey and colleagues reported that three-day-old sprouts of certain broccoli and cauliflower cultivars carry 10 to 100 times the glucoraphanin of the corresponding mature plants. The same paper notes that sprouts of many broccoli cultivars hold negligible indole glucosinolates, which predominate in the mature vegetable.
- Growing conditions and storage. Both sulfur availability in the soil and time since harvest move the result.
- What was measured. Glucoraphanin content and sulforaphane yield are different quantities. Converting between them requires assumptions about hydrolysis that frequently go unstated.
- The assay. HPLC after controlled enzymatic hydrolysis, cyclocondensation assay for total isothiocyanates, and estimation from total glucosinolates give different answers and are not interchangeable.
A figure without its method attached cannot be compared to anything. Every row below names its assay, and where the assay could not be read from the paper the row says that instead of leaving the column empty.
The table
| Food, and how it was prepared | Compound measured | Figure as published | Weight basis | Assay | Source |
|---|---|---|---|---|---|
| Mature broccoli, 50 accessions grown under uniform conditions | Glucoraphanin | 0.8 to 21.7 µmol/g, lowest in EV6-1 and highest in Brigadier | Dry weight | Not stated in the abstract; full text paywalled | Kushad 1999, PMID 10564014 |
| Broccoli sprouts, 11 days from germination, cv. Traditional, untreated | Sulforaphane | 16.6 ± 0.4 µmol/g | Dry weight | Reverse-phase HPLC-DAD, C18 column, 254 nm, methylene chloride extraction, sulforaphane standard curve | Mahn 2022, PMID 35804720 |
| Broccoli sprouts, same batch, blanched at 61 °C for 4.8 min | Sulforaphane | 54.3 ± 0.20 µmol/g, a 3.3-fold rise | Dry weight | As above | Mahn 2022, PMID 35804720 |
| Broccoli sprouts, raw, the 68 g portion fed to subjects | Glucoraphanin | 218.4 ± 24.4 µmol per 68 g portion | Fresh weight, whole portion | UPLC-MS/MS; sprouts steamed five minutes before analysis to destroy myrosinase | Clarke 2011, PMID 21928849 |
| Broccoli seed extract supplement, the 6-pill dose fed to the same subjects | Glucoraphanin | 220.3 ± 3.3 µmol per 6 pills | Per dose | UPLC-MS/MS | Clarke 2011, PMID 21928849 |
| Broccoli sprout homogenate, blended with water and 2 percent daikon sprouts, held at 37 °C for 2 h to convert the precursor | Sulforaphane | 0.283 µmol/ml of homogenate | Per volume of preparation | Cyclocondensation assay | Riedl 2009, PMID 19028145 |
Two rows measure the precursor and three measure sulforaphane itself, so the numbers cannot be lined up against each other. Glucoraphanin becomes sulforaphane only when myrosinase reaches it, and the fraction that converts is the subject of its own literature. Clarke's two rows are the useful comparison in the table: a 68 g portion of raw sprouts and six pills of broccoli seed extract were matched on glucoraphanin, 218.4 against 220.3 µmol, which is why that trial could test preparation rather than dose. Over 24 hours the supplement group excreted a 5-fold lower quantity of sulforaphane metabolites and an 8-fold lower quantity of erucin metabolites than the sprout group, from the same precursor dose. The authors report that they could not measure plasma concentrations accurately because of sample processing, so the urinary figures are the ones to use.
Why kale and Brussels sprouts are not sulforaphane sources
Most lists of foods high in sulforaphane include kale, cabbage, Brussels sprouts and cauliflower. The measurement behind that habit does not support it.
Kushad and colleagues grew 65 accessions across five groups of Brassica oleracea under uniform cultural conditions and measured the glucosinolates in each. In broccoli the predominant glucosinolates were glucoraphanin, gluconapin and glucobrassicin. In Brussels sprouts, cabbage, cauliflower and kale the predominant glucosinolate was sinigrin, at 8.9, 7.8, 9.3 and 10.4 µmol per gram dry weight.
Sinigrin is not the precursor of sulforaphane. It yields allyl isothiocyanate, the compound responsible for the heat in mustard and horseradish. Glucoraphanin is the only common glucosinolate that yields sulforaphane, and among these five groups it predominates in broccoli alone.
So a vegetable can be rich in glucosinolates, rich in isothiocyanates, and still deliver almost no sulforaphane. Lists that rank kale highly are counting the wider family. If the compound you want is sulforaphane, the evidence points at broccoli and at broccoli sprouts, and the rest of the brassicas are a different isothiocyanate.
| Vegetable | Predominant glucosinolate | Amount | Isothiocyanate it yields |
|---|---|---|---|
| Kale | Sinigrin | 10.4 µmol/g dry weight | Allyl isothiocyanate |
| Cauliflower | Sinigrin | 9.3 µmol/g dry weight | Allyl isothiocyanate |
| Brussels sprouts | Sinigrin | 8.9 µmol/g dry weight, plus gluconapin at 6.9 | Allyl isothiocyanate |
| Cabbage | Sinigrin | 7.8 µmol/g dry weight | Allyl isothiocyanate |
Kushad reported glucobrassicin alongside sinigrin in all four, at 3.2, 0.9, 1.3 and 1.2 µmol per gram dry weight for Brussels sprouts, cabbage, cauliflower and kale. The paper gives no glucoraphanin figure for any of the four, so this table carries none. Fahey's observation that cauliflower sprouts can be glucoraphanin-rich applies to the three-day sprout, not to the mature head in this table.
Why no figure here is converted to fresh weight
Three of the six rows are per gram dry weight, two are per stated portion of fresh sprouts, and one is per milliliter of homogenate. Reporting them on one scale would be more convenient and would be an invention.
Converting a dry-weight figure to a fresh-weight one needs the moisture content of that specific sample. None of these papers states it. Broccoli is mostly water, so a generic assumption would move the result by about an order of magnitude and would carry none of the measurement's actual precision into the answer. The basis column stays, and the conversion is left to anyone who has the moisture figure for their own sample.
The same applies across assays. A cyclocondensation figure counts total dithiocarbamates and is not specific to sulforaphane. An HPLC figure against a sulforaphane standard is. Mahn's 16.6 µmol/g and Riedl's 0.283 µmol/ml were produced by different methods on different material and are two separate facts.
How to read a figure from this table
Every figure above tells you what was in the sample those researchers measured. None of them tells you what you will absorb, and the gap between the two is large.
Between the two sit preparation and conversion. Boiling destroys myrosinase and much of the yield goes with it. Steaming briefly preserves more. Chopping and resting before cooking allows conversion to happen before heat arrives. Chewing does work that swallowing does not. That is what makes the two Clarke rows worth having: the portion and the pills were matched on glucoraphanin to within 1 percent, so anything that differed downstream came from the preparation and not from the dose.
A figure here is also one batch in one lab. Kushad's 27-fold spread across accessions is the reason to treat any single number as a sample rather than a property of the vegetable. Mahn's blanching result is one cultivar, one harvest age and one laboratory, and nobody has fed it to a person.
The table gives you the starting quantity. The page on how much sulforaphane per day covers how much of a dose people absorb, and how to eat broccoli sprouts covers the preparation steps that have been tested in people. For the chemistry that connects the precursor to the compound, see glucoraphanin.