Broccoli: the enzyme you cook off, and how to get it back

There is no sulforaphane in broccoli. There is glucoraphanin and an enzyme called myrosinase, and sulforaphane appears when the two are allowed to meet. Cook the broccoli hard and you destroy the enzyme, so what you do next decides how much you get. Two minutes in the microwave instead of five and a half gave people about three times the yield. Stirring a teaspoon of mustard powder into already cooked broccoli took urinary sulforaphane from 9.8 to 44.7 micromoles per gram of creatinine, more than four times as much, because mustard brings its own myrosinase to replace the one that was cooked away. What the rest of the meal was made of barely mattered. Then the inconvenient part. In two trials the broccoli that lowered LDL cholesterol was a specially bred variety carrying three times the glucoraphanin. Ordinary broccoli, the same 400 grams a week, the same twelve weeks, did not lower it significantly in either trial.

The numbers, per 100 g

How much is actually in it

• In two trials the broccoli that lowered LDL cholesterol was a specially bred one. Ordinary broccoli, eaten in the same amount for the same twelve weeks, did not lower it by a significant amount in either trial. — volunteers aged 50 to 77 in study 1 with a 10-year cardiovascular risk of 10 to 20%, and men and women at mild to moderate cardiovascular risk in study 2 (n = 130 volunteers in total, 37 in study 1 and 93 in study 2) Evidence B source
  In study 1 high-glucoraphanin broccoli reduced LDL cholesterol by 7.1% (95% CI -1.8% to -12.3%, p = 0.011) while standard broccoli reduced it by 1.8% (95% CI +3.9% to -7.5%, not significant); in study 2 the figures were 5.1% (95% CI -2.1% to -8.1%, p = 0.001) against 2.5% (95% CI +0.8% to -5.7%, not significant), and combining both studies the high-glucoraphanin reduction was significantly greater than standard (p = 0.031)
• The two broccolis in that trial looked identical and were coded by an outside party so nobody could tell them apart. One carried three times the glucoraphanin of the other. — the high-glucoraphanin and standard broccoli cultivars, standard being cultivar Ironman, grown and harvested with standard agronomic practice then floreted, blanched and frozen commercially (n = two genotypes across two trials) Evidence B source
  The high-glucoraphanin broccoli contained 21.6 plus or minus 1.60 micromoles per gram dry weight of glucoraphanin and 4.5 plus or minus 0.34 of glucoiberin, while the standard broccoli contained 6.9 plus or minus 0.44 of glucoraphanin and 0.7 plus or minus 0.33 of glucoiberin, with no difference in indole glucosinolates between them

What a real portion looks like

• A floret of broccoli weighs ten grams. The cup that nutrition advice keeps talking about is nine of them, and the amount that lowered cholesterol in trials was about four hundred grams spread over a whole week. — Broccoli, raw, in the WWEIA category Broccoli (n = FNDDS 5,432 foods and 22,046 household measures) Evidence E source
  Broccoli, raw (fdc_id 2709643, FNDDS code 72201100): 1 cup 90 g, 1 piece 10 g, 1 floweret 10 g, quantity not specified 45 g; for comparison the dietary intervention that reduced LDL cholesterol used 400 g per week, which is roughly 57 g or two thirds of a cup per day

What your body absorbs

• Cooking broccoli destroys the enzyme that makes sulforaphane. Stir a teaspoon of mustard powder into the cooked broccoli and you get more than four times as much of it, because mustard brings the enzyme back. — healthy adults (n = 12 adults, each acting as their own control) Evidence B source
  Mean urinary sulforaphane N-acetyl-l-cysteine after cooked broccoli alone was 9.8 plus or minus 5.1 micromoles per gram of creatinine, rising significantly to 44.7 plus or minus 33.9 micromoles per gram when mustard powder was added, which the authors describe as over four times greater bioavailability
• Two minutes in the microwave instead of five and a half gave people three times as much sulforaphane. What the broccoli is served with barely matters, and how long it was cooked matters a lot. — healthy adult volunteers (n = 12 volunteers) Evidence B source
  The estimated in vivo yield of sulforaphane was about three-fold higher after lightly cooked broccoli than after fully cooked broccoli; absorption of allyl isothiocyanate from mustard was about 1.3-fold higher with the meat-containing meal, while the meal matrix did not significantly influence hydrolysis of glucoraphanin or its excretion from broccoli

What cooking and storage change

• Steam broccoli and it keeps most of its vitamin C and folate. Boil it and pour the water away, and you throw out nearly half the vitamin C, two fifths of the folate and almost half the potassium. — green vegetables by cooking method in the USDA table; green broccoli raw, steamed and boiled in unsalted water in CoFID (n = USDA table 270 group-by-method combinations; CoFID 2,886 foods) Evidence E source
  USDA retention: VEG,OTHER,STEAMED (3784) keeps 85% of vitamin C and 85% of folate; VEG,GREENS,BOILED,WATER USED (3006) keeps 70% and 75%; VEG,GREENS,BOILED,WATER COVER DRAIN (3005) keeps only 55% and 60%, with potassium down to 85%. Measured CoFID values per 100 g run the same way: raw (13-502) 79 mg vitamin C, 95 µg folate, 397 mg potassium; steamed (13-504) 60, 72 and 373; boiled in unsalted water (13-503) 44, 34 and 212

Safety, limits and interactions

• Eating a lot of broccoli and its relatives speeds up one of the liver enzymes that clears medicines, by a fifth to two fifths. For most people that changes nothing. For someone on a drug that enzyme handles, it can change the dose that reaches them. — humans in dietary intervention trials; cruciferous vegetables represented included broccoli, Brussels sprout, cabbage, cauliflower, radish and watercress (n = 23 dietary intervention trials) Evidence A source
  Meta-analysis showed a significant effect on CYP1A2 and on glutathione S-transferase-alpha, with cruciferous vegetable consumption increasing the activities of these enzymes by 20 to 40% and 15 to 35% respectively; the authors conclude that patients on CYP1A2 or GST-alpha substrates could have altered drug exposure if they regularly eat large or variable amounts of cruciferous vegetables

What people believe that the data does not support

• A review of every human trial of broccoli and sulforaphane over a decade found the steadiest results for blood sugar and blood fats. For protection against cancer, which is what most people are asking about, the evidence was the weakest of the lot. — humans in intervention studies with broccoli, glucoraphanin or sulforaphane; the predominant intervention was broccoli sprouts (n = 17 studies selected) Evidence A source
  More consistent results were obtained for blood glucose, lipid profile and molecular parameters of oxidative stress, indicating improvement after intervention, while less solid evidence was found for decreased inflammation, Helicobacter pylori colonisation and protection against cancer; the review concludes that the evidence for use of broccoli, glucoraphanin and sulforaphane in humans is limited
• Nine health claims have been filed in Europe for broccoli, sulforaphane and glucosinolates. Every single one was turned down, including the two most repeated ones about immunity and protecting cells from damage. — claims filed for authorisation on broccoli and its constituents in the European Union (n = 9 distinct claims across the three searches, 0 authorised, 9 non-authorised) Evidence E source
  POL-HC-6817 broccoli for a healthy immune system, POL-HC-6818 broccoli to protect cells from oxidation, POL-HC-6819 Brassicaceae as rich in compounds protecting cells and DNA, POL-HC-6826 broccoli sprout powder against oxidative stress, POL-HC-7997 sulphoraphane glucosinolate, POL-HC-7196 glucosinolates to strengthen defences, and POL-HC-7220 and POL-HC-7221 broccoli seed extracts for gastrointestinal health and prostate function, all recorded as Non-authorised

What is still unknown

• Ten grams of dried broccoli sprouts a day for a month did nothing for blood vessel function in people with high blood pressure. The apparent improvement came from two participants out of twenty. — adults with essential hypertension, without diabetes and with normal cholesterol (n = 40 hypertensive individuals) Evidence B source
  Flow mediated dilation went from 4% to 5.8% in the intervention group and stayed at 4% to 3.9% in controls, but the change was mainly due to a marked change in two participants and the observed differences were not statistically significant; no significant changes in blood pressure or blood samples were detected between or within groups, and systolic pressure fell a non-significant 9 mm Hg from a baseline of 153
• Folate in raw broccoli ranged from 15 to 182 micrograms per hundred grams across eight samples. That is a twelvefold difference inside one vegetable, and every table that prints a single number hides it. — Broccoli, raw (n = 8 samples for minerals and folate, 4 to 6 samples for amino acids and carotenoids) Evidence E source
  Folate total 65.0 µg mean with a range of 15.0 to 182.0 and a median of 45.0 across 8 samples, a spread of 257%; beta-carotene 93.0 µg ranging 54.0 to 118.0 across 6 samples, spread 69%; iron 0.69 mg ranging 0.51 to 0.98, spread 68%; calcium 46.0 mg ranging 34.0 to 58.0, spread 52%; total dietary fibre 2.4 g ranging 2.0 to 2.7 across 4 samples, spread 29%

The bottom line

Steam it, and keep it brief. Steamed broccoli holds 85 percent of its vitamin C and 85 percent of its folate. Boiled with the water poured away it holds 55 and 60, and the measured British values run the same way, from 79 mg of vitamin C raw down to 44 after boiling. The amount that did anything in the cholesterol trials was 400 grams a week, around 57 grams a day, two thirds of a cup, six florets. That is less than most people picture. Three things to hold lightly. Ten grams of dried broccoli sprouts a day for a month did nothing measurable for vessel function in people with high blood pressure, and the apparent improvement came from two participants out of twenty. A review of every human trial of broccoli and sulforaphane over a decade found its steadiest results for blood sugar and blood fats, and its weakest evidence for protection against cancer, which is the question most readers came with. Nine health claims have been filed in Europe for broccoli, sulforaphane and glucosinolates, and all nine were refused, including the two about immunity and about protecting cells from damage. One safety line is worth a phone call rather than a worry. Eating a lot of broccoli and its relatives speeds up a liver enzyme called CYP1A2 by 20 to 40 percent. For most people that changes nothing. If you take a medicine that enzyme clears, a large or wildly varying amount of cruciferous vegetables can change how much of the drug reaches you, and a pharmacist can tell you in a minute whether yours is one of them. Under all of it sits a gap. No composition table anywhere measures sulforaphane, not the American ones and not the British ones, so how much is in the head you bought is genuinely unknown. Even folate in raw broccoli ran from 15 to 182 micrograms per 100 grams across eight USDA samples.

Sources

1. brc-f-04 · randomised controlled trial
   In study 1 (37 volunteers), the HG broccoli diet reduced plasma LDL-C by 7.1% (95% CI: -1.8%, -12.3%, p = 0.011), whereas standard broccoli reduced LDL-C by 1.8% (95% CI +3.9%, -7.5%, ns).
   Armah et al., Molecular Nutrition and Food Research, 2015 · checked 2026-09-21
2. brc-f-05 · randomised controlled trial
   The HG broccoli contained 21.6 ± 1.60 μmol/g dry weight glucoraphanin (4-methylsulphinylbutyl glucosinolate) and 4.5 ± 0.34 μmol/g dry weight glucoiberin (3-methylsulphinylpropyl glucosinolate), whereas the standard broccoli contained 6.9 ± 0.44 μmol/g dry weight glucoraphanin and 0.7 ± 0.33 μmol/g dry weight glucoiberin.
   Armah et al., Molecular Nutrition and Food Research, 2015 · checked 2026-09-21
3. brc-f-11 · reference dataset
   FNDDS 2709643 Broccoli, raw (72201100, Broccoli) — 1 cup 90 г · 1 piece 10 г · 1 floweret 10 г · Quantity not specified 45 г
   USDA FNDDS 2021-2023, FoodData Central · checked 2026-09-21
4. brc-f-01 · randomised crossover trial
   When study subjects ingested cooked broccoli alone, mean urinary SF-NAC excreted was 9.8 ± 5.1 μmol per g creatinine, and when cooked broccoli was consumed with mustard powder, this increased significantly to 44.7 ± 33.9 μmol SF-NAC per gram creatinine.
   Okunade et al., Molecular Nutrition and Food Research, 2018 · checked 2026-09-21
5. brc-f-02 · randomised controlled crossover experiment
   The estimated yield of sulforaphane in vivo was about 3-fold higher after consumption of lightly cooked broccoli than fully cooked broccoli...The main influence on the production of isothiocyanates in vivo is the way in which brassica vegetables are cooked, rather than the effect of the meal matrix.
   Rungapamestry et al., British Journal of Nutrition, 2007 · checked 2026-09-21
6. brc-f-09 · reference dataset
   USDA-RETN-R6:3784 VEG,OTHER,STEAMED — vitamin_c_mg 85% · folate_total_ug 85% || USDA-RETN-R6:3006 VEG,GREENS,BOILED,WATER USED — vitamin_c_mg 70% · folate_total_ug 75% || USDA-RETN-R6:3005 VEG,GREENS,BOILED,WATER COVER DRAIN — vitamin_c_mg 55% · folate_total_ug 60% · potassium_mg 85% || CoFID 13-502 Broccoli, green, raw — Vitamin C 79 mg · Folate 95 µg · Potassium 397 mg || CoFID 13-504 steamed — 60 · 72 · 373 || CoFID 13-503 boiled in unsalted water — 44 · 34 · 212
   USDA Table of Nutrient Retention Factors R6 (2007) and CoFID 2021, Public Health England / OGL v3.0 · checked 2026-09-21
7. brc-f-03 · systematic review and meta-analysis of intervention trials
   The meta-analyses performed demonstrated a significant effect on CYP1A2 and glutathione S-transferase-alpha (GST-α), with consumption of Cruciferae increasing the activities of these enzymes by 20-40% and 15-35%, respectively.
   Clinical Pharmacology and Therapeutics, 2020 · checked 2026-09-21
8. brc-f-07 · systematic review and meta-analysis
   Less solid evidence was found with regard to decreased inflammation, Helicobacter pylori colonization, and protection against cancer...Although being relevant, the evidence for the use of broccoli, GRA and SFN in humans are limited; thus, further intervention studies are needed to evaluate outcomes more consistently and reach better grounded conclusions.
   Nutricion Hospitalaria, 2014 · checked 2026-09-21
9. brc-f-08 · regulatory register
   POL-HC-6817 Brassica olaracea var italica (broccoli) Helps maintain a healthy immune system. Non-authorised
   EU Register on nutrition and health claims, European Commission · checked 2026-09-21
10. brc-f-06 · randomised controlled trial
    The change in FMD in the interventional group was mainly due to a marked change in FMD in two participants while the other participants did not have marked changes in FMD. The observed differences were not statistically significant.
    Christiansen et al., PLoS One, 2010 · checked 2026-09-21
11. brc-f-10 · reference dataset
    Broccoli, raw — Folate, total 65.0 UG діапазон 15.0–182.0 (медіана 45.0), зразків 8, розкид 257% · Carotene, beta 93.0 UG діапазон 54.0–118.0, зразків 6, розкид 69% · Iron, Fe 0.69 MG діапазон 0.51–0.98, зразків 8, розкид 68% · Calcium, Ca 46.0 MG діапазон 34.0–58.0, зразків 8, розкид 52% · Fiber, total dietary 2.4 G діапазон 2.0–2.7, зразків 4, розкид 29%
    USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-09-21