Sulforaphane (broccoli sprout extract)
Summary
Sulforaphane comes from glucoraphanin in broccoli sprouts and seeds. In a 74-person prediabetes trial, broccoli sprout extract lowered fasting glucose slightly but missed its target (grade D). Small trials found lower liver enzymes and more excretion of tobacco toxins. How much sulforaphane forms depends on gut bacteria.
Key facts
- An isothiocyanate released when the plant enzyme myrosinase or gut bacteria convert glucoraphanin from broccoli sprouts or seeds[1][3]
- Broccoli sprout extract for 12 weeks lowered fasting glucose by 0.2 mmol/L in 74 adults with prediabetes, short of the 0.3 mmol/L target; responders had different gut bacteria[1]
- Only about 10–11% of glucoraphanin was recovered as sulforaphane metabolites in smokers given a seed and sprout extract with active enzyme[3]
- In 44 young men with autism, 50–150 µmol of sulforaphane a day for 18 weeks improved caregiver-rated behaviour scores[5]
- 4 graded human outcomes on this page
- October 11, 2026
How it works
ProposedSulforaphane switches on phase II detoxification enzymes; in smokers, higher-dose extract increased urinary excretion of benzene, acrolein and crotonaldehyde metabolites.[3]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Metabolic | Grade D | Mixed | RCT · n = 74 · 2025 | 2 rows |
| Healthy aging | Grade D | Improved | Crossover RCT · n = 49 · 2022 | 1 row |
| Immune | Grade D | Mixed | RCT · n = 47 · 2021 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Fasting blood glucose in prediabetes | Mixed | Grade D | RCT · n = 74 · 2025 Drug-naive adults with prediabetes Form: Broccoli sprout extract · Dose: Not stated in the abstract (once daily) · Duration: 12 weeks Fasting glucose fell 0.2 mmol/L more than with placebo (p = 0.04) but missed the prespecified 0.3 mmol/L target; gut side effects, no severe adverse events. | 39929977 (opens PubMed)Source [1] |
| Liver enzymes in fatty liver | Improved | Grade D | RCT · n = 52 · 2015 Japanese men with fatty liver Form: Glucoraphanin-rich broccoli sprout extract · Dose: Not stated in the abstract · Duration: 2 months ALT, GGT and ALP fell from baseline with the extract but not with placebo; a urinary oxidative-stress marker also fell. | 26604653 (opens PubMed)Source [2] |
| Excretion of tobacco carcinogens | Improved | Grade D | Crossover RCT · n = 49 · 2022 Current smokers Form: Broccoli seed and sprout extract (with myrosinase) · Dose: 148 or 296 µmol glucoraphanin/day · Duration: 2 weeks per dose The higher dose increased urinary excretion of benzene, acrolein and crotonaldehyde metabolites. | 35565256 (opens PubMed)Source [3] |
| Nasal airflow and symptoms in grass-pollen allergy | Mixed | Grade D | RCT · n = 47 · 2021 Adults with grass-pollen allergic rhinitis Form: Broccoli sprout extract tablets · Dose: Not stated in the abstract · Duration: 3 weeks Nasal airflow after allergen challenge improved most when extract was combined with a steroid spray; symptom scores improved only at early time points; cytokines did not change. | 33920642 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Broccoli sprout or seed extract (glucoraphanin) | Varies[3] | About 10–11% of glucoraphanin appeared as sulforaphane metabolites with an enzyme-active extract; conversion without the enzyme depends on gut bacteria.[3] | Gut side effects were reported in the prediabetes trial; no severe adverse events.[1] | Blood glucose, liver enzymes, detoxification markers |
Studied doses
Doses studied in human trials ranged from 148 to 296 µmol of glucoraphanin a day (about 65–129 mg) for 2 weeks, and 50–150 µmol of sulforaphane a day for 18 weeks.[3][5]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Sensitive digestion
- Gastrointestinal side effects were reported in the prediabetes trial.[1]
- Pregnancy and breastfeeding
- No safety data were found in the trials we cite.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Where to buy Sulforaphane (broccoli sprout extract)
Products from brands we partner with that contain Sulforaphane (broccoli sprout extract). Listing a product is not a claim that it works; check the amount per serving against the doses studied above, and the label for other ingredients.
- SupersmartPaid linkBroccoli Sulforaphane Glucosinolate2 capsules: 600 mg broccoli seed extract standardized to 10% glucoraphanin (about 60 mg, roughly 138 µmol); 30 servings. In the range studied, but the label does not list myrosinase, so conversion relies on gut bacteria.Shop at Supersmart (opens in new tab)Price and label checked 2026-10-11 on the brand’s site.
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Frequently asked questions
Is sulforaphane the same as glucoraphanin?
No. Glucoraphanin is the precursor in broccoli; sulforaphane forms when the plant enzyme myrosinase or gut bacteria convert it.[1][3]
Does sulforaphane lower blood sugar?
In one 74-person prediabetes trial, the effect was small (0.2 mmol/L) and missed its target; people with certain gut bacteria responded more.[1]
How much is absorbed?
In smokers given an enzyme-active extract, about 10–11% of the glucoraphanin dose appeared as sulforaphane metabolites.[3]
Sources
- [1]Effect of broccoli sprout extract and baseline gut microbiota on fasting blood glucose in prediabetes: a randomized, placebo-controlled trial.. Nat Microbiol, 2025. RCT
- [2]Sulforaphane-rich broccoli sprout extract improves hepatic abnormalities in male subjects.. World J Gastroenterol, 2015. RCT
- [3]Randomized Crossover Trial Evaluating Detoxification of Tobacco Carcinogens by Broccoli Seed and Sprout Extract in Current Smokers.. Cancers (Basel), 2022. crossover-RCT
- [4]The Effect of Broccoli Sprout Extract on Seasonal Grass Pollen-Induced Allergic Rhinitis.. Nutrients, 2021. RCT
- [5]Sulforaphane treatment of autism spectrum disorder (ASD).. Proc Natl Acad Sci U S A, 2014. RCT
What changed
- First draft. Every PMID checked against NCBI E-utilities (title, year and journal taken from the PubMed record) and abstracts read for each cited row. Product details in Where to buy read from the brand page on the date shown. Self-reviewed in a second strict pass (no independent reviewer yet).