Sulforaphane is an isothiocyanate generated from glucoraphanin in cruciferous vegetables, richest in broccoli sprouts, and the most-studied natural activator of the Nrf2 defense pathway. Its human RCT ledger is real but mixed: small trials show a replicated benefit on schizophrenia negative symptoms and clean pollutant-detoxication data, while prediabetes and lung-chemoprevention trials missed their primary endpoints. The practical catch is conversion: glucoraphanin supplements only work if your gut microbes or an added enzyme supply myrosinase.
Summary drafted from this entry’s sources; editorial review pending.
01Key questions
Does sulforaphane work for psychiatric conditions?
There is a small replicated signal. Two schizophrenia add-on RCTs (n=42 and n=77) found negative-symptom improvement (d about 0.8), a 63-child ADHD trial reported large effects, and the 2014 autism trial (n=44) improved behavior scores. Small samples and single-program dominance keep it short of proven.13
Does sulforaphane lower blood sugar?
Not generally. The 74-patient prediabetes RCT missed its primary endpoint (-0.2 versus a target of -0.3 mmol/L), though a responder subgroup defined by a Bacteroides myrosinase-gene operon reached -0.4. The effect looks phenotype- and microbiome-dependent rather than a general glucose drug.1115
Do sulforaphane supplements actually work?
Only with conversion. Glucoraphanin needs the enzyme myrosinase, which cooking destroys and most supplements lack; gut bacteria carrying a specific operon predict who responds. Fresh sprouts, pre-formed SFN extracts, or adding mustard-seed myrosinase bypass the bottleneck.1911
Is sulforaphane safe?
Tolerability across the RCTs is placebo-level, with mild GI effects the main issue, and a systematic review found no thyroid-function effect from Brassica vegetables in humans. One rarely cited counter-signal: sulforaphane worsened cholesterol and transaminases in diabetic rats at the studied doses.2731
Sulforaphane (SFN) is an isothiocyanate from cruciferous vegetables — generated from the glucosinolate glucoraphanin by the enzyme myrosinase when plant tissue is damaged. Broccoli sprouts are the richest source (Fahey/Talalay, PNAS 1997, PMID 9294217). It is the most-studied natural activator of the Nrf2 (NF-E2-related factor 2) cytoprotective pathway, with a human RCT literature now spanning autism, schizophrenia, ADHD, diabetes, airborne-pollutant detoxication, and cancer-chemoprevention biomarkers. This file maps that literature with this library's evidence hierarchy — including the nulls and missed endpoints.
Sulforaphane was absent from this library until now despite being one of the few supplements where investigators have run repeated double-blind RCTs in humans with psychiatric and metabolic endpoints — arguably closer to a low-dose pharmacological Nrf2 agonist than a "vegetable extract."
02Mechanism
1. Nrf2–Keap1–ARE activation (the primary axis)
- SFN is an electrophilic isothiocyanate that covalently modifies cysteine sensors on Keap1, releasing Nrf2 to translocate to the nucleus and bind Antioxidant Response Elements (Dinkova-Kostova et al., PMID 12193649).
- Transcriptional output: phase-II detoxication and antioxidant enzymes — glutathione S-transferases (GSTs), NQO1, heme oxygenase-1 (HO-1), γ-glutamylcysteine synthetase (GSH synthesis), UDP-glucuronosyltransferases.
- This is hormetic in the strict sense: a mild electrophilic provocation that upregulates endogenous defense capacity, mechanistically parallel to the stressor-adaptation logic in Overview - Biohacking and Optimization and Cold and Heat Therapy.
- Demonstrated in human airway: oral SFN dose-dependently increased phase-II enzymes in nasal epithelium (Riedl et al., PMID 19028145).
2. Beyond Nrf2
- HDAC inhibition: SFN metabolites (sulforaphane-cysteine) inhibit histone deacetylases — epigenetic chemoprevention mechanism (Myzak lineage, PMID 16652377). The schizophrenia trialists explicitly cite HDAC inhibition as a rationale (PMID 39832347).
- NF-κB suppression and downstream inflammatory cytokines (reviewed PMID 40686501).
- Anti-AGE/RAGE activity — isothiocyanates interfere with advanced-glycation signaling (PMID 39770075), mechanistically adjacent to Advanced Glycation and Crosslink Breakers.
- Hepatic gluconeogenesis suppression — Nrf2-dependent downregulation of glucose-production genes (preclinical + T2D context; tested clinically below).
3. Geroprotection framing
- Reviews now position cruciferous isothiocyanates as candidate geroprotectors acting on oxidative stress, inflammation, and proteostasis (Adv Pharmacol 2025, PMID 40716930); neuroprotective mechanisms reviewed in PMID 40686501 and 31334360.
03Bioavailability — the part most users get wrong
| Form | Content | Conversion | Notes |
|---|---|---|---|
| Fresh broccoli sprouts | Glucoraphanin + endogenous myrosinase | Efficient; chewing releases both | ~30–100× glucoraphanin of mature heads (PMID 9294217); dose varies by cultivar/seed |
| Glucoraphanin supplement (most common) | Precursor only | Requires gut-microbiota myrosinase | Conversion highly variable between individuals (see microbiome section) |
| SFN-rich extract | Pre-formed sulforaphane | None needed | Chemically labile; heat-sensitive |
| Glucoraphanin + mustard-seed myrosinase | Precursor + exogenous enzyme | Restored to near-sprout levels | Mustard myrosinase significantly increased SFN bioavailability (Sci Rep 2026, PMID 41692762) |
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- Plasma quantitation requires thiol-blocking LC-MS/MS methods (PMID 37584212) — an analytic reason older supplement studies report wildly variable kinetics.
- Microbiome dependency: baseline gut microbiota predicts systemic SFN exposure. Responders in the Gothenburg prediabetes trial carried a Bacteroides-encoded transcriptional regulator (gene operon) required for glucoraphanin→SFN conversion; operon abundance correlated with serum SFN (Nat Microbiol 2025, PMID 39929977). Ties directly to Gut Microbiome and Postbiotics — your sprout supplement may be a no-op without the right converter organisms.
- Cooking destroys myrosinase: boiled broccoli behaves like a glucoraphanin-only supplement.
04Human Evidence (RCTs and trials, by condition)
Neuropsychiatry — the most active 2024–2026 frontier
| Trial | Population | Design | Result | PMID |
|---|---|---|---|---|
| Singh 2014 (PNAS) | 44 young men, moderate-severe ASD | DB-RCT, 50–150 µmol SFN/day, 18 wk + 4 wk | ABC and SRS improved vs placebo; benefit reverted after discontinuation | 25313065 |
| Singh 2021 (Mol Autism) | Children with ASD | DB-RCT + metabolomics | Identified SFN-responsive metabolite fingerprints | 34034808 |
| Children ASD RCT 2023 (Nutrients) | Children with autism | Prospective RDB | Positive behavioral signal | 36771424 |
| Huang 2025 (J Clin Psychiatry) | 77 schizophrenia, add-on to antipsychotics | DB-RCT, high-dose SFN (1,700 mg glucoraphanin-tablets ≈ Avmacol Extra Strength) × 24 wk | PANSS negative symptoms ↓ (p=.01); d = 0.8 at wk 24; not mediated by depression/cognition | 39832347 |
| Chen 2025 (J Psychiatr Res) | 42 chronic schizophrenia (same program, NCT04521868) | DB-RCT × 24 wk | PANSS 5-factor negative score ↓ (p=.007); cognition (MCCB) null | 40133020 |
| Kassar 2025 (BMC Psychiatry) | 5 RCTs | Meta-analysis | Negative symptoms improved; cognition not | 41184790 |
| Eur Arch Psychiatry 2026 | Nrf2 activators (SFN trials included) | Meta-analysis | Signals maintained across Nrf2-activator class | 42154264 |
| Ghannadi 2025 (Clin Neuropharmacol) | 63 children (6–11 y) ADHD, add-on to methylphenidate | DB-RCT, 30 mg/d × 8 wk | ADHD-RS total/inattention/hyperactivity ↓, teacher- and parent-rated, Cohen's d ≈ 1.0–1.4; side effects = placebo | 41604557 |
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Interpretation: the schizophrenia negative-symptom signal is replicated across two independent analyses of the Xiangya program plus meta-analytic aggregation — one of the few nutritional compounds with a consistent psychiatric effect size (d = 0.8). Cautions: Chinese single-center programs dominate, sample sizes are small (42–77), and cognition is consistently null. ASD data rest on a small famous trial plus follow-ons (systematic review: PMID 33013262).
Cognition / dementia prevention
- 42-month DB-RCT pilot (n=25 completers aged 63–90, 30 mg/day glucoraphanin): significant group×time interaction favoring GLR on Memory Performance Index (p=.012); immediate and delayed recall better (p<.001, p=.012); MCI subgroup drove the effect (p=.029). Funded by KAGOME Co. with funder involvement — pilot-grade only (Front Nutr 2026, PMID 41669080).
Metabolic
| Trial | Population | Result | PMID |
|---|---|---|---|
| Bahadoran 2012 | 81 T2D patients, broccoli sprout powder 5/10 g vs placebo × 4 wk | ↓ fasting insulin, ↓ HOMA-IR (dose-dependent) | 22537070 |
| Dwibedi 2025 (Nat Microbiol) | 74 drug-naive prediabetes, BSE vs placebo × 12 wk | Missed primary endpoint (target −0.3 mmol/L; achieved −0.2 mmol/L, p=.04); responder subgroup (mild obesity, low IR) −0.4 mmol/L; responder status predicted by Bacteroides myrosinase-gene operon | 39929977 |
| NAFLD pilot 2026 | Women with NAFLD, broccoli sprouts ± Pilates | Liver-enzyme improvement | 42228225 |
| Muscle recovery 2026 | Eccentric-damage model, glucoraphanin DB-RCT | Short-term recovery endpoints | 41754227 |
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The prediabetes null-with-subgroup is the honest headline: sulforaphane is not a general glucose drug; hepatic-gluconeogenesis effects appear phenotype- and microbiome-dependent (diabetes-complications nutraceutical review: PMID 37703962).
Detoxication of airborne pollutants (the strongest pharmacodynamic data)
- Qidong, China crossover (n=50): glucoraphanin-rich and SFN-rich broccoli-sprout beverages increased urinary excretion of pollutant-derived mercapturic acids (benzene, acrolein metabolites) — sustained, dose-tractable (Kensler 2012, PMID 22045030).
- Dose-dependent benzene detoxication confirmed in a dedicated RCT (Am J Clin Nutr 2019, PMID 31268126). This is the cleanest human demonstration of induced phase-II metabolism by any dietary compound.
Cancer chemoprevention (biomarker trials — mixed)
- Prostate: SFN and metabolites measurable in human prostate tissue after oral dosing (PMID 36014767); chemopreventive biomarker activity in men scheduled for biopsy (PMID 31155953). Earlier PSA-doubling-time trials (Cramer 2001; Alumkal 2010) were mixed and are not PMIDs-cited here — treat prostate indication as biomarker-grade only.
- Breast: 54 women pre-biopsy, glucoraphanin supplement modified biomarkers in blood and breast tissue (Atwell 2015, PMID 26511489).
- Lung (2025, the key null): 43 former smokers, 95 µmol/day × 12 months, bronchial biopsy endpoints. Histopathology: no significant effect. Ki-67 proliferation index reduced; apoptosis markers unaffected (Cancer Prev Res 2025, PMID 40041932). Twelve months of high-dose SFN did not reverse bronchial dysplasia — the most important negative in the file.
- Systematic review of SFN in breast cancer progression/radiation outcomes exists (PMID 40013196) but is low-certainty.
Airway / asthma
- Improved bronchoprotective response in asthmatics via Nrf2-mediated gene expression (PMID 26369337); broccoli-sprout beverage RCT increased airway antioxidant gene expression in polluted environments (PMID 27130714); neutrophilic airway inflammation proof-of-concept (PMID 27450419).
Stroke / neuroprotection (drug-grade delivery)
- SFX-01 (stabilized SFN, Evgen Pharma) 300 mg BD × 28 days after subarachnoid hemorrhage: multicenter DB-RCT (SAS study) — safe, SFN measurable in plasma and CSF; vasospasm/delayed-ischemia efficacy not established from the published primary results (Transl Stroke Res 2025, PMID 39028412). A pharma-grade SFN molecule reaching CSF is itself a proof-of-concept for CNS delivery.
05Animal and In-Vitro Evidence (separate tier)
- STZ-diabetic rats: SFN partially normalized glycemia, insulin sensitivity, TAG, urea/creatinine — but worsened total cholesterol and transaminases at the same doses (J Med Food 2012, PMID 22925073). A rarely-mentioned counter-signal worth keeping in the ledger.
- Nrf2/KEAP1/ARE in diabetic kidney disease — extensive mechanistic base (PMID 36139066).
- Alzheimer's models: preclinical neuroprotection plausible via Nrf2 + anti-amyloid mechanisms (PMID 33805772); no human AD trial.
- Immune enhancement review (PMID 33535560) — mostly in-vitro.
06Evidence Ledger (honest accounting)
| Claim | Verdict |
|---|---|
| Induces human phase-II enzymes | Strong (airway biopsies, pollutant-metabolite excretion) |
| Schizophrenia negative symptoms (add-on) | Promising, replicated small (d=0.8; meta-analyzed; single-program risk) |
| ASD behavior | Promising, small (one classic + follow-ons; reverses on discontinuation) |
| ADHD (add-on) | Single RCT, large effects, needs replication |
| Prediabetes glucose lowering | Null on primary endpoint; subgroup responders only |
| Lung-chemoprevention histopathology | Null (12-mo biopsy trial) |
| Prostate/breast chemoprevention | Biomarker-grade only |
| General cognition | Pilot-grade (funder-run, n=25) |
| Cognition in schizophrenia | Consistently null (MCCB) |
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07Safety and Conflicts
- Tolerability consistently placebo-level; main adverse events are mild GI (39929977). No severe signals in the RCTs above.
- Thyroid: comprehensive systematic review found no significant effect of Brassica vegetables on thyroid function in humans (PMID 38612798) — the goitrogen fear is mostly in-vitro/iodine-deficient-animal territory. Prudence in overt hypothyroidism remains reasonable.
- Conflicts are structural: trial materials often supplied by supplement makers (Avmacol/Nutramax in the schizophrenia program; Lantmännen in Gothenburg; KAGOME funded the cognition pilot with funder involvement; Fahey/Talalay held Brassica-related IP disclosed in 39929977). Academic enthusiasm and commerce are entangled here as usual — rate accordingly.
08Practical Context
- Dose context from trials: 50–150 µmol SFN/day (Singh ASD); ~30 mg glucoraphanin/day (cognition pilot, ADHD trial); up to 1,700 mg/day of glucoraphanin-containing extra-strength tablets (schizophrenia); 95 µmol/day (lung trial); 300 mg BD stabilized SFN (SFX-01). No single validated "optimal" dose exists; trials cluster around the equivalent of a few dozen mg glucoraphanin with myrosinase, or tens of µmol preformed SFN.
- Form matters more than brand: glucoraphanin-only products depend on your microbiome (39929977). Sprout powder + mustard myrosinase (41692762), fresh sprouts, or SFN-rich extracts bypass that dependency.
- Fresh 3–4-day-old broccoli sprouts: a practical whole-food route; glucoraphanide content varies by seed lot — dose consistency is inherently poor.
- Heating: light steaming preserves glucoraphanin while destroying myrosinase (boiling leaches glucosinolates). Adding raw mustard powder to cooked broccoli is the kitchen-level implementation of 41692762.
- Effects on Nrf2-dependent enzymes are pharmacodynamic (measurable in days); psychiatric trials ran 8–24 weeks before full separation — this is not an acute nootropic.
- Any evaluation should separate systemic exposure (microbiome-dependent) from pharmacodynamic response — without myrosinase conversion, the compound never reaches target.
09Notes — Open Questions
- Does the schizophrenia negative-symptom effect (d=0.8) replicate outside the Xiangya/NKI program? Independent replication is the single highest-value missing study.
- Can responder status (Bacteroides myrosinase-operon abundance) be turned into a practical pre-test for metabolic indications?
- The STZ-rat cholesterol/transaminase worsening (22925073) has no human follow-up — worth watching lipid/liver panels in long-duration users.
- SFX-01 pipeline (Evgen) is the bridge from supplement to drug — track it as pharma-grade SFN evidence.
- Interaction with Autophagy and NAD+ pathways (NAD+ and Sirtuin Activators) is mechanistically plausible but clinically untested; combine claims cautiously.
What studies and practitioners report
Amounts as reported in the cited sources: trial doses with the population studied, and practitioner-reported ranges marked as such. Not medical advice.
- Trial 50–150 µmol/day · Sulforaphane young men with autism, n=44 PMID 25313065
Further reading: detailed protocols
- FoundMyFitness: sulforaphane topic overview foundmyfitness.com
10Connections
11Sources
- PubMed 9294217PubMed 9294217
- PubMed 12193649PubMed 12193649
- PubMed 19028145PubMed 19028145
- PubMed 16652377PubMed 16652377
- PubMed 39832347PubMed 39832347
- PubMed 40686501PubMed 40686501
- PubMed 39770075PubMed 39770075
- PubMed 40716930PubMed 40716930
- PubMed 41692762PubMed 41692762
- PubMed 37584212PubMed 37584212
- PubMed 39929977PubMed 39929977
- NCT04521868NCT04521868
- PubMed 33013262PubMed 33013262
- PubMed 41669080PubMed 41669080
- PubMed 37703962PubMed 37703962
- PubMed 22045030PubMed 22045030
- PubMed 31268126PubMed 31268126
- PubMed 36014767PubMed 36014767
- PubMed 31155953PubMed 31155953
- PubMed 26511489PubMed 26511489
- PubMed 40041932PubMed 40041932
- PubMed 40013196PubMed 40013196
- PubMed 26369337PubMed 26369337
- PubMed 27130714PubMed 27130714
- PubMed 27450419PubMed 27450419
- PubMed 39028412PubMed 39028412
- PubMed 22925073PubMed 22925073
- PubMed 36139066PubMed 36139066
- PubMed 33805772PubMed 33805772
- PubMed 33535560PubMed 33535560
- PubMed 38612798PubMed 38612798
12Entry history
Latest content update.
Heretic informs and never prescribes. Where amounts appear, they describe what published studies used. Talk to a qualified clinician before acting on anything here.