Sulforaphane for Oxidative Stress

Verdict: Weak, inconsistent human evidence for oxidative stress

Sulforaphane is a well-established activator of the body's NRF2 antioxidant pathway in the lab, but human trials are mixed: it raises some detoxification markers, yet controlled trials that directly measured antioxidant gene activity found no effect. The evidence is too weak and contradictory to conclude it meaningfully lowers oxidative stress in people.

C 🟠 C Weak Evidence Published

🔬Why this grade7-layer evidence engine

The grade rests on five small RCTs (all under 500 participants) that point in conflicting directions. On the positive side, two China-based broccoli sprout trials showed sulforaphane boosts a downstream detox marker: Egner 2014 (PMID 24913818, n=291) found urinary excretion of glutathione-bound pollutants rose (benzene +61%, acrolein +23%), and Kensler 2012 (PMID 22045030, n=50) reported 20-50% increases. An autism trial, Singh 2014 (PMID 25313065, n=44), saw behavioral gains, but reduced oxidative stress was only the presumed mechanism, not a measured outcome.

The decisive weakness is that the two trials directly measuring antioxidant gene activation were null. In asthmatics, Sudini 2016 (PMID 27130714, n=40) found no induction of antioxidant genes despite clear absorption of sulforaphane into the blood. In COPD patients, Wise 2016 (PMID 27832073, n=89) likewise saw no NRF2 target-gene activation at either dose, again despite confirmed absorption. So the substance gets into the body but does not reliably switch on the defenses it is marketed for.

Authorities reinforce the caution. The FDA notes sulforaphane is not an approved drug and broccoli-sprout products are sold as supplements never evaluated for treating or preventing disease, while the EU's EFSA has left such botanical claims on hold with no authorization; major clinics (Mayo, Cleveland Clinic, Harvard Health) take a cautious stance. Crucially, a rise in a urinary detox marker is not proof of better health, which is why this lands at a weak C rather than higher.

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Scoring transparency

All scores computed by a 7-layer evidence engine — fully auditable

Raw score 0.46

← counter-evidence / ineffectiveeffective / strong evidence →

Final grade

C · Published

Confidence

57%

Conflicting evidence

Evidence level

Multiple smaller RCTs (n<500)

How strongly each layer supports this effect

lower = less supportive

L2 PubMedPrimary literature

0.40

L5 Clinical bodiesAuthoritative stance

0.45

L1 ExamineGlobal benchmark

0.50

L3 MechanismPlausibility

0.50

L11 AI re-checkIndependent read

0.50

Against Mixed Supports

▸View the full decision path (audit trail)

compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.457
tier_from_score — 依分數區間映射至 tier letter
apply_hec_rules — 無高階證據可裁決
tier_strict_requirement_check — Tier 條件達標，未降階
detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
decide_status — 依 tier + dispute 結果決定 status

📄PubMed studies (5)L2 · primary research & systematic reviews

Rapid and sustainable detoxication of airborne pollutants by broccoli sprout beverage: results of a randomized clinical trial in China

PMID: 24913818 2014 RCT (placebo-controlled) n = 291

Finding: Statistically significant increases in urinary excretion of glutathione conjugates of benzene (61%, P<=0.01) and acrolein (23%), sustained over 12 weeks without decline; crotonaldehyde conjugate not significantly increased. Demonstrates enhanced phase II / glutathione-dependent detoxification (a downstream readout of NRF2 activation and antioxidant-defense engagement).

Government Effect size: Benzene conjugate +61%, acrolein conjugate +23% urinary excretion

View on PubMed

Modulation of the metabolism of airborne pollutants by glucoraphanin-rich and sulforaphane-rich broccoli sprout beverages in Qidong, China

PMID: 22045030 2012 RCT (crossover) n = 50

Finding: Statistically significant 20-50% increases in excretion of glutathione-derived pollutant conjugates, confirming enhanced glutathione/phase II detoxification (NRF2 pathway downstream readout) with both glucoraphanin-rich and sulforaphane-rich preparations.

Government Effect size: 20-50% increase in glutathione-conjugate excretion

View on PubMed

Sulforaphane treatment of autism spectrum disorder (ASD)

PMID: 25313065 2014 RCT (double-blind, placebo-controlled) n = 44

Finding: Substantial behavioral improvement vs placebo (ABC ~34%, SRS ~17%), reverting toward baseline after washout. Selected explicitly for capacity to counter oxidative stress / glutathione depletion; behavioral benefit is an indirect clinical readout, with oxidative-stress reduction as the proposed (not directly proven per-patient) mechanism.

Effect size: ABC -34%, SRS -17% vs placebo (behavioral)

View on PubMed

A Randomized Controlled Trial of the Effect of Broccoli Sprouts on Antioxidant Gene Expression and Airway Inflammation in Asthmatics

PMID: 27130714 2016 RCT (double-blind, placebo-controlled) n = 40

Finding: NULL. Despite marked rises in serum sulforaphane, broccoli sprout consumption did NOT induce cytoprotective antioxidant genes in PBMCs or nasal epithelial cells, and did not improve FENO, oxidative-stress markers, inflammatory biomarkers, or asthma symptoms. Important negative trial: biochemical absorption did not translate into measurable NRF2-target antioxidant gene induction in vivo.

Government Effect size: No significant antioxidant gene induction (null)

View on PubMed

Lack of Effect of Oral Sulforaphane Administration on Nrf2 Expression in COPD: A Randomized, Double-Blind, Placebo Controlled Trial

PMID: 27832073 2016 RCT (double-blind, placebo-controlled, Phase 2) n = 89

Finding: NULL. Sulforaphane at 25 and 150 micromol/day for 4 weeks did NOT stimulate NRF2 target gene expression or affect other antioxidants or inflammation markers, despite confirmed plasma absorption. Directly contradicts the assumption that oral sulforaphane reliably activates NRF2-mediated antioxidant defenses in humans at these doses.

Government Effect size: No NRF2 target gene induction (null)

View on PubMed

🏛️Regulatory & authoritative positionsL4/L5 · FDA / EMA / NIH ODS / Cochrane / Mayo …

L4a US FDA

Cautious

Sulforaphane is not an approved drug and broccoli sprout / glucoraphanin products are marketed as dietary supplements; FDA has not evaluated them for the diagnosis, treatment, cure, or prevention of any disease. source↗

L4b EU EFSA

Neutral

1,548 claims on 'botanicals' have been placed on hold by the Commission pending further consideration on how to proceed with these source↗

L4d TW TFDA / 衛福部

Cautious

食品不得標示或廣告宣稱醫療效能 source↗

L5b Mayo Clinic

Cautious

L5c Cleveland Clinic

Cautious

L5d Harvard Health

Cautious

✓PMID 100% verifiedevery citation checked via NCBI Entrez

🔬5 PubMed studiesindependently re-checked by multiple sub-agents

engine_version: v1.0 claim_id: CLM-COND-oxidative-stress-INT-sulforaphane-001 繁體中文版 →