What is sulforaphan?
Sulforaphan is an isothiocyanate — a sulfur-rich plant compound found in cruciferous vegetables (Brassica family): broccoli, Brussels sprouts, cabbage, kohlrabi. It does not exist directly in the plant but is formed when the precursor molecule glucoraphanin comes into contact with the enzyme myrosinase during chewing or cutting.
What makes sulforaphan particularly interesting is its mechanism: it activates Nrf2 (Nuclear factor erythroid 2-related factor 2) — a transcription factor that upregulates hundreds of genes for cellular defence and detoxification systems. Nrf2 is considered one of the most important endogenous protection mechanisms against oxidative stress, inflammation, and chemical toxins.
Nrf2: the master regulator
When sulforaphan activates Nrf2, the cell produces more:
- Glutathione (central antioxidant)
- Heme oxygenase-1 (anti-inflammatory)
- Phase 2 detoxification enzymes (detoxification of carcinogens)
- Thioredoxin (reduces oxidative stress)
This mechanism distinguishes sulforaphan from direct antioxidants like vitamin C: it induces the body’s own antioxidant capacity rather than scavenging radicals directly.
What does the evidence actually show?
Comparatively well studied
- Detoxification: RCTs show measurably increased excretion of aflatoxin and benzene metabolites
- Inflammatory markers: CRP and NF-κB activity decline in multiple studies
- Nrf2 activation: biomarker studies consistently positive
Promising
- Cognitive function (schizophrenia, ASD studies)
- Blood pressure reduction
- Glucose metabolism
Not (yet) established
- Cancer prevention in humans via RCTs (only epidemiological and preclinical data)
- Direct lifespan extension
The preparation problem
Normal cooking destroys myrosinase — and with it, sulforaphan formation. Brief steaming (3–4 minutes) preserves enzyme activity better. Alternatively: sulforaphan supplements from stabilized broccoli sprouts.
Tip: add mustard or horseradish to steamed broccoli — they contain myrosinase and can initiate sulforaphan formation even from cooked broccoli.
Is sulforaphan safe?
At typical supplement doses (10–50 mg/day), it is considered likely safe. At very high doses, possible thyroid issues (isothiocyanates inhibit iodine uptake) — no risk with normal iodine intake. Do not use high doses during pregnancy.