Sulforaphane
Brassica oleracea (source: broccoli sprouts)
The most potent natural activator of the Nrf2 detoxification pathway, concentrated in broccoli sprouts, with moderate human evidence for detoxifying air pollutants and preliminary evidence in autism, diabetes, and H. pylori.
At a Glance
- Best known for
- Activates Nrf2 and phase II detoxification enzymes, Increases excretion of airborne pollutants (benzene, acrolein), Improved behavior scores in young men with autism (one RCT)
- Evidence
- Moderate
- Typical dose
- 10–20 mg sulforaphane daily
- Type
- Compound
What is Sulforaphane?
Sulforaphane is a sulfur-containing compound that cruciferous vegetables — broccoli, cabbage, kale, Brussels sprouts — produce as a chemical defense. The plant stores a precursor, glucoraphanin, and an enzyme, myrosinase, in separate compartments; when the plant is chewed or chopped the two meet and sulforaphane forms. Three-day-old broccoli sprouts contain 20–50 times more glucoraphanin than mature broccoli, which is why sprouts are the main food source used in research. Discovered at Johns Hopkins in 1992, sulforaphane is the best-studied natural inducer of the body's own detoxification and antioxidant enzymes.
Known Health Benefits
How It Works
Sulforaphane reacts with cysteine residues on KEAP1, the protein that normally holds the transcription factor Nrf2 in check. Freed Nrf2 moves into the nucleus and switches on over 200 genes, including glutathione S-transferases, NQO1, and heme oxygenase-1, which neutralize reactive oxygen species and conjugate toxins for excretion. This indirect antioxidant effect lasts days, unlike direct antioxidants like vitamin C that are consumed in minutes. Sulforaphane also inhibits histone deacetylases (an epigenetic effect studied in cancer), suppresses NF-κB inflammation, activates heat shock proteins (relevant to its autism research), and is directly bactericidal to Helicobacter pylori.
What Research Says
Human research on sulforaphane is more substantial than for most phytochemicals. A 12-week randomized trial of 291 people in a heavily polluted region of China found that a broccoli sprout beverage increased urinary excretion of benzene by 61% and acrolein by 23% — evidence that Nrf2 activation works in people. A 2014 placebo-controlled trial of 44 young men with moderate-to-severe autism found that 50–150 µmol sulforaphane daily for 18 weeks significantly improved social interaction and behavior scores, with symptoms returning after stopping; a later larger trial showed smaller, less consistent benefits. A 2017 trial in 97 people with type 2 diabetes found that concentrated broccoli sprout extract lowered fasting glucose and HbA1c in obese participants with poor glycemic control. Small trials show reduced H. pylori colonization and improved markers in schizophrenia and prostate cancer, but these need replication. Doses, formulations, and sulforaphane yield vary enormously between studies, which complicates interpretation.
Active Compounds
Sulforaphane (an isothiocyanate), formed when the enzyme myrosinase acts on glucoraphanin in crushed or chewed cruciferous vegetables
Forms & Bioavailability
Sulforaphane itself is absorbed well (around 70–80%) and peaks in blood within 1–3 hours. The challenge is making it. If a supplement contains only glucoraphanin without myrosinase, conversion depends on gut bacteria and yields are low and unpredictable, often under 10%. Products that combine glucoraphanin with active myrosinase, or fresh sprouts chewed thoroughly, convert efficiently. Boiling broccoli destroys myrosinase, but adding a pinch of mustard seed powder to cooked broccoli restores conversion. Cooking sprouts or extracts at low heat (around 60–70°C) can actually improve yield by inactivating a protein that otherwise diverts glucoraphanin into an inactive nitrile.
Dosage Guidance
| Use Case | Dosage |
|---|---|
| General detoxification / antioxidant support | 10–20 mg sulforaphane daily |
| Air pollutant detoxification (studied) | Beverage providing 600 µmol glucoraphanin + 40 µmol sulforaphane daily |
| Autism (studied) | 50–150 µmol (9–27 mg) daily by body weight |
| Blood sugar support (studied) | 150 µmol (about 27 mg) daily |
| H. pylori adjunct | 70 g sprouts daily for 8 weeks |
Always consult a healthcare provider for personalized dosing.
Natural Food Sources
- Broccoli sprouts (3–4 days old — richest source)
- Fresh broccoli, lightly steamed (boiling destroys myrosinase)
- Brussels sprouts, cabbage, kale, cauliflower
- Mustard seed, radish, arugula, watercress (contain myrosinase that can 'activate' cooked broccoli)
- Broccoli seed powder
Potential Side Effects
Gas, bloating, loose stools; mild insomnia or increased irritability reported in some autism participants; sprout products carry a small food-safety risk if not handled properly
Who Should Avoid It
- Hypothyroidism with iodine deficiency — cruciferous goitrogens can worsen; usually not a problem at typical doses with adequate iodine
- Warfarin therapy (broccoli sprouts are high in vitamin K; keep intake consistent)
- Immunocompromised people should avoid raw sprouts (bacterial contamination risk) and use extracts instead
- Active chemotherapy — discuss with oncologist; Nrf2 activation could in theory protect tumor cells
Pregnancy & Lactation
Cruciferous vegetables and broccoli sprouts as food are safe and beneficial in pregnancy. Pregnant women should wash sprouts carefully or lightly cook them to reduce bacterial risk. Concentrated sulforaphane supplements have not been studied in pregnancy or lactation; a small study suggested sulforaphane metabolites appear in breast milk at low levels. Prefer food sources during pregnancy and nursing.
Known Drug Interactions
Induces CYP and phase II enzymes — may speed clearance of some drugs; theoretical additive effect with diabetes medications; caution with warfarin given vitamin K in broccoli; may interact with chemotherapy (discuss with oncologist)
Evidence Classification
Supported by cohort studies, case-control studies, or multiple observational studies with consistent findings.
Frequently Asked Questions
Why broccoli sprouts instead of broccoli?
Sprouts contain 20–50 times more glucoraphanin by weight than mature broccoli, so a small handful matches a large serving of adult broccoli. Sprouts also retain active myrosinase if eaten raw, so conversion to sulforaphane is efficient. You can grow them at home from broccoli seeds in 3–5 days, which is the cheapest way to get a meaningful dose.
Are sulforaphane supplements worth it?
Only some. Many 'broccoli extract' capsules contain glucoraphanin but no myrosinase, and conversion in your gut is unreliable. Look for products that state actual sulforaphane yield in milligrams or that combine glucoraphanin with myrosinase from mustard seed or broccoli. Fresh sprouts remain the most reliable and well-studied source.
Does sulforaphane help prevent cancer?
Population studies consistently link high cruciferous vegetable intake with lower rates of several cancers, and sulforaphane is a leading candidate for why. In human trials it raises protective enzymes in tissue biopsies and reduces some cancer biomarkers, but no trial has shown that sulforaphane supplements reduce cancer incidence. Eating cruciferous vegetables several times a week is a reasonable and well-supported strategy; supplements are not a proven cancer preventive.
Will sulforaphane affect my thyroid?
Cruciferous vegetables contain goitrogens that can interfere with iodine uptake, but the effect is small at normal intakes and mainly a concern if iodine is deficient. Studies giving people broccoli sprout extracts have not found changes in thyroid hormone levels. If you have hypothyroidism, ensure adequate iodine and avoid eating very large amounts of raw crucifers daily.
References
- Broccoli sprouts: an exceptionally rich source of inducers of enzymes that protect against chemical carcinogens. Fahey JW, Zhang Y, Talalay P. Proc Natl Acad Sci USA (1997)View study
- Sulforaphane treatment of autism spectrum disorder (ASD). Singh K, Connors SL, Macklin EA, et al.. Proc Natl Acad Sci USA (2014)View study
- Rapid and sustainable detoxication of airborne pollutants by broccoli sprout beverage: results of a randomized clinical trial in China. Egner PA, Chen JG, Zarth AT, et al.. Cancer Prev Res (2014)
- Sulforaphane reduces hepatic glucose production and improves glucose control in patients with type 2 diabetes. Axelsson AS, Tubbs E, Mecham B, et al.. Sci Transl Med (2017)
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This entry is for educational purposes only. It is not medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement regimen, especially if you take medications or have health conditions.