Written by David Roberts, MPH
Sulforaphane is a compound from broccoli sprouts and the most potent natural activator of Nrf2, a transcription factor that switches on hundreds of protective genes at once. It does not neutralize damage itself. It instructs cells to build their own defenses.
Key Takeaways
- ✓It is an inducer, not an antioxidant.
- ✓One signal switches on hundreds of protective genes.
- ✓The enzymes it builds stay active long after the SFN has cleared.
- ✓Human evidence is strongest for inflammation and detox.
- ✓Brain and immune findings are mostly from animals.
Most compounds sold for health do one thing. Sulforaphane is interesting because it does much more than one thing.
It is also one of the most studied molecules in nutritional science, with more than 125 clinical trials and thousands of studies behind it. [1]
This article covers what it is, the mechanism that explains its range, and where the human evidence is strong versus where it is still animal work.
What is sulforaphane and where does it come from?
Sulforaphane is an isothiocyanate produced by broccoli, but found in much higher quantities in broccoli sprouts.
The plant stores a precursor called glucoraphanin in one compartment and an enzyme called myrosinase in another, and they meet only when the tissue between them is damaged.
Chewing raw broccoli or sprouts breaks those compartments open. Myrosinase converts glucoraphanin into sulforaphane in the mouth.
The compound was identified at Johns Hopkins in 1992 by Paul Talalay's group, and the research program that followed has run for more than three decades. [1]
Why do researchers describe it as a master switch?
Sulforaphane acts on a transcription factor rather than on a single target, and that transcription factor controls hundreds of genes.
The transcription factor is Nrf2. Under ordinary conditions, a partner protein called KEAP1 holds Nrf2 in the cytoplasm and routes it for destruction within minutes, so its levels stay near zero. [2]
Sulforaphane modifies a cysteine residue on KEAP1. KEAP1 loses its grip, Nrf2 accumulates, crosses into the nucleus and binds a short DNA sequence called the antioxidant response element. [2]
That sequence sits in front of a coordinated set of genes. Mapping work using ChIP-Seq in mouse cells identified 645 genes under direct Nrf2 control at baseline and 654 under stress conditions. [3]
Jed Fahey, who spent 27 years on the Johns Hopkins faculty and directed its Cullman Chemoprotection Center, describes sulforaphane as "the most potent naturally occurring inducer of the Keap1-Nrf2 pathway." [1]
This is the structural answer to why one compound shows up in research on inflammation, detoxification, the brain and immunity at once. Those systems share a regulator, and sulforaphane acts on the regulator.
Is sulforaphane an antioxidant?
Vitamin C is a direct antioxidant, but sulforaphane is more like an inducer.
A direct antioxidant neutralizes a reactive molecule by reacting with it, and is used up doing so. Sulforaphane does not work that way. Researchers classify it as an indirect antioxidant, meaning it induces the cell's own antioxidant machinery. [4]
One review explains that sulforaphane "is not directly antioxidant" and in isolation exhibits a weak pro-oxidant effect, which is part of how it signals. Its antioxidant effect comes from inducing glutathione and related defenses. [5]
| Direct antioxidant | Indirect antioxidant | |
|---|---|---|
| What it does | Neutralizes a reactive molecule itself | Signals the cell to build its own defenses |
| What happens to it | Consumed in the reaction, needs replacing | Not consumed. Acts catalytically [4] |
| Scale of effect | Roughly one molecule per reactive species | One signal, hundreds of genes [3] |
| Duration | Lasts while the molecule is present | Enzymes persist after the molecule is gone |
| Examples | Vitamin C, vitamin E | Sulforaphane and other Nrf2 inducers |
A supplement aisle full of direct antioxidants is selling you molecules to be spent. This is a different proposition: a signal that changes what the cell manufactures.
How long does sulforaphane stay in your body?
In human pharmacokinetic work, sulforaphane peaked in plasma about an hour after a dose and had a half-life of 1.77 hours. Roughly 58% of the dose was excreted within 8 hours. [6]
If sulforaphane were a direct antioxidant, that would be the end of the story. Because it is an inducer, what matters is what it leaves behind.
The enzymes it switches on keep working after it is gone. In human skin, NQO1 activity measured 24 hours after dosing was 1.5 times baseline following one dose and 4.5 times baseline following three daily doses. [7]
That also explains why consistency matters more than any single large dose. The response builds across repeated exposures rather than peaking with one.
What does sulforaphane do about inflammation?
It acts on both sides of the inflammatory switch, and in human trials the measurable result has been lower inflammatory markers.
The first side is Nrf2 activation, which raises the cell's antioxidant and detoxification capacity and reduces the oxidative signaling that sustains inflammation. [2]
The second is NF-kB, the transcription factor that drives production of inflammatory enzymes including COX-2 and iNOS. Sulforaphane suppresses it, and the two pathways cross-regulate each other. [5]
In 40 overweight adults eating 30 g of fresh broccoli sprouts daily for 10 weeks, IL6 (an inflammatory marker) fell from 4.76 to 2.11 pg/mL. It was still below baseline 90 days after they stopped. [8]
A randomized, double-blind, placebo-controlled trial of broccoli sprout powder in people with type 2 diabetes found high-sensitivity CRP fell by 20.5% at the higher dose over four weeks. [9]
How does sulforaphane support detoxification?
Sulforaphane impacts detoxification of the body by acting most strongly on the second of three phases, which is the phase that does the neutralizing. It is also active in Phases 1 and 2.
| Phase | What happens |
|---|---|
| Phase I | Cytochrome P450 enzymes make fat-soluble compounds more reactive, not less. Some procarcinogens become carcinogens at this step [10]. Sulforaphane slows this phase down to avoid the "detox flu" symptoms common with many detoxes that only act in Phase 1. |
| Phase II | Transferase enzymes attach glutathione or a similar group, neutralizing the compound and making it water-soluble. This is where sulforaphane acts most strongly. [10] |
| Phase III | Transporters move the conjugated product out of the cell so it can be excreted in urine or bile. Sulforaphane supports the liver and kidneys in this phase. |
Sulforaphane raises Phase II output through Nrf2, and also inhibits some Phase I enzymes, which lets Phase II keep pace with what Phase I produces. [5]
The human demonstration comes from a randomized placebo-controlled trial of 291 adults in a region with heavy air pollution.
Participants drinking a broccoli sprout beverage excreted 61% more of a benzene conjugate and 23% more of an acrolein conjugate than placebo. A third pollutant measured, crotonaldehyde, showed no significant change. [11]
That is detoxification measured as a rate of excretion, in people, with the null result reported alongside the positive ones.
What does the research show about the brain?
Brain research on sulforaphane has shown strong protective findings in rodents and one human functional result.
In mouse models of Parkinson's disease, sulforaphane prevented the loss of dopaminergic neurons. The protection disappeared in mice lacking Nrf2, which ties the effect to the pathway rather than to something incidental. [12][13]
In rodent stress models and in mouse microglia, it increased transcription of brain-derived neurotrophic factor (BDNF), a protein involved in neuron maintenance. [12]
The human evidence is about function rather than tissue. In a randomized controlled trial of 144 healthy adults aged 60 to 80, the supplemented group improved on a processing-speed task over 12 weeks, with an adjusted p value of 0.03. [14]
Two caveats on that trial: it used glucoraphanin, the precursor rather than sulforaphane itself, and three of its five authors were employees of the company that funded it. [14]
What does it do for immune function?
The most interesting immune findings come from a pair of trials that gave people a live attenuated influenza vaccine and watched what happened.
In 29 healthy nonsmokers, broccoli sprout homogenate increased production of granzyme B by circulating natural killer cells after the vaccine challenge. Granzyme B is the protein those cells use to kill infected cells. [15]
In a separate randomized, double-blind trial, smokers taking broccoli sprout homogenate around the vaccine had significantly less influenza sequence in nasal fluid, with a p value of 0.01, along with lower interleukin-6 and higher NQO1 in nasal cells. [16]
Nonsmokers in that trial trended the same direction without reaching significance, and the virus involved was a vaccine strain rather than a wild influenza infection.
The finding that sulforaphane reverses age-related immune decline traces to a study in aged mice, where it restored a Th1 response through its effect on dendritic cells. That has not been reproduced in people. [17]
Does sulforaphane affect bacteria?
Sulforaphane inhibits the growth of many bacteria and fungi in vitro. [5]
One organism, tested in humans, is H Pylori. Sulforaphane inactivates the urease enzyme that Helicobacter pylori depends on to survive stomach acid.
In a controlled trial, 48 infected adults ate 70 g of broccoli sprouts daily for eight weeks. Markers of colonization and gastritis fell during the intervention and returned to baseline eight weeks after stopping. [18]
The authors were careful about what that means: colonization was reduced, and the bacterium was not eradicated. In the mouse arm of the same study, the benefit disappeared in animals lacking Nrf2. [18]
How strong is the evidence behind each of these?
The table below sorts the findings in this article by the kind of study behind them.
| Finding | Evidence |
|---|---|
| Raises excretion of airborne pollutants | Human RCT, 291 adults, placebo-controlled [11] |
| Reduces high-sensitivity CRP | Human RCT, double-blind, placebo-controlled [9] |
| Reduces H. pylori colonization | Human controlled trial, 48 adults, plus mice [18] |
| Less influenza sequence in nasal fluid | Human RCT, significant in smokers only [16] |
| Raises NK cell granzyme B | Human RCT, 29 participants [15] |
| Raises NQO1 enzyme activity | Human, skin, topical dosing [7] |
| Reduces interleukin-6 | Human, 40 adults, no placebo arm [8] |
| Improves processing speed | Human RCT, precursor form, industry-funded [14] |
| Protects neurons from dying | Mice, effect absent without Nrf2 [12][13] |
| Increases BDNF transcription | Rodents and mouse cells [12] |
| Restores Th1 immunity with age | Aged mice only [17] |
| Suppresses NF-kappa B | Cells and animals, not measured in people [5] |
| Reaches the brain | Mice, by injection. Never measured in humans [12] |
| Promotes new neuron formation | Not established. No supporting study [12] |
The pattern is consistent. Where sulforaphane has been tested against a measurable biological output in people, it has generally moved it. Where the claim is about a specific disease outcome, the work is mostly still in animals.
Can you get enough sulforaphane from food?
You can get some, but how much varies more than most people realize.
Broccoli sprouts harvested at three to seven days hold 20 to 50 times more glucoraphanin (often labeled as "sulforaphane potential") than mature broccoli, which makes them the most concentrated food source of the precursor.
Eaten raw and chewed thoroughly, they release plant myrosinase and conversion begins in the mouth. The trials described above used 30 to 70 g of fresh sprouts daily. [8][18]
Cooking is where the process breaks down. Myrosinase is heat-sensitive, and steaming can inactivate it in as little as three minutes, leaving the precursor with no enzyme to convert it. [19]
When the enzyme is absent, the job falls to gut bacteria, and conversion efficiency by colonic microflora has been reported to range from roughly 1% to 40% between individuals. [19]
That variability is also the central problem with precursor-based supplements, which is covered in more depth in our recent post: Why Broccoli Supplements Work for Some People and Not Others.
Frequently Asked Questions
What does sulforaphane do in the body?
Sulforaphane activates Nrf2, a transcription factor that switches on a coordinated set of protective genes. It modifies a cysteine residue on the KEAP1 protein that normally holds Nrf2 for destruction, allowing Nrf2 to accumulate and enter the nucleus. ChIP-Seq mapping in mouse cells identified 645 genes under direct Nrf2 control, including the Phase II detoxification enzymes and the glutathione system.
Is sulforaphane an antioxidant?
Not a direct one. Direct antioxidants such as vitamin C neutralize reactive molecules themselves and are consumed doing it. Sulforaphane is classified as an indirect antioxidant: it is not directly antioxidant, and its effect comes from inducing the cell to produce glutathione and other antioxidant enzymes, which then work catalytically.
How long does sulforaphane last in the body?
The compound itself clears quickly, with a measured plasma half-life of 1.77 hours and roughly 58% of a dose excreted within 8 hours. The enzymes it induces persist longer. In human skin, NQO1 activity 24 hours after dosing was 1.5 times baseline after a single dose and 4.5 times baseline after three daily doses.
Which sulforaphane benefits are proven in humans?
Randomized controlled trials in people have shown increased excretion of airborne pollutants, reduced high-sensitivity CRP, reduced Helicobacter pylori colonization, lower influenza sequence in nasal fluid among smokers, and increased natural killer cell granzyme B. Neuroprotection, BDNF increases and reversal of age-related immune decline have been shown in rodents, not in people.
Does cooking destroy sulforaphane?
Cooking destroys myrosinase, the plant enzyme that converts glucoraphanin into sulforaphane, and steaming can inactivate it in as little as three minutes. The precursor survives, but without active enzyme the conversion depends on gut bacteria, and that efficiency has been reported to range from roughly 1% to 40% between individuals.
Where does sulforaphane come from?
Sulforaphane comes from cruciferous vegetables including broccoli, broccoli sprouts, kale, cabbage and Brussels sprouts. It does not exist ready-made in the intact plant: the precursor glucoraphanin and the enzyme myrosinase are stored in separate compartments and only combine when the tissue is crushed or chewed. The compound was identified at Johns Hopkins in 1992.
Sources
[1] Fahey, J.W., Moreno, D.A., Licciardi, P., Grassi, F., Karagiannis, T.C., Mazarakis, N. "Editorial: Sulforaphane and isothiocyanates in health." Frontiers in Nutrition, 2025;12:1558025.
https://doi.org/10.3389/fnut.2025.1558025
[2] Dinkova-Kostova, A.T., Fahey, J.W., Kostov, R.V., Kensler, T.W. "KEAP1 and done? Targeting the NRF2 pathway with sulforaphane." Trends in Food Science & Technology, 2017;69:257-269.
https://pmc.ncbi.nlm.nih.gov/articles/PMC5725197/
[3] Malhotra, D., Portales-Casamar, E., Singh, A., et al. "Global mapping of binding sites for Nrf2 identifies novel targets in cell survival response through ChIP-Seq profiling and network analysis." Nucleic Acids Research, 2010;38(17):5718-5734.
https://doi.org/10.1093/nar/gkq212
[4] Dinkova-Kostova, A.T., Talalay, P. "Direct and indirect antioxidant properties of inducers of cytoprotective proteins." Molecular Nutrition & Food Research, 2008;52(S1):S128-S138.
https://doi.org/10.1002/mnfr.200700195
[5] Houghton, C.A. "Sulforaphane: Its 'Coming of Age' as a Clinically Relevant Nutraceutical in the Prevention and Treatment of Chronic Disease." Oxidative Medicine and Cellular Longevity, 2019; Article ID 2716870. The author founded a company that manufactures a sulforaphane-yielding supplement ingredient.
https://doi.org/10.1155/2019/2716870
[6] Ye, L., Dinkova-Kostova, A.T., Wade, K.L., Zhang, Y., Shapiro, T.A., Talalay, P. "Quantitative determination of dithiocarbamates in human plasma, serum, erythrocytes and urine: pharmacokinetics of broccoli sprout isothiocyanates in humans." Clinica Chimica Acta, 2002;316(1-2):43-53.
https://doi.org/10.1016/S0009-8981(01)00727-6
[7] Dinkova-Kostova, A.T., Fahey, J.W., Wade, K.L., et al. "Induction of the phase 2 response in mouse and human skin by sulforaphane-containing broccoli sprout extracts." Cancer Epidemiology, Biomarkers & Prevention, 2007;16(4):847-851.
https://doi.org/10.1158/1055-9965.EPI-06-0934
[8] López-Chillón, M.T., Carazo-Díaz, C., Prieto-Merino, D., Zafrilla, P., Moreno, D.A., Villaño, D. "Effects of long-term consumption of broccoli sprouts on inflammatory markers in overweight subjects." Clinical Nutrition, 2019;38(2):745-752.
https://doi.org/10.1016/j.clnu.2018.03.006
[9] Mirmiran, P., Bahadoran, Z., Hosseinpanah, F., Keyzad, A., Azizi, F. "Effects of broccoli sprout with high sulforaphane concentration on inflammatory markers in type 2 diabetic patients: A randomized double-blind placebo-controlled clinical trial." Journal of Functional Foods, 2012;4(4):837-841.
https://doi.org/10.1016/j.jff.2012.05.012
[10] Linus Pauling Institute, Oregon State University. "Isothiocyanates." Micronutrient Information Center.
https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/isothiocyanates
[11] Egner, P.A., Chen, J.G., Zarth, A.T., et al. "Rapid and Sustainable Detoxication of Airborne Pollutants by Broccoli Sprout Beverage: Results of a Randomized Clinical Trial in China." Cancer Prevention Research, 2014;7(8):813-823.
https://doi.org/10.1158/1940-6207.CAPR-14-0103
[12] Bessetti, R.N., Litwa, K.A. "Broccoli for the brain: a review of the neuroprotective mechanisms of sulforaphane." Frontiers in Cellular Neuroscience, 2025;19:1601366.
https://doi.org/10.3389/fncel.2025.1601366
[13] Jazwa, A., Rojo, A.I., Innamorato, N.G., Hesse, M., Fernández-Ruiz, J., Cuadrado, A. "Pharmacological targeting of the transcription factor Nrf2 at the basal ganglia provides disease modifying therapy for experimental parkinsonism." Antioxidants & Redox Signaling, 2011;14(12):2347-2360.
https://doi.org/10.1089/ars.2010.3731
[14] Nouchi, R., Hu, Q., Ushida, Y., Suganuma, H., Kawashima, R. "Effects of sulforaphane intake on processing speed and negative moods in healthy older adults: Evidence from a randomized controlled trial." Frontiers in Aging Neuroscience, 2022;14:929628. Funded by Kagome Co.; three of the five authors were employees of the funder.
https://doi.org/10.3389/fnagi.2022.929628
[15] Müller, L., Meyer, M., Bauer, R.N., et al. "Effect of Broccoli Sprouts and Live Attenuated Influenza Virus on Peripheral Blood Natural Killer Cells: A Randomized, Double-Blind Study." PLOS ONE, 2016;11(1):e0147742.
https://doi.org/10.1371/journal.pone.0147742
[16] Noah, T.L., Zhang, H., Zhou, H., et al. "Effect of broccoli sprouts on nasal response to live attenuated influenza virus in smokers: a randomized, double-blind study." PLOS ONE, 2014;9(6):e98671.
https://doi.org/10.1371/journal.pone.0098671
[17] Kim, H.J., Barajas, B., Wang, M., Nel, A.E. "Nrf2 activation by sulforaphane restores the age-related decrease of T(H)1 immunity: Role of dendritic cells." Journal of Allergy and Clinical Immunology, 2008;121(5):1255-1261.
https://doi.org/10.1016/j.jaci.2008.01.016
[18] Yanaka, A., Fahey, J.W., Fukumoto, A., et al. "Dietary sulforaphane-rich broccoli sprouts reduce colonization and attenuate gastritis in Helicobacter pylori-infected mice and humans." Cancer Prevention Research, 2009;2(4):353-360.
https://doi.org/10.1158/1940-6207.CAPR-08-0192
[19] Houghton, C.A., Fassett, R.G., Coombes, J.S. "Sulforaphane and Other Nutrigenomic Nrf2 Activators: Can the Clinician's Expectation Be Matched by the Reality?" Oxidative Medicine and Cellular Longevity, 2016; Article ID 7857186.
https://doi.org/10.1155/2016/7857186
This article is educational and is not medical advice. Talk with a qualified healthcare professional before making changes to your diet or supplement routine, particularly if you are pregnant, nursing, taking medication, or managing a health condition.
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