What does the research show about sulforaphane?

Sulforaphane

In two trials in a polluted region of China, a broccoli sprout drink raised urinary excretion of benzene by about 60%. In prediabetes, fasting glucose fell by 0.2 mmol/L and missed the trial's target. Pooled trials found lower social responsiveness scores in autism. No trial measured lifespan. Gastrointestinal side effects were reported, and thyroid tests did not change.

Add to Bio HackChecked 2026-11-09

Status: Dietary supplement in the US.
Also called: broccoli sprout extract, broccoli seed extract, glucoraphanin, SFN, isothiocyanate, Nrf2 activator, Avmacol
Taken for: slowing aging, longer life, detox, Nrf2 activation, blood sugar, autism, brain health, mood, cancer prevention, inflammation

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help4

ModerateShown to raise urinary excretion of benzene about 61% in adults exposed to air pollution in China, only at the full dose. Disease was not measured.
ModerateShown to lower autism symptom scores modestly against placebo in people with autism. Reviews disagree on irritability.
LimitedOne trial found fasting glucose fell 0.2 mmol/L more than placebo in adults with prediabetes, missing the trial's own target.
LimitedOne trial found faster processing speed and less negative mood over 12 weeks in healthy older adults. Three authors worked for a food company.

Reported risks1

LimitedLimited evidence: stomach side effects were seen, with no severe adverse events. Adverse events matched placebo in autism trials.

What people take it for, and what was found

Shown to help4

Moderate

Clearing air pollutants

Shown to raise urinary excretion of benzene about 61% in adults exposed to air pollution in China, only at the full dose. Disease was not measured.

The numbers and sources

Effect: Over 12 weeks, a broccoli sprout drink raised urinary excretion of the glutathione conjugates of benzene by 61% and acrolein by 23% over placebo. Crotonaldehyde excretion did not change [1]. In a dose trial, benzene conjugate excretion rose 63.2% at the full dose. Half and one-fifth doses did not differ from placebo [2].
Population: 291 adults in Qidong, China, exposed to air pollution [1]; 170 adults in Qidong over 10 days [2].
Sources: [1], [2]
Caveats: Both trials come from one research collaboration in one region. Excretion is a marker, and neither trial measured disease.

Limited

Blood sugar

One trial found fasting glucose fell 0.2 mmol/L more than placebo in adults with prediabetes, missing the trial's own target.

The numbers and sources

Effect: Over 12 weeks, broccoli sprout extract lowered fasting glucose by 0.2 mmol/L (95% CI -0.44 to -0.01) against placebo. This missed the prespecified 0.3 mmol/L target. An exploratory subgroup with mild obesity, low insulin resistance and reduced insulin secretion fell by 0.4 mmol/L [3].
Population: 74 drug-naive adults with prediabetes [3].
Sources: [3]
Caveats: One trial. The responder subgroup was defined after the fact [3].

Moderate

Autism symptoms

Shown to lower autism symptom scores modestly against placebo in people with autism. Reviews disagree on irritability.

The numbers and sources

Effect: Across 6 trials, sulforaphane lowered Social Responsiveness Scale scores against placebo at 4 to 5 weeks and at 8 to 10 weeks [4]. A second meta-analysis of 6 RCTs found lower total symptom scores (SMD -0.27, 95% CI -0.42 to -0.12), aberrant behavior (SMD -0.43), hyperactivity (SMD -0.58) and social interaction scores (SMD -0.43). Irritability, anxiety and sensory sensitivity did not change [5]. A third reported improved irritability and hyperactivity on the Aberrant Behavior Checklist [6].
Population: 333 participants with autism spectrum disorder in 6 RCTs [4]. RCTs to September 2024 [5].
Sources: [4], [5], [6]
Caveats: Two of the three abstracts give no pooled effect sizes [4][6]. The reviews disagree on irritability [5][6]. Results varied with assessment tools, assessors and treatment length [5]. The first paper combines the meta-analysis with computer modeling, which is not evidence of effect in people [4].

Limited

Thinking speed and mood in older adults

One trial found faster processing speed and less negative mood over 12 weeks in healthy older adults. Three authors worked for a food company.

The numbers and sources

Effect: Over 12 weeks, processing speed improved and negative mood fell more on sulforaphane than placebo. Markers of oxidative stress, inflammation and neural plasticity did not change [8].
Population: 144 healthy older adults [8].
Sources: [8]
Caveats: One trial. Three authors were full-time employees of Kagome, a food company. The abstract reports no effect sizes.

Not shown to help1

Moderate

Schizophrenia symptoms

Not shown to improve total or positive symptoms of schizophrenia alongside antipsychotics. Negative symptoms improved briefly at 12 weeks, and cognition did not change.

The numbers and sources

Effect: Sulforaphane did not improve PANSS total or positive symptom scores. Negative symptoms improved at 12 weeks (MD -1.06, 95% CI -1.95 to -0.16), and this was not maintained at the latest follow-up. General psychopathology scores improved (MD -1.5, 95% CI -2.78 to -0.23). Cognition did not change [7].
Population: 369 patients with schizophrenia in 4 RCTs, taking sulforaphane alongside antipsychotics [7].
Sources: [7]
Caveats: Few trials with heterogeneity, as the authors note [7].

Claimed, not studied in people1

Untested

Longer life

Not studied in people. In roundworms, sulforaphane lengthened lifespan and improved mobility through the FOXO aging pathway.

No study in people. This rests on animal studies, how it acts in the body.

The numbers and sources

Effect: In wild-type C. elegans worms, sulforaphane prolonged lifespan and increased mobility and food intake. The effect depended on the TRA-1 and DAF-16 genes, the worm versions of human GLI and FOXO, and disappeared when either was blocked [12].
Population: C. elegans roundworms, wild-type and 4 mutant strains [12].
Sources: [12]
Caveats: A worm study. No mammal lifespan study or human study of lifespan was located.

Doses studied

The 12-week pollution trial gave a drink with 600 μmol glucoraphanin and 40 μmol sulforaphane a day [1]. The dose trial found an effect at a drink strength producing about 25 μmol of urinary sulforaphane metabolites a day [2]. A COPD trial used 25 or 150 μmol a day for 4 weeks [9]. A lung trial in former smokers used up to 95 μmol a day for 12 months [10].

Risks

Mixed results1

Limited

Gastrointestinal side effects

Limited evidence: stomach side effects were seen, with no severe adverse events. Adverse events matched placebo in autism trials.

The numbers and sources

Effect: Gastrointestinal side effects were observed on broccoli sprout extract, with no severe adverse events [3]. Pooled trials in autism found no difference in adverse event rates from placebo [4][5]. In schizophrenia, discontinuation was lower on sulforaphane (RR 0.68, 95% CI 0.49 to 0.95) [7].
Population: 74 adults with prediabetes [3]; 333 participants with autism [4]; 369 patients with schizophrenia [7].
Sources: [3], [4], [7]
Caveats: The prediabetes abstract does not give rates [3].

Checked, no increase found2

Limited

Long-term use

One small 12-month trial in former smokers found no severe adverse events on sulforaphane. Longer use was not studied.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In 43 former smokers randomized to sulforaphane or placebo for 12 months, 37 of whom completed the study, no severe adverse event was observed [10].
Population: 43 former smokers at high risk for lung cancer, 17 on sulforaphane and 20 on placebo completing [10].
Sources: [10]
Caveats: One small trial. The abstract reports only severe events, not milder ones or their rates. No trial longer than 12 months was located.

LimitedStudied in women

Thyroid function

One trial found no change in thyroid function or thyroid autoimmunity after 84 days in women.

The numbers and sources

Effect: After 84 days of a sulforaphane and glucoraphanin drink, TSH, free thyroxine and thyroglobulin did not change, and thyroid autoimmunity status did not change [11].
Population: 45 women in a randomized trial [11].
Sources: [11]
Caveats: One trial in women. It was done because Nrf2 activators had raised concern about thyroid effects [11].

Claims tested and not found

That sulforaphane activates Nrf2 antioxidant genes in the lungs. In COPD, 4 weeks at 25 or 150 μmol a day did not change Nrf2 target gene expression, inflammation or lung function [9].
That sulforaphane reverses precancerous lung changes. Over 12 months in former smokers, bronchial histopathology did not change. The Ki-67 proliferation index fell 20% on sulforaphane and rose 65% on placebo [10].
That sulforaphane improves cognition in schizophrenia. No cognitive benefit was found across 4 RCTs [7].

Sources

Egner PA, Chen JG, Zarth AT, 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. https://doi.org/10.1158/1940-6207.CAPR-14-0103
Chen JG, Johnson J, Egner P, et al. Dose-dependent detoxication of the airborne pollutant benzene in a randomized trial of broccoli sprout beverage in Qidong, China. The American Journal of Clinical Nutrition. 2019. https://doi.org/10.1093/ajcn/nqz122
Dwibedi C, Axelsson AS, Abrahamsson B, et al. Effect of broccoli sprout extract and baseline gut microbiota on fasting blood glucose in prediabetes: a randomized, placebo-controlled trial. Nature Microbiology. 2025. https://doi.org/10.1038/s41564-025-01932-w
Long J, Liao X, Tang Z, et al. Investigating the clinical efficacy, safety and molecular mechanism of sulforaphane in autism spectrum disorder: an integrated study combining meta-analysis, network pharmacology, and computational biology. BMC Pharmacology and Toxicology. 2025. https://doi.org/10.1186/s40360-025-01052-5
Wang R, Ren Z, Li Y. The effect of sulforaphane on autism spectrum disorder: systematic review and meta-analysis. EXCLI Journal. 2025. https://pubmed.ncbi.nlm.nih.gov/40458076/
Guo J, Wang Y, He W, et al. Effects of sulforaphane on ABC and SRS scales in patients with autism spectrum disorder: a meta-analysis. Brain and Development. 2025. https://doi.org/10.1016/j.braindev.2025.104321
Kassar O, Mansour MEM, Farag N, et al. Efficacy and safety of sulforaphane in schizophrenia: a systematic review and meta-analysis of randomized controlled trials. BMC Psychiatry. 2025. https://doi.org/10.1186/s12888-025-07515-7
Nouchi R, Hu Q, Ushida Y, et al. 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. https://doi.org/10.3389/fnagi.2022.929628
Wise RA, Holbrook JT, Criner G, et al. Lack of Effect of Oral Sulforaphane Administration on Nrf2 Expression in COPD: A Randomized, Double-Blind, Placebo Controlled Trial. PLOS ONE. 2016. https://doi.org/10.1371/journal.pone.0163716
Yuan JM, Kensler TW, Dacic S, et al. Randomized Phase II Clinical Trial of Sulforaphane in Former Smokers at High Risk for Lung Cancer. Cancer Prevention Research. 2025. https://doi.org/10.1158/1940-6207.CAPR-24-0386
Chartoumpekis DV, Ziros PG, Chen JG, et al. Broccoli sprout beverage is safe for thyroid hormonal and autoimmune status: Results of a 12-week randomized trial. Food and Chemical Toxicology. 2019. https://doi.org/10.1016/j.fct.2019.02.004
Ji H, Qi Z, Schrapel D, et al. Sulforaphane Targets TRA-1/GLI Upstream of DAF-16/FOXO to Promote C. elegans Longevity and Healthspan. Frontiers in Cell and Developmental Biology. 2021. https://doi.org/10.3389/fcell.2021.784999

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