Sulforaphane

Sulforaphane has one of the richest mechanistic backstories in nutritional pharmacology and one of the thinner human evidence bases. It is the most studied Nrf2 activator in nutrition: a single oral dose induces phase II detoxification enzymes (NQO1, glutathione S-transferase, heme oxygenase 1) in a way that is biochemically convincing across cell, animal, and short-term human biomarker work. The problem is that the leap from "Nrf2 induction in a Western blot" to "clinical benefit in a real person" has been made for only a handful of indications, and only one of those replicates well.

The product story matters more than the dose story. Sulforaphane is the bioactive molecule, but most supplements ship its inert precursor glucoraphanin, which only becomes sulforaphane when an enzyme called myrosinase cleaves it. Myrosinase is destroyed by heat and stomach acid, so products that omit it rely entirely on gut bacteria to generate sulforaphane and produce wildly variable plasma levels. Fahey 2015 showed that adding active myrosinase to glucoraphanin gives 3-4x higher and far less variable sulforaphane exposure than glucoraphanin alone. This is why the Avmacol formula (glucoraphanin from broccoli seed extract plus a stabilized myrosinase blend) became the standard in clinical trials and why most pre-formed "stabilized sulforaphane" capsules underperform on third-party assay.

The strongest replicated human signal is in autism behavioral symptoms. Singh 2014 (Talalay group, n=40 young men, 50-150 μmol/day glucoraphanin for 18 weeks) reported 34% improvement on the Aberrant Behavior Checklist and 17% improvement on the Social Responsiveness Scale, with scores drifting back toward baseline after stopping. The 2021 Zimmerman replication in 45 children (Molecular Autism) missed its primary OACIS endpoint but showed a significant 15-week improvement on the Aberrant Behavior Checklist secondary outcome and produced clean biomarker shifts in glutathione, mitochondrial respiration, and inflammatory markers. Honest read: a real biological signal that has not yet produced a clean positive primary endpoint in a replication trial.

The pollutant-detoxification work is mechanistically convincing but stops short of clinical endpoints. Egner 2014, a randomized broccoli sprout beverage trial in 291 adults living in heavily air-polluted Qidong, China, showed 61% higher urinary excretion of benzene-mercapturic acid and 23% higher acrolein conjugates over 12 weeks. That is a real Nrf2-driven phase II conjugation effect on real environmental carcinogens. It is not the same thing as a lower cancer rate, and no human prevention trial with hard cancer endpoints has been completed.

The remaining indications are early signal or conflicted. Yanaka 2009 showed broccoli sprouts modestly suppressed H. pylori colonization markers in 48 infected patients for 8 weeks, but the effect reversed on discontinuation and the bacteria were not eradicated. Bahadoran 2012 (n=81, 10g/day broccoli sprout powder, 4 weeks) showed a HOMA-IR improvement in type 2 diabetes, and Axelsson 2017 reported modest HbA1c improvement in a Swedish obese T2D cohort with broccoli sprout extract, but glucose results are mixed across trials and effect sizes are small relative to standard medications. Cardiovascular biomarker trials have shown LDL and inflammatory marker reductions in small samples but no endpoint trials.

Practical bottom line: sulforaphane is one of the better-supported nutraceuticals for the narrow goal of Nrf2 activation and phase II enzyme induction. If you want to act on the Singh autism data or the Egner pollutant data, use an Avmacol-class product with active myrosinase and accept that you are following a thin, mostly-Talalay-group evidence base. Skip pre-formed sulforaphane capsules unless the brand publishes a third-party sulforaphane content assay. Eating roughly 100g of broccoli sprouts most days is a defensible no-pill alternative that delivers the trial-grade exposure with intact native myrosinase.