Know2eat

Sulforaphane and glucoraphanin

Isolated Compounds

What sulforaphane and glucoraphanin may help with

Ranked by how strong the human evidence is — best supported first.

Best supportedOxidative stress markersModerate evidence· 4 sources

Then, in order

About Sulforaphane and glucoraphanin

An isothiocyanate formed when the enzyme myrosinase acts on glucoraphanin, a glucosinolate concentrated in broccoli sprouts. Most supplements contain the inactive precursor glucoraphanin, with or without added myrosinase.

Sulforaphane is one of the better-characterised food-derived compounds, with a specific and well-mapped mechanism — activation of the NRF2 transcription factor, which switches on a battery of phase II conjugation and antioxidant enzymes. The human trials that exist are mostly short and mostly measure biomarkers: excretion of airborne pollutant conjugates in the Johns Hopkins Qidong trials, Helicobacter markers, and in a widely discussed small trial, autism behaviour scores. The critical practical fact is that a capsule of glucoraphanin without active myrosinase converts to sulforaphane only through gut bacteria, at a fraction of the efficiency, and conversion varies enormously between people. Products differ dramatically in whether they deliver any sulforaphane at all.

Sold as
Broccoli seed extract capsule (glucoraphanin), Glucoraphanin with added myrosinase, Stabilised sulforaphane capsule, Broccoli sprout powder
Standardised to
Milligrams of glucoraphanin, or of sulforaphane potential; the presence of active myrosinase is the variable that matters most — a product without this marker may not resemble what was studied.
Also known as
Broccoli sprout extract, Glucoraphanin, SGS, Broccoli seed extract

Regulation: Sold as a dietary supplement in the US with no pre-market efficacy review. There is no standard assay requirement, and independent testing has found large differences between labelled glucoraphanin and measurable sulforaphane yield.

What the research used

The amounts, forms and durations published trials of Sulforaphane and glucoraphanin actually administered.

These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.

  • Studied for Air pollutant conjugate excretion

    400 µg

    Moderate

    Broccoli sprout beverage, sulforaphane equivalent, daily · 12 weeks

    From the Qidong trials in China. The intervention was a fresh sprout beverage prepared for the study, not a retail capsule.

  • Studied for Autism behaviour scores

    50–150 µmol

    Limited

    Sulforaphane, daily, scaled to body weight · 18 weeks

    A small randomised trial in young men that drew wide attention. Subsequent replication attempts have been mixed and the sample was small.

  • Studied for Retail supplement use

    10–60 mg

    Limited

    Glucoraphanin capsule, daily

    What most products contain. Without active myrosinase, the sulforaphane actually produced is a small and highly variable fraction of this, dependent on an individual's gut bacteria.

This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.

None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.

  • On an empty stomach

    Limited

    Some products advise taking it away from hot food because myrosinase is destroyed by heat, which is the same reason lightly cooked broccoli yields more sulforaphane than boiled. That is chemistry rather than a tested timing comparison in people.

    Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.

The evidence in depth

Best supported: Moderate

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.

Oxidative stress markers

Antioxidant & Oxidative Stress
Moderate evidence

Human trials consistently show that sulforaphane exposure increases NRF2-dependent enzyme activity and accelerates urinary excretion of conjugates of airborne pollutants such as benzene and acrolein. These are mechanistic biomarkers rather than health outcomes, but the effect on them is reproducible.

What may be going on: Sulforaphane modifies cysteine residues on KEAP1, releasing NRF2 to enter the nucleus and switch on phase II conjugation and antioxidant genes.

Moderate evidence. Several human studies point the same way, with real caveats.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Digestive comfort

Gut & Digestive Health
Limited evidence

Small Japanese and American trials report reductions in markers of Helicobacter pylori colonisation and gastritis during broccoli sprout intake, with the effect fading after intake stops. Eradication was not achieved.

Limited evidence. Early human work, or mostly lab and animal research.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Inflammatory markers

Inflammation
Limited evidence

Small trials report reductions in inflammatory markers and in nasal inflammatory responses to particulate challenge. The studies are short and the participant numbers small.

Limited evidence. Early human work, or mostly lab and animal research.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Insulin sensitivity

Blood Sugar & Metabolic Health
Limited evidence

A trial of concentrated broccoli sprout extract in people with type 2 diabetes reported reduced fasting glucose and HbA1c, with the effect concentrated in obese participants with poor control. It is a single trial and needs replication.

Limited evidence. Early human work, or mostly lab and animal research.

View the 1 source

Deep research mode adds each paper’s own conclusion and stated limitations.

Things to know

Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.

  • Worth knowing

    Most capsules deliver far less than the label suggests

    Glucoraphanin is inert until myrosinase converts it. Many products contain no active enzyme, leaving conversion to gut bacteria, which is inefficient and varies several-fold between people. Independent analyses have found large discrepancies between labelled glucoraphanin and measurable sulforaphane yield, which makes cross-product comparison close to meaningless.

  • Worth knowing

    Thyroid considerations at high intake

    Glucosinolate breakdown products include compounds that can interfere with iodine uptake by the thyroid. This is a concern mainly at high intakes with low iodine status, and it is worth flagging for anyone with existing thyroid disease.

  • Too much

    Gas, bloating and a sulphurous taste

    Flatulence and bloating are the common complaints, along with a sulphurous smell and taste. High doses have caused nausea and vomiting in trials.

  • Worth knowing

    Raw sprouts carry a food-safety issue supplements do not

    The trials that used fresh sprouts inherit the food-safety problems of raw sprouts, which have been implicated in Salmonella and E. coli outbreaks. That is an argument for the extract in some populations, not against the food generally.

In the food catalogue

The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.

BroccoliThe parent food; broccoli sprouts contain many times more…Brussels sproutsAnother cruciferous source of glucosinolates, though of a different…CauliflowerA related crucifer with a lower glucoraphanin content.

Evidence ratings on this page: 1 moderate evidence, 3 limited evidence.

Supplements are sold in the US without pre-market review of efficacy or safety. Nothing on this page is a recommendation to take Sulforaphane and glucoraphanin, or a dose to follow.