Sulforaphane Dosage: Human Trial Doses, µmol to mg & Myrosinase

There is no single established sulforaphane dosage that applies to everyone—and the biggest source of confusion is that “dose” can describe completely different things.

A label might report grams of broccoli, milligrams of broccoli extract, micromoles of glucoraphanin, milligrams of a combined glucoraphanin/myrosinase formula, or milligrams of sulforaphane itself. Those numbers cannot be compared as if they were the same unit of exposure.

The rule: identify what the number measures before deciding whether a dose is low, high or comparable with a clinical trial.

The four dose languages you need to separate

Human sulforaphane doses used in clinical studies

µmol to mg: how to convert pure sulforaphane

Clinical research often reports sulforaphane in micromoles (µmol). Using a molecular weight of about 177.29 g/mol, 1 µmol of pure sulforaphane is approximately 0.177 mg.

Do not apply this conversion to broccoli-extract or glucoraphanin weight. One hundred milligrams of glucoraphanin is not 17.7 mg of sulforaphane, and 500 mg of broccoli extract is not 500 mg of sulforaphane.

Why the administered dose can be nothing like the delivered dose

Cooking can change exposure by an order of magnitude

Eight men consumed the same 200 g amount of broccoli raw or cooked. Estimated sulforaphane bioavailability was about 37% after raw broccoli and 3.4% after cooked broccoli, with much faster peak exposure after the raw preparation.^[8]

Same broccoli weight. Very different internal dose.

Myrosinase changes precursor conversion

A 2026 crossover study found average sulforaphane bioavailability of 39.8% when mustard-seed myrosinase was added to a glucoraphanin-rich extract versus 18.6% without the added enzyme.^[9]

Another crossover feeding study showed that adding 1 g of brown mustard powder to cooked broccoli increased urinary sulforaphane-N-acetylcysteine more than fourfold.^[10]

A supplement can contain precursor and still deliver little sulforaphane

Fresh broccoli sprouts produced substantially higher and earlier plasma and urinary sulforaphane-metabolite exposure than a tested broccoli supplement whose myrosinase had been inactivated.^[11]

This is why “broccoli supplement 500 mg” is not a clinically useful dose description by itself.

Stomach conditions and delivery design can matter too

A human pilot using glucoraphanin-rich broccoli seed/sprout extract with active myrosinase found that conversion varied with omeprazole treatment and enteric coating.^[12] The practical point is not that everyone should take a proton-pump inhibitor—far from it. It is that active myrosinase can still be affected by how and where a formulation releases.

Is there an official recommended daily allowance?

No. There is no established Recommended Dietary Allowance, universal optimal daily dose or validated long-term tolerable upper intake level for sulforaphane supplements.

Human studies provide studied exposures, not a single dose prescription for healthy consumers. Disease trials often choose doses for a specific mechanistic or clinical question and should not be treated as everyday wellness recommendations.

Does taking more sulforaphane work better?

Not reliably. A pollution-biomarker trial found a dose-response pattern for one benzene-related endpoint, with the full tested beverage concentration producing the clearest effect.^[13] But the COPD trial included a 150 µmol/day arm and remained negative for its prespecified airway NRF2 and clinical endpoints.^[4]

At much higher direct sulforaphane exposure, the SFX-01 Phase I trial also shows that tolerability becomes part of the dose question. Seventeen of 18 active-treatment participants reported treatment-emergent adverse events, most commonly gastrointestinal symptoms, although most were mild and transient.^[7]

More exposure is not automatically more benefit.

Once daily or split dosing?

A small human feeding study compared once-daily with divided exposure and found that splitting the total daily intake helped sustain plasma sulforaphane metabolites later in the dosing interval.^[14]

That is pharmacokinetically plausible, but the study did not show that split dosing improves clinical outcomes. For a commercial supplement, the tested product instructions are a more defensible starting point than inventing an optimization protocol from plasma curves.

How to evaluate the dose on a supplement label

1. Identify the measured compound. Is the number broccoli extract, glucoraphanin, sulforaphane or combined formula weight?
2. If it is glucoraphanin, look for active myrosinase.
3. Do not infer sulforaphane from total extract weight.
4. Be suspicious of cross-product dose comparisons that mix µmol, mg of precursor and mg of total blend.
5. Match the trial to the formulation. A study of stabilized direct sulforaphane is not an equivalent-dose study of a glucoraphanin capsule.
6. Use tolerability and clinical context, not the largest number, to judge whether a dose is sensible.

Bottom line

The question “How much sulforaphane per day?” has no defensible one-number answer. Human trials study exposures ranging from single-digit milligram-equivalents to pharmacologic direct-sulforaphane doses, but the effective internal dose depends on formulation.

First identify what the label is measuring. Then ask how glucoraphanin becomes sulforaphane, how the product handles myrosinase and delivery, and whether the trial being cited actually tested the same type of formulation. For the broader product framework, see our sulforaphane supplement guide; for safety, see sulforaphane side effects.