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Moderate evidenceLongevity & antioxidants

Glucoraphanin

The broccoli-seed compound that the gut converts into sulforaphane, an activator of the Nrf2 detoxification pathway. Human trials show real but conditional effects on blood glucose and on clearance of some pollutants.

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What the science says

  • Fasting blood glucose in dysregulated metabolism Moderate evidence

    A randomised trial of concentrated broccoli sprout extract in type 2 diabetes reduced fasting glucose and HbA1c, with the effect concentrated in obese participants with poor control. A later placebo-controlled trial in prediabetes found the glucose response depended on the participant's baseline gut microbiota, which helps explain why results are inconsistent between individuals.

  • Detoxification of airborne pollutants Moderate evidence

    In a randomised dose-response trial in a highly polluted region of China, a broccoli sprout beverage increased urinary excretion of benzene metabolites in a dose-dependent way. This is a biomarker of accelerated clearance, not a demonstration that disease risk falls.

  • Longevity or general antioxidant benefit Limited evidence

    The Nrf2 mechanism is well characterised in cells and animals, but no human trial has tested glucoraphanin against ageing, mortality or hard clinical endpoints. The longevity framing is extrapolation from mechanism.

Dosage & safety

Studied doseTrials have used broccoli sprout preparations supplying roughly 100–200 micromol of glucoraphanin per day; the pollutant detoxification study used higher daily doses of up to about 600 micromol. Absorption varies widely because conversion to sulforaphane depends on plant myrosinase or on gut bacteria.
SafetyGenerally well tolerated; the commonest complaints are gas, bloating and the sulphur taste. Isothiocyanates in large amounts can interfere with thyroid iodine uptake, which matters mainly for people with low iodine intake or existing thyroid disease. Not studied in pregnancy or breastfeeding.

How to take it

TimingTiming does not matter.
With food?With food, but not stirred into something piping hot, since heat destroys the myrosinase enzyme that converts it to sulforaphane.
Worth knowingAbsorption depends almost entirely on that conversion, so choose a product with active myrosinase or eat a little raw cruciferous veg alongside it — otherwise you rely on gut bacteria and yield varies enormously between people.

Frequently asked questions

Does glucoraphanin or broccoli sprout extract lower blood sugar?

Glucoraphanin (broccoli sprout extract) has moderate but conditional evidence: a trial in type 2 diabetes lowered fasting glucose and HbA1c, mainly in obese participants with poor control. In prediabetes the response depended on each person's gut microbiota, which explains inconsistent results.

Does sulforaphane help detox?

In a randomised trial in a highly polluted region of China, a broccoli sprout drink supplying glucoraphanin increased urinary excretion of benzene metabolites in a dose-dependent way. That is moderate evidence for faster pollutant clearance, not proof that disease risk falls.

How much glucoraphanin per day?

Trials used broccoli sprout preparations supplying roughly 100–200 micromol of glucoraphanin per day, and up to about 600 micromol in the pollutant study. Choose glucoraphanin with active myrosinase or eat some raw cruciferous vegetables alongside it, because conversion to sulforaphane varies enormously between people.

Is glucoraphanin bad for your thyroid?

Large amounts of isothiocyanates such as sulforaphane from glucoraphanin can interfere with thyroid iodine uptake, which matters mainly if your iodine intake is low or you have thyroid disease. Otherwise glucoraphanin is generally well tolerated, with gas, bloating and a sulphur taste as the usual complaints.

Scientific references

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