Also known as: Broccoli sprout extract, Glucoraphanin, Myrosinase, SFN
BotanicalGood evidence
A compound formed when broccoli is chopped or chewed, and one of the most potent activators of the body's own antioxidant defences. Most supplements are built wrong, and the reason is worth understanding.
Typical dose
10.0–40.0 mg per day
With food; take with a myrosinase source if the product lacks it
What it is
Sulforaphane does not exist in intact broccoli. The plant stores an inactive precursor called glucoraphanin in one compartment and an enzyme called myrosinase in another. Damage the plant by chopping or chewing, the two meet, and sulforaphane is formed.
Broccoli sprouts contain many times more glucoraphanin than mature broccoli, which is why supplements use sprouts.
Here is the problem with most products. Many supply glucoraphanin alone, with the myrosinase destroyed by processing. Without the enzyme, conversion depends entirely on gut bacteria and is poor and highly variable between people. A product declaring glucoraphanin without active myrosinase is selling you a precursor and hoping.
How it works
Sulforaphane activates Nrf2, a transcription factor that switches on the genes for the body's own antioxidant and detoxification enzymes.
This is a different approach from taking an antioxidant directly. Rather than neutralising one reactive molecule per dose, it upregulates the systems that produce enzymes doing that work continuously, which is why the effect outlasts the compound itself.
Sulforaphane is among the most potent naturally occurring Nrf2 activators identified, and it also influences inflammatory signalling through separate pathways.
What the evidence shows
Nrf2 activation and the resulting increase in antioxidant enzyme expression are well demonstrated in humans, and the effect on detoxification enzyme activity has been measured directly in several trials.
There is a reasonable body of work on markers of oxidative stress and inflammation, with generally favourable findings.
Where the evidence thins is in outcomes a person would notice. Trials linking sulforaphane to changes in how people feel or perform are limited, and much of the enthusiasm rests on the strength of the mechanism rather than on demonstrated results.
Dosing
Effective doses are around 10 to 40 mg of sulforaphane, or the glucoraphanin equivalent with active myrosinase present.
Check the label for myrosinase. A product supplying glucoraphanin alone relies on your gut bacteria to do the conversion, and a substantial proportion of people convert poorly.
Eating broccoli sprouts is a legitimate and cheap alternative. If you cook broccoli, chopping it and leaving it to stand for 40 minutes before heating allows the enzyme to work first, since myrosinase is destroyed by heat. Mustard powder added after cooking supplies myrosinase from another source and restores some conversion.
Plasma sulforaphane clears within hours; enzyme induction persists for days
Timing
With food; take with a myrosinase source if the product lacks it
Competition status
Permitted — not on the WADA Prohibited List
Category
Botanical
Safety and side effects
Sulforaphane has a good safety record and extensive dietary exposure through cruciferous vegetables. Digestive upset and gas are the most commonly reported effects.
As a cruciferous compound it carries the same theoretical thyroid consideration as other brassicas, which is unlikely to matter at supplemental doses with adequate iodine status, though worth knowing if your thyroid function is being monitored.
Because it upregulates detoxification enzymes, it may affect how the body processes other compounds. Speak to your doctor before use if you take regular medication.
Who should avoid it
Speak to your doctor before use if you take regular medication, since sulforaphane upregulates the enzymes that process other compounds. Take care if your thyroid function is being monitored. Avoid if sensitive to cruciferous vegetables. Not established at supplemental doses in pregnancy or breastfeeding.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
