Isothiocyanate concentrations and interconversion of sulforaphane to erucin in human subjects after consumption of commercial frozen broccoli compared to fresh broccoli.
Level 2 - randomized trial
Individual randomized controlled trial measuring pharmacokinetic bioavailability in humans
PubMed 23109475 · doi:10.1002/mnfr.201200225
What was done
Eighteen healthy volunteers consumed soups made from lightly cooked fresh or frozen broccoli florets. Sulforaphane thio-conjugates were quantified in plasma and urine to compare bioavailability, and the bioconversion of glucoraphanin and sulforaphane to erucin and other metabolites by human gut microflora was evaluated.
What was found
Sulforaphane bioavailability was about tenfold higher from soups prepared from fresh broccoli compared to frozen broccoli, with the reduction attributed to the destruction of myrosinase activity during commercial blanching-freezing. Sulforaphane appeared in plasma and urine as free forms and several thio-conjugates. Erucin N-acetyl-cysteine conjugate was identified as a significant urinary metabolite, and gut microflora were shown to produce sulforaphane, erucin, and their nitriles from glucoraphanin.
Why it matters
Commercial blanching significantly reduces the bioavailable sulforaphane obtainable from frozen broccoli, highlighting the critical role of intact plant myrosinase for isothiocyanate absorption.
Limits
The abstract describes a small sample of 18 subjects, does not provide precise numerical concentrations or statistical variance metrics, and tests acute pharmacokinetic endpoints rather than clinical health outcomes.
Cited by
- partial The majority of the conversion of glucoraphanin to sulforaphane is performed by gut bacteria in the colon.