Protection of humans by plant glucosinolates: efficiency of conversion of glucosinolates to isothiocyanates by the gastrointestinal microflora.
Level 3 - non-randomized controlled study
Non-randomized human pharmacokinetic/metabolism study across two cohort groups
PubMed 22318753 · doi:10.1158/1940-6207.CAPR-11-0538
What was done
Single oral doses of glucosinolates (GS) or isothiocyanate (ITC)-containing broccoli sprout extracts were administered to two dissimilar populations: rural Han Chinese and racially mixed Baltimoreans. Researchers measured urinary excretion of dithiocarbamates (DTC) to evaluate inter- and intra-individual conversion efficiency by gut microflora, excretion kinetics, and the influence of diurnal timing.
What was found
Conversion of GS to urinary DTC ranged widely between individuals in both populations, from approximately 1% to more than 40% of the dose. Direct administration of ITC-containing extract resulted in uniformly high conversion (70%–90%). Repeated determinations within individuals were consistent. Excretion rates (slow or fast) were unrelated to total conversion magnitude. Conversion of GS to DTC was higher during the day, whereas conversion of ITC to DTC was more efficient at night.
Why it matters
When crucifers are cooked and plant myrosinase is inactivated, conversion to bioactive isothiocyanates depends on gut microflora, resulting in up to 40-fold differences in internal dose among individuals receiving identical dietary amounts.
Limits
The abstract omits the total sample size (n), participant demographics, dose amounts, and variance metrics. Clinical health endpoints and the specific bacterial species driving conversion differences were not evaluated.
Cited by
- supports Direct administration of sulforaphane results in approximately 70% to 80% bioavailability in 24-hour urine.
- supports The bioavailability of sulforaphane from Prostaphane tablets was found to be essentially identical to that from laboratory-prepared freeze-dried broccoli sprout powder extracts.
- supports Administering a Fleet enema alongside preoperative antibiotics depletes intestinal bacteria by 5 to 6 orders of magnitude and reduces human conversion of glucoraphanin to sulforaphane to zero.
- supports Following antibiotic and enema-induced bowel clearance, human subjects gradually recover their capacity to convert glucoraphanin to sulforaphane within two to four weeks.