Human metabolism and excretion of cancer chemoprotective glucosinolates and isothiocyanates of cruciferous vegetables.
Level 4 - case-series / case-control
Series of small human metabolic feeding and pharmacokinetic experiments without randomization.
What was done
In a series of feeding experiments with healthy human volunteers, researchers measured the metabolic conversion and urinary excretion of dietary glucosinolates and isothiocyanates as dithiocarbamates. The studies compared cruciferous vegetables (kale, broccoli, green cabbage, turnip roots) to non-cruciferous controls (corn, tomatoes, green beans, carrots), tested graded doses of horseradish (12.3–74 µmol isothiocyanates), evaluated broccoli with heat-inactivated versus active myrosinase, and assessed the effect of gut microflora depletion via mechanical cleansing and antibiotics.
What was found
Urinary dithiocarbamates were detected only after consuming cruciferous vegetables and were absent after non-cruciferous controls. Graded horseradish ingestion led to rapid, first-order urinary excretion of 42% to 44% of ingested isothiocyanates. Ingestion of broccoli with heat-inactivated myrosinase yielded 10% to 20% urinary recovery of dithiocarbamates, whereas broccoli pretreated with myrosinase yielded 47% recovery. When bowel microflora were depleted by cleansing and antibiotics, glucosinolate conversion became negligible.
Why it matters
This study establishes that dietary glucosinolates and isothiocyanates are predictably converted to urinary dithiocarbamates in humans, validating urinary dithiocarbamates as a practical biomarker of crucifer intake and enabling clinical investigations into dietary chemoprotection.
Limits
The abstract does not state the total number or demographic details of participants. The studies focused entirely on short-term pharmacokinetic excretion kinetics and did not measure tissue-level phase 2 enzyme induction or clinical cancer outcomes.
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