Safety, tolerance, and metabolism of broccoli sprout glucosinolates and isothiocyanates: a clinical phase I study.
Level 2 - randomized trial
Individual double-blind, placebo-controlled randomized phase I trial
PubMed 16965241 · doi:10.1207/s15327914nc5501_7
What was done
A double-blind, placebo-controlled randomized phase I trial evaluated the safety, tolerance, and pharmacokinetics of broccoli sprout extracts containing glucosinolates (principally glucoraphanin) or isothiocyanates (principally sulforaphane) in 12 healthy inpatient volunteers following a 5-day crucifer-free diet. Subjects were divided into three cohorts, each containing 3 treated individuals and 1 placebo recipient. Broccoli sprout extracts were administered orally every 8 hours for 7 days (21 doses), followed by 3 days of monitoring. Dosages tested were 25 µmol glucosinolate (Cohort A), 100 µmol glucosinolate (Cohort B), and 25 µmol isothiocyanate (Cohort C). Urinary dithiocarbamate excretion and 32 hematologic and chemistry tests (including liver transaminases and thyroid function markers) were measured.
What was found
Mean cumulative excretion of dithiocarbamates as a fraction of dose was 17.8 ± 8.6% in Cohort A (25 µmol glucosinolate), 19.6 ± 11.7% in Cohort B (100 µmol glucosinolate), and 70.6 ± 2.0% in Cohort C (25 µmol isothiocyanate). Across 32 hematology and chemistry parameters, including liver enzymes and thyroid function (TSH, total T3, free T4), no significant or consistent subjective or objective adverse events or toxicities were observed.
Why it matters
This phase I trial establishes initial clinical safety and pharmacokinetic benchmarks for oral broccoli sprout preparations, demonstrating that preformed isothiocyanates achieve much higher urinary excretion consistency and recovery than glucosinolates.
Limits
The study is limited by a very small sample size (n = 12 total, with only 3 treated participants and 1 control per cohort) and a brief 7-day dosing duration. The strictly controlled inpatient setting and crucifer-free baseline diet also limit direct extrapolation to long-term free-living dietary supplement intake.
Cited by
- supports Clinical studies on sulforaphane typically target a daily dosage of between 50 and 100 micromoles.