Glutathione S-transferase M1 polymorphism and metabolism of sulforaphane from standard and high-glucosinolate broccoli.
Level 2 - randomized trial
Individual randomized crossover trial
PubMed 16332662 · doi:10.1093/ajcn/82.6.1283
What was done
Sixteen subjects participated in a randomized, 3-phase crossover dietary trial comparing the metabolism of standard broccoli, high-glucosinolate broccoli (super broccoli), and water. Sulforaphane and its thiol conjugates were measured in plasma and urine using liquid chromatography linked to tandem mass spectrometry to evaluate differences between GSTM1-null and GSTM1-positive individuals.
What was found
GSTM1-null participants had statistically significantly higher plasma area under the curve (AUC) for sulforaphane metabolites, higher urinary excretion rates in the first 6 hours post-consumption, and a higher percentage of sulforaphane excreted after 24 hours compared to GSTM1-positive subjects (exact values not reported in abstract). High-glucosinolate broccoli consumption resulted in a 3-fold greater increase in plasma AUC and maximum concentrations of sulforaphane metabolites, a higher 6-hour urinary excretion rate, and a lower percentage of sulforaphane excreted after ingestion compared to standard broccoli.
Why it matters
The findings demonstrate that GSTM1 genotype alters the pharmacokinetics of dietary sulforaphane, providing a potential mechanistic explanation for genotype-dependent variations in cancer protection observed in epidemiological studies.
Limits
The sample size was small (n = 16), and the abstract does not report baseline participant characteristics, exact numerical values, or confidence intervals for the pharmacokinetic parameters. Only acute metabolic endpoints were assessed rather than clinical outcomes.
Cited by
- supports When ingested, sulforaphane is rapidly taken up by human cells, conjugated with glutathione, and excreted into urine.