In vivo formation and bioavailability of isothiocyanates from glucosinolates in broccoli as affected by processing conditions.
Level 2 - randomized trial
Randomized controlled trial in human volunteers.
PubMed 24687744 · doi:10.1002/mnfr.201300894
What was done
Fifteen human volunteers ingested five differently processed broccoli products containing similar levels of glucoraphanin and glucoiberin but varying residual myrosinase (MYR) activity. Researchers measured the formation, bioavailability, excretion half-lives, and peak excretion times of sulforaphane (SR) and iberin (IB) conjugates in urine.
What was found
An 80% reduction in MYR activity (20% residual activity) did not reduce total urinary excretion of SR and IB compared to the product with 100% MYR activity. Complete MYR inactivation resulted in the lowest urinary recovery of SR (10%) and IB (19%), while 2% residual MYR yielded intermediate recovery (17% for SR and 29% for IB). Excretion half-lives averaged 2.5 hours across all preparations, while maximum excretion peak times ranged from 2.3 to 6.1 hours, appearing faster when residual MYR was higher.
Why it matters
These results clarify the threshold of thermal or food processing tolerated before isothiocyanate bioavailability from broccoli is substantially impaired.
Limits
The study sample was small (n = 15). The abstract does not report participant demographics, randomization or crossover details, confidence intervals, statistical significance values, or clinical health endpoints.
Cited by
- supports When glucoraphanin is ingested alone without myrosinase, the average bioavailability in 24-hour urine collections is approximately 10%.