This 2023 clinical trial with broccoli sprout powder investigated ways of improving blood plasma measurements:
“Quantifying sulforaphane (SFN) and its thiol metabolites in biological samples using liquid chromatography-tandem mass spectrometry is complicated by SFN’s electrophilic nature and the facile dissociation of SFN-thiol conjugates. We used the alkylating agent iodoacetamide (IAA) to both release SFN from protein thiols and force the dissociation of SFN metabolites.
After 15 min of incubation, approximately 90% of the SFN was recovered. After 2 hours of incubation, SFN loss to thiol conjugation was significant, with approximately 30% recovered. The percentage of SFN lost in this manner in human plasma upon protein precipitation would likely be greater than the loss we observed in fetal bovine serum (FBS), as free thiols in human plasma are approximately 6 times higher than in FBS.

Subjects were 12 healthy, young (19–30 y), men (n = 4), and women (n = 8). They consumed three EnduraCell capsules with water.
Per the manufacturer, each capsule contained 700 mg of 100% whole broccoli sprout powder, including active myrosinase and 21 mg of glucoraphanin, which upon full conversion to SFN would yield ∼8 mg, equaling ∼24 mg of SFN total per three-capsule dose. We note that full conversion to SFN, even with active myrosinase in the supplement, is not expected.
SFN concentrations in plasma increased for all subjects, with the highest being 193 nM for subject 4 one hour post consumption. Asterisks for the 2 and 3 hour time points indicate a p-value of <0.05, comparing that time point to the previous time point for that participant.

This thiol-blocking method increased SFN percent recovery from FBS from 32 to 94 ± 5%. Applying the method to clinical samples, SFN concentrations were on average 6 times greater than when IAA was omitted.”
https://pubs.acs.org/doi/10.1021/acs.jafc.3c01367 “Bioavailable Sulforaphane Quantitation in Plasma by LC–MS/MS Is Enhanced by Blocking Thiols”
I didn’t highlight subject bioavailability statistics or researcher generalizations. Someday, researchers will be interested and forward-thinking enough about their field to plan ahead and investigate likely occurrences such as:
- What caused Subjects 3 and 4 to have much higher responses than Subjects 2 and 6?
- What caused Subjects 5 and 11 to have their highest sulforaphane levels at their 3-hour points, whereas 3-hour points were most other subjects’ lowest levels?
And, of course, what was the actual sulforaphane intake by researcher measurements vs. relying on manufacturer statements? Especially when researcher lab equipment was available to measure that.
This study’s proof of concept demonstrated a 10% sulforaphane loss after 15 minutes, and a 68% loss after two hours. Applying their finding to home sprouting, I wouldn’t expect any advance preparation method of broccoli sprouts or seeds to adequately address sulforaphane degradation.
I’d suggest microwaving up to 60°C (140°F) and/or grinding and/or blending broccoli sprouts and seeds just before eating to optimize your sulforaphane intake. Also, taking the very reactive sulforaphane by itself to optimize your results.

























