A 2023 review of 28 human clinical trials investigating broccoli sprout compounds brought up this post’s title by omitting discussion of it:

“In order to determine the effective reference dose of a broccoli sprouts beverage for detoxifying carcinogenic air pollutants (benzene), Chen et al. administrated a drink enriched with glucoraphanin (GR) and sulforaphane (SFN) from 3-day-old broccoli sprouts to healthy adults. Researchers focused on excretion of metabolites SFN-NAC, SFN-CYS, and non-esterified SFN, which represent 80–81%, 12–14%, and 5–7% of total SFN forms, respectively.

Excretion percentage did not change during the intervention, indicating that bioavailability remained constant.

Enhanced excretion of the urinary biomarker of benzene detoxification S-phenylmercapturic acid (SPMA) was measured in urine collected every 12 h during the 10-day intervention. Out of 132 samples analyzed, >95% had detectable concentrations of SPMA, being significantly increased after consumption of the high dose of beverage (600 and 40 μmol GR and SFN, correspondingly), suggesting that consumption of >10 μmol SFN per 24 h may represent the lowest effective dose of the BSE affecting this biomarker.“

https://www.mdpi.com/2072-6643/15/6/1424 “Systematic Review on the Metabolic Interest of Glucosinolates and Their Bioactive Derivatives for Human Health”

These reviewers did much hand waving to draw their conclusions. They ignored that the only way randomized trials become better than non-randomized trials is in dealing with confounders.

The largest confounder with glucoraphanin is that an individual’s gut microbiota, not their human cells, metabolize it into isothiocyanates. A glucoraphanin randomized trial has to have sufficient numbers of subjects in each group to adequately deal with confounding individual differences in gut microbiota.

I highlighted the largest of the 28 trials:

Sulforaphane studies have fewer confounders. Even so, Upgrade your brain’s switchboard with broccoli sprouts stated:

“Power analysis calculations suggest that a sample size of n = 50 would yield a significant result.”

An insufficient number of subjects in both the half dose and full dose groups caused that study’s researchers to frame their results as “suggesting that consumption of >10 μmol SFN per 24 h may..” rather than asserting significant results.

Addressing this post’s title, it’s been ten years since epigenetic clocks came into use. This review highlighted by omission that there still hasn’t been even one investigation of isothiocyanates’ effects on human biological age as measured by epigenetic clocks.

A 40 μmol ≈ 7 mg sulforaphane “high” dose of the cited study is easily achievable with microwaved 3-day-old broccoli sprouts. There’s little question that healthy people activating AMPK, Nrf2, and associated signaling pathways, and inhibiting pro-inflammatory pathways such as NF-κB with sulforaphane, will experience beneficial effects.

The cited study found no change in sulforaphane treatment bioavailability over ten days, and a predecessor study found the same over 12 weeks. I’ll guess those bioavailability findings will extend over longer time periods.

Where are the researchers who will take the next step to show isothiocyanate treatments cause positive changes in epigenetic clock / biological age measurements?