Reviewing clinical trials of broccoli sprouts and their compounds

This 2020 Spanish review analyzed recent clinical trials that used broccoli sprouts and their compounds. Stringent criteria for study selection resulted in few trials being considered:

  • “We reduced the timeframe to the last years, from 2012 to the present.
  • We focused our work on the data of studies carried out with human adults with different pathologies.
  • Articles [that] did not provide us with specific information about consumption of cruciferous foods or ingredients derived from Brassicaceae products, documents based on healthy volunteers, and patients with pathologies unrelated to our objective of study were also not included in the analysis.”

None of the 15 analyzed clinical trials were unqualified successes. Some of the problems noted were summarized in this critique of the largest study:

“The authors presented the results that there was a risk for T2DM [type 2 diabetes mellitus] with the intake of cruciferous foods and glucosinolates. However, this study presented big limitations because:

  • It did not review or consider the cooking procedures,
  • It did not quantify the amount of vegetables consumed on a daily or weekly basis, and
  • It did not quantify the glucosinolate contents in the different vegetables consumed. Besides,
  • The population sample was homogenous, because all of the participants were health-area workers, and the results are not extrapolatable to the general population. Finally, it should be highlighted that
  • Other nutrients and confounding factors were not considered in the study, and they could affect the development of these pathologies.”

“Figure 1 – General scheme of the glucosinolates (GSLs) and common hydrolysis products. ESP: Epithiospecifer proteins.” “The Role of Brassica Bioactives on Human Health: Are We Studying It the Right Way?”

The reviewers’ answer to the title’s question “Are We Studying It the Right Way?” was NO. The 15 analyzed trials lacked one or more clearly defined measurements related to their target diseases:

“It is crucial that the outcome measure is of biological relevance; biomarkers or risk factors measured must be associated to the latter development of a disease. The degree of progression of the disease greatly influences the response observed.”

So: Why not consider Aging as a disease for clinical trials with broccoli sprouts and their compounds?

  1. “Lack of cure goes hand in hand with inability to accept that this [aging] is disease. It used to be that, please do not diagnose that there’s bacterial meningitis, because there is no cure. Whatever else you can come up with, do it first. Now, diagnose it as fast as possible, so we can put patients on antibiotics immediately. The same will happen to aging.”
  2. Several of the clinical trials’ methodological and statistical problems could be resolved with recognizing aging as a disease. “Healthy” old people who have no other diseases may be scarce, but there are large populations to sample control groups from among healthy and unhealthy young people, and unhealthy old people.
  3. The reviewers already have experience in using “healthy” 46 ± 6 year-old people in a clinical trial of broccoli sprouts and their compounds.
  4. A wide range of epigenetic clocks are available to test the efficacy of broccoli sprouts and their compounds with respect to human aging phenotypes.

As far as I can tell, epigenetic clocks haven’t been used in the subject area thus far! The review’s reference [7] from 2015 didn’t mention them.

Reference [55] was the October 2019 Sulforaphane: Its “Coming of Age” as a Clinically Relevant Nutraceutical in the Prevention and Treatment of Chronic Disease, which I’ve been using as the most current and comprehensive of the subject todate. Its references of broccoli sprouts and their compounds with respect to aging included:

“Nrf2 [nuclear factor erythroid 2-related factor 2] transcriptional activity declines with age, leading to age-related GSH [reduced glutathione] loss among other losses associated with Nrf2-activated genes. This effect has implications, too, for decline in vascular function with age. Some of the age-related decline in function can be restored with Nrf2 activation by SFN [sulforaphane].

A potent Nrf2 activator is capable of inducing hundreds of genes simultaneously. Of the phytochemicals with Nrf2 inducer capacity, Brassica-derived SFN is the most potent naturally occurring biomolecule known at this time.”

However, it had only one reference of DNA methylation, the 2015 The Role of Sulforaphane in Epigenetic Mechanisms, Including Interdependence between Histone Modification and DNA Methylation. Even that was a review rather than a study, and it had no mention of epigenetic clocks.

Maybe broccoli sprouts and their compounds’ effects on human aging is an area that just hasn’t drawn attention and funding?


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