I'm not clear on exactly what equol might do to DHT.
Maybe
@Swoop knows?
Either way, we have several possibilities, maybe it's just not clear and people are making sh*t up.
1) Dr. Brotzu says equol works by blocking 5AR. If that is the case, equol is just finasteride. Might have a different sensitivity curve in the skin/blood/brain, who knows.
2) This article from 2003
http://www.ncbi.nlm.nih.gov/pubmed/14681200?dopt=Abstract
It is written by researchers at major American institutions.
Says that equol blocks the effect of DHT in rats which are given DHT directly (as opposed to 5ar). Says equol thus attacks DHT. blood DHT levels stayed at the same levels. Says equol has no effect on testosterone, estrogen, or dehydroepiandrosterone. Says equol does not bind to prostatic androgen receptor, but does bind to Estrogen-B receptor.
Equol apparently binds to SHBG.
The anti-androgenic properties of equol are unique in that equol does not bind the androgen receptor (AR) but specifically binds 5α-dihydrotestosterone (DHT) with high affinity, and thereby prevents DHT from binding the AR.
They took some castrated rats. The ones given only equol showed no change in prostate size. The ones given DHT showed increase prostate size. The ones given both DHT and equol showed showed no change in prostate size. The same is true of the effect of DHT on luteinizing hormone (LH). Since the DHT was given directly, this shows that equol's effect on DHT has nothing to do with 5AR. See the figures below:
3) In this case study,
http://www.ncbi.nlm.nih.gov/pubmed/21353476
a man lost his libido and his erectile function after going on a vegan diet. The authors argue it's because of Soy's estrogen-like properties. After he quit the vegan diet, it took him a year for his sexual function and other hormones to recover.
4) In this study
http://www.ncbi.nlm.nih.gov/pubmed/15735098
Soy protein consumptions reduced DHT and DHT/T in healthy young men by modest amounts (~15%), and it's independent of the dose of isoflavones. The effects on other hormones are very small.
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Separately, does topical equol go systemic? To what extent?