TC's article states:
"Resveratrol has a whole lot of good things going for it, but the one we're most interested in has to do with estrogen. You see, resveratrol acts as a potent estrogen antagonist (while also acting as an agonist in some tissues, similar to the drugs clomiphene and tamoxifen).
In higher concentrations, it acts as an aromatase inhibitor. That means that it stops the body from whittling away at your Testosterone.
This is cool because if a substance stops Testosterone from being converted to estrogen or estradiol, it not only prevents the nasty effects of estrogen (loss of muscle and strength and accrual of body fat), but it increases your level of Testosterone, leading to additional strength and muscle!
What's equally important is that it won't cause your Testicles to go on vacation, i.e. shrink. The testicles don't get a signal from the pituitary to shut down because estrogen has been curtailed!
There's a lot of good data in animal models to back this up. Studies have demonstrated a resveratrol-fueled increase in Luteinizing Hormone and Follicle Stimulating Hormone (the pituitary hormones that signal the testicles to start producing Testosterone) that's 2.7 times greater than placebo.
Additionally, resveratrol caused a 76% increase in sperm count, all of this without any adverse effects. (1)
The aromatase inhibition is thought to occur through two mechanisms: reducing the expression of aromatase, as well as binding to the enzyme and preventing it from doing its dirty work.
And, unlike conventional aromatase inhibitors, resveratrol doesn't cause a decline in endothelial (blood vessel) function. In fact, it seems to improve it! (2-12)
And remember those nasty xenoestrogens I mentioned earlier? Resveratrol seems to occupy the receptor sites, or biological "parking lots," so that these xenoestrogens can't "park" in their spots. That's good."
I think this explains it pretty well. I also have been using it as a standard good health supplement, like Flameout, since it's release. During this time I have brought my body-fat down considerably while my lifting numbers continue to improve. I believe the over all health benefits (my Dr. had even heard of the health benefits of resveratrol and agreed it was good) combined with the added help to boost Testosterone and keep estro in check make it a vital part of my supplementation.