I’d love to see some actual data about that, MrMontpetit. All I’ve found was this article from the Straight Dope . Interestingly enough, they do talk about photoestrogens (a plant form of estrogen, which is the primary female sex hormone), and they mention that hops do contain a high amount of it. But he follows that up with this interesting point:
For women who do produce enough estrogen of their own, phytoestrogens actually decrease overall estrogen activity by competing with the homegrown estrogen for positions on estrogen receptor sites; when phytoestrogens latch onto these sites, they push aside the real estrogen and provide only a weaker version. In fact, that could be their real benefit, some experts think—by lowering the body’s effective estrogen level, phytoestrogens may reduce a woman’s chance of developing breast cancer. But here’s the thing: if so, they’d likely make breasts smaller, not larger.
And his conclusion seems pretty definitive.
In short, whatever uses phytoestrogens may have, increasing breast size isn’t one of them. Many breast-enlargement products contain only small amounts of phytoestrogens anyway, and none has been proven to work in double-blind laboratory tests.
I’m a girl of science, so his last phrase is enough to seal the deal for me. Debunked.