Phytoestrogens are unique in that they are anywhere from 1/100th to 1/1000th the potency of human estrogen or chemical estrogens (called xenoestrogens, like the kinds we find in plastics). We have two different estrogen receptors on our cells, alpha and beta. Stimulating the alpha receptor is like ringing the alarm bell inside the cell, while stimulating the beta is actually more of a calming signal. When phytoestrogens occupy the alpha receptor, they do so very weakly and block the receptor site from our endogenous estrogens and the xenoestrogens. Human estrogens and xenoestrogens typically have a more potent stimulus to either estrogen receptor and may have a greater affinity for the alpha receptor. Excess stimulation of the alpha receptor has been associated with cell proliferation and cancer in hormone sensitive tissues. An oversimplified description to be sure, but the point is that phytoestrogens play a positive role with both of these receptors and can actually reduce the impact of estrogen on our bodies.