Soy isoflavones activate your body's estrogen receptors, proteins that detect the presence of estrogen and carry out effects such as changes in gene expression. However, isoflavones do so more weakly than your body's natural estrogen. If estrogen is absent, isoflavones weakly activate the estrogen receptor, mitigating the effect of low estrogen. If estrogen is abundant, isoflavones interfere with the activity of natural estrogen, limiting the effect of high estrogen levels. Since the structure of isoflavones is similar to estrogen, isoflavones may decrease your body's production of estrogen and increase the rate of estrogen degradation due to feedback mechanisms that control estrogen levels.