Isoflavones are part of a group of plant-based chemicals called phytoestrogens, and are found in soy and red clover. When you ingest isoflavones, bacteria in your intestines breaks it down into its more active forms that are very similar to estrogen, but less potent. Once in your body, isoflavones bind to the same receptors as estrogen. This can mimic the effects of estrogen, reducing hot flushes and other symptoms of menopause. Isoflavones should not be taken at the same time as HRT, as this results in competitive inhibition at the receptors.
As yet there is no hard data on major outcome measures such as coronary heart disease, fractures or long term safety. There are many studies looking at the effectiveness of the food substances but the results are variable and generally show little value.