I was investigating soy products for us & came across this site:

http://nccam.nih.gov/health/supplements/wiseuse.htm

http://nccam.nih.gov/health/menopause/menopausesymptoms.htm

If you are taking any estrogen containing medications or tamoxifen do not take soy without speaking to your physician first. Some studies show that it could alter the effects of your medication.