tamoxifen

I've not heard of that but there is a substance called diindolylmethane (DIM) which is thought to have anti-estrogen affects in the body thereby lowering your risk of BC recurrance. It is derived from cruciferous vegies like broccoli and kale. But of course theDIM in the supplement is much more concentrated than the amount you could get from just eating vegetables. There is a study being done at the University of Arizona currently on whether taking DIM with tamoxifen is more effective than taking tamoxifen alone. 

I am taking a DIM supplement myself  as well as my tamoxifen. I don't like taking the tamoxifen but I'm too scared to not take it. (Just reading the storeis here of women with secondary BC is enought to make me take my pill everyday.) My supplement which is called Breast Balance also contains some other nutrients commonly found to be deficient in women with breast cancer - vitamin D, selenium and iodine. 

From what I understand taxoxifen only inceases the risk of uterine cancer by about 1-2% and it can reduce your risk of BC recurring by significantly more than that. In my case my oncologist said it would reduce my risk by about 11%. That is substantial enough for me to take it. Hopefully the DIM is reducing my risk even further. But I must stress it is not a proven alternative. It may be better than nothing but you're probably better off taking your tamoxifen. Not everyone gets side effects. Good luck.