How Soy Isoflavones interacts with tamoxifen

Interaction type: Interactions

Interaction rating: Study Supported

An animal study done on mice noted that the soy isoflavone, genistein, offset the ability of tamoxifen to inhibit estrogen responsive breast cancer tumor growth. Women on tamoxifen for estrogen responsive breast cancer should talk to their healthcare provider before using dietary genitstein. (1)


  1. View Abstract: Ju YH, Doerge DR, Allred KF, Allred CD, Helferich WG. Dietary Genistein Negates the Inhibitory Effect of Tamoxifen on Growth of Estrogen-dependent Human Breast Cancer (MCF-7) Cells Implanted in Athymic Mice. Cancer Res. May2002;62(9):2474-7.