Background
Phytoestrogens are plant-derived, bioactive substances with a chemical structure similar to that of 17β-oestradiol. Women previously treated for breast cancer may increase their phytoestrogen intake to avoid conventional hormone replacement therapy or because of a belief that they may help avoid recurrence [1, 2]. There is no recommended daily intake and there are some concerns about phytoestrogen safety in this group, although the evidence is conflicting and more research is needed [3, 4].