However a recent study (5) indicates that concomitant administration of 50mg/kg/day of Soyselect^® in mice carrying estrogen-dependent breast cancer have slightly potentiated the effect of the estrogen antagonist fulvestrant drug, whereas a dose of 100 mg/kg/day partially negated the tumor reduction activity of the same drug.
It is advisable not to recommend the consumption of isoflavone supplements in conjunction of fulvestrant therapy in post menopausal women with estrogen-dependent breast cancer.

In a recent study on Soyselect^®, Gallo et al. (6) showed that 100 mg/kg/day by oral route in ovariectomized rats did not affect the weight and the histology of the uterus and reduced the expression of Ki67, an epithelial marker of proliferation. On the contrary, 17betaestradiol significantly increased uterine weight, induced hyperplasia in the majority of rats and enhanced Ki67 epithelial expression. Data from this pubblication improve our understanding on the effects of Soyselect^® confirming its favourable tissue-specific modulation of cell-cycle control.

In a second study on Soyselect^®, Gallo et al. (7) showed in an animal model that estrogens and soy phytochemicals similarly polarize the immune system toward a type 2 immune response. Even if data from preclinical models may not be entirely representative of the effects potentially accruing in humans, these finding is suggesting that soy phytochemicals should be used with caution in postmenopausal women with active TH2-related diseases (such as SLE), although they could be beneficial in women with TH1-related inflammatory disorders (eg, RA and multiple sclerosis).