To determine the associations between
isoflavone (49.72%
genistin, 5.32%
daidzin, 34.54%
glycitin) and
breast cancer risk, 150 rats were given 5 mg
7,12-dimethylbenz(a)anthracene and half of them were ovariectomized. Then normal rats and ovariectomized rats were divided into 5 groups: control group,
isoflavone high (HI), middle (MI), or low (LI) dose group consuming 100, 500, or 1000 mg
isoflavones/kg diet,
estrogen group (2.5 mg stilboestrol/kg diet). After 24 weeks,
tumor incidences were 73% in control group, 7% in HI, 7% in MI, 27% in LI, and 80% in
estrogen group for normal rats; 60% in control group, 13% in HI, 7% in MI, 13% in LI, and 73% in
estrogen group for ovariectomized rats.
Isoflavone treatment decreased
tumor incidence and mean
tumor number per rat and increased mean latent period compared with those in control group and
estrogen group group significantly (p<0.05). The
mRNA and
protein expression of
estrogen receptor β were significantly higher in
isoflavone treatment groups than those in control group group. Moreover,
isoflavone treatment significantly decreased
8-hydroxydeoxyguanosine content and increased
superoxide dismutase level in normal rats and decreased
malondialdehyde concentrations in ovariectomized rats compared with control group. In conclusions,
isoflavone intake significantly inhibited the development of premenopausal and postmenopausal mammary
tumors.