Soy foods contain high levels of phytoestrogens, mainly in the form of isoflavones.
Isoflavones are natural estrogen receptor modulators that possess both estrogen like and antiestrogen properties.
Have nearly a pure estrogen receptor beta effect.
Constituents of soy have anticancer effects including the inhibition of DNA topisomerases I and II, proteases, tyrosine kinases, inositol phosphate, and angiogenesis and may boost immune responses and possess antioxidative effects (Taylor CK).
Soy consumption inversely related to risk of breast cancer.
In a study of 5042 patients breast cancer patients in a Shangai Breast Cancer Survival Study indicated that soy consumption was significantly associated with decreased risk of death and recurrence with adjusted 4 year mortality rates of 10.3% and 7.4% and 4 year recurrence rates os 11.2% and 8%, respectively, for women in the lowest and highest quartiles of soy protein intake (Shu XO).
In a multicenter, randomized, double-blind, placebo-controlled 24-month trial conducted to assess the effect of 80 or 120 mg of daily aglycone hypocotyl soy isoflavone supplementation on quality of life in 403 postmenopausal women using a validated Menopause-Specific Quality of Life questionnaire: scores at 1 year and 2 years were similar to baseline. and there no differences in domain scores among treatment groups (Amato P et al)..
Daily consumption of a supplement containing soy protein isolate for 2 years after radical prostatectomy does not reduce biochemical recurrence of prostate cancer in men at high risk of PSA failure(Bosland MC et al).