Possible Interaction: Estradiol and Isoflavones

“Compared with the control diet, increased isoflavone consumption decreased urinary excretion of estradiol , estrone, estriol, and total estrogens, as well as excretion of the hypothesized genotoxic estrogen metabolites, 16alpha-hydroxyestrone, 4-hydroxyestrone, and 4-hydroxyestradiol.”

“ Isoflavones circulate at concentrations that are 13,000-22,000-fold higher than plasma estradiol concentrations in early life.”

“Mammographic density is not affected by soy or phytoestrogen products and recent in vitro work shows only a weakly proliferative effect of soy isoflavone on breast cancer cells and evidence that soy isoflavone blocks the proliferative effect of estradiol on these cells.”

“ Isoflavone had a significant tendency to be negatively associated with estradiol in boys and to be positively associated with testosterone in girls.”

“The negative correlations observed between isoflavones and estradiol in women as a whole became no longer significant when we excluded women with ESR1 PvuII CC genotype, indicating that the correlations observed were due mainly to this group of women.”

“However, isoflavones (at 10(-8) and above concentrations) were also antiestrogenic when combined with estradiol (E(2)) (P < 0.05).”

“The purpose of this study was to investigate whether the acceleration of VO by IF (1) has a critical window, (2) is modified by IF exposure combined with 17beta-estradiol (E2), and (3) has any relation with gene expressions of estrogen-related receptors (ERRs).”

“An increase in mRNA for both genes was noted after estradiol treatment and with the highest dose of IFs.”