The specific role of isoflavones on estrogen metabolism in premenopausal women
Citations:112
Influential Citations:5
Interventional (Human) Studies
82
Low RoB
Enhanced Details
Methods
Double-blind, randomized, placebo-controlled trial of healthy premenopausal omnivorous women aged 25–55. 97 screened; 66 completed (33 per group). Exclusions included history of cancer; pregnancy or birth control use within 12 months; current use of hormones; perimenopausal status; irregular menstrual cycles; BMI > 38; antibiotic use within 3 months; vegans. Recruited from the Tampa Bay area. Intervention spanned from cycle Days 4–7 after the first day of menses in the first cycle to cycle Days 4–7 after three complete cycles. Outcomes included anthropometric, nutritional, and hormonal biomarkers (estradiol, estrone, SHBG) and menstrual cycle measures.
Intervention
Daily oral soy isoflavone supplement delivering 40 mg genistein per day (administered as two 20 mg doses) starting cycle Days 4–7 after the first day of menses and continuing for 12 weeks (through three complete menstrual cycles).
Results
Mean menstrual cycle length increased by 3.52 days by the third cycle in the soy group (P = 0.04) versus a 0.06-day decrease with placebo. Serum free estradiol and estrone decreased; SHBG increased in 41.4% of soy users vs 37.5% in placebo, though differences in hormone levels between groups were not statistically significant. Follicular phase length increased by 1.46 days with soy vs 0.14 days with placebo (P = 0.08). Increased isoflavone intake may modulate estrogen metabolism and extend cycle length, potentially reducing lifetime breast carcinoma risk, likely via SHBG-mediated reductions in bioavailable estrogen and antiestrogenic effects.
Limitations
66 completers out of 97 recruited; small sample size; short duration (12 weeks); some hormonal outcomes not statistically significant; results may not generalize to other populations.
Abstract
There is increasing evidence that dietary factors may play a role in the production, metabolism, and bioavailability of sex hormones and their impact on target tissues. The specific objective of this study was to evaluate the effectiveness of supplem...
There is increasing evidence that dietary factors may play a role in the production, metabolism, and bioavailability of sex hormones and their impact on target tissues. The specific objective of this study was to evaluate the effectiveness of supplementing a group of premenopausal women who were free of breast carcinoma with a dietary supplement of isoflavones (40 mg per day) in producing a change in steroid hormones and menstrual cycle length.