Across 3 studies, 2 reported beneficial small-to-moderate effects of soy isoflavones on reducing menopausal symptoms, while 1 neutral review found no clear benefit. The highest-quality evidence (a meta-analysis) shows a small but statistically significant effect (Hedges' g = -0.25, 95% CI [-0.42 to -0.08]). One RCT (60 mg soy isoflavones daily) observed progressive reductions over 365 days in symptomatic postmenopausal women. The median study duration was 365 days (from one study), but evidence is limited by the small number of available studies.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. The beneficial effects are primarily driven by one meta-analysis and one RCT; the neutral review with low evidence score adds uncertainty. The single dose finding (60 mg/day) comes from one RCT combining soy isoflavones with Lactobacillus sporogenes, so it is unclear whether the effect is attributable to soy alone.
mammographic density, endometrial thickness and hepatic function did not show significant differences between groups
from: Endometrial, breast and liver safety of soy isoflavones plus Lactobacillus sporogenes in psoy isoflavones were effective for treating menopausal symptoms (seven studies, 533 participants, Hedges' g = -0.25, 95% CI [-0.42 to -0.08], p = 0.00)
menopausal symptoms were progressively and significantly reduced in severity and frequency during treatment with soy isoflavones plus Lactobacillus sporogenes versus calcium plus vitamin D₃
alleviate menopausal symptoms