Research synthesisLow evidenceModerate effect3 studies · 3 beneficial · 0 neutral · 0 harmful
Across 3 studies, all reported beneficial effects of soy intake on reducing breast cancer recurrence, with effect sizes ranging from moderate to large. The most-studied dose range was approximately 25-50 mg isoflavones daily (2-3 servings of traditional soy foods), primarily in women with breast cancer or breast cancer survivors. All 3 studies found statistically significant results, though the evidence base is small.
- Effective dose range: 25-50 mg isoflavones per day (approximately 2-3 servings of traditional soy foods)
- Studied populations: women with breast cancer, breast cancer survivors (including postmenopausal and estrogen receptor-positive survivors)
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). The highest-quality study (systematic review) had a relatively small sample size (n=131), and the most recent review (2025) had a low evidence score. Most evidence comes from observational studies and reviews of observational data, not randomized controlled trials.
Generated Jun 15, 2026