Effect of Soy Isoflavones on Measures of Estrogenicity: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Bibliographic record
Abstract
Despite recommendations to increase plant food consumption for public and planetary health and the role that soy foods can play in plant-predominant diets, controversies around the effects of soy foods, especially soy isoflavones, are a barrier to their intake. Given their cardioprotective effects and ability to alleviate menopausal symptoms, addressing these concerns is particularly relevant to women. This systematic review and meta-analysis of randomized controlled trials aimed to determine the effect of soy isoflavones on measures of estrogenicity in postmenopausal women. MEDLINE, Embase, and Cochrane Library were searched through August 2024 for randomized trials ≥ 3-mo investigating soy isoflavones compared with non-isoflavone controls in postmenopausal women. Outcomes included endometrial thickness (ET), vaginal maturation index (VMI), follicle-stimulating hormone (FSH), and estradiol. Independent authors extracted data and assessed risk of bias. Grading of Recommendations, Assessment, Development and Evaluation was used to assess certainty of evidence. We included 40 trials (52 trial comparisons, n = 3285) assessing the effect of a median reported dose of 75 mg/d of soy isoflavones in substitution for non-isoflavone controls over a median of 24 wk. Soy isoflavones had no statistically significant effect on any measure of estrogenicity; ET [mean difference, –0.22 mm (95% confidence interval, –0.45, 0.01 mm), P MD = 0.059], VMI [2.31 (–2.14, 6.75), P MD = 0.310], FSH [–0.02 IU/L (–2.39, 2.35 IU/L), P MD = 0.987], and estradiol [1.61 pmol/L (–1.17, 4.38 pmol/L), P MD = 0.256]. The certainty of evidence was high to moderate for all outcomes. Current evidence suggests that soy isoflavones do not exhibit estrogenic effects compared with non-isoflavone controls on 4 measures of estrogenicity in postmenopausal women. This synthesis supports that soy isoflavones likely act as selective estrogen receptor modulators, differing clinically from the hormone estrogen. Addressing public health concerns may promote soy foods as high-quality plant protein sources with low environmental impact and cost, particularly benefiting postmenopausal women and aligning with sustainable dietary patterns and guidelines. This study was registered in PROSPERO as CRD42023439239.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.025 | 0.016 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.078 | 0.015 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; both teacher heads agree on what is shown here.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".