Effect of soy isoflavones on measures of estrogenicity: A systematic review and meta-analysis of randomized trials
Bibliographic record
Abstract
Abstract Background Despite dietary recommendations to consume more plant foods for public and planetary health and the role that soy foods can play in plant-predominant diets, controversies around the effects of soy foods and their components, especially isoflavones, are a barrier to their intake. Given the cardioprotective effects and ability to alleviate menopausal symptoms, addressing this issue is particularly relevant to women. We therefore undertook a systematic review and meta-analysis of randomized controlled trials in postmenopausal women to determine the effect of soy isoflavones on measures of estrogenicity. Methods MEDLINE, Embase, and Cochrane Library were searched through July 2023 for randomized controlled trials 3-months investigating soy isoflavones versus non-isoflavone controls in postmenopausal women. The four outcomes included endometrial thickness (ET), vaginal maturation index (VMI), follicle-stimulating hormone (FSH), and estradiol. Independent authors extracted data and assessed risk of bias. GRADE (grading of recommendations assessment, development, and evaluation) was used to assess certainty of evidence. Results We included 40 trials (52 trial comparisons, n=3285) assessing the effect of a median daily dose of 75 mg of soy isoflavones in substitution for non-isoflavone control over a median of 24 weeks. Isoflavones had no statistically significant effects on any of the measures of estrogenicity; ET (mean difference, -0.22mm [95% confidence interval, -0.45 to 0.01mm], PMD=0.059), VMI (2.31 [-2.14 to 6.75], PMD=0.310), FSH (-0.02IU/L [-2.39 to 2.35IU/L], PMD=0.987), and estradiol (1.61pmol/L [-1.17 to 4.38pmol/L], PMD=0.256). The certainty of evidence was high-to-moderate for all outcomes. Conclusion Current evidence provides a good indication that soy isoflavones do not have an estrogenic effect versus non-isoflavone controls on 4 measures of estrogenicity in postmenopausal women. This synthesis supports the classification of soy isoflavones as selective estrogen receptor modulators and that isoflavones differ clinically from the hormone estrogen where no assumptions about the health effects of soy foods or isoflavones should be based on an understanding of the effects of the hormone estrogen. Addressing public health concerns around soy foods may support their intake as high-quality plant protein foods with low environmental impact and cost, especially relevant for postmenopausal women, and aligning with sustainable dietary patterns and guidelines. Registration: PROSPERO (CRD42023439239)
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.027 | 0.064 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.023 | 0.036 |
| Bibliometrics | 0.006 | 0.007 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.004 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 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; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
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".