Cohort studyindependent cross-checkabstract checked I-LEG-131 standard review
Soy formula and uterine fibroids
Soy-Based Infant Formula Feeding and Ultrasound-Detected Uterine Fibroids among Young African-American Women with No Prior Clinical Diagnosis of Fibroids.
Overview
Upson K et al.. Environ Health Perspect 2016 · PMID 26565393 · DOI 10.1289/ehp.1510082
Women fed soy formula as babies did not have more fibroids, but those who had fibroids had larger ones.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test soy formula and fibroids.
- How was the study done?
Cohort with ultrasound.
- How many people, animals or samples were studied?
1,553 women.
- What was actually found?
Prevalence null; size larger.
- How large was the observed effect?
aPR 0.9; diameter +32%.
- What do the results mean in everyday life?
Unclear long-term effect.
- What are the study's limitations?
Secondary finding.
- What does it say about Elawady's specific claim?
Mixed for C-LEG-10.
- Do the results apply to Germany and Europe?
Plausible.
- What can explicitly not be concluded from this study?
It does not show harm from other legumes.
Scientific in-depth review
1. Full reference
- Authors
- Upson K et al.
- Journal
- Environ Health Perspect
- Year
- 2016
- Identifier
- PMID 26565393 DOI 10.1289/ehp.1510082 · PMC4892927
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref works API
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
NIH intramural; no competing interests declared.
2. Research question
Is infant soy formula feeding associated with ultrasound-detected uterine fibroids?
3. Study design and population
- Study design
- Cohort study – Cross-sectional analysis within a cohort (SELF) with ultrasound screening
- Population
African-American women aged 23-34 y without prior fibroid diagnosis
- Country
USA
- Period
SELF baseline
- Sample size
1,553 (345 with fibroids)
- Inclusion and exclusion criteria
No prior clinical fibroid diagnosis.
4. Methods and endpoints
- Exposure / intervention
Infant soy formula (mostly maternal report)
- Comparator
Not fed soy formula
- Endpoints
Fibroid prevalence, number, size
- Statistical methods
Log-binomial and linear regression
5. Actual results
- Results
No association with fibroid prevalence (aPR 0.9, 0.7-1.3) or number; among women with fibroids, soy formula associated with 32% larger diameter of the largest fibroid (6%-65%) and 127% larger total volume (12%-358%).
- Absolute risks
Not reported
- Authors' conclusion
Larger fibroids in exposed women support persistent effects of early-life phytoestrogen exposure on the uterus.
6. Strengths
- Ultrasound-detected outcome
7. Weaknesses
- Subgroup finding (size) after null main result
- Recall
8. Risk of bias
- Orienting tool
- ROBINS-E
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Post-hoc emphasis on size.
9. Assessment of the statistical interpretation
Primary outcome null; secondary size association imprecise.
10. Relevance to the specific claim
Mixed: no excess fibroids, but larger fibroids; keeps the question of hormonal effects open (C-LEG-10).
11. Independent contrary findings
12. Transferability to Germany and Europe
Plausible.
13. Overall methodological judgement
Weak, mixed evidence.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | low |
| Directness | direct |
| Reproducibility | not replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Replication.