Cohort studyindependent cross-checkabstract only checked★ key study I-LEG-10 in-depth review
Adults fed soy formula as babies
Exposure to soy-based formula in infancy and endocrinological and reproductive outcomes in young adulthood.
Overview
Strom BL et al.. JAMA 2001 · PMID 11497534 · DOI 10.1001/jama.286.7.807
No major health differences in young adulthood; slightly longer menstrual bleeding in women.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Long-term soy formula effects
- How was the study done?
Retrospective cohort
- How many people, animals or samples were studied?
811 adults
- What was actually found?
Mostly no differences
- How large was the observed effect?
+0.37 days bleeding
- What do the results mean in everyday life?
Reassuring for soy formula.
- What are the study's limitations?
Self-report
- What does it say about Elawady's specific claim?
Limits concern
- Do the results apply to Germany and Europe?
Moderate
- What can explicitly not be concluded from this study?
Cannot exclude subtle effects.
Scientific in-depth review
1. Full reference
- Authors
- Strom BL et al.
- Journal
- JAMA
- Year
- 2001
- Identifier
- PMID 11497534 DOI 10.1001/jama.286.7.807
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Long-term effects of infant soy formula.
3. Study design and population
- Study design
- Cohort study – Retrospective cohort of adults fed soy or cow-milk formula in controlled feeding studies 1965-1978
- Population
Adults aged 20-34
- Country
USA (Iowa)
- Period
Follow-up 1999
- Sample size
811 (248 soy, 563 cow-milk formula)
- Inclusion and exclusion criteria
Former participants of infant feeding studies
4. Methods and endpoints
- Exposure / intervention
Soy formula
- Comparator
Cow-milk formula
- Endpoints
>30 self-reported outcomes incl. puberty, menstrual and reproductive health
- Statistical methods
Adjusted comparisons
5. Actual results
- Results
No significant differences in >30 outcomes; women fed soy formula reported slightly longer menstrual bleeding (0.37 days; 95% CI 0.06-0.68) and more discomfort (RR 1.77; 1.04-3.00).
- Absolute risks
not reported
- Authors' conclusion
Soy formula does not appear to lead to different general health or reproductive outcomes; findings reassuring.
6. Strengths
- Long follow-up
- Feeding assigned in original studies
7. Weaknesses
- Self-report
- Many outcomes (multiple testing)
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
Self-report; attrition unknown.
9. Assessment of the statistical interpretation
Mostly null.
10. Relevance to the specific claim
Limits C-LEG-10.
11. Independent contrary findings
None.
12. Transferability to Germany and Europe
Moderate.
13. Overall methodological judgement
Reassuring but limited.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Subtle effects.
15. Linked fact checks
- Soy phyto-oestrogens reach hormonally concerning levels in infants fed soy formula (6-11 fold the hormonally active adult dose; plasma isoflavones 13,000-22,000 times oestradiol). – Studies contradicting or limiting the claim