Narrative reviewcited by the Tayebat archiveabstract only checked A-LEG-08 standard review
Soy and the thyroid
Goitrogenic and estrogenic activity of soy isoflavones.
Overview
Doerge DR, Sheehan DM. Environ Health Perspect 2002 · PMID 12060828 · DOI 10.1289/ehp.02110s3349
Soy compounds inhibit a thyroid enzyme in the lab, but thyroid function in rats stayed normal; iodine deficiency is key.
Does the study support the specific claim? Unclear · Methodological quality: low
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Review soy toxicity
- How was the study done?
Narrative review
- How many people, animals or samples were studied?
Animal/in-vitro
- What was actually found?
Enzyme inhibition, no overt thyroid disease
- How large was the observed effect?
Up to 80% TPO reduction (rat)
- What do the results mean in everyday life?
Iodine sufficiency matters.
- What are the study's limitations?
Animal data
- What does it say about Elawady's specific claim?
Indirect
- Do the results apply to Germany and Europe?
Low
- What can explicitly not be concluded from this study?
Cannot show human harm.
Scientific in-depth review
1. Full reference
- Authors
- Doerge DR, Sheehan DM
- Journal
- Environ Health Perspect
- Year
- 2002
- Identifier
- PMID 12060828 DOI 10.1289/ehp.02110s3349 · PMC1241182
- Verification
- verified – PubMed E-utilities efetch, 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Oestrogenic and goitrogenic activity of soy isoflavones.
3. Study design and population
- Study design
- Narrative review – Narrative review incl. rat and in-vitro data
- Population
Rats, humans (review)
- Country
Not applicable
- Period
Not applicable
- Sample size
Not applicable
- Inclusion and exclusion criteria
Not reported
4. Methods and endpoints
- Exposure / intervention
Genistein/soy
- Comparator
Not applicable
- Endpoints
Thyroid peroxidase, thyroid function
- Statistical methods
Not applicable
5. Actual results
- Results
Genistein inactivated thyroid peroxidase in vitro (rat TPO reduced up to 80%), but serum T3, T4, TSH, thyroid weight and histology in rats were normal; iodine deficiency increases antithyroid effects; additional factors needed for overt toxicity.
- Absolute risks
not reported
- Authors' conclusion
Possible harm via oestrogenic/goitrogenic activity is of concern; rigorous research needed.
6. Strengths
- Mechanistic detail
7. Weaknesses
- Animal/in-vitro
- Authors' concern-oriented framing
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- not assessable
- Rationale
Narrative review.
9. Assessment of the statistical interpretation
Not applicable.
10. Relevance to the specific claim
Mixed relevance for C-LEG-10.
11. Independent contrary findings
Normal in-vivo thyroid measures in the same data.
12. Transferability to Germany and Europe
Low.
13. Overall methodological judgement
Hypothesis-level evidence.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | low |
| Risk of bias | not assessable |
| Precision of results | not applicable |
| Directness | very indirect |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | low |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Human relevance with adequate iodine.
15. Linked fact checks
Use by the Tayebat archive
Note: according to the archive, the studies were compiled by the archive operators. Whether Dr. Elawady himself cited this study is not established.
- What the archive says about the study
Bibliography only.
- A. What was actually studied?
Soy isoflavone thyroid/oestrogen effects.
- B. What did the authors find?
TPO inhibition without in-vivo thyroid dysfunction in rats; iodine critical.
- C. What conclusions do the authors themselves draw?
Concern; research needed.
- D. What does the archive derive from it?
Supports soy concern.
- E. Is this derivation scientifically justified?
Concern is legitimate as a research question; does not show harm and does not concern fava/lentils.
- Adequacy of the interpretation (by the archive)
- not applicable