Nezam El-Tayebat Fact CheckA scientific assessment of the “نظام الطيبات” nutrition system
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Unclear / insufficient evidence Overinterpreted Certainty of evidence: very low provisional C-ABX-10

Antibiotic use is associated with breast cancer (archive bibliography).

In short: Unclear: some studies find a weak association between heavy antibiotic use and breast cancer, others do not, and the pattern suggests confounding rather than a causal effect.
Conclusion: Unclear: weak and inconsistent associations, causality not established.
  1. Original statement
  2. Scientific assessment
  3. Scientific evidence in detail
  4. In plain language
  5. Studies on this claim
  6. Regional context
  7. What applies in my country?
  8. References

Original statement

No Arabic original wording available.

Translation

Antibiotic use is associated with breast cancer (archive bibliography).

Origin

Source status
Archive editors
Attribution
Archive editors (eltayebat.com)
Origin
https://eltayebat.com/rule/antibiotic-overuse/
Attribution uncertainty
Archive bibliography only (A-ABX-17).
Claimed mechanism

Immune/estrogen metabolism effects.

Claimed health effect

Breast cancer.

Population concerned

Women

Geographic restriction by Elawady

none found

Scientific assessment

Unclear / insufficient evidence – The data do not allow an assessment either way.

Certainty of evidence: very low – Any assessment is very uncertain.

1. What was claimed?

Antibiotics and breast cancer.

2. What is demonstrably correct?

Velicer 2004 found a dose-related association (OR up to 2.14) (A-ABX-17).

3. What is wrong or exaggerated?

The authors wrote: 'It cannot be determined from this study whether antibiotic use is causally related to breast cancer' (A-ABX-17). A UK replication found no association (ORs 0.9-1.2, all CIs including 1; I-ABX-126); a meta-analysis of 5 case-control studies gave OR 1.175 (0.994-1.387), not statistically significant (I-ABX-125). A Korean cohort found a small association only after more than a year of cumulative use (aHR 1.15; I-ABX-127).

4. What remains unclear?

Causality.

5. Which studies support it?

A-ABX-17; I-ABX-127 (aHR 1.15 for >365 days of use).

6. Which studies contradict it?

I-ABX-126 (UK replication: no association); I-ABX-125 (pooled OR 1.175, CI includes 1); A-ABX-17 (authors' caveat).

7. What applies to Germany and Europe?

A UK primary-care study found no association (I-ABX-126).

8. What is known about Egypt?

No Egyptian data were reviewed.

9. What practical conclusion is appropriate?

Not a basis for decisions.

Assessment details

Rationale for certainty of evidence

Single case-control study; authors themselves state causality cannot be determined; confounding by indication likely.

Source quality

Archive lists the study without interpretation.

Regional scope of the claim
not specified
Last reviewed
26 October 2026 provisional

Scientific evidence in detail

Overinterpreted – A real finding exists, but the claim draws more from it than the data allow (e.g. association taken as cause, animal data applied to humans, small effect presented as large).

Research question: Is antibiotic use associated with (or causally related to) breast cancer?

Research question in detail (PECO)
Population
Women
Intervention or exposure
Cumulative antibiotic use
Comparison
Non-use
Geographic scope
Universal
Outcomes
  • Incident breast cancer

Study results as reported by the authors. Our assessment follows below.

What speaks for the claim?

What speaks against the claim?

What does the overall evidence say?

Editorial assessment based on the studies above – not itself a study result.

Which position is better supported?

Evidence for an association is weak and inconsistent; where present, it is small and lacks drug-class specificity and temporal pattern, suggesting non-causal explanations.

Why some studies weigh more

Replication studies and meta-analysis weigh more than single positive studies.

Is a causal relationship established? Not established Inconsistent results; no class specificity (Tamim 2008 screened); confounding by health-care use likely.

Remaining uncertainty

Residual small association at very high cumulative use.

Justified conclusion

Not a basis for conclusions.

Why do studies seem to disagree?

Positive (Velicer, Hong) vs null (García Rodríguez) studies differ in populations and exposure measurement; associations without specificity point to confounding.

Does this depend on the country?
General biological effects
Universal.
Eating habits
Not applicable (medicine use, not diet).
Legal rules
Not applicable.
Actual monitoring data
Not applicable.

A regional difference that changes the conclusion is not supported by robust data.

Statistical re-check
  • CI symmetry – OR 1.175 (0.994-1.387) symmetric; includes 1. recalculated
  • CI symmetry – aHR 1.15 (1.09-1.21) symmetric. recalculated
Certainty of the overall evidence (GRADE, simplified)
Main outcome
Breast cancer after antibiotic use
Starting level
low (observational studies)
Reasons for downgrading
  • inconsistency
  • risk of bias (confounding)
Result
very low

Simplified assessment by a single reviewer, following the GRADE approach; not a formal GRADE panel. GRADE rates the body of evidence for one outcome, not individual studies.

Search strategy

Documented literature searches for this review (search strings in the original database syntax).

DatabaseDateSearchLooking forHitsIncluded
Europe PMC26 October 2026TITLE:(antibiotic*) AND TITLE:("breast cancer" OR "breast neoplasm*")both directions82
Europe PMC26 October 2026(antibiotic*) AND ("breast cancer") AND (risk OR incidence) AND (PUB_TYPE:"Systematic Review" OR TITLE:"meta-analysis" OR TITLE:"systematic review")both directions1037
Europe PMC26 October 2026TITLE:(antibiotic*) AND TITLE:("breast cancer") AND PUB_YEAR:[2004 TO 2012]both directions32

Open questions

Studies with negative-control exposures.

How deeply was this checked?

4 linked studies: 0 checked in full text (0 of them with a structured risk-of-bias assessment), 4 on the basis of the abstract, 0 bibliographically only. No formal assessment with two independent reviewers and no independent human expert review has taken place yet.

Last scientific review: 26 October 2026

History of the verdict
  1. 25 October 2026 · Phase 1 · Initial assessment: Unclear / insufficient evidence (very low)
  2. 26 October 2026 · Phase 4 (systematic evidence review) · Re-examined with extended evidence; verdict unchanged: Unclear / insufficient evidence (very low)
    New studies are inconsistent and do not establish causality.
    New sources: I-ABX-125 I-ABX-126 I-ABX-127

In plain language

One study found that women who used more antibiotics were more often diagnosed with breast cancer. The authors said they could not tell whether antibiotics were the cause. This single finding is not enough to draw conclusions.

Studies on this claim

Studies supporting the claim (1)

  • Very long antibiotic use slightly linked to breast cancer in Korea

    Hong J et al.. Cancer Prev Res (Phila) 2025 · PMID 39648494 · DOI 10.1158/1940-6207.CAPR-24-0154
    Cohort studyindependent cross-checkabstract checked

    Women with over a year of total antibiotic use had a 15% higher relative risk.

    aHR 1.15 for >365 days of use

    Does the study support the specific claim? Partly · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim

    Original publication · Scientific details

    Study explained simply
    What did the researchers want to find out?

    Check antibiotic use and breast cancer in Korea

    How was the study done?

    National cohort

    How many people, animals or samples were studied?

    4.1 million women

    What was actually found?

    Small increase with long use

    How large was the observed effect?

    aHR 1.15

    What do the results mean in everyday life?

    Small; may reflect other factors

    What are the study's limitations?

    Observational

    What does it say about Elawady's specific claim?

    Weakly supports an association

    Do the results apply to Germany and Europe?

    Low

    What can explicitly not be concluded from this study?

    Cause and effect

    Scientific details →

Studies contradicting or limiting the claim (1)

  • UK study: antibiotics not linked to breast cancer

    García Rodríguez LA et al.. Am J Epidemiol 2005 · PMID 15781950 · DOI 10.1093/aje/kwi087
    Case-control studyindependent cross-checkabstract checked

    A UK replication found no rise in breast cancer with antibiotic use.

    UK replication: no association

    Does the study support the specific claim? No · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim

    Original publication · Scientific details

    Study explained simply
    What did the researchers want to find out?

    Replicate the antibiotic-breast cancer link

    How was the study done?

    Nested case-control

    How many people, animals or samples were studied?

    3708 cases

    What was actually found?

    No association

    How large was the observed effect?

    OR 1.0 to 1.2 (all CIs include 1)

    What do the results mean in everyday life?

    No sign of risk

    What are the study's limitations?

    Observational

    What does it say about Elawady's specific claim?

    Contradicts the claim

    Do the results apply to Germany and Europe?

    High

    What can explicitly not be concluded from this study?

    Not applicable

    Scientific details →

Studies with mixed or unclear results (2)

  • Antibiotics and breast cancer

    Velicer CM et al.. JAMA 2004 · PMID 14970061 · DOI 10.1001/jama.291.7.827
    Case-control studycited by the Tayebat archiveabstract checked

    More antibiotic use was linked to breast cancer, but cause and effect could not be determined.

    Does the study support the specific claim? Unclear · Methodological quality: low · Certainty of evidence: see overall assessment of the claim

    Original publication · Scientific details

    Study explained simply
    What did the researchers want to find out?

    Link.

    How was the study done?

    Case-control.

    How many people, animals or samples were studied?

    2266 cases.

    What was actually found?

    Association.

    How large was the observed effect?

    OR up to 2.14.

    What do the results mean in everyday life?

    Not proof.

    What are the study's limitations?

    Poor adjustment.

    What does it say about Elawady's specific claim?

    Unclear.

    Do the results apply to Germany and Europe?

    Moderate.

    What can explicitly not be concluded from this study?

    Causation.

    Scientific details →

  • Antibiotic use and breast cancer: weak, uncertain link

    Sergentanis TN et al.. Pharmacoepidemiol Drug Saf 2010 · PMID 20845408 · DOI 10.1002/pds.1986
    Meta-analysisindependent cross-checkabstract checked

    Pooling 5 studies gave a slightly raised but not statistically significant risk.

    Pooled OR 1.175 (0.994-1.387)

    Does the study support the specific claim? Unclear · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim

    Original publication · Scientific details

    Study explained simply
    What did the researchers want to find out?

    Pool studies on antibiotics and breast cancer

    How was the study done?

    Meta-analysis

    How many people, animals or samples were studied?

    5 studies

    What was actually found?

    Slight, uncertain association

    How large was the observed effect?

    OR 1.175 (0.994-1.387)

    What do the results mean in everyday life?

    No clear risk

    What are the study's limitations?

    Few studies

    What does it say about Elawady's specific claim?

    Neither confirms nor refutes

    Do the results apply to Germany and Europe?

    Moderate

    What can explicitly not be concluded from this study?

    Cause and effect

    Scientific details →

Regional context

Germany / EU

A UK primary-care study found no association (I-ABX-126).

Egypt

No Egyptian data were reviewed.

What applies in my country?

General scientific assessment

Unclear / insufficient evidence Unclear: weak and inconsistent associations, causality not established.

This statement concerns biological or medical relationships. The scientific assessment above applies regardless of the country; country-specific food data do not change it.

References

  1. Association between Antibiotic Use and Subsequent Risk of Breast Cancer: A Nationwide Retrospective Cohort Study in South Korea.. Hong J et al.. Cancer Prev Res (Phila) 2025 · PMID 39648494 · DOI 10.1158/1940-6207.CAPR-24-0154
  2. Use of antibiotics and risk of breast cancer.. García Rodríguez LA et al.. Am J Epidemiol 2005 · PMID 15781950 · DOI 10.1093/aje/kwi087
  3. Antibiotic use in relation to the risk of breast cancer.. Velicer CM et al.. JAMA 2004 · PMID 14970061 · DOI 10.1001/jama.291.7.827
  4. Is antibiotic use a risk factor for breast cancer? A meta-analysis.. Sergentanis TN et al.. Pharmacoepidemiol Drug Saf 2010 · PMID 20845408 · DOI 10.1002/pds.1986

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