Cross-sectional studyindependent cross-checkabstract checked I-SRC-122 standard review
Caffeine and constipation
Association Between Caffeine Intake and Stool Frequency- or Consistency-Defined Constipation: Data From the National Health and Nutrition Examination Survey 2005-2010.
Overview
Li Y et al.. J Neurogastroenterol Motil 2025 · PMID 40205901 · DOI 10.5056/jnm23181
In 13,941 US adults, caffeine intake was not linked to constipation.
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?
Test caffeine-constipation link
- How was the study done?
Cross-sectional survey
- How many people, animals or samples were studied?
13,941 adults
- What was actually found?
No association
- How large was the observed effect?
OR 1.01 per 100 mg
- What do the results mean in everyday life?
Caffeine drinks do not seem to constipate
- What are the study's limitations?
Not tea-specific
- What does it say about Elawady's specific claim?
Indirectly contradicts the claim
- Do the results apply to Germany and Europe?
Moderate
- What can explicitly not be concluded from this study?
Effect of tea tannins
Scientific in-depth review
1. Full reference
- Authors
- Li Y et al.
- Journal
- J Neurogastroenterol Motil
- Year
- 2025
- Identifier
- PMID 40205901 DOI 10.5056/jnm23181
- Verification
- verified – PubMed efetch 2026-10-26; Crossref works record checked
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
No conflicts.
2. Research question
Is caffeine intake associated with constipation?
3. Study design and population
- Study design
- Cross-sectional study – Cross-sectional analysis (NHANES 2005-2010)
- Population
US adults
- Country
USA
- Period
2005-2010
- Sample size
13,941
- Inclusion and exclusion criteria
Adults with bowel-health questionnaire and diet data
4. Methods and endpoints
- Exposure / intervention
Caffeine intake (per 100 mg)
- Comparator
Lower intake
- Endpoints
Constipation defined by stool frequency or consistency
- Statistical methods
Weighted logistic regression
5. Actual results
- Results
Per 100 mg more caffeine: OR 1.01 (0.94-1.10) for frequency-defined and 1.01 (0.98-1.05) for consistency-defined constipation; inverse association only in a high-cholesterol-intake subgroup (OR 0.80, 0.64-1.00).
- Absolute risks
not applicable
- Authors' conclusion
Caffeine consumption is not associated with constipation.
6. Strengths
- Large national sample
7. Weaknesses
- Cross-sectional
- Caffeine from all sources, not tea specifically
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
Cross-sectional; subgroup finding likely chance (multiplicity).
9. Assessment of the statistical interpretation
Null main estimate with narrow CI; subgroup interaction (p=0.037) is exploratory.
10. Relevance to the specific claim
Indirect evidence against 'tea causes constipation' via its main active compound (caffeine). No tea-specific outcome study was found.
11. Independent contrary findings
Tannins could act differently from caffeine (not studied here).
12. Transferability to Germany and Europe
US data.
13. Overall methodological judgement
Weak indirect evidence; constipation claim remains unstudied for tea itself.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | high |
| Directness | indirect |
| Reproducibility | unknown |
| Consistency with the overall evidence | unknown |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Tea-specific constipation studies.