Randomised controlled trialindependent cross-checkabstract checked★ key study I-WHT-122 in-depth review
Five days of gluten did not make the gut leakier in living people
Impact of Acute and Sub-Acute Gluten Exposure on Gastrointestinal Symptoms and Psychological Responses in Non-Coeliac Gluten Sensitivity: A Randomised Crossover Study.
Overview
Iven J et al.. United European Gastroenterol J 2025 · PMID 40138597 · DOI 10.1002/ueg2.70014
In 36 adults, eating 16 g of gluten daily for 5 days did not change gut permeability or inflammation markers compared with gluten-free food.
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 gluten effects in vivo.
- How was the study done?
Randomised crossover.
- How many people, animals or samples were studied?
36 adults.
- What was actually found?
No biomarker changes; symptoms not gluten-specific.
- How large was the observed effect?
No differences.
- What do the results mean in everyday life?
Lab permeability effects did not show up in people.
- What are the study's limitations?
Small, single-blind.
- What does it say about Elawady's specific claim?
Contradicts applying lab findings to everyone.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Cannot rule out long-term subtle effects.
Scientific in-depth review
1. Full reference
- Authors
- Iven J et al.
- Journal
- United European Gastroenterol J
- Year
- 2025
- Identifier
- PMID 40138597 DOI 10.1002/ueg2.70014 · PMC12463691
- Verification
- verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
One author: unrestricted grant and consultancy fees from Nestle, Danone, The Akkermansia Company (unrelated).
2. Research question
Does gluten affect symptoms, mood and biological markers including intestinal permeability in NCGS and healthy controls?
3. Study design and population
- Study design
- Randomised controlled trial – Randomised single-blind crossover trial (acute and 5-day gluten challenge)
- Population
Healthy controls and people with NCGS
- Country
not stated in abstract (Belgian/Australian funding agencies)
- Period
not stated in abstract
- Sample size
36 (20 healthy, 16 NCGS)
- Inclusion and exclusion criteria
not stated in abstract
4. Methods and endpoints
- Exposure / intervention
16 g gluten (acute) and 16 g/day gluten muffins for 5 days
- Comparator
Whey (acute) or gluten-free muffins
- Endpoints
Mood, GI symptoms, intestinal permeability, hs-CRP, cortisol awakening response
- Statistical methods
Generalised linear mixed models
5. Actual results
- Results
No group-by-nutrient interactions. Tension higher after gluten than placebo in both groups (p=0.01 acute; p=0.05 sub-acute). NCGS had more fatigue, abdominal pain and bloating regardless of gluten or placebo. No differences in biological markers (including intestinal permeability).
- Absolute risks
not reported
- Authors' conclusion
NCGS is characterised by baseline affect differences and symptoms that are not gluten-specific; nocebo effects may explain them.
6. Strengths
- In vivo permeability measured
- Includes healthy controls
- Registered
7. Weaknesses
- Single-blind
- Small
- Short exposure
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Single-blind design.
9. Assessment of the statistical interpretation
Null for biomarkers in a small sample; cannot exclude small effects.
10. Relevance to the specific claim
Direct in vivo test: 5 days of 16 g gluten/day did not change intestinal permeability or inflammation markers in healthy people or NCGS.
11. Independent contrary findings
I-WHT-121 (ex vivo effect).
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Important human counter-evidence to generalising lab findings.
| 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 | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Longer exposures.
15. Linked fact checks
- Gliadin (a wheat gluten protein) increases intestinal permeability via zonulin, which the archive presents (by listing the studies under the white-flour rule) as relevant to everyone eating white flour. – Studies contradicting or limiting the claim
- 'There is no such thing as gluten sensitivity'; the real problem is only that white flour turns into a glue-like substance. – Studies supporting the claim