Randomised controlled trialindependent cross-checkabstract checked I-WHT-119 standard review
Glycaemic index did not affect heartburn, but carbohydrate amount did
Higher Carbohydrate Amount and Lower Glycemic Index Increase Hunger, Diet Satisfaction, and Heartburn in Overweight and Obese Adults in the OmniCarb Randomized Clinical Trial.
Overview
Wu Y et al.. J Nutr 2021 · PMID 34049396 · DOI 10.1093/jn/nxab128
In a feeding trial, high-GI diets did not increase heartburn, while higher-carbohydrate diets increased it by about half.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Carbohydrate and symptoms.
- How was the study done?
Crossover feeding trial.
- How many people, animals or samples were studied?
163 adults.
- What was actually found?
GI no effect; amount increased heartburn.
- How large was the observed effect?
RR 1.49 vs 0.89.
- What do the results mean in everyday life?
Refinement per se may not drive heartburn.
- What are the study's limitations?
Not GERD patients.
- What does it say about Elawady's specific claim?
Contradicts specific blame on refined flour.
- Do the results apply to Germany and Europe?
Moderate.
- What can explicitly not be concluded from this study?
Cannot test white-flour elimination.
Scientific in-depth review
1. Full reference
- Authors
- Wu Y et al.
- Journal
- J Nutr
- Year
- 2021
- Identifier
- PMID 34049396 DOI 10.1093/jn/nxab128 · PMC8349117
- 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
NIH grants
2. Research question
Do carbohydrate amount and glycaemic index affect hunger, satisfaction and GI symptoms?
3. Study design and population
- Study design
- Randomised controlled trial – Randomised crossover feeding trial (OmniCarb), secondary outcomes
- Population
Overweight or obese adults
- Country
USA
- Period
not stated (NCT00608049)
- Sample size
163
- Inclusion and exclusion criteria
BMI >=25
4. Methods and endpoints
- Exposure / intervention
High GI (>=65) and/or high carbohydrate (58% kcal) DASH-style diets, 5 weeks each
- Comparator
Low GI (<=45), low carbohydrate (40% kcal)
- Endpoints
Hunger, satisfaction, GI symptoms incl. heartburn
- Statistical methods
Relative risks in crossover
5. Actual results
- Results
All diets decreased heartburn vs baseline. Higher vs lower carbohydrate: heartburn RR 1.49 (1.09-2.04). Higher vs lower GI: heartburn RR 0.89 (0.70-1.13), i.e. no effect.
- Absolute risks
not reported
- Authors' conclusion
Higher carbohydrate amount can increase heartburn in overweight adults.
6. Strengths
- Controlled feeding
- Crossover
7. Weaknesses
- Secondary outcomes
- Not GERD patients
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
Secondary analysis.
9. Assessment of the statistical interpretation
CIs log-symmetric (stats/C-WHT-08); GI (a proxy for refined starch) did not affect heartburn.
10. Relevance to the specific claim
Contradicts the idea that refined (high-GI) carbohydrate specifically causes reflux: GI had no effect on heartburn; total carbohydrate amount did.
11. Independent contrary findings
12. Transferability to Germany and Europe
Moderate.
13. Overall methodological judgement
Useful controlled-feeding evidence.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | indirect |
| Reproducibility | not replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
GERD patients.
15. Linked fact checks
- Stopping all white-flour products for about 5-10 days (in one video: within seven days) resolves reflux so that acid-reducing medicines are no longer needed. – Studies contradicting or limiting the claim