Meta-analysisindependent cross-checkabstract only checked★ key study I-WHT-01 in-depth review
Fibre and whole grains and health
Carbohydrate quality and human health: a series of systematic reviews and meta-analyses.
Overview
Reynolds A et al.. Lancet 2019 · PMID 30638909 · DOI 10.1016/S0140-6736(18)31809-9
High fibre/whole grain intake linked to 15-30% lower risk of several diseases; GI/GL evidence weaker.
Does the study support the specific claim? Partly · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Carbohydrate quality
- How was the study done?
Systematic reviews with GRADE
- How many people, animals or samples were studied?
185 cohorts, 58 trials
- What was actually found?
Fibre and whole grain protective
- How large was the observed effect?
15-30% lower risk
- What do the results mean in everyday life?
Eat more fibre and whole grains
- What are the study's limitations?
Observational core
- What does it say about Elawady's specific claim?
Supports whole grains, not glue mechanism; GI/GL arguments weak
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
Harm from moderate refined grains
Scientific in-depth review
1. Full reference
- Authors
- Reynolds A et al.
- Journal
- Lancet
- Year
- 2019
- Identifier
- PMID 30638909 DOI 10.1016/S0140-6736(18)31809-9
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
Erratum: Lancet 2019;393(10170):406
- Extent checked
- abstract only
- Conflicts of interest and funding
Funding: Health Research Council of NZ, WHO, others (abstract). Erratum published (Lancet 2019;393:406).
2. Research question
Which carbohydrate-quality markers predict NCD outcomes?
3. Study design and population
- Study design
- Meta-analysis – Series of systematic reviews/meta-analyses of cohorts and RCTs with GRADE (WHO-commissioned)
- Population
Adults without chronic disease
- Country
Global
- Period
Cohorts to April 2017; RCTs to Feb 2018
- Sample size
185 prospective studies, 58 trials (4635 participants); ~135 million person-years
- Inclusion and exclusion criteria
Excluded chronic disease, weight-loss and supplement trials
4. Methods and endpoints
- Exposure / intervention
Dietary fibre, whole grains, GI/GL
- Comparator
Lower intakes
- Endpoints
Mortality, CHD, stroke, T2D, colorectal cancer, risk factors
- Statistical methods
Random effects; GRADE
5. Actual results
- Results
Highest vs lowest fibre: 15-30% lower all-cause and CV mortality, CHD, stroke, T2D, colorectal cancer; greatest risk reduction at 25-29 g/day; similar findings for whole grains; smaller or no reductions for low GI/GL. Certainty: moderate (fibre), low to moderate (whole grains), low to very low (GI/GL).
- Absolute risks
not reported in abstract
- Authors' conclusion
Replace refined grains with whole grains and increase fibre.
6. Strengths
- Comprehensive, GRADE
7. Weaknesses
- Observational core
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Duplicate extraction, GRADE.
9. Assessment of the statistical interpretation
Relative reductions.
10. Relevance to the specific claim
Overall body of evidence on whole grains/fibre (C-WHT-04/05) and the low certainty of GI/GL (relevant to C-FRU-01).
11. Independent contrary findings
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Key reference: whole grain and fibre benefits are well supported; GI/GL evidence weak.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | high |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- Replacing refined grains with whole grains lowers all-cause mortality by 17% and coronary heart disease by 19%, while refined grains offer no protective benefit (archive interpretation of Aune 2016). – Studies supporting the claim
- Diets rich in rapidly absorbed carbohydrates (high glycaemic index/load) and poor in cereal fibre raise type 2 diabetes risk by about 50%, and each 10 g/day of cereal fibre lowers risk by 25%; refined flour therefore promotes diabetes. – Studies with mixed or unclear results
- Heavy intake of refined grains (white bread etc.) is associated in the largest population studies with higher mortality and major cardiovascular disease (archive: PURE, +27% mortality, +33% major cardiovascular events at >=350 g/day). – Studies with mixed or unclear results
- Freekeh and corn (maize) are allowed staple carbohydrates. – Studies supporting the claim