Meta-analysisindependent cross-checkabstract checked★ key study I-WHT-108 in-depth review
Whole grains linked to lower heart risk; refined grains mostly neutral
Consumption of whole grains and refined grains and associated risk of cardiovascular disease events and all-cause mortality: a systematic review and dose-response meta-analysis of prospective cohort studies.
Overview
Hu H et al.. Am J Clin Nutr 2023 · PMID 36789934 · DOI 10.1016/j.ajcnut.2022.10.010
In 1.6 million people, each 30 g/day of whole grains was linked to 6-8% lower CVD and death risk; refined grains showed no clear link with heart disease.
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?
Summarise grain intake and CVD/death.
- How was the study done?
Meta-analysis of cohorts.
- How many people, animals or samples were studied?
1,624,407 participants.
- What was actually found?
Whole grains protective; refined mostly null.
- How large was the observed effect?
Mortality RR 0.94 per 30 g whole grain.
- What do the results mean in everyday life?
Choose whole grains; moderate white bread not shown harmful.
- What are the study's limitations?
Observational.
- What does it say about Elawady's specific claim?
Supports whole-grain claim; weakens refined-harm claim.
- Do the results apply to Germany and Europe?
Moderate-high.
- What can explicitly not be concluded from this study?
Cannot prove causation.
Scientific in-depth review
1. Full reference
- Authors
- Hu H et al.
- Journal
- Am J Clin Nutr
- Year
- 2023
- Identifier
- PMID 36789934 DOI 10.1016/j.ajcnut.2022.10.010
- 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
not stated in abstract
2. Research question
How are whole and refined grain intakes associated with CVD events and all-cause mortality?
3. Study design and population
- Study design
- Meta-analysis – Systematic review and dose-response meta-analysis of prospective cohorts (NutriGrade)
- Population
Adults in prospective cohorts
- Country
International
- Period
Searches to 15 March 2022
- Sample size
24 articles (68 studies: 46 whole grain, 22 refined grain); 1,624,407 participants
- Inclusion and exclusion criteria
Prospective cohorts
4. Methods and endpoints
- Exposure / intervention
Whole grains; refined grains
- Comparator
Lower intake
- Endpoints
Stroke, CHD, heart failure, CVD, all-cause mortality
- Statistical methods
Random effects; restricted cubic splines; NutriGrade
5. Actual results
- Results
Per 30 g/day whole grain: stroke RR 0.98 (0.96-1.00), CHD 0.94 (0.92-0.97), HF 0.97 (0.89-1.07), CVD 0.92 (0.88-0.96), all-cause mortality 0.94 (0.92-0.97). Refined grains: no significant association with stroke, CHD, HF or CVD; positive association with all-cause mortality only in the restricted cubic spline. Meta-evidence quality: whole grains moderate-high; all refined-grain evidence low.
- Absolute risks
not reported
- Authors' conclusion
Whole grains rather than refined grains may help prevent CHD, CVD and mortality; refined-grain associations should be interpreted cautiously (low-quality evidence).
6. Strengths
- Large, recent
- Dose-response
- Evidence grading
7. Weaknesses
- Observational
- Overlap with Aune 2016 cohorts
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Observational primary studies; overlap with earlier meta-analyses.
9. Assessment of the statistical interpretation
Per 30 g RR 0.94 corresponds to about 0.83 per 90 g, consistent with Aune 2016 (stats/C-WHT-03_04).
10. Relevance to the specific claim
Confirms whole-grain benefit; finds refined grains largely not associated with CVD, with low-quality evidence for mortality.
11. Independent contrary findings
PURE (A-WHT-01) found harm at very high refined intake.
12. Transferability to Germany and Europe
Moderate-high.
13. Overall methodological judgement
Key updated synthesis; overlaps with A-WHT-02 (not independent confirmation).
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | high |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Refined-grain effects at very high intakes in low/middle-income countries.
15. Linked fact checks
- 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 contradicting or limiting the claim
- 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