Meta-analysisindependent cross-checkabstract checked★ key study I-WHT-110 in-depth review
No long trials have tested whether whole grains prevent heart attacks
Whole grain cereals for the primary or secondary prevention of cardiovascular disease.
Overview
Kelly SA et al.. Cochrane Database Syst Rev 2017 · PMID 28836672 · DOI 10.1002/14651858.CD005051.pub3
A Cochrane review found 9 short trials and none measured heart attacks or deaths; cholesterol did not change.
Does the study support the specific claim? No · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test whole grains in RCTs.
- How was the study done?
Cochrane review.
- How many people, animals or samples were studied?
1414 participants.
- What was actually found?
No hard-outcome data; no lipid effect.
- How large was the observed effect?
MD 0.07 mmol/L.
- What do the results mean in everyday life?
Evidence for whole grains is observational.
- What are the study's limitations?
Short, small trials.
- What does it say about Elawady's specific claim?
Limits the causal claim.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Does not show whole grains are useless.
Scientific in-depth review
1. Full reference
- Authors
- Kelly SA et al.
- Journal
- Cochrane Database Syst Rev
- Year
- 2017
- Identifier
- PMID 28836672 DOI 10.1002/14651858.CD005051.pub3 · PMC6484378
- Verification
- verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
- Retracted
- no
- Corrections
Update of the 2007 Cochrane review (CD005051.pub2); no retraction.
- Extent checked
- abstract only
- Conflicts of interest and funding
One author reported consultancy with Unilever and a patent; review funded by Department of Health (UK).
2. Research question
Do whole grain diets prevent cardiovascular disease?
3. Study design and population
- Study design
- Meta-analysis – Cochrane systematic review and meta-analysis of RCTs (GRADE)
- Population
Healthy adults or at increased CVD risk
- Country
International
- Period
Searches to August 2016
- Sample size
9 RCTs, 1414 participants
- Inclusion and exclusion criteria
RCTs >=12 weeks, whole grain vs refined/lower whole grain
4. Methods and endpoints
- Exposure / intervention
Whole grain diets
- Comparator
Refined grain or lower whole grain
- Endpoints
Mortality, CVD events, lipids, blood pressure
- Statistical methods
Fixed-effect MD; GRADE
5. Actual results
- Results
No trials reported CVD mortality or events. Total cholesterol MD 0.07 mmol/L (-0.07 to 0.21; 6 studies, 722 participants; low quality). All trials unclear/high risk of bias; none longer than 16 weeks; several partly funded by cereal-interested organisations.
- Absolute risks
not reported
- Authors' conclusion
Insufficient RCT evidence of an effect of whole grain diets on CVD outcomes or major risk factors.
6. Strengths
- Cochrane methods
- GRADE
7. Weaknesses
- Few small short trials
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
High-quality review of low-quality trials.
9. Assessment of the statistical interpretation
No hard-outcome RCTs exist; risk-factor effects null.
10. Relevance to the specific claim
Limits causal wording: RCTs have not shown that swapping refined for whole grains lowers CVD events.
11. Independent contrary findings
I-WHT-111 (some risk-factor improvements in a broader 2020 meta-analysis).
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Important limitation.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | low |
| Directness | direct |
| Reproducibility | not replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Long-term outcome trials.