Meta-analysisindependent cross-checkabstract checked I-WHT-111 standard review
Swapping to whole grains slightly improves cholesterol and blood sugar markers
The Effect of Replacing Refined Grains with Whole Grains on Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials with GRADE Clinical Recommendation.
Overview
Marshall S et al.. J Acad Nutr Diet 2020 · PMID 32933853 · DOI 10.1016/j.jand.2020.06.021
In 22 pooled trials, whole grains (especially oats) modestly lowered LDL cholesterol, HbA1c and CRP.
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?
Test whole vs refined grains on risk factors.
- How was the study done?
Meta-analysis of RCTs.
- How many people, animals or samples were studied?
25 RCTs.
- What was actually found?
Modest improvements.
- How large was the observed effect?
SMD -0.22 to -0.57.
- What do the results mean in everyday life?
Small benefits in markers.
- What are the study's limitations?
Short trials.
- What does it say about Elawady's specific claim?
Partly supports the claim.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Does not show fewer heart attacks.
Scientific in-depth review
1. Full reference
- Authors
- Marshall S et al.
- Journal
- J Acad Nutr Diet
- Year
- 2020
- Identifier
- PMID 32933853 DOI 10.1016/j.jand.2020.06.021
- 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
Do whole grains vs refined grains improve CVD risk factors?
3. Study design and population
- Study design
- Meta-analysis – Systematic review and meta-analysis of RCTs with GRADE
- Population
Adults with or without chronic disease
- Country
International
- Period
Searches to February 2020
- Sample size
25 RCTs (22 meta-analysed)
- Inclusion and exclusion criteria
RCTs >=12 weeks (>=2 weeks for inflammation)
4. Methods and endpoints
- Exposure / intervention
Whole grain or pseudo-grain
- Comparator
Refined grain or placebo
- Endpoints
40 CVD risk factor outcomes
- Statistical methods
SMD; Cochrane RoB; GRADE
5. Actual results
- Results
Whole-grain oats improved total cholesterol (SMD -0.54; -0.95 to -0.12) and LDL (SMD -0.57; -0.84 to -0.31); whole grains overall improved HbA1c (SMD -0.33; -0.61 to -0.04) and CRP (SMD -0.22; -0.44 to -0.00).
- Absolute risks
not reported
- Authors' conclusion
Whole grains can improve total and LDL cholesterol, HbA1c and CRP; insufficient evidence to recommend them for CVD prevention or treatment.
6. Strengths
- RCTs only
- GRADE
7. Weaknesses
- Short trials
- Effect driven partly by oats
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
Many small trials.
9. Assessment of the statistical interpretation
Standardised effects of small to moderate size on surrogate markers.
10. Relevance to the specific claim
RCT evidence that replacing refined with whole grains modestly improves some risk factors.
11. Independent contrary findings
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Moderate support for mechanism.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Hard outcomes.