Meta-analysisindependent cross-checkabstract checked★ key study I-CAN-114 in-depth review
Which foods affect bowel cancer risk
Foods and beverages and colorectal cancer risk: a systematic review and meta-analysis of cohort studies, an update of the evidence of the WCRF-AICR Continuous Update Project.
Overview
Vieira AR et al.. Ann Oncol 2017 · PMID 28407090 · DOI 10.1093/annonc/mdx171
More red/processed meat and alcohol raised bowel cancer risk; whole grains and dairy lowered it; poultry and legumes showed no link.
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?
Foods and colorectal cancer.
- How was the study done?
Meta-analysis of 111 cohorts.
- How many people, animals or samples were studied?
Millions of adults.
- What was actually found?
Meat/alcohol up; whole grains/dairy down.
- How large was the observed effect?
Dairy RR ~0.87 per 400 g/d; meat RR 1.12 per 100 g/d.
- What do the results mean in everyday life?
Banning dairy or legumes is not supported for bowel cancer prevention.
- What are the study's limitations?
Observational.
- What does it say about Elawady's specific claim?
Partly supports, partly contradicts the forbidden-food list.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Effects for every cancer type.
Scientific in-depth review
1. Full reference
- Authors
- Vieira AR et al.
- Journal
- Ann Oncol
- Year
- 2017
- Identifier
- PMID 28407090 DOI 10.1093/annonc/mdx171
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
WCRF/AICR CUP; COI not stated in abstract
2. Research question
Dose-response between foods/beverages and colorectal cancer risk
3. Study design and population
- Study design
- Meta-analysis – Systematic review and dose-response meta-analysis of cohort studies (WCRF/AICR Continuous Update Project)
- Population
Adults in 111 prospective cohorts
- Country
International
- Period
Searches to 31 May 2015
- Sample size
About 400 study estimates from 111 cohorts
- Inclusion and exclusion criteria
Prospective studies with adjusted RRs
4. Methods and endpoints
- Exposure / intervention
Food groups and beverages
- Comparator
Per-increment dose-response
- Endpoints
Colorectal cancer incidence
- Statistical methods
Random-effects dose-response meta-analysis
5. Actual results
- Results
Red and processed meat +12% per 100 g/day (95% CI 4-21%, I2 70%); alcohol +7% per 10 g/day ethanol (5-9%); whole grains -17% per 90 g/day (11-21%, I2 0%); dairy -13% per 400 g/day (10-17%, I2 18%). Vegetables weakly inverse (RR 0.98 per 100 g/d). Fruits, coffee, tea, cheese, poultry and legumes not associated.
- Absolute risks
not reported
- Authors' conclusion
Red/processed meat and alcohol increase CRC risk; milk and whole grains may be protective.
6. Strengths
- Large, systematic, dose-response
- Low heterogeneity for dairy and whole grains
7. Weaknesses
- Observational
- Search to 2015
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
Standardised CUP methods (abstract-level judgement).
9. Assessment of the statistical interpretation
Percentages converted to RRs; small apparent CI asymmetry explained by rounding of percentage limits.
10. Relevance to the specific claim
Directly tests foods the Tayebat system forbids (dairy, poultry, legumes) against colorectal cancer: no harm signal; dairy inversely associated.
11. Independent contrary findings
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Contradicts the cancer-prevention rationale for banning dairy, poultry and legumes; supports limiting processed meat and alcohol.
| 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
Other cancer sites (e.g. prostate and dairy).
15. Linked fact checks
- Cross-system summary: avoiding the system's forbidden foods (industrial eggs, chicken, dairy, white flour, UPF, soft drinks, leafy greens, legumes, acid blockers, supplements) prevents cancer. – Studies contradicting or limiting the claim
- Third-party site: the Tayebat system can serve as a preventive lifestyle against cancer (less processed meat, refined sugar, fried food, soft drinks), not as treatment; cancer patients must follow their oncology team and keep screening. – Studies supporting the claim