Risk assessmentindependent cross-checkabstract only checked★ key study I-CAN-02 in-depth review
Four in ten cancers in the USA are linked to avoidable risk factors, led by smoking
Proportion and number of cancer cases and deaths attributable to potentially modifiable risk factors in the United States, 2019.
Overview
Islami F et al.. CA Cancer J Clin 2024 · PMID 38990124 · DOI 10.3322/caac.21858
Smoking accounted for 19% of cancers and 29% of cancer deaths; excess weight and alcohol followed.
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?
Estimate preventable cancers.
- How was the study done?
PAF analysis.
- How many people, animals or samples were studied?
US 2019.
- What was actually found?
40% of cases attributable.
- How large was the observed effect?
Smoking 19.3%/28.5%.
- What do the results mean in everyday life?
Not smoking, healthy weight, less alcohol and a diet with fibre, fruit and vegetables lower risk.
- What are the study's limitations?
Model assumptions.
- What does it say about Elawady's specific claim?
Diet matters but is not the main cause.
- Do the results apply to Germany and Europe?
Moderate.
- What can explicitly not be concluded from this study?
Individual cause.
Scientific in-depth review
1. Full reference
- Authors
- Islami F et al.
- Journal
- CA Cancer J Clin
- Year
- 2024
- Identifier
- PMID 38990124 DOI 10.3322/caac.21858
- Verification
- verified – PubMed esummary + efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Cancer cases/deaths attributable to modifiable risk factors.
3. Study design and population
- Study design
- Risk assessment – Population attributable fraction analysis
- Population
US adults >=30 y
- Country
USA
- Period
2019
- Sample size
1,781,649 cancers; 595,737 deaths
- Inclusion and exclusion criteria
Invasive cancers excl. non-melanoma skin
4. Methods and endpoints
- Exposure / intervention
Smoking, second-hand smoke, excess weight, alcohol, red/processed meat, low fruit/vegetables, low fibre, low calcium, inactivity, UV, 7 infections
- Comparator
Theoretical minimum exposure
- Endpoints
Attributable cases and deaths
- Statistical methods
PAF from national prevalence and pooled RRs
5. Actual results
- Results
40.0% of cancers and 44.0% of cancer deaths attributable to evaluated factors. Smoking 19.3% of cases and 28.5% of deaths; excess body weight 7.6%/7.3%; alcohol 5.4%/4.1%. For 19 of 30 cancers, >50% attributable.
- Absolute risks
713,340 cases and 262,120 deaths attributable in 2019
- Authors' conclusion
Large numbers of cancers are preventable through modifiable risk factors.
6. Strengths
- Up-to-date national data
- Multiple risk factors
7. Weaknesses
- Assumes causal RRs
- US-specific prevalence
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Model-based; depends on RR inputs.
9. Assessment of the statistical interpretation
Diet-related factors (red/processed meat, low fruit/vegetables, fibre, calcium) contribute, but smoking dominates.
10. Relevance to the specific claim
Ranks causes of cancer: smoking first; diet one of several; low fruit/vegetable/fibre/calcium intake counted as risk factors.
11. Independent contrary findings
12. Transferability to Germany and Europe
Moderate.
13. Overall methodological judgement
Key causation context.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| 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
Egyptian estimates.
15. Linked fact checks
- Smoking (and similar exposures) should not be blamed for cancer; only massive exposures such as Hiroshima cause cancer, and there is 'no such thing as early death' from smoking. – Studies contradicting or limiting the claim
- Cancer is the body's own plan ('a self plan'): body cells are ordered to transform because this was necessary for the person's life; it is not caused by external agents. – 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
- 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 with mixed or unclear results
- The idea that 'sugar feeds cancer' should be dropped: sugar feeds every cell (and microbe), so cancer patients need not fear sugar. – Studies with mixed or unclear results
- Chronic disease is mostly a cumulative reaction to what enters the body daily - contaminated food, medicines and cosmetics - not a fate that comes from outside. – Studies contradicting or limiting the claim
- Cigarettes are beneficial or at least not harmful: asked whether cigarettes are beneficial he answered 'Yes, beneficial'; elsewhere he said smoking has nothing to do with atherosclerosis and is 'not harmful at all' organically. – Studies contradicting or limiting the claim