Systematic reviewindependent cross-checkabstract only checked I-INTA-12 in-depth review
What causes bad breath?
Aetiology and associations of halitosis: A systematic review.
Overview
Memon MA et al.. Oral diseases 2023 · PMID 35212093 · DOI 10.1111/odi.14172
80-90% of bad breath comes from the mouth itself (tongue coating, gum disease, poor hygiene).
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Causes of halitosis
- How was the study done?
Systematic review
- How many people, animals or samples were studied?
Studies 2014-2020
- What was actually found?
Mostly intra-oral causes
- How large was the observed effect?
80-90% intra-oral
- What do the results mean in everyday life?
Bad breath is usually treated in the mouth, not by avoiding eggs
- What are the study's limitations?
Narrative synthesis
- What does it say about Elawady's specific claim?
Contradicts eggs as a general cause of bad breath
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
Individual food-related odours
Scientific in-depth review
1. Full reference
- Authors
- Memon MA et al.
- Journal
- Oral diseases
- Year
- 2023
- Identifier
- PMID 35212093 DOI 10.1111/odi.14172
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Intra-oral and extra-oral causes and associations of halitosis
3. Study design and population
- Study design
- Systematic review – Systematic review
- Population
Studies on people with halitosis
- Country
Multinational
- Period
January 2014 to December 2020
- Sample size
not stated in abstract
- Inclusion and exclusion criteria
MEDLINE, Google Scholar, Wiley; studies on causes of oral malodour
4. Methods and endpoints
- Exposure / intervention
Intra-oral and extra-oral factors
- Comparator
Not applicable
- Endpoints
Halitosis
- Statistical methods
Narrative synthesis
5. Actual results
- Results
80-90% of halitosis is caused by intra-oral factors (coated tongue, periodontal disease, poor oral hygiene); 10-20% by extra-oral factors associated with systemic diseases.
- Absolute risks
Not applicable
- Authors' conclusion
Most halitosis is of intra-oral origin.
6. Strengths
- Systematic search
7. Weaknesses
- Narrative synthesis
- Limited time window
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
Simplified.
9. Assessment of the statistical interpretation
Proportions summarised from included studies.
10. Relevance to the specific claim
Bad breath mainly has oral causes; eggs are not an established cause.
11. Independent contrary findings
Food odours can cause transient breath odour (not assessed here).
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Reliable overview.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | not applicable |
| Directness | indirect |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
None for this claim.
15. Linked fact checks
- Food should not be judged by its nutrient components (such as choline and lecithin in eggs); eggs cause sinus allergy, fermentation in the stomach, bad breath, protein leakage into the urine, Alzheimer's disease, foul-smelling discharge and recurrent vaginal infections (the passage continues with recurrent urinary infections). – Studies contradicting or limiting the claim