Meta-analysisindependent cross-checkfull text checked★ key study I-DRY-03 in-depth review
Hip fractures: milk neutral, yogurt and cheese linked to fewer fractures
Dairy product consumption and risk of hip fracture: a systematic review and meta-analysis.
Overview
Bian S et al.. BMC Public Health 2018 · PMID 29357845 · DOI 10.1186/s12889-018-5041-5
Yogurt RR 0.75 and cheese RR 0.68 in 3 cohort studies each; milk RR 0.91 (not significant), though the cohort dose curve rose up to about 600 g/day.
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?
Dairy and hip fracture.
- How was the study done?
Meta-analysis of 18 studies.
- How many people, animals or samples were studied?
Adults.
- What was actually found?
Milk overall null (cohorts) with a rising nonlinear dose curve; yogurt and cheese linked to fewer fractures in few studies.
- How large was the observed effect?
Yogurt RR 0.75 (0.66-0.86).
- What do the results mean in everyday life?
Milk does not seem to increase fractures.
- What are the study's limitations?
Observational; high heterogeneity for milk; only 3 cohorts for yogurt and cheese; case-control recall bias.
- What does it say about Elawady's specific claim?
Does not support a clear milk-fracture harm, but does not fully exclude a modest increase at high intake; contradicts banning yogurt on bone grounds.
- Do the results apply to Germany and Europe?
Includes Europe.
- What can explicitly not be concluded from this study?
Causation.
Scientific in-depth review
1. Full reference
- Authors
- Bian S et al.
- Journal
- BMC Public Health
- Year
- 2018
- Identifier
- PMID 29357845 DOI 10.1186/s12889-018-5041-5
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- full text
- Conflicts of interest and funding
Competing interests: none declared. Funding: National Natural Science Foundation of China (grant no. 81702110).
2. Research question
Dairy product consumption and hip fracture risk.
3. Study design and population
- Study design
- Meta-analysis – Systematic review and meta-analysis of observational studies (PubMed, EMBASE to 17 April 2017, no language restriction): 10 cohort studies (one of which is the Kanis pooled analysis of 6 cohorts) and 8 case-control studies, pooled separately with random-effects models; Greenland-Longnecker dose-response for milk; NOS quality scoring.
- Population
Adults in cohort and case-control studies
- Country
Multinational
- Period
Search to April 2017
- Sample size
18 studies; 381,987 participants. Cohorts: 363,557 participants, 8,613 hip fractures, follow-up 3-22 years. Case-control: 3,815 cases, 6,415 controls.
- Inclusion and exclusion criteria
Cohort or case-control studies with clearly defined exposure to total dairy, milk, cheese, yogurt or cream; hip fracture defined by ICD-10 or medical records; reporting OR/RR with 95% CI; most recent publication per study. Excluded letters, reviews, comments, animal studies; Bischoff-Ferrari meta-analysis excluded (duplicate data), Kanis meta-analysis included.
4. Methods and endpoints
- Exposure / intervention
Milk, yogurt, cheese, cream, total dairy.
- Comparator
Highest vs lowest intake category; milk per 200 g/day.
- Endpoints
Hip fracture.
- Statistical methods
Random-effects pooling by design; I2 and Q; subgroup and meta-regression; Egger, Begg, contour-enhanced funnel plots, trim-and-fill; linear and nonlinear dose-response (milk only).
5. Actual results
- Results
Cohorts, highest vs lowest: milk RR 0.91 (0.74-1.12; 9 studies, I2 = 75%); yogurt 0.75 (0.66-0.86; 3 studies); cheese 0.68 (0.61-0.77; 3 studies); total dairy 1.02 (0.93-1.12; 2 studies); cream not associated (1 study). Trim-and-fill for milk (cohorts) 1.06 (0.91-1.23). Case-control: milk OR 0.71 (0.55-0.91; I2 = 54%); trim-and-fill 0.74 (0.57-0.97); yogurt, cheese, total dairy not associated. Dose-response per 200 g/day milk: cohorts RR 1.00 (0.94-1.07; I2 = 87%), case-control OR 0.89 (0.64-1.24; I2 = 68%). Nonlinear cohort dose-response (7 studies): positive association with a rapid increase in risk from 0 to 600 g/day and no further increase from 600 to 1,200 g/day (P nonlinearity <0.01).
- Absolute risks
not reported in full text
- Authors' conclusion
Yogurt and cheese were associated with lower hip-fracture risk in cohort studies; total dairy and cream were not associated; the evidence on milk is inconsistent and no conclusion can be drawn; a lower threshold of 200 g/day milk may be beneficial while effects of higher intake are unclear.
6. Strengths
- Duplicate independent screening, extraction and quality assessment
- Cohort and case-control studies pooled separately
- Dose-response and nonlinear analyses for milk; publication-bias assessment
7. Weaknesses
- Yogurt and cheese estimates rest on only 3 cohort studies each, cream on 1; no subgroup or heterogeneity analysis possible for them
- High heterogeneity for milk (I2 75-87%)
- Inclusion of a pooled meta-analysis (Kanis) as one 'study' alongside primary studies risks overlap
- Case-control studies prone to recall bias and diet change after fracture
- No registered protocol reported; NOS only
- Abstract statement that 200 g/day 'may have beneficial effects' is not well matched by the cohort nonlinear curve, which shows rising risk from 0 to 600 g/day
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- structured assessment based on the full text by a single reviewer (no formal double review)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Simplified single-reviewer AMSTAR 2 from full text (one critical weakness: no registered protocol; several partial). Corresponds to low confidence on AMSTAR 2 rating rules. A formal assessment needs two independent reviewers.
| Domain | Judgement | Rationale |
|---|---|---|
| Item 2 protocol registered (critical) | high | A protocol is mentioned in author contributions but no registration or a priori protocol is reported. |
| Item 4 comprehensive search (critical) | some concerns | Two databases, no language restriction, reference lists; no grey literature. |
| Items 5-6 duplicate selection and extraction | low | Two independent investigators for each. |
| Item 7 list of excluded studies (critical) | some concerns | Selection procedure in supplement; reasons partly given in flowchart. |
| Item 9 risk of bias of included studies (critical) | some concerns | NOS applied to 17 studies; not applied to the included pooled analysis. |
| Item 11 appropriate meta-analytic methods (critical) | some concerns | Random effects, designs separated; but pooled analysis included with primary cohorts and yogurt/cheese based on 3 studies. |
| Item 13 risk of bias in interpretation (critical) | some concerns | Limitations discussed in detail; but yogurt/cheese benefit stated without caveat of 3 studies; cohort nonlinear positive curve underemphasised. |
| Item 15 publication bias (critical) | low | Funnel plots, Egger, Begg and trim-and-fill reported for milk. |
| Item 16 conflicts of interest | low | Declared none; public funding. |
Full-text review (25 October 2026): Added participant/case counts, number of studies per subtype (yogurt 3, cheese 3, cream 1), I2 values, trim-and-fill, funding, and the cohort nonlinear dose-response showing rising hip-fracture risk from 0 to 600 g/day milk (not in prior entry). Structured AMSTAR 2 added; overall unchanged (some_concerns).
9. Assessment of the statistical interpretation
Milk: null on highest-vs-lowest and linear dose-response in cohorts, with high heterogeneity and a nonlinear curve suggesting higher risk up to ~600 g/day; protective only in case-control studies (recall bias). Yogurt and cheese: moderately strong inverse associations but based on 3 cohorts each; no absolute risks.
10. Relevance to the specific claim
Contradicts C-DRY-03 and C-DRY-11 (yogurt forbidden despite favourable association).
11. Independent contrary findings
12. Transferability to Germany and Europe
Includes Europe.
13. Overall methodological judgement
Milk is not clearly associated with hip fracture overall, but the cohort dose-response curve leaves open a modest positive association at higher intakes; yogurt and cheese show favourable associations based on few studies.
| 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 | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Causality; confirmation of yogurt/cheese associations in more cohorts; source of nonlinear milk association.
15. Linked fact checks
- High milk consumption raises mortality (women drinking 3+ glasses/day had 93% higher mortality) and increases rather than prevents hip fractures. – Studies with mixed or unclear results
- Fresh milk, yogurt (incl. laban rayeb, ayran, labneh) and white/cottage cheese are harmful and must be avoided, whereas aged cheeses (cheddar, mozzarella, romi), processed cheese triangles, cream (qeshta), butter and ghee are allowed. – Studies contradicting or limiting the claim