Randomised controlled trialindependent cross-checkabstract checked I-DRY-115 standard review
Lactose, not the A1 protein, explained milk symptoms
Tolerance of protein-hydrolyzed lactose-free A1 milk and A2 milk in lactose-tolerant and lactose-intolerant volunteers: A randomized crossover trial with 2 parallel groups.
Overview
Mannila E et al.. J Dairy Sci 2025 · PMID 40614809 · DOI 10.3168/jds.2025-26712
No difference between A2 and A1 milk in lactose-tolerant people; no rise in inflammation markers.
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?
Separate lactose from A1 protein effects.
- How was the study done?
Crossover RCT.
- How many people, animals or samples were studied?
36 adults.
- What was actually found?
Lactose mattered; A1 did not.
- How large was the observed effect?
No significant differences.
- What do the results mean in everyday life?
Lactose-free milk may help sensitive people.
- What are the study's limitations?
Very short and small.
- What does it say about Elawady's specific claim?
Contradicts A1-inflammation claim.
- Do the results apply to Germany and Europe?
Applicable.
- What can explicitly not be concluded from this study?
Cannot rule out long-term effects.
Scientific in-depth review
1. Full reference
- Authors
- Mannila E et al.
- Journal
- J Dairy Sci
- Year
- 2025
- Identifier
- PMID 40614809 DOI 10.3168/jds.2025-26712
- Verification
- verified – PubMed efetch 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Do A2 milk and hydrolysed lactose-free A1A2 milk differ in gut symptoms and inflammation markers?
3. Study design and population
- Study design
- Randomised controlled trial – Three-leg, 3-day randomised crossover trial; groups by lactase genotype
- Population
Self-reported milk-sensitive volunteers
- Country
not stated in abstract
- Period
not stated
- Sample size
36
- Inclusion and exclusion criteria
Self-reported milk sensitivity
4. Methods and endpoints
- Exposure / intervention
A2 milk; protein-hydrolysed lactose-free A1A2 milk
- Comparator
Each other; milk-free run-in
- Endpoints
GI symptoms, faecal calprotectin, plasma hs-CRP and cytokines
- Statistical methods
Crossover analysis by genotype group
5. Actual results
- Results
No difference in perceived gut symptoms between A2 and hydrolysed A1A2 milk in the lactose-tolerant group; symptoms increased with lactose content in the lactose-intolerant group. Calprotectin and hs-CRP did not increase during any milk period compared with the milk-free run-in. Weak, non-significant cytokine changes.
- Absolute risks
not reported
- Authors' conclusion
Protein-hydrolysed lactose-free A1A2 milk was as tolerated as A2 milk in lactose-tolerant volunteers and better tolerated by lactose-intolerant volunteers.
6. Strengths
- Genotype-based lactase status
- Milk-free baseline
- Objective inflammation markers
7. Weaknesses
- Very short (3 days)
- Small
- Processed products differ in more than beta-casein
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Small, short.
9. Assessment of the statistical interpretation
Null for beta-casein type; lactose explains symptoms.
10. Relevance to the specific claim
Suggests lactose, not A1 beta-casein, drives symptoms, and that milk did not raise gut (calprotectin) or systemic (hs-CRP) inflammation markers.
11. Independent contrary findings
12. Transferability to Germany and Europe
Population not described in abstract.
13. Overall methodological judgement
Low-certainty evidence against A1-driven inflammation.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | low |
| Directness | direct |
| Reproducibility | unknown |
| Consistency with the overall evidence | mixed |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Longer trials.
15. Linked fact checks
- A1 beta-casein in conventional milk releases beta-casomorphin-7, which triggers gut inflammation, slower transit and worse symptoms (shown in a 2016 randomised trial). – Studies contradicting or limiting the claim
- Dairy products harm health and cause inflammation. – Studies contradicting or limiting the claim