Randomised controlled trialindependent cross-checkabstract checked I-DRY-116 standard review
A2 milk helped only lactose-intolerant women
Comparison of the impact of bovine milk beta-casein variants on digestive comfort in females self-reporting dairy intolerance: a randomized controlled trial.
Overview
Milan AM et al.. Am J Clin Nutr 2020 · PMID 31773165 · DOI 10.1093/ajcn/nqz279
Fewer symptoms with A2 milk in 10 lactose-intolerant women; no difference in others.
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?
Separate lactose and A1 effects.
- How was the study done?
Blinded crossover.
- How many people, animals or samples were studied?
40 women.
- What was actually found?
A2 helped lactose-intolerant women only.
- How large was the observed effect?
Nausea 8 v 15 mm.
- What do the results mean in everyday life?
A1 may matter for some lactose-intolerant people.
- What are the study's limitations?
Tiny groups; single meals.
- What does it say about Elawady's specific claim?
Partly supports.
- Do the results apply to Germany and Europe?
Applicable.
- What can explicitly not be concluded from this study?
Cannot show inflammation or long-term effects.
Scientific in-depth review
1. Full reference
- Authors
- Milan AM et al.
- Journal
- Am J Clin Nutr
- Year
- 2020
- Identifier
- PMID 31773165 DOI 10.1093/ajcn/nqz279
- 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
Are digestive symptoms after milk due to lactose or beta-casein type?
3. Study design and population
- Study design
- Randomised controlled trial – Double-blind randomised crossover (single servings of 750 mL)
- Population
Women 25 y with varying self-reported dairy tolerance (New Zealand)
- Country
not stated in abstract (registered in ANZCTR)
- Period
not stated
- Sample size
40 (10 lactose intolerant, 20 non-lactose dairy intolerant, 10 tolerant)
- Inclusion and exclusion criteria
Classified by 50-g lactose challenge
4. Methods and endpoints
- Exposure / intervention
a2 Milk; lactose-free conventional milk
- Comparator
Conventional milk
- Endpoints
Symptoms, breath hydrogen over 3-12 h
- Statistical methods
Mixed models
5. Actual results
- Results
In lactose-intolerant women, A2 milk reduced nausea (8 v 15 mm) and faecal urgency (4 v 10 mm) and the breath-hydrogen rise (59 v 98 ppm at 150 min) v conventional milk. Non-lactose dairy-intolerant women had rapid transient symptoms irrespective of lactose or beta-casein type.
- Absolute risks
not reported
- Authors' conclusion
In lactose-intolerant individuals, digestive comfort with lactose-containing milk was improved with A2-only milk; self-reported intolerance without malabsorption is independent of lactose or beta-casein type.
6. Strengths
- Blinded
- Lactose challenge classification
7. Weaknesses
- Single meals
- Very small subgroups
- Funding not checked
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 subgroups.
9. Assessment of the statistical interpretation
Small subgroup effects; multiple outcomes.
10. Relevance to the specific claim
Partly supports an A1 effect, but only in lactose-intolerant women; in other intolerant women beta-casein type made no difference.
11. Independent contrary findings
12. Transferability to Germany and Europe
Applicable.
13. Overall methodological judgement
Mixed, low-certainty.
| 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
Mechanism of the lactose-A2 interaction.