Systematic reviewindependent cross-checkabstract only checked I-DRY-05 standard review

Industry-linked review: A1 milk effects mostly shown in rodents

Systematic Review of the Gastrointestinal Effects of A1 Compared with A2 β-Casein.

Overview

Brooke-Taylor S et al.. Adv Nutr 2017 · PMID 28916574 · DOI 10.3945/an.116.013953

Human evidence limited to a few studies.

Does the study support the specific claim? Partly · Methodological quality: low

Study explained simply

What did the researchers want to find out?: A1 vs A2 GI effects.
How was the study done?: Review of 39 studies.
How many people, animals or samples were studied?: Mostly rodents.
What was actually found?: Effects in animals; little in humans.
How large was the observed effect?: n/a
What do the results mean in everyday life?: Weak evidence for people.
What are the study's limitations?: COI; animal data.
What does it say about Elawady's specific claim?: Weak support.
Do the results apply to Germany and Europe?: Moderate.
What can explicitly not be concluded from this study?: Effects in humans in general.

Authors: Brooke-Taylor S et al.
Journal: Adv Nutr
Year: 2017
Identifier: PMID 28916574 DOI 10.3945/an.116.013953
Verification: verified – PubMed efetch 2026-10-25
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: Author disclosures: NK, no conflicts of interest. SB-T previously consulted for the a2 Milk Company (Australia) Pty. Ltd. as an independent scientific adviser on food-labeling compliance matters, including undertaking a systematic review to meet Australia New Zealand food regulatory requirements related to health claims on food products. KD received an honorarium from the A2 Corporation to attend a meeting and grant support for an independent project. KW consulted for the A2 Corporation as an independent scientific adviser. This is a free access article, distributed under terms (http://www.nutrition.org/publications/guidelines-and-policies/license/) that permit unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Gastrointestinal effects of A1 vs A2 beta-casein.

Study design: Systematic review – Systematic review of in vitro and in vivo (all species) GI effects of A1 vs A2 beta-casein.
Population: Rodents and humans (39 studies)
Country: Multinational
Period: To 12 April 2017
Sample size: 39 studies
Inclusion and exclusion criteria: English primary studies; milk/fresh milk products; cheese and fermented products excluded.

Results: Rodents: A1 delays transit (opioid-mediated), increases inflammatory markers; humans: limited evidence of delayed transit (1 study) and looser stools (2 studies); discomfort correlated with inflammatory markers for A1.
Absolute risks: not applicable
Authors' conclusion: Further human research required.

Narrative only.

Supporting C-DRY-07 (weak).

Moderate.

Industry-linked review; limited human data.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	low
Risk of bias	high
Precision of results	not applicable
Directness	indirect
Reproducibility	unknown
Consistency with the overall evidence	mixed
Regional transferability	moderate
Adequacy of the interpretation (by the archive)	not applicable

Cheese and fermented products.