A1 protein free milk benefits mood and subjective cognition in free-living Australian adults: a pragmatic, exploratory, open label randomised controlled trial

Carlene Starck; Michelle Blumfield; Peter Petocz; Emily Duve; Lucy Downey; Kylie Abbott; Flavia Fayet-Moore

doi:10.3389/fnut.2025.1579986

A1 protein free milk benefits mood and subjective cognition in free-living Australian adults: a pragmatic, exploratory, open label randomised controlled trial

Carlene Starck^*, Michelle Blumfield, Peter Petocz, Emily Duve, Lucy Downey, Kylie Abbott, Flavia Fayet-Moore^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Background: Adverse effects of milk containing A1-type β-casein on digestion, immune response, and cognition have been identified in milk-intolerant individuals, but health effects in healthy individuals without symptoms of milk intolerance are yet to be examined.

Objective: The objective was to explore the impact of reducing A1 type β-casein intake via switching milk type from conventional A1/A2-type β-casein milk (A1/A2 milk) to A1-type β-casein protein free milk (A1PF) on brain, immune response, gastrointestinal, and skin (BIGS) outcomes in a real-world setting.

Methods: An open-label, pragmatic, exploratory randomised controlled trial was conducted in 997 healthy, free-living Australian older adolescents and adults (16–65 years) who regularly consume A1/A2 protein-containing milk and milk products. Participants were randomised into two groups, to consume ≥250 mL/day of A1/A2 milk (control) or to switch to ≥250 mL/day of A1PF milk (intervention) for 28 days, while continuing to follow their usual diet (including up to 1 serve a day of A1/A2 dairy products). A sub-group of 265 participants conducted stool, saliva and cognitive testing on days 0 and 28. All participants completed subjective questionnaires on days 0, 14, and 28.

Results: No differences in gut microbiome composition, alpha-diversity, or function were found by switching milk type. After switching to A1PF milk, a small increase in stool consistency was reported (−0.16, p = 0.007), and females experienced a marginal reduction in gastrointestinal symptoms (p = 0.015) and improved subjective cognition (p = 0.03). Switching to A1PF milk reduced anxiety (−0.61; p = 0.002), depression (−0.56; p = 0.023), stress (−0.70, p = 0.012) and fatigue (p = 0.001; females only), compared to drinking A1/A2 milk, with stronger effects in females. No consistent effects on markers of immune response or skin health were identified.

Conclusion: Switching from conventional A1/A2 milk to A1PF milk may benefit mood and subjective cognition, particularly in females, without the need for complete elimination of A1 β-casein from the diet. Further investigations are warranted.

Clinical trial registration: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=385966, identifier ACTRN12623000628640.

Original language	English
Article number	1579986
Pages (from-to)	1-16
Number of pages	16
Journal	Frontiers in Nutrition
Volume	12
DOIs	https://doi.org/10.3389/fnut.2025.1579986
Publication status	Published - 3 Jun 2025

Bibliographical note

Copyright © 2025 Starck, Blumfield, Petocz, Duve, Downey, Abbott and Fayet-Moore. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

A1 protein free milk
brain health
gastrointestinal microbiome
gut-brain axis
mental health
mood
pragmatic clinical trial
β-casein

Access to Document

10.3389/fnut.2025.1579986Licence: CC BY

Publisher version (open access)Final published version, 3.17 MBLicence: CC BY

Cite this

@article{d588713a4eb24fb1ac55fccf8dad4cde,

title = "A1 protein free milk benefits mood and subjective cognition in free-living Australian adults: a pragmatic, exploratory, open label randomised controlled trial",

abstract = "Background: Adverse effects of milk containing A1-type β-casein on digestion, immune response, and cognition have been identified in milk-intolerant individuals, but health effects in healthy individuals without symptoms of milk intolerance are yet to be examined.Objective: The objective was to explore the impact of reducing A1 type β-casein intake via switching milk type from conventional A1/A2-type β-casein milk (A1/A2 milk) to A1-type β-casein protein free milk (A1PF) on brain, immune response, gastrointestinal, and skin (BIGS) outcomes in a real-world setting.Methods: An open-label, pragmatic, exploratory randomised controlled trial was conducted in 997 healthy, free-living Australian older adolescents and adults (16–65 years) who regularly consume A1/A2 protein-containing milk and milk products. Participants were randomised into two groups, to consume ≥250 mL/day of A1/A2 milk (control) or to switch to ≥250 mL/day of A1PF milk (intervention) for 28 days, while continuing to follow their usual diet (including up to 1 serve a day of A1/A2 dairy products). A sub-group of 265 participants conducted stool, saliva and cognitive testing on days 0 and 28. All participants completed subjective questionnaires on days 0, 14, and 28.Results: No differences in gut microbiome composition, alpha-diversity, or function were found by switching milk type. After switching to A1PF milk, a small increase in stool consistency was reported (−0.16, p = 0.007), and females experienced a marginal reduction in gastrointestinal symptoms (p = 0.015) and improved subjective cognition (p = 0.03). Switching to A1PF milk reduced anxiety (−0.61; p = 0.002), depression (−0.56; p = 0.023), stress (−0.70, p = 0.012) and fatigue (p = 0.001; females only), compared to drinking A1/A2 milk, with stronger effects in females. No consistent effects on markers of immune response or skin health were identified.Conclusion: Switching from conventional A1/A2 milk to A1PF milk may benefit mood and subjective cognition, particularly in females, without the need for complete elimination of A1 β-casein from the diet. Further investigations are warranted.Clinical trial registration: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=385966, identifier ACTRN12623000628640.",

keywords = "A1 protein free milk, brain health, gastrointestinal microbiome, gut-brain axis, mental health, mood, pragmatic clinical trial, β-casein",

author = "Carlene Starck and Michelle Blumfield and Peter Petocz and Emily Duve and Lucy Downey and Kylie Abbott and Flavia Fayet-Moore",

note = "Copyright {\textcopyright} 2025 Starck, Blumfield, Petocz, Duve, Downey, Abbott and Fayet-Moore. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.",

year = "2025",

month = jun,

day = "3",

doi = "10.3389/fnut.2025.1579986",

language = "English",

volume = "12",

pages = "1--16",

journal = "Frontiers in Nutrition",

issn = "2296-861X",

publisher = "Frontiers Media SA",

}

TY - JOUR

T1 - A1 protein free milk benefits mood and subjective cognition in free-living Australian adults

T2 - a pragmatic, exploratory, open label randomised controlled trial

AU - Starck, Carlene

AU - Blumfield, Michelle

AU - Petocz, Peter

AU - Duve, Emily

AU - Downey, Lucy

AU - Abbott, Kylie

AU - Fayet-Moore, Flavia

N1 - Copyright © 2025 Starck, Blumfield, Petocz, Duve, Downey, Abbott and Fayet-Moore. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

PY - 2025/6/3

Y1 - 2025/6/3

N2 - Background: Adverse effects of milk containing A1-type β-casein on digestion, immune response, and cognition have been identified in milk-intolerant individuals, but health effects in healthy individuals without symptoms of milk intolerance are yet to be examined.Objective: The objective was to explore the impact of reducing A1 type β-casein intake via switching milk type from conventional A1/A2-type β-casein milk (A1/A2 milk) to A1-type β-casein protein free milk (A1PF) on brain, immune response, gastrointestinal, and skin (BIGS) outcomes in a real-world setting.Methods: An open-label, pragmatic, exploratory randomised controlled trial was conducted in 997 healthy, free-living Australian older adolescents and adults (16–65 years) who regularly consume A1/A2 protein-containing milk and milk products. Participants were randomised into two groups, to consume ≥250 mL/day of A1/A2 milk (control) or to switch to ≥250 mL/day of A1PF milk (intervention) for 28 days, while continuing to follow their usual diet (including up to 1 serve a day of A1/A2 dairy products). A sub-group of 265 participants conducted stool, saliva and cognitive testing on days 0 and 28. All participants completed subjective questionnaires on days 0, 14, and 28.Results: No differences in gut microbiome composition, alpha-diversity, or function were found by switching milk type. After switching to A1PF milk, a small increase in stool consistency was reported (−0.16, p = 0.007), and females experienced a marginal reduction in gastrointestinal symptoms (p = 0.015) and improved subjective cognition (p = 0.03). Switching to A1PF milk reduced anxiety (−0.61; p = 0.002), depression (−0.56; p = 0.023), stress (−0.70, p = 0.012) and fatigue (p = 0.001; females only), compared to drinking A1/A2 milk, with stronger effects in females. No consistent effects on markers of immune response or skin health were identified.Conclusion: Switching from conventional A1/A2 milk to A1PF milk may benefit mood and subjective cognition, particularly in females, without the need for complete elimination of A1 β-casein from the diet. Further investigations are warranted.Clinical trial registration: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=385966, identifier ACTRN12623000628640.

AB - Background: Adverse effects of milk containing A1-type β-casein on digestion, immune response, and cognition have been identified in milk-intolerant individuals, but health effects in healthy individuals without symptoms of milk intolerance are yet to be examined.Objective: The objective was to explore the impact of reducing A1 type β-casein intake via switching milk type from conventional A1/A2-type β-casein milk (A1/A2 milk) to A1-type β-casein protein free milk (A1PF) on brain, immune response, gastrointestinal, and skin (BIGS) outcomes in a real-world setting.Methods: An open-label, pragmatic, exploratory randomised controlled trial was conducted in 997 healthy, free-living Australian older adolescents and adults (16–65 years) who regularly consume A1/A2 protein-containing milk and milk products. Participants were randomised into two groups, to consume ≥250 mL/day of A1/A2 milk (control) or to switch to ≥250 mL/day of A1PF milk (intervention) for 28 days, while continuing to follow their usual diet (including up to 1 serve a day of A1/A2 dairy products). A sub-group of 265 participants conducted stool, saliva and cognitive testing on days 0 and 28. All participants completed subjective questionnaires on days 0, 14, and 28.Results: No differences in gut microbiome composition, alpha-diversity, or function were found by switching milk type. After switching to A1PF milk, a small increase in stool consistency was reported (−0.16, p = 0.007), and females experienced a marginal reduction in gastrointestinal symptoms (p = 0.015) and improved subjective cognition (p = 0.03). Switching to A1PF milk reduced anxiety (−0.61; p = 0.002), depression (−0.56; p = 0.023), stress (−0.70, p = 0.012) and fatigue (p = 0.001; females only), compared to drinking A1/A2 milk, with stronger effects in females. No consistent effects on markers of immune response or skin health were identified.Conclusion: Switching from conventional A1/A2 milk to A1PF milk may benefit mood and subjective cognition, particularly in females, without the need for complete elimination of A1 β-casein from the diet. Further investigations are warranted.Clinical trial registration: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=385966, identifier ACTRN12623000628640.

KW - A1 protein free milk

KW - brain health

KW - gastrointestinal microbiome

KW - gut-brain axis

KW - mental health

KW - mood

KW - pragmatic clinical trial

KW - β-casein

UR - https://www.scopus.com/pages/publications/105008230876

U2 - 10.3389/fnut.2025.1579986

DO - 10.3389/fnut.2025.1579986

M3 - Article

AN - SCOPUS:105008230876

SN - 2296-861X

VL - 12

SP - 1

EP - 16

JO - Frontiers in Nutrition

JF - Frontiers in Nutrition

M1 - 1579986

ER -

A1 protein free milk benefits mood and subjective cognition in free-living Australian adults: a pragmatic, exploratory, open label randomised controlled trial

Abstract

Bibliographical note

Keywords

Access to Document

Other files and links

Fingerprint

Cite this