The Impact of A1- and A2 β-Casein on Health Outcomes: A Comprehensive Review of Evidence from Human Studies

The digestion of A1 β-casein present in conventional milk releases β-casomorphin-7 (βCM-7), a bioactive peptide with potential implications for gastrointestinal and neurological health. A scoping review was performed to respond to the following research question: What are the health effects of consu...

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Main Authors: Nerea González-Rodríguez, Natalia Vázquez-Liz, Ana Rodríguez-Sampedro, Patricia Regal, Cristina Fente, Alexandre Lamas
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Applied Sciences
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Online Access:https://www.mdpi.com/2076-3417/15/13/7278
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Summary:The digestion of A1 β-casein present in conventional milk releases β-casomorphin-7 (βCM-7), a bioactive peptide with potential implications for gastrointestinal and neurological health. A scoping review was performed to respond to the following research question: What are the health effects of consuming milk containing the A1 β-casein variant compared to the exclusive consumption of the A2 variant in humans? The evidence collected in this review of human studies with different populations (i.e., children, middle-aged adults, athletes) suggests that the consumption of milk containing A1 β-casein may negatively influence gut health by altering microbial composition, reducing intestinal motility, and increasing colonic fermentation, leading to elevated gas production and altered short-chain fatty acid (SCFA) profiles. The release of βCM-7 upon digestion can also compromise intestinal-barrier integrity, which may exacerbate symptoms of lactose intolerance, irritable bowel syndrome (IBS), or other allergy-related sensitivities. Its ability to cross the blood–brain barrier raises concerns about potential neurological effects. In contrast, milk containing exclusively A2 β-casein is associated with improved gastrointestinal outcomes, including the enhanced abundance of beneficial bacteria such as <i>Bifidobacterium</i> spp. and reduced inflammatory markers.
ISSN:2076-3417