Beta-casein is one of the major proteins in cows' milk. It exists primarily in two genetic variants — A1 and A2 — that differ by a single amino acid at position 67 (histidine in A1, proline in A2). This single change affects how the protein is digested.

Beta-casomorphin-7 (BCM-7) is a seven-amino-acid opioid peptide released during digestion of A1 beta-casein. BCM-7 is not produced from A2 beta-casein. Most published research on beta-casein focuses on whether the presence or absence of BCM-7 affects gastrointestinal comfort, inflammation, infant feeding outcomes, and other physiological endpoints.

What is the difference between A1 and A2 milk?

A1 milk contains A1 beta-casein (which releases BCM-7 during digestion); A2-only milk contains only A2 beta-casein (which does not release BCM-7). Conventional cows' milk typically contains a mix of both. A2-only milk is produced by herds that are homozygous A2/A2.

Who is this research library for?

betacasein.org is intended for researchers and healthcare professionals seeking peer-reviewed scientific literature on bovine beta-casein protein. It is not a source of medical advice for individual consumers.

Welcome to betacasein.org

The purpose of this site is to provide a comprehensive, accessible library of peer-reviewed research and publications relevant to bovine beta-casein and associated physiological outcomes.

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Studies on beta-casomorphin-7 (BCM-7)

Beta Casein Variants: Genetics and Physical Properties

Featured

Effects of A1-type β-casein protein free bovine milk on mothers and infants: a randomized double-blind controlled trial

Yang F, Sun Y, Wang ZX · A randomized, double-blind, controlled trial on the effects

2025ClinicalInfantsImmune

Compared with mothers who drank conventional cow's milk, full-term mothers who drank A1PF milk showed lower levels of gastrointestinal and systemic inflammatory markers and improved gastrointestinal symptoms, and this effect may also be transmitted to full-term breastfed infants. This conclusion requires further research to confirm.

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Featured

Beneficial effect of consuming milk containing only A2 beta-casein on gut microbiota: A single-center, randomized, double-blind, cross-over study

Song CH, Kim N, Choi Y, Kim S, Kim KS, Park MH, Lee SH, Lee DH · Beneficial effect of consuming milk containing only A2 beta-

2025ClinicalDigestion

Two weeks of A2 milk consumption led to significant alterations in gut microbiota, promoting beneficial microbes and related functions. A2 milk could be a suitable alternative for subjects who experience milk-intake-related GI discomfort.

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