A2 Milk and BCM-7 Peptide as Emerging Parameters of Milk Quality

Abstract

Beta-casein makes up about 30% of the total protein contained in milk and can be present in cows' milk in two distinct forms (A1 or A2) or as a combination of the two. The only difference between these two variants of β-casein (β-CN) is a single amino acid substitution. This results in a different behavior of the protein upon enzymatic cleavage, following human consumption or due to microbial action. In most of the commercially available milk containing A1 or A1/A2 β-CN variants, the β-casomorphin-7 peptide (BCM-7) is released upon digestion and during cheese manufacturing/ripening, while this does not happen with A2 milk. BCM-7 is a known μ-opioid receptor agonist that may influence the gastro-intestinal physiology directly and may also exert effects elsewhere in the body, such as on the cardiovascular, neurological and endocrine systems. The present article is aimed at a revision of prior review papers on the topic, with a focus on the impact of ingestion of A1 β-CN milk and A2 β-CN milk on any health-related outcomes and on the impact of A1 or A2 β-CN variant on technological properties of cows' milk. When systematic reviews were considered, it was possible to conclude that A2 β-CN exerts beneficial effects at the gastrointestinal level compared with A1 β-CN, but that there is no evidence of A1 β-CN having negative effects on human health. Physicochemical differences among cows' milk containing either β-CN A2 or β-CN A1 and their effects on technological properties are discussed.

Gastric Emptying of New-World Milk Containing A1 and A2 Β-Casein Is More Rapid as Compared to Milk Containing Only A2 Β-Casein in Lactose Maldigesters: A Randomized, Cross-Over Trial Using Magnetic Resonance Imaging

“…Transit and inflammation were mediated by opioid receptors in rodents [ 22 ]. BCM-7 is a pro-inflammatory opioid peptide [ 30 ] and has an affinity to the micro-opioid receptors in the gastrointestinal tract of humans [ 31 , 32 , 33 ]. Casomorphin slows the transit by decreasing gastrointestinal motility, which is similar to the effect of an opioid and opioid agonist [ 34 , 35 , 36 ].…”

Bovine milk β‐casein: Structure, properties, isolation, and targeted application of isolated products

“…This results in a significant difference between the hydrolyzed peptides produced by the body after digestion and absorption of A1 and A2 β‐casein, despite the small difference of only one amino acid in their structure (Boutrou et al., 2013). Hydrolysis of A2 type β‐casein does not produce β‐casein‐7 (BCM‐7) (Giglioti et al., 2020; Giribaldi et al., 2022), whereas A1 releases BCM‐7 (Kamiński et al., 2006; Lambers et al., 2021). BCM‐7 is an exorphin that prolongs the digestion process of milk proteins and interacts with various body systems (Barnett et al., 2014; Jianqin et al., 2016).…”

Devising a technique for improving the biological value of A2 milk by adding carrot powder

“…In the enzymatic hydrolysis of milk A1, a peptide β-casomorphine-7 (BCM-7) is formed, which is a well-known agonist of μ-opioid receptors. It can directly affect the physiology of the gastrointestinal tract, as well as other systems, for example, the cardiovascular, nervous, and endocrine [7]. Often, the cause of such disorders is considered lactose intolerance.…”