LE VARIANTI DELLA BETA-CASEINA QUALI NUOVI MARCATORI DELLA QUALITÀ DEL LATTE

So called "A2 milk" is cow's milk containing beta-casein as the A2 variant, instead of the A1 variant, or a mixture of the two, as in conventional milk. Cow's milk contains around 34 g of proteins per liter, 80% of which are caseins. Beta-casein is the second most abundant protein in cow's milk and it makes up about 30% of total caseins. Beta casein A1 variant appeared in EU livestock from a mutation of A2 variant, around 5000-10000 years ago. The two proteins just differ for 1 aminoacid. Both proteins are made up by 209 aminoacids: at position 67 A1 variant has a proline, while A2 variant has a histidine. Due to this subtle difference, the two variants are differently digested at gastric level: A1 variant releases the BCM-7 opiod peptide, a casomorphin, while A2 variant does not. The first studies carried out to evaluate the possible difference in health effect when consuming one or the other milk types, were funded by the "A2 Milk company", from New Zealand, that first commercialized this type of milk in early 2000s. In 2009, EFSA published a scientific opinion on A2 milk and casomorphins containing milk, that stated that "a cause-effect relationship between the oral intake of BCM7 or related peptides and aetiology or course of any suggested non-communicable diseases cannot be established". EFSA also concluded that "casomorphins can have different effects in the intestinal lumen and the intestinal mucosa, such as regulatory effects on gastro-intestinal motility and on gastric and pancreatic secretions". More recent studies, both in animal models and on human subjects, indicate that A2 milk consumption results in lower intestinal inflammation and lower intestinal transit time, when compared to conventional milk. In some cases, it has been reported that feeding A2 milk favors the selection towards a more health favorable gut microflora. Human studies concluded that A2 milk improves gastrointestinal symptoms and gut inflammation. In particular, gastrointestinal transit time, stool index and inflammation markers are lower in subjects fed with A2 milk. The underlying hypothesis is that A1 beta-casein containing milk, that releases the opioid peptide BCM7 upon digestion, has a direct effect on muscles of the intestinal wall, thus reducing the transit time, and that this eventually results in the observed inflammation status.