A1 and A2 beta-casein are two types of casein proteins found in milk. A1 beta-casein results from a genetic mutation in European cows18, whereas A2 beta-casein is the original protein found in cows from Asia and Africa, as well as most goats and sheep.
“The A1 and A2 casein variants differ in their amino acid composition19, leading to changes in the structure of the casein protein,” Svetlana Nepocatych, Ph.D., RDN, a registered dietitian nutritionist and associate professor at the Elon University Department of Exercise Science, previously told mindbodygreen.
Some studies suggest that A2 beta-casein may be easier to digest and less likely to cause gastrointestinal symptoms20, such as bloating and diarrhea, than A1 beta-casein. “A2 casein tends to be less inflammatory and less likely to cause gut issues,” functional medicine doctor Mark Hyman, M.D., says on the mindbodygreen podcast.
However, more research is needed20 to confirm these findings and determine if one type of casein is definitively better for individuals with GI sensitivity.
