A2 protein is a type of beta-casein protein found in cows milk that is different from A1 protein by one amino acid. Originally, all milk contained only A2 protein, but a genetic mutation resulted in many cattle now producing mostly A1 protein. A2 milk is marketed as being easier to digest and absorb than other types of milk, and some studies have shown that it might be more digestible for people who experience symptoms of lactose intolerance. However, there is no widely accepted scientific work identifying a direct link between A1 protein and any adverse effect on health. A2 milk is produced by cows that only produce A2 protein in their milk. While A2 milk is growing in popularity globally, it is still just a small portion of the US market, as most commercially available dairy products still contain a mixture of both A1 and A2 proteins.