Beta-casein is a type of protein found in milk, particularly in cow's milk. It is one of the main components of casein, which makes up about 80% of the protein in milk. Beta-casein exists in different forms, known as variants, which can influence how it is digested and its effects on health. Research suggests that the different variants of beta-casein may have varying impacts on digestion and may be linked to certain health outcomes. For example, the A1 variant has been associated with digestive discomfort in some individuals, while the A2 variant is often marketed as being easier to digest.