Among the many types found in milk, there’s one called beta-casein, which comes in two forms: A1 and A2. Whether your milk has A1, A2, or both, rest assured—they’re completely natural and perfectly healthy to enjoy.

Milk contains many different types of proteins. One of these is beta-casein, which comes in two forms: A1 and A2. Whether milk contains A1, A2, or a combination of both depends on the genetic makeup of the cows. Most regular milk contains both A1 and A2 proteins, but some farmers selectively breed cows to produce milk with only A2 protein by ensuring their herds have the A2/A2 genotype.

What’s the difference when it comes to health?
Some studies suggest that people with lactose maldigestion or lactose intolerance may experience less digestive discomfort, such as stomach upset, when drinking milk containing only A2 protein. Although more research is needed on larger groups of people, these findings are encouraging for individuals who experience discomfort after consuming regular dairy milk. 

The good news? Regardless of whether milk contains A1 and A2 proteins or only A2, both are natural components of milk and are considered healthy to drink. 

References

1. Givens I, Aikman P, Gibson T et al. Proportions of A1, A2, B and C β-casein protein variants in retail milk in the UK. Food Chem. 2012; 139:549-552
2. Ramakrishnan M et al. Milk Containing A2 β-Casein ONLY, as a Single Meal, Causes Fewer Symptoms of Lactose Intolerance than Milk Containing A1 and A2 β-Caseins in Subjects with Lactose Maldigestion and Intolerance: A Randomized, Double-Blind, Crossover Trial. Nutrients. 2020 Dec 17;12(12):3855.
3. European Food Safety Authority. 2009. Review of the potential health impact of β-casomorphins and related peptides. EFSA J7, 231.