A picture of different types of milk products in glasses on a bench.

A1 and A2 Proteins in Milk

What is A1 and A2 milk?

There are many different types of milk proteins. One particular protein, beta casein, comes in two forms: A1 and A2.

About 60% of beta casein comes in A2, but how much is in each milk depends on different breeds of dairy cows.

A2 protein in milk:

  • Guernsey: more than 70% A2
  • Holstein Friesian, Jersey, Brown Swiss: more than 46-70% A2
  • Ayrshire, red and white: 20-45% A2

A1 protein in milk:

  • Holstein, Ayrshire, red and white: 46-70% A1
  • Jersey, Brown Swiss and Guernsey: 3-24% A1

A1 and A2 proteins in milk are both safe to consume. Some studies have been published which evaluate the benefits of milks which only contain A2 protein, but so far there is no convincing evidence that these milks are a healthier option than regular milk which contains both A1 and A2 protein.

Whether milk contains predominantly A2 protein or a mixture of A1 and A2, they are both safe to drink and contain the same essential nutrients.