Milk is a staple food for many people worldwide, and cow’s milk is the most commonly consumed milk. However, recent research has shown that cow’s milk, specifically the A1 protein found in Holstein and Friesian cows, may have a negative impact on human health. In this article, we’ll explore the chemistry behind A1 and A2 proteins in cow’s milk and their effects on the immune system.

The Main Components of Cow’s Milk

Cow’s milk is composed of water, fat, carbohydrates, and proteins. The two main types of proteins in cow’s milk are whey and casein, with casein being the more abundant protein.

The Chemistry of A1 and A2 Proteins

β-casein is the major type of casein in milk and is a type of phosphoprotein. There are two types of β-casein: A1 and A2. The only difference between the two types is that A1 contains histidine, while A2 contains proline.

Milk from Jersey cows and goats is predominantly A2, while milk from Holstein and Friesian cows, which are the predominant milk source in America, is predominantly A1.

A1 Protein and Auto-Immune Responses

Clinical research has shown that A1 protein is the source of problems for auto-immune responses. A1 protein can be rejected by the body because it doesn’t process and eliminate the casomorphin. The body may not have the enzyme to break down this type of casein, leading to gut inflammation and digestive discomfort.

Moreover, A1 protein stimulates the production of harmful amino acids called BCM-7, which trigger inflammation. In America, most of the dairy milk, regardless if it’s organic or not, contains A1 protein. This makes cow’s milk consumption problematic for individuals who are predisposed to auto-immune disorders.

A2 Protein and Gut Health

On the other hand, A2 protein has been found to be more beneficial for gut health. Research suggests that A2 protein may reduce inflammation in the gut and promote better digestion. This makes milk from Jersey cows and goats a better option for individuals who are predisposed to gut inflammation.


In conclusion, the chemistry behind cow’s milk proteins plays a significant role in how it affects our health. While milk is a good source of nutrients, it may not be suitable for everyone due to the A1 protein’s potential harmful effects on the immune system. If you’re someone who is predisposed to auto-immune disorders or gut inflammation, you may want to consider switching to milk from Jersey cows or goats, which contain predominantly A2 protein.