A2 milk has recently gained popularity due to its perceived health benefits over traditional A1 milk. A2 milk comes from cows that only produce the A2 beta-casein protein, whereas A1 milk comes from cows that produce both A1 and A2 beta-casein proteins. But what is the difference between these two proteins and why is A2 milk considered better for our health?

What are beta-casein proteins?

First, let’s talk about beta-casein proteins in general. Beta-casein is one of the two types of casein proteins found in cow’s milk, the other being alpha-casein. Casein proteins make up about 80% of the protein content in cow’s milk. Beta-casein proteins play an important role in the structure and function of milk, including its ability to form curds and ease of digestion.

A1 and A2 beta-casein proteins

A1 and A2 beta-casein proteins are two different variations of beta-casein proteins that differ by a single amino acid. A1 beta-casein has a histidine amino acid at position 67, whereas A2 beta-casein has a proline amino acid at the same position.

When A1 beta-casein protein is digested in the gut, it releases beta-casomorphin-7 (BCM-7), a peptide that has been linked to various health issues such as digestive discomfort, inflammation and autoimmune diseases. In contrast, A2 beta-casein protein release a shorter peptide that has no known harmful effects.

The difference between A1 and A2 beta-casein proteins is believed to be due to a genetic mutation in the A1 beta-casein gene that occurred in domesticated European cows around 5000-10,000 years ago. This mutation resulted in the production of A1 beta-casein in these cows, whereas the ancestral cows produced only A2 beta-casein.

Should we avoid A1 beta-casein protein?

Scientific studies have shown mixed results regarding the potential harm of A1 beta-casein in milk. Some studies have suggested a link between A1 beta-casein and increased risk of type 1 diabetes, heart disease and some cancers. However, other studies have failed to support these claims.

It is worth noting that these studies are often observational in nature and do not establish causation. Furthermore, the amount of BCM-7 released from A1 beta-casein digestion is thought to be highly variable between individuals and dependent on other factors such as gut microbiota.

On the other hand, there is some evidence that A2 beta-casein protein may have benefits for digestion and overall health. For example, a study published in the European Journal of Clinical Nutrition found that A2 milk resulted in less bloating and gastrointestinal symptoms than A1 milk in lactose-intolerant individuals.

Is A2 milk healthier than A1 milk?

While the evidence for the benefits of A2 milk is still inconclusive, many people have reported subjective improvements in digestive health after switching to A2 milk. A2 milk is also becoming more widely available in stores and is marketed as a more natural and healthy alternative to traditional A1 milk.

It is worth noting that A2 milk is not lactose-free and individuals with lactose intolerance will still experience digestive symptoms after consuming A2 milk. Additionally, A2 milk may not be suitable for those with a milk allergy, as A2 milk still contains milk proteins that can trigger allergic reactions.

In conclusion, the difference between A1 and A2 beta-casein proteins lies in a single amino acid variation that results in different digestion products. While the evidence for the benefits of A2 milk is inconclusive, many people have reported subjective improvements in digestive health after switching to A2 milk. However, A2 milk is not lactose-free and may not be suitable for those with a milk allergy. As always, it is important to listen to your body and make informed decisions about your diet based on your individual needs and preferences.


  1. Effects of milk containing only A2 β-casein versus milk containing both A1 and A2 β-casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cow’s milk” provides evidence for the digestive benefits of A2 milk over A1 milk in individuals who experience discomfort after consuming traditional cow’s milk.
  2. Milk proteins and human health: A1/A2 milk hypothesis“This study explores the potential health benefits and drawbacks of consuming milk containing different protein variants, specifically A1 and A2 milk. The study suggests that A2 milk may offer certain benefits, such as reducing inflammation and improving digestion, while A1 milk may be linked to negative health outcomes, such as an increased risk of heart disease and type 1 diabetes.
  3. Type I (insulin-dependent) diabetes mellitus and cow milk: A1 β-casein= culprit antigen or innocent bystander?” Examines the potential link between A1 beta-casein in milk and the development of type 1 diabetes.

Disclaimer: This post is for informational purposes only and should not be construed as medical advice. Please consult a healthcare professional for personalized dietary recommendations based on individual needs and health conditions.

Related Blogs