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What is A2 Milk? The Science of A1 vs. A2 Milk

By Liam McAuliffe M.T.S. Updated on

Table of Contents

A2 milk is gaining in popularity. But if you’re like most people, you’re probably asking, what is A2 Milk? And what’s the deal with A1 vs. A2 milk? The short answer is that A2 refers to one of two types of milk proteins called casein. Regular milk from cows contains both A1 and A2 casein proteins. But A2 milk only contains A2 protein. 

This matters because when digested, A1 proteins break down into beta-casomorphin 7, a molecule that has been preliminarily linked to cardiovascular and autoimmune disease. 1 2 3 

Your body digests A2 milk protein in a different way that may have beneficial health effects. 

In this article, we’ll explore what the latest research can tell us about what A2 milk is, the possible problems with A1 milk, and benefits of switching to A2 milk. 

What is A2 Milk Protein? 

There are two primary proteins in milk, casein and whey. With casein making up 80% of milk protein. 

A1 and A2 are variants of a type of casein protein called beta-casein, which makes up 30% of the protein in milk. 

Looking back 10,000 years ago, before cows were domesticated, they produced only A2 beta-casein protein. Then around 8,000 years ago a natural single-gene mutation in Holsteins, resulted in the production of A1 beta-casein protein.4

Because the holstein breed is the most common dairy cow in North America, Europe, and Australia, the milk in these countries is primarily A1. 

By contrast, human, sheep, goat, donkeys, yaks, camel, buffalo, and sheep milks are all A2. 

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A1 vs. A2 Milk

The debate about A1 vs. A2 milk centers on how these proteins affect the body. 

The A1 protein is broken down into beta-casomorphin-7. This peptide is absorbed by the intestines and passed into the blood. 

Some research suggests that beta-casomorphin-7 plays a role in diseases including: 

  • Type 1 diabetes, 
  • Cardiovascular diseases 
  • Autism (in people with immune deficiencies) 
  • Schizophrenia (in people with immune deficiencies) 
  • Sudden infant death syndrome 
  • Apnea 
  • Constipation 

Examples of the effects of beta-casomorphin-7’s effects are that it destroys pancreatic beta cells, which contributes to type 1 diabetes. And it affects T and B immunity cells leading to negative effects on the autoimmune system.5 6 7 8

While BCM is associated with these negative health outcomes, the exact role it plays is not fully understood. 

For instance, numerous studies on healthy adults who drink A1 cow’s milk have not found BCM-7 in the blood. And only a few tests show BCM-7 present in infants. 9 10 11 

Let’s take a closer look at what the science has to say about the associations between A1 milk and disease. 

Type 1 diabetes

Typically diagnosed in children, Type 1 diabetes involves a lack of insulin. 

Numerous observational studies show an association between drinking A1 milk in childhood and an increased risk of type 1 diabetes. 12 13 14 15

It’s worth noting that these observational studies only show that people consuming more A1 protein are at higher risk, but do not prove A1 protein causes type 1 diabetes. 

To date, there have been no human trials specifically isolating A1 proteins for their effects on type 1 diabetes. 

In animal trials, the results have been mixed. And the A1 has not been ingested orally in milk, but injected into the test subjects bypassing the normal digestive process. 16 17 18 19 

Heart disease

At this stage of the research two observational studies have revealed a positive link between A1 milk and an increased risk of heart disease. 20 21

However, two other small clinical trials on people found no significant difference in the effects of A1 and A2 proteins on various markers of heart disease risk factors including blood vessel function, blood cholesterol, and blood pressure. 22 23

Sudden Infant Death Syndrome

Sudden Infant Death Syndrome (SIDS) is the unexpected death of infants without an identifiable cause. SIDS is the most common cause of death among infants under 12 months. 24

SIDS researchers speculate that in some cases of SIDS, BCM-7 may be a factor.

A 2011 study found that infants who temporarily stopped breathing during sleep, a condition known as sleep apnea, had high levels of BCM-7 in their blood. Sleep apnea increases the risk of SIDS. 25

The researchers concluded that some children may have sensitivities to the A1 protein, but more research needs to be done to confirm its role in SIDS. 


Researchers theorize that various peptides including BCM-7 may factor in the development of autism. 

Autism comprises a range of disorders centering on challenges with social skills, repetitive behaviors, speech, and non-verbal communication. 

Studies looking at the theorized connections between BCM-7 and autism have been negative. 26 27 28.  However other studies suggest that concern is warranted, even if the mechanism has not been identified. 

A 2009 study found that infants fed cow’s milk had higher levels of BCM-7 than breastfed infants. In some infants, BCM-7 dropped quickly, while in others it remained high. 

The persistently high levels of BCM were strongly associated with impaired ability to plan and perform actions. 29

A study from 1995 found that consuming A1 cow’s milk could worsen behavioral problems in autistic children. However, subsequent studies haven’t been able to find similar effects on behavior. 30 31

To date, there haven’t been trials comparing the effects of A1 vs. A2 milk on autism. 

A1 vs. A2 Milk for Digestion

When it comes to milk and digestive problems, issues like bloating, diarrhea, and gas are most often attributed to lactose intolerance. Lactose is a milk sugar that can be difficult for many people to digest. 

Though A1 and A2 milk contain the same amounts of lactose, many people report that A2 milk causes less digestive discomfort. 

Lending credence to these anecdotal experiences, studies have revealed that there are other compounds in milk that can negatively impact digestion. 32 33

Studies looking specifically at the roles effects of A1 and A2 milk on digestion have found that A1 milk causes softer stools and that consuming A2 milk resulted in significant reductions in digestive discomfort. 34 35

A1 vs. A2 Milk on Inflammation

Numerous studies on both animal and human subjects strongly suggest that A1 beta-casein increases inflammation in the digestive system resulting in various negative health impacts. 36 37 38 

A 2016 study compared A1 vs. A2 milk proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cows’ milk. 

The researchers concluded that “consumption of milk containing A1 β-casein was associated with increased gastrointestinal inflammation, worsening of post-dairy digestive discomfort, delayed transit, and decreased cognitive processing speed and accuracy. Because elimination of A1 β-casein attenuated these effects, some symptoms of lactose intolerance may stem from inflammation it triggers and can be avoided by consuming milk containing only the A2 type of beta-casein.” 39

A2 Milk Brands

Due to the preliminary links between A1 milk and these negative health outcomes, enterprising dairy farmers have begun breeding cows and offering milk with only A2 proteins. 

Though A2 milk is relatively new to the mainstream dairy consumer, it is available at over 6000 locations across the U.S. 

Two of the most accessible producers of A2 milk are The A2 Milk Company and Alexander Family Famers. 

The a2 Milk Company

The a2 milk company was founded to produce milk with only the A2 protein. 

A2 dairy cows are bred to produce only A2 milk. The A2 milk company tests the DNA of their cows, and then tests the milk for purity after production. 

Alexander Family Farms A2/A2 Organic Milk 

Alexander Family Farms is America’s first certified regenerative dairy. Located in Northern California, they produce the only organic A2 milk, branded as “A2/A2 Organic Milk”. 

They are also the only producers of full-fat A2/A2 keto-friendly yogurt

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A2 Milk Nutrition

A2 milk nutrition is going to look essentially identical to that of standard A1 milk. You will find variations in A2 milk nutrition between A2 milk brands. 

For instance, Alexander Family Farms produces 6% milkfat A2 milk, offering more fat and fewer carbs than a2 milk company wholemilk. Whereas a2 Milk Company adds vitamin D to their milk, and Alexander Family Farms does not. 

The high milkfat of Alexander Family Farms A2/A2 milk makes it suitable for a ketogenic diet  when consumed in moderate amounts. 

Nutrients per 1 Cup (240 mL)The a2 Milk Company (4% milkfat)Alexander Family Farms A2/A2 Organic Milk (6% whole milk)
Total Fat9g14g
Saturated fat5g10g
Total Carbs13g11g
Vitamin D2.5mcg (15%)0
Calcium300mg (25%)250mg (20%)
Vitamin A114mcg (15%)?
Potassium400mg (8%)300mg (6%)

What is A2 Milk? The Bottom Line

A1 and A2 beta-casein are milk proteins that can cause different health effects in people. 

Most milk contains a combination of A1 and A2 beta-casein. 

Due to the prevalence of digestive issues with milk dairy farmers and researchers have been exploring the effects of producing and consuming milk with only A2 beta-casein. 

The early science looking at the health effects of A1 vs. A2 milk suggests that A2 milk may reduce digestive issues, inflammation, and cognitive issues in some people. 

However, research on A1 vs. A2 milk is in its infancy, and more studies need to be done to make definitive conclusions. This is especially true with regards to the links between A1 milk and type 1 diabetes and autism. 

However, there appears to be enough clinical and anecdotal evidence to suggest that people that have issues digesting standard milk, give A2 milk a try. 


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