Four years ago, I wrote an article and filmed a video about the differences between A1 and A2 milk.  The A1 versus A2 factor refers to the different type of casein in raw milk from various breeds of cows.
Note that sheep milk, goat milk, and camel milk are all A2 milk regardless of breed.
Much of the hubbub regarding A1 versus A2 milk at that time and in the ensuing years resulted from an article written by Dr. Tom Cowan based on the book The Devil in the Milk which claims that cows made a genetic split about 5,000 years ago which resulted in Holsteins and Friesians (black and white cows) becoming favored for domestication because of calmness and other traits.
These cows became the A1 dominant cows of today which supposedly produce milk which acts like an opiate when consumed and which epidemiological studies have implicated in heart disease, Type 1 diabetes, autism and schizophrenia.
The book also claims that old fashioned breeds of cows produce A2 milk that is far healthier and that genetic testing is required to determine if a cow has A1 or A2 genetics.
As I have read more about this issue, it seems that in reality, we have no way of knowing whether any of this is true or not. There is no other research that confirms this historical split. If this genetic divergence truly occurred 5,000 years ago and A1 milk  is one of the sources of heart disease and makes autism worse, why doesn’t this match up with what other researchers are finding?
Unnatural feeding of dairy cows, confinement and pasteurization/homogenization that got started early in the last century are far more likely culprits for any health issues associated with milk consumption, not cow genetics.
If fact, in the comments section of that post I wrote four years ago, Mark McAfee, Founder of Organic Pastures Dairy in California, said the following:
Sarah,
I agree with much of what you have shared….but let me help out by filling in the blanks a little. I am very close to this A-2 subject matter and can help clear the air.
Dr. Cowan has privately apologized to me for writing the forward to The Devil in the Milk. He said that if he knew then what he knows now he would not have said what he wrote.
The A-2 story is far from conclusive. Instead of “The Devil is in the Milk”….the better statement is.. “The Real Devil is in the CAFO Grain Feeding of the Cows and Processing of the Milk”.
Keep up the great teaching and nutritional work!!
Most kind regards,
Mark McAfee
Founder Organic Pastures Dairy Company
Fresno CA
I recently emailed Mark to see if he had any additional information on the A1 and A2 milk issue, and he responded by saying that he would be attending the upcoming International Milk Genomics conference in Aarhus, Denmark, where A2 will be discussed in depth. Â But, at the present time, his opinion is the same – that the jury is still out on the A1 versus A2 milk issue and whether cow genetics is of any importance whatsoever.
Should You Care About A1 and A2 Milk?
While it is clear that cow genetics plays a role in how a herd responds to environmental conditions and can be used to select the most appropriate breed for a given locale, it is far less certain whether cow genetics plays a role in production of the best milk from a nutritional point of view.
The most important thing for the consumer at the present time is to ensure that the farm they purchase their milk from has a healthy herd which grazes on well kept, unsprayed green pasture. In addition, visual examination of the milk to assess the size and color of the creamline indicating the presence of fat soluble vitamins and co-factors is most important.
Organic Pastures Dairy in California seems to be of the same mindset. Â The FAQ on the OP website says the following:
We do not test for A1/A2 genetics. It is our opinion that raw, non-homogenized milk, from organic cows that graze on pasture makes the most nutritious milk. We have 10 different breeds that make our milk delicious and nutritious. We believe the genetic diversity of our cows adds to the overall nutritional diversity of their milk.
Well said.
Sarah, The Healthy Home Economist
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I have learned so much from you and have started overhauling my eating habits. Thank you so much for presenting all of this information so that I can make good healthy decisions. I finally, found an excellent farm with organic pastured Jersey cows within an hours drive from me. My question is – is it alright to drink raw milk with pre diabetes?
Milk even when raw has a lot of sugar (lactose). Check with your doctor, but it is was me, I would stick with fermented dairy such as 24-hour yogurt or kefir where all the lactose is gone.
Thank you so much for your comment. I feel better about buying milk. Do you think that if I can buy raw milk, either would be okay- A1 or A2? Would milk that is brought from a health store be the same?
Either would be fine if you are not sensitive. Yes, some healthfood stores around the country, depending on state law, do carry raw milk and that’s fine too.
You are all a bunch of liars. The problem with a lot of milk today is that they started shooting up the cows with hormones or steroids to produce more milk and have more meat. Problem is when we digest it,we start having problems with our digestive system and anger,weight, autism and other mental problems as well as an increase in cancer. It has nothing to do with A2 or A1. You are lying so much to the public about this noncence. People drank milk since time began. As a kid we lived on it and had stronger bones then people today. They have all these protein allergies because of you scientist playing god with our food. We are people not test subjects. I pray you are all found out and sued for your lies and trouble you cause. You poison our water with flouride, which roots our teeth and bones and cause many problems. Our meat and other foods including baby food with arcenic. You are the problem and you need to stop or pay the price. God is watching you.
We have an A1/A1 Jersey Cow. I was a little apprehensive about buying her after I read articles about the A1/A2 debate, but decided it would still be better to consume raw A1 milk than pasturized/homogenized milk from the grocery store. We’ve had no issues and are so glad we got our Bella. She has been a wonderful cow that produces wonderfully nutritious milk. Thank you for all of your articles!
Another anecdotal comment. A1 milk will give me a sinus headache within 24° of eating any dairy product made with A1 cow milk. If I continue to eat dairy from A1 cows, I develop seborrheic dermatitis and psoriasis. If I continue to eat dairy from A1 cows, I develop keratosis pilaris, which is another skin problem. Doesn’t matter if the A1 milk is homogenized, pasteurized or raw. If I eat dairy from goats, I have none of the above mentioned symptoms. I discovered this long before I knew about A1 or A2 beta casein. Of course I’m assuming all of the dairy products sold in typical supermarkets are from Holstein and Friesian cows, because aren’t most commercial dairies made up of these cows?
I now buy sheep and goat cheese, and raw milk from private farmers who have Jersey cows. I do not get the above mentioned health issues from these milk products.
Even more recently, i discovered the possible link. There is an amino acid substitution in a particular area on the casein protein chain. I cannot give you the exact location of the substitution. The substitution is the proline amino acid in the A2 casein protein chain to histadine in the A1 casein protein chain. It results in a different shape to the protein chain. If the shape if a protein is changed, it changes the “function” of that protein chain.
Why is this relevent? I also recently found out I have a genetic issue with histamine overload in my gut. I have impaired ability to break down histamine caused by food. This is not the same thing as an allergy, which is an IgE antibody histamine response. This is an IgA antibody response. Gut bacteria break histadine into histamine. Histamine overload causes the above named adverse reactions, the inflammation in my sinuses and my skin. I do not have lactose intolerance. I have a problem with a certain milk protein.
Perhaps the problem with the genetic research about A1 and A2 cows is that it is only trying to prove there is no difference in the nutrition value. Perhaps the research should focus on the effect the amino acid substitution has on the function of the protein, ie the histamine connection caused by the histadine amino acid substitution.