Understanding Dairy Intolerance + the A2 Milk Protein

a2 milk dairy intolerance to casein protein

As you will know if you have explored other articles on my blog, I am really interested in the topic of food intolerance.

Over a year ago, I discovered through a food intolerance test that I don’t tolerate milk well. My first food intolerance test through York Test gave me no more information than that.

However, knowing that food intolerance testing of this kind tests intolerance to proteins in foods, and knowing that there are several types of milk protein, I went on a quest to find out more.

My next food intolerance test (and the one that I would recommend to anyone) from CNS revealed my ‘milk’ intolerance to be to casein specifically.

Since then, I haven’t generally consumed dairy products, and in particular, I have avoided buying and drinking cow’s milk.

Within the last month, I have bought and drunk cow’s milk again for the first time in at least a year after learning that there are different types of casein in milk.

I can't believe how little we are taught about what different components are in the milk that we as a population consume so much of. Read on to learn more about that and how it relates to the different types of dairy intolerance.

Especially if you think you may have some kind of dairy intolerance yourself, this might help you find a solution to enjoy dairy again.

Dairy intolerance: what is it?

Many people believe they have an intolerance to dairy. However, because there are several components within dairy (scroll down to read more on this!), it can be difficult to identify exactly what is it that doesn’t agree with you.

Lactose intolerance

Lactose is a sugar that naturally occurs in milk. People develop a lactose intolerance if they lack the enzymes needed to break lactose down in the body. A hydrogen breath test can diagnose lactose intolerance.

Intolerance to milk proteins

There are several proteins in milk, described in more detail below. The protein that people are commonly reactive to is casein.

A reaction to a protein elicits an igG response in the body. It is the IgG antibodies specific to antigenic food proteins that are monitored in food intolerance tests.

The symptoms of lactose intolerance and casein intolerance are similar, because all food intolerance elicits the same response: inflammation.

This can lead to digestive symptoms like bloating, wind and cramp. There are also lots of other non-digestive symptoms associated with food intolerance, which you can find detailed in my Food Intolerance Guide.

A lot of people assume that a disagreement with milk means a lactose intolerance.

However, lactose intolerance is said to affect less than 5% of the UK population. A much more common intolerance is to the A1 beta-casein found in cow’s milk.

The problems with cutting out dairy

Many people, assuming that they have an intolerance, cut dairy from their diet. While this can be really important if symptoms are severe, it can be really useful to gain understanding of the intolerance (lactose or casein?) before cutting out a food group. Firstly, because it can be inconvenient, but second, there may be other problems that arise from this restriction...


By having a good awareness of what I consume, and from working with a dietician, I know that there’s a chance I might not be consuming enough calcium in my diet since reducing my dairy intake.

This can often be the case in people who do not consume dairy.

I found this calcium information sheet from the BDA (The Association of UK Dieticians) incredibly helped me to recognise which foods are calcium-rich.

So helpful, in fact, that I’m sharing a section of it here in this article to ensure that you don’t miss seeing it!

While a lot of people assume that they are still consuming enough calcium through other sources, such as green veg, the quantity of calcium in other foods is negligible compared to the quantity in dairy produce.

Calcium rich foods nutrition factsheet

Artificial ingredients

I really like milk alternatives like almond milk and coconut milk, and these are often fortified with calcium, which is great. However, I am conscious of the additives in them, such as emulsifiers, stabilisers and acidity regulators.

Problems with the dairy industry

Of course, it could definitely be argued that there are also problems besides food intolerance with consuming dairy.

It’s very hard to gain a true insight into the dairy industry, but I am conscious that antibiotics and hormones given to cows can end up in the milk that we consume. The problem is no doubt worse in countries outside of the UK where regulation isn’t so stringent, but regardless, it’s an issue that remains at the back of my mind.

Anatomy of milk.png

The anatomy of milk

Cow’s milk is mostly water, with about 13% solids, which is composed of carbohydrates (the milk sugar lactose), fat, minerals and protein.

The protein is around 20% whey and 80% casein. There are three major types of casein protein in milk, one of which is beta-casein. There are then two main types of beta-casein, called A1 and A2.

Some milk can contain both A1 and A2 proteins, in which case A1 is usually dominant. Some milk contains no A2 protein at all.

A1 and A2 beta-casein are genetic variants of the beta-casein milk protein. These are produced by cows based on their genetic ability to produce one or the other.

The A1 and A2 type proteins differ by only one amino acid. This difference in protein composition between the A1 and A2 type of beta-casein may affect how these proteins are broken down during digestion.

To be even more specific and technical, the different between A1 and A2 proteins is this: a proline (amino acid) occurs at position 67 in the chain of amino acids that make up the A2 beta-casein, while in A1 beta-casein a histidine (amino acid) occurs at that position. Studies in cells found that the digestive enzymes that break down these proteins interact with beta-casein precisely at that location, so that A1 and A2 beta-casein proteins are processed differently by the body.

It is the A1 protein that is suspected to promote intestinal inflammation and exacerbate gastrointestinal symptoms.

Is the solution a2-only milk?

For a while I’ve known that I’m tolerant to a the casein component of dairy. I’ve heard that the milk industry caters for lactose intolerant individuals by processing milk to remove the lactose. However, I’ve wondered for a while if there is also milk out there that has had the casein removed…

And then I discovered a2 milk™ from the a2 milk company. This is milk without the supposedly problematic casein protein (A1).

However, it hasn’t had to undergo any processing in order to remove that protein. The company simply selects milk from cows that naturally produce A!-free milk based on their genetic profile.

It’s a fairly simple difference between whether cows are A1 or A2; like us having blue or brown eyes! It just requires basic genetic testing.

How can a2 milk™ be trademarked?

If the A2 protein occurs naturally in milk, I wondered how it is the case that ‘a2’ is trademarked throughout the brand’s website and other online content.

I found out that the a2 Milk Company was founded in New Zealand to test and market a2 milk™. A method for identifying A1 and A2 was developed and the company has the patent to test herds and produce pure a2 milk™.

What is a2 milk™ like?


It has been a long time since I drank regular cow’s milk. But to me, and to people around me who tried it, it tastes no different. And neither should it!

Shelf life

Another thing that I noticed about a2 milk is that the expiration date on it seems to be longer, and the milk keeps longer once the bottle is opened than is indicated on the bottle of regular cow’s milk. I’ve yet to find out exactly why this is, but it’s pretty handy!


a2 milk™ is £1.39 per litre in supermarkets, which is a little more expensive than other milk. But then again, other milk is often sold below cost price by large supermarkets, which I don’t think is a good thing. I’d much rather pay a small premium for a product that has research behind it, especially when it’s something that I’m putting into my body!

a2 easy to digest milk
a2 milk beta-casein protein


I’m not recommending that everyone go out and buy a2 milk and drink it by the litre. I’m not even saying that it will definitely make you feel better if you have any issues with dairy. But without doubt, we should be learning about the things that we put in our body.

I loved discovering a2 milk and building on my knowledge of the components of foods that I’m putting in my body. I found it really interesting to learn more about the proteins and other elements that make up such a common drink, and understanding a little more about the milk industry globally.

I also like that I have one more option available to me, to ensure that I’m not missing out on vital nutrients by having to avoid dairy products completely and consistently.

Had you heard of a2 milk before? Is it something that you have tried, or are interested to try? Let me know by commenting below or tweeting me @_nataliejohanna