All About Dairy Intolerance (Lactose, Casein & Whey)

Dairy is a complicated food group. There are many components that can disagree with you; the proteins, the sugar and/or the fat molecules. You could be sensitive to one or all of these things!

Intolerance can cause abdominal pain, discomfort, and nausea. It also causes embarrassing symptoms like flatulence and diarrhoea. Other symptoms linked to food intolerances include muscle or joint pain, headaches, exhaustion, and even skin symptoms like rashes and eczema.

Dairy is just one of those foods that many people seem to be intolerant to. Let’s talk about the main components of milk that people react to: lactose, casein, and whey.

Milk sugar (lactose) intolerance

It’s estimated that up to 75% of adults are lactose intolerant. Lactose is the carbohydrate “milk sugar” naturally found in most dairy products. Lactose intolerance is so common you can buy lactose-free milk in your regular grocery store. Lactose-free products are treated with the enzyme “lactase” that breaks the lactose down before you ingest it. It’s this lactase enzyme that is lacking in most people who are lactose intolerant.


The lactase enzyme is naturally released from your intestine as one of your digestive enzymes. It breaks down the lactose sugar in the gut. When someone doesn’t have enough lactase, the lactose doesn’t get broken down the way it should.  Undigested lactose ends up being food for the resident gut microbes. As they ferment the lactose, they create gases that cause bloating, flatulence, pain, and sometimes diarrhoea.

Lactose is in dairy but is in lower amounts in fermented dairy (e.g. cheese & yoghurt) and butter. Steering clear of lactose isn’t that easy as it is added to other foods like baked goods, soups, and sauces. And if you’re taking any medications or supplements, check to see if it’s in there too, as lactose is a common ingredient in them.

If you have symptoms of lactose intolerance, keep an eye on food, medication, and supplement labels.

Milk protein (casein & whey) allergy

Milk is a known, and common, food allergen. In the UK, it is considered an “allergen” and must be declared on food labels.

So, what are the allergens in milk? You’ve heard of “curds and whey?” Well, these are the two main proteins in milk. The solid bits are the curds (made of casein), and the liquid is the dissolved whey.

Unlike lactose intolerance, casein and whey can cause an actual immune response. It’s an allergy. And this immune response can cause inflammation. In fact, we don’t know how many people have these milk allergies, but most estimates put it far below that of lactose intolerance.

Like lactose, these allergenic milk proteins can be found in other products too. They’re not just in dairy but are often in protein powders as well (Have you heard of “whey” protein powders?).

Some of the symptoms of milk protein allergy differ from that of lactose intolerance; things like nasal congestion and mucus (phlegm) are more common here. And casein seems to be linked with belly fat.

Interestingly, people who have gluten intolerance are often allergic to milk proteins like whey and casein as well. These can go hand-in-hand.

Like lactose intolerance, if you’re allergic to casein and whey keep an eye on labels so you can avoid these.


A1 & A2 Casein

Image result for a2 milkOkay, this is where it gets a little more complicated. For those that are sensitive to casein, it could be that you are sensitive to only A1 casein, found in milk from Friesian cows. A2 casein, found in goat milk, sheep milk and Jersey cow milk is often better tolerated. A1 casein is cleaved into casomorphin within the guts of some people. This is an opioid-like substance, with similar effects as opioids. Symptoms such as constipation, dairy ‘addiction’ and brain fog are common. This casomorphin also stimulates the production of histamine, which can cause skin symptoms like hives and eczema. Histamine can also stimulate the ovaries to produce more oestrogen. As such, A1 intolerance can cause PMS type symptoms, acne and can make weight loss more difficult. Personally, I find that consuming A1 dairy gives me acne.


If you get gassy, bloated, or diarrhoea after eating dairy, you may have lactose intolerance. If you often get a stuffy nose and mucus, then you may be allergic to casein and/or whey. And do note, you could have both! 

While dairy may be an entire food group, it is not an essential nutrient. In fact, in Canada dairy has been removed from the nutrition guidelines. All the nutrients in dairy are available in other foods. If you experience these symptoms, you can try removing dairy from your diet. You may find improved digestion and fewer gut issues. Or you may find improved nasal congestion, or even less belly fat.

If you suffer from lactose intolerance you should see improvements within days after removal. As for casein and whey intolerance, it can take a fair bit longer for improvements when you remove dairy. It could be weeks or months.

If you decide to (or have already) removed dairy from your diet, let me know your experience in the comments below.

If you’ve removed dairy and are still struggling with symptoms then get in touch; you could have a digestive imbalance that could easily be resolved with the right support.

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