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A1 vs. A2 Milk
Cheese, Mutant Cows, Opioids & Constipation

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A1 vs. A2 Milk: Cheese, Mutant Cows, Opioids & ConstipationShareFollow us 261.1k

Quick Summary tl;dr

A1 casein from cows can be converted into an opioid in the body that can cause inflammation and gastrointestinal distress.

Non-cow dairy sources (sheep, goat, buffalo) don’t have A1 casein (they have A2 casein) and, therefore, may be safer to consume for people with troubled tummies.

For more information about dairy, also see:

If you love dairy but have a temperamental stomach, you’ll want to read this one. If you have an iron gut… well… actually… with a title like "Cheese, Mutant Cows, Opioids & Constipation," I bet you’ll probably find this interesting as well.

What Is The Difference Between A1 and A2 Dairy?

You may or may not know that much of the protein in cheese is a protein called "casein."

While most mammals make a particular type of casein called "A2" casein, many domesticated cattle also evolved a genetic mutation that allow them to make a second type of casein called "A1 casein" (sorry for the confusing nomenclature; the mutant second casein is the A1).

The difference between A2 and A1 caseins is that A1 casein protein differs in a single building block. (For those of you with some biochemistry background, A1 casein includes a Pro67His ( 1) point mutation. Non-nerds can feel free to ignore this parenthetical.)

Dairy from sources other than cows, such as from goats, sheep, and buffalo, doesn't contain A1 casein, only A2 casein.

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A1 Dairy May Be More Addictive and Cause Constipation

The consequence of this change in structure is that A1 casein, but not A2 casein, is broken down in our guts to make a chemical called β casomorphin 7, which, as its name suggests is a morphine-like opioid!

Now, as a scientist, I don’t feel qualified to comment further on the potential addictive properties of cheese opioids. But, as a recovering cheese addict, I can’t help but smile and sympathize with the hypothesis. Roquefort is my favorite. What’s yours?

But even if it isn’t strongly physiologically addictive, β casomorphin 7 has been shown to bind to receptors in the gut and cause constipation and other unpleasant gut symptoms.

A1 casein from cows can be converted into an opioid in the body that can cause inflammation and gastrointestinal distress.

So, if you’re like me and love cheese (and may even be addicted) but also have a temperamental stomach, what are you to do!?

Well, remember I said that only cattle evolved the genetic mutation to make A1 casein, and that only A1 casein can be broken down into β casomorphin 7?

This implies that if you consume dairy sourced from other animals, your stomach won’t make β casomorphin 7 and you may experience less tummy trouble. There is even research to support this hypothesis ( 2).

So, next time cheese upsets your stomach, don’t despair, just try to eat goat, sheep, or buffalo milk cheese instead.

Non-cow dairy sources (sheep, goat, buffalo) don’t have A1 casein (they have A2 casein) and, therefore, may be safer to consume for people with troubled tummies.

Easy A1 to A2 Dairy Swaps

Now, here's what you really came for, the practical tips!

Try substituting Parmesan with Pecorino Romano. They taste highly similar, but Pecorino is from sheep, is A2, and is far less inflammatory.

When you get mozzarella get Buffalo Mozzarella! It's not only A2, but richer and tastier than mozzarella from cows.

Other great cheeses that are probably easy to find and are made from sheep or goat dairy include Feta, Manchego, Halloumi (great for pan-frying), and Roquefort.

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Comments (52)

Thank you for sharing this informative article! I had no idea about the differences between A1 and A2 casein proteins in dairy and their potential impact on gut health. It's fascinating to learn about the opioid-like properties of A1 casein and how it can contribute to gastrointestinal distress. The practical tips for incorporating A2 dairy alternatives into our diets are incredibly helpful. I'll definitely be trying out some sheep and goat cheese options to see if they're easier on my stomach. Keep up the great work in providing valuable insights into nutrition and health!

Parmesan is safe. They don’t have a1 cows in Italy.

Outside the EU, the name "Parmesan" can legally be used for similar cheeses, with only the full Italian name unambiguously referring to PDO Parmigiano-Reggiano. But yes you can specifically but A2 parm R…

1) Do you think high consumption of A2 grass-fed dairy can also cause constipation? Like 100-150g of grass-fed A2 cheese or 1/2 cup heavy cream per day? I see dairy causing so many gut issues for many, so wondering if even A2 dairy can cause issues.
2) What are your thoughts on views that say "An animal's milk like cow or goat's is designed by its mother for its kid to grow to its structure/size. A cow weighs ~600 kg which is 5-6x that of human's. The cows milk has nutritional values that are designed for its calf to grow and the human body doesn't completely understand the structure of some other animal's milk. Lactase stops being produced in humans in between the age of 2 to 5 after the baby feeds on mother's milk. Isn't this nature's way of saying that drinking milk should happen below the age of 5 while the baby is growing and should be stopped afterwards? The only milk a mammal should consume is its own mother's milk. So human's should consume only their mother's milk while growing and stop drinking milk afterwards"

Yes, in some people even A2 dairy can cause issues. It may not be the casein itself, but possibly lactose or histamine or tyramine. Different people have different sensitivities to different foods/food components & different "diatheses" for different symptoms. With regards to the quote by anonymous, I have 4 main comments. 1. milk is the only natural compound rich in both carbs and fats. Why? Yes, because it's designed to help mammals grow.  However, cheese is low in carbs because the lactose is removed in the whey runoff. 2. human milk and cow's milk contain approximately the same amount of fat (in fact, I think human milk is fattier). That undermines the point about cow's weighing 600 kg. That's irrelevant. 3. A decent number (albeit a minority) of humans exhibit lactase persistence, whereby lactase is continually expressed throughout life. 4. We have developed techniques to help us exogenously process lactose. For example, fermented dairy products, like yogurt and kefir, contain bacteria that possess a lactase digesting enzyme. When the mixture hits the intestines, bile acids can cause the release of this enzyme from the bacteria into the gut lumen, allowing us to "steal" bacteria's enzymes for our own purposes.

What are your views on organic A1 heavy cream powder? I couldn't buy organic heavy cream in my place so thought of buying a quality heavy cream powder to use for coffee/french toast etc. Heavy cream does have casein in it, so it is best to have it A2?

I have no qualms about heavy cream powder itself. I think most brands just have sweet cream solids as a single ingredient. I don’t think it’s as good as real whole cream simply because of a bit more processing, but if it works for you it’s not something I would think to vilify. A2 is better, but that carb count is so low in heavy cream that if you tolerate what you have, then I wouldn’t worry. Plus, where does one buy goat’s heavy cream powder?  

I would love to be able to get plain and simply goat's heavy cream which is not always available. I can't image finding goat's cream powder. I would love that though 😊

How bad is it to pasteurize goat milk at 72ºC for 15 seconds which is standard for dairy products? Would we lost the beneficial bacteria?

I’m a fan of raw, but you’re almost always going to get pasteurized. It’s fine. I wouldn’t be going to milk for probiotics anyway. If you want probiotic dairy, go for raw cheeses and especially A2 blue cheese like Roquefort. Also, Red mill farms Goat’s milk kefir is a favorite of mine. Keep in mind that, in cheese making, probiotic bacteria can be added after pasteurization, as in blue cheeses and kefir.

Something practical:
I just found this cool website, not surprisingly called “” that allows you to sort cheeses by milk type, texture, country, color, or alphabetically. Nice resource. I thought I would share it.

Nick, that's a fantastic resource! Thank you!

Can you please recommend a good healthy A2 substitute for cheddar? And maybe Brie? Much obliged!

Oh, for all the complicated nutrition science questions below this may be the hardest. An aged goat’s Gouda might work for cheddar. For Brie you can get goat Brie or do Brebisrousse, which is similarly sweet and spreadable. Honestly, Martina is the chef here. Martina? Ideas?

Hi Chesny, apologies for the delayed response (it happens when I'm working on a new book!). I'd say that Gouda is a very good alternative to cheddar - it's not the same but closest from all the options I've tried. Another option is Manchego. I get goat's milk brie from a farmer here in the UK. It's an online store (not local where I live). It may be worth checking where you live. I hope this helps!

Martina, do you have thoughts on what spices pair best with feta?

Hi Joanne, you can use Greek style herbs like oregano, basil, mint, maybe some olives (depending on the recipe) and definitely plenty of extra virgin olive oil.
These work really well:
Low-Carb Vegetarian Greek Briam
Low-Carb Vegetarian Greek-Style Superfood Bowl
Low-Carb Bruschetta Feta Dip
Low-Carb Mediterranean Cauliflower Couscous
You could also use it with spices like cumin, coriander, turmeric and chile powder. It would work well in a classic shakshuka topped with feta - similar to this: Keto Southern Goat Cheese Shakshuka
I hope this helps! 😊

Do you have any thoughts on pasteurization of cheese? Is raw cheese safe? I want to get the probiotic effects of cheese but also don't want to get a bacterial infection.  

Good question. I don't want to state that 100% of raw cheeses are safe because were you to take that as medical advise and get sick I'd feel horrible. But, I can say that pasteurization was invented (actually for preventing wine from spoiling) back when we knew less about microbiology. Now, cheese raising practices are more sophisticated such that we are pretty good at preventing the growth of pathogenic (disease causing) bacteria. I always choose raw cheese if I have the choice for the very reason you mentioned: probiotic.

What an interesting, helpful, and lovely post. Thank you. I will be certain to eat less A1 cheese. In general though, I try to keep my dairy intake on the lower end because dairy is higher in saturated fat, which isn't great for heart health, right? I was googling cheese and heart heart and reading about something called the "French Paradox." Have you hear of this? Basically, the French eat a lot of cheese and have low levels of heart disease.

First, with respect to saturated fat being bad for the heart, that's a fallacy, plain and simple. But don't take my word for it. See this new state of the art review from the Journal of the American College of Cardiology (JACC):
It says, quote, "The recommendation to limit dietary saturated fatty acid (SFA) intake has persisted despite mounting evidence to the contrary. Most recent meta-analyses of randomized trials and observational studies found no beneficial effects of reducing SFA intake on cardiovascular disease (CVD) and total mortality..."
On the topic of the French paradox, yes, the French consume 58 pounds of cheese per person per year and have among the lowest rates of cardiovascular disease in the world. This may have to do with the heart healthy benefits of certain cheeses, particularly molded cheeses like Roquefort, Camembert, and Gorgonzola. Here's a cool review on the topic:

What do you think about autoimmune diseases and dairy? I've heard dairy should be avoided, is it a valid concern? I'm T1D and I also have psoriasis.... thank you!

As far as I'm aware, all the correlations between autoimmune diseases (most literature is on RA) and dairy are related to cow's dairy and the mechanism is generally simply that cow's dairy is pro-inflammatory. A2 dairy is far less inflammatory.
With respect to T1D specifically, this paper says, "We present evidence that A1 β-casein cows’ milk protein is a primary causal trigger of type 1 diabetes in individuals with genetic risk factors... We present epidemiological, animal-based, in vitro and theoretical evidence for A1 β-casein and its β-casomorphin-7 derivative as dominant causal triggers of type 1 diabetes."
This mouse experiment seems to conform that A1 casein can contribute to T1D:
And more here:
Basically what I'm saying is I think A2 dairy should be safe because it would appear the thing that makes A1 "bad," and the reason this blog was written, is the thing that might cause concern with respect to dairy and T1D. What I can say is if you have T1D and choose to have dairy, definitely go for the A2 😊.

Wonderful post Nick and Martina! One of my favourites. I had a question on behalf of my cousin who has Parkinson's disease. She's been told not to have aged dairy, or fermented dairy or blue cheeses. I shared this post and we were talking and she doesn't know why. Any idea why her doctor told her this?
Thank you,

Chelsea, first let me say that I’m rather impressed her doctor made this comment. Fewer neurologists are into diet and nutrition and it seems that your cousin’s is! She’s a keeper! I’m relatively confident this advice has to do with the fact that aged, fermented, and blue cheeses are rich in a molecule called “tyramine.” Tyramine is made from the amino acid (protein building block) “tyrosine.” Tyrosine can also be made into dopamine, the molecule that is depleted in Parkinson’s disease. For this reason, some Parkinson’s patients are put on drugs called monoamine oxidase inhibits to boost dopamine levels, but this would also impair the breakdown of the tyramine in aged, fermented, and blue cheeses. If tyramine builds up it can cause unpleasant side effects, like headaches. It may be worth asking your cousin if she’s on an “MAOI.” If the answer is yes, then there’s a very high chance I’m right.

The only problem is that I love cheese... too much! I could easily go through a whole package in one sitting. I couldn't understand why it is that once I start I can't stop. Seems like it has almost the same effect on (my) brain as fructose... just as addictive. Any portion control tips for a recovering cheese addict? :-D

Haha, I feel you helen! Same problem! I can’t buy a block of Roquefort without eating the whole block, even if it’s 500 grams. Therefore, I
(1) avoid buying those cheeses to which I know I’m addicted too often.
(2) set up cheese meals during which I’m allowed cheese and non-cheese meals where I’m not.
(3) Use blue cheeses (my fav) less as foods in their own right and more as garnishes or accents. For example, I’ll tell myself Roquefort isn’t a food right now, it’s like a spice for your omelet.
(4) Play food golf. If you ever want to decrease intake of something make it a game my recording the amount you intake week to week and trying to beat you score each week.
(5) Set up a commitment device where you have to give away money if you overeat cheese, as determined by some specific threshold.
(6) Have an accountability buddy to report to.
(7) make yourself work for it. Eg 1 push-up per gram you eat.
Any of those sound workable?

Thank you SO much! This is more than I expected. Thank you for your hard work, you're making a real difference!

Of course 😊. Here's more on shaping habits:
Best of luck!

Wow! I love this! I’m definitely buying A2 from now on! Martina, do you have any Roquefort recipes? If not, could you make some!?

Hi Benny, you could use it just like blue cheese so any recipes with blue cheese will work. I think I may need to add a filter for A2 based recipes 😊
Keto Buffalo Deviled Eggs
Low-Carb Buffalo Ranch Chicken Sheet Pan Dinner

Hey, Martina, not a bad idea on the filter...

Right?! We are actually working on allergy filtering in the app now so I'll see how easy it would be to add this.

If I could add my vote the the mess, yes to A2 filter!

This is great! I've been keto for almost three months and now I'm thinking about going dairy-free. I've always had minor issues caused by dairy but they were not bad enough to avoid the one thing I love most - cheese. I was surprised how many types of cheese is A2!
An unrelated thought in case you know the answer... I lost 15 pounds on keto but now I need to lose another 20 and the weight loss stopped. If A2 dairy is less likely to cause tummy issues, could it possibly have an effect on weight loss?

Directly... no. Indirectly, you never know. Here's the thing... I doubt that swapping parmesan for pecorino is going to cause you to drop 20 lbs, but having a healthy weight is simply a side effect of being healthy. Weight itself is a horrible metric of health. And, if someone is genuinely overweight (like most are) than by simply eating a clean, low-carb, low-inflammation diet, their body tends to correct itself. This has been shown in human studies, such as Forsythe...Volek, 2009, Lipids, "Comparison of low fat and low carbohydrate diets on circulating fatty acid composition and markers of inflammation." In this study, putting overweight people on clean Keto cause them to spontaneously reduce calories to 1,500 until their weight corrected. Go see this lecture: , you can skip to 15:45 if you want. Best of luck on your journey and congrats on the first 3 months and 15 lbs!

Thank you! So if I follow a clean keto diet I'll be less likely to have cravings... There's this trend called dirty keto that only focuses on weight loss and although it's not what I've been doing, I think I can do better. Sometimes I'd have a Quest bar or eat bunless take out burgers... 😬

Nobody is perfect, but you're correct in that clean Whole Foods diet is best. It's the dirty keto that gives keto a bad name. Beef jerky, cheese wiz, and walnuts could be a keto diet, but it's not healthy. the same goes for any diet. For example, a diet of only Oreos is vegan. In my opinion, when comparing diets it's only fair to make the best reasonable case for each, and that means Whole Foods whether you're vegan, keto, carnivore, paleo, pescatarian, etc.

Thank you! So many people out there promoting dirty keto as if it's healthy. Is all jerky bad or only the one with sugar and additives...? Why walnuts, these are whole foods right?

Sorry, I wasn't trying to single out jerky and walnuts. It was more an example of a set of foods that together were an incomplete dirty keto diet. Having said that, jerky usually does have sugar and jerky that lacks sugar may have an unbalanced sodium load. Ideally you want your potassium and sodium in balance. As for walnuts, a few are probably okay, but keep in mind they are an Omega-6 bomb. 1 ounce (28 grams) of walnuts has 11 grams Omega-6, far more than any other nut. At the very least, it's important not to heat walnuts above 130C for more than 20 min or else you get high levels of Omega-6 oxidation. Better substitutes for walnuts are macadamia or hazelnuts, with the former having negligible amounts of omega-6, anti-nutrients (like phytic acid), and load's of the monounsaturated fats oleic acid (as in olive oil) and Palmitoleic acid (omega-7 fat that's rare in the diet and very healthy!).

Oh I see, I haven't thought of that! I'm still learning and I am so grateful for your help and patience. Omega 6 is the part of my diet I haven't paid much attention to. Thank you so much, I am looking forward to reading more! Tracy

Tracy, I commend you for wanting to learn! That's the number 1 biggest step. Once you see nutrition as a fun learning journey of self-improvement, everything else falls into place. If you want to decrease your Omega-6, watching you nut intake (except macadamias and hazelnuts, which are high in MUFA), limiting seed/nut oils (other than macadamia oil, extra virgin olive oil, avocado oil, and coconut oil), and main sure to buy all your animal protein 100% grass-fed (meat) or pastured (poultry and eggs) is a good place to start. Also, you want to probably increase your Omega-3s with fatty fish like salmon, sardines, and mackerel. If you choose to supplement Omega-3s, krill oil is the best source (complicated, has to do with lyso-DHA). Best of luck!

Hey Nick, which cheeses have the most calcium?
Also, how much do different dairy sources, like sheep and buffalo, differ from cow in terms of their micronutrients?
Thanks in advance,

Because of how cheese is made, harder cheese tend to have more calcium than softer cheeses. That’s a good guideline.  
According to this website, Parmesan and Pecorino (Parm’s sheepy superior) win the day at >300 mg per ounce (28 grams). Gruyere and hard (not soft) goat cheese were ranked numbers three and four.
I have a particular thing for Pecorino. And, hey, here’s a peer-reviewed scientific publication specifically on Pecorino for bone health!
With regards to mineral content, check out this comparison table:
It looks like sheep’s milk wins in most categories, including calcium, magnesium, zinc, manganese, iodine, and selenium. In fact, it appears to crush it with the iodine and selenium, which are thyroid-supporting micronutrients. Goat’s milk appears to be best for potassium, which helps with blood pressure.

Thank you Nick, I'm one of those A1 intolerant people. I'm fine with goat and sheep cheese but I can't have mozzarella, not even buffalo. Is that common? Oh by the way have you ever tried camel milk? It's delicious but seems to have more carbs. I wonder if I could use it to make cheese 😊

My best guess is that you're both A1 intolerant and lactose intolerant. In fact, "lactose persistence" (where you continue to express the lactase enzyme into adulthood) is the evolutionary latecomer that impacts a small proportion of people. In effect, people who can have lactose are the mutants, haha.
The reason I think this is because lactose is water-soluble, meaning it's removed from dairy when the water component is extracted or cheeses are dried. Mozzarella, even from buffalo, is quite soft and not aged, meaning it's likely to be higher in lactose as compared to harder cheeses. How do you do with Brie or Camembert? How do you do with Manchego or Pecorino?
And, no, I haven't tried camel's milk. Sounds yummy! If it's ever a possibility I want to try polar bear milk or blue whale milk cheese. Those are the fattiest creamiest milks in nature... but something tells me they would be hard to produce on scale...

Lactose that's a good point! Thank you. I'll stick with my aged goats cheese, it's my safest bet 😊 Oh I'm dying to try all these options they must be so creamy. The more fat the better!

Something yummy to try is pan frying halloumi goat's milk cheese in ghee. The halloumi shouldn't melt and the ghee is casein free. Super yummy!

This explains a lot about why have an issue with A1. I always thought it was lactose but I can eat goat's cheese with no issues. I didn't realise mozzarella can be A2! Is there such a thing as buffalo burrata? Thank you!

Found one!
"This burrata is made entirely from 100 percent grass-fed buffalo milk."
Let us know how it is!

Lovely Article! Nick, I too LOVE Roquefort, but I have this strange problem with it. Whenever I have it, the next day my face is reddish and a bit puffy. Any idea why? Because of this I’ve been avoiding Roquefort, and it’s one of my favorites!
But the even weirder thing is that a couple other dairy products cause the same effect, like sour cream from my butcher, but NOT sour cream from the chain grocery store near my house! I know, I probably sound crazy, but I’m pretty observant and it’s a reliable “phenotype” (I hope I used that word right, sorry I’m trying to learn science but don’t have a background in it).

Actually, you don't sound crazy and I think I have an answer. Have you heard of histamine or, maybe seen ads for "anti-histamines" for allergies. Histamine is a molecule released from your immune cells during an immune reaction. It causes an inflammatory response, which can lead to the symptoms you described - reddening of the face puffiness. (The puffiness happens because of water retention. Basically, the histamine makes your small blood vessels, called capillaries, more leaky so that white blood cells can get out of circulation and attack invaders as part of the immune response. Because the blood vessels are more leaky, more water leaks out).
Now, here's the thing, some foods have histamine in them too, including aged and fermented dairy! Some people have a genetic predisposition to be histamine sensitive. You can actually get generic testing for this, but I don't think that's necessary. It's not super common, but common enough that I'd bet that's what you're dealing with. It also may actually explain the sour cream phenomenon! I suspect that the sour cream from your butcher (or maybe you mean cheese monger? do butchers sell cheese?) is real sour cream of higher quality that's been fermented, whereas the supermarket sour cream may be a sort of imposter. (Don't get me started on imposter dairy. It infuriates me that many American supermarkets carry cheese that should be A2 as mostly A1s, like feta).
The short of it is that Roquefort and real sour cream are rich in histamine and that might be causing your problem with redness and puffiness. Here's a solution to try, other than the obvious elimination of histamine-rich foods: Diamine Oxidase (DAO) Supplement. DAO is the enzyme that breaks down histamine, and you can actually get it in pill form. I'm not sure if you need a prescription, but if you do, just ask your PCP. This may allow you to have the world's best cheese (I love that we share that opinion) without redness or puffiness. Give it a go?
Fingers crossed for you!