Key takeaways:
The difference between regular and A2 milk is the type of casein protein they contain. A2 milk contains only A2 casein, while most regular milk contains both A1 and A2 casein.
A2 milk tastes like regular cow’s milk and has comparable vitamins and minerals. Like regular milk, A2 milk contains lactose unless the label says lactose-free.
If regular milk gives you gas or bloating, talk with a healthcare professional about possible causes. A2 milk may be worth trying after ruling out lactose intolerance, milk allergy, and other digestive conditions.
Some people have trouble digesting milk. Many assume their stomach issues are caused by lactose intolerance, but this isn’t always the case. A protein in milk called A1 casein might also cause symptoms such as gas and bloating and may be mistaken for lactose intolerance.
You may have seen A2 milk in the grocery store. It doesn’t contain A1 casein protein. But is it a promising alternative to regular milk?
What is A2 milk?
A2 milk is cow’s milk that contains only the A2 form of casein, which is one of several casein proteins in milk. Most cow’s milk contains both A1 and A2 casein.
Aside from this protein difference, A2 milk looks and tastes much like regular milk. It also contains lactose unless it’s processed and labeled as lactose-free (more on this later).
A2 milk is available in many of the same varieties as regular milk, including whole, reduced-fat, and fat-free options. Some brands also sell lactose-free A2 milk.
Where does A2 milk come from?
A2 milk comes from cows that naturally produce only A2 casein. This trait is determined by the cow’s genes. Farmers can test cows to identify those with two copies of the A2 gene. By breeding and milking these cows separately, they can create milk that doesn’t contain A1 casein.
Regular milk vs. A2 milk nutrition
A2 milk and regular milk have similar nutrient profiles. But the exact amounts of calories, protein, vitamins, and minerals vary by brand, fat percentage, and fortification. The table below compares 1 cup of 2% regular milk with 1 cup of 2% A2 milk.
Nutrient | Regular 2% milk (1 cup) | A2 2% milk (1 cup) |
|---|---|---|
Calories | 122 | 130 |
Protein | 8 g | 9 g |
Fat | 5 g | 5 g |
Carbohydrate | 12 g | 12 g |
Calcium | 309 mg | 389 mg |
Potassium | 390 mg | 389 mg |
Sodium | 95 mg | 125 mg |
Vitamin D | 111 IU | 199 IU |
Is A2 better for you than regular milk?
For most people, A2 milk isn’t better than regular milk from a nutrition standpoint. They have very similar nutrient profiles.
Some research suggests that A2 milk may cause fewer digestive symptoms in people who experience discomfort after drinking regular milk.
One small study of 45 adults who felt intolerant to regular milk compared milk with both A1 and A2 protein against milk with only A2 protein. When people drank A2-only milk, they reported less stomach discomfort, lower levels of some inflammation markers, and better scores on a thinking (cognitive) test.
A more recent study in people who felt discomfort after regular milk found that 2 weeks of A2 milk was linked to less abdominal pain and urgency, compared with regular milk. They also had more “good” gut bacteria.
But, for most people, A2 milk doesn’t have a proven health advantage over regular milk. Claims that A2 milk prevents diseases such as diabetes or heart disease are not proven. These ideas come mostly from population and animal studies, not from well-controlled human trials. For people with milk-related stomach discomfort, A2 milk is one option to try, but it’s not the only one.
Read more like this
Explore these related articles, suggested for readers like you.
A2 milk benefits
Research hasn’t established unique long-term health benefits of A2 milk. The most promising findings involve possible digestive benefits for some people who report feeling discomfort after drinking regular milk.
That said, since A2 milk has a similar nutrition profile as regular cow’s milk, it provides many of the same nutrients, including protein, calcium, potassium, and vitamin D (when fortified).
Benefits associated with milk or dairy in general include:
Support for bone health: Milk provides protein and calcium and may also be fortified with vitamin D, all of which support healthy bones.
Support for heart health: Studies show dairy is associated with better heart health. The calcium, potassium, and magnesium found in milk may help lower blood pressure and heart disease risk.
Reduced colon cancer risk: Studies show a link between people who drink milk and a lower risk of colon cancer. The protective effects are thought to come from calcium and vitamin D, though more research is needed to understand this possible connection.
A2 milk side effects
A2 milk has the same general risks as other types of cow’s milk. Unless it’s lactose-free, it may cause gas, bloating, cramps, or diarrhea if you have lactose intolerance. It’s also not a safe option if you have a milk allergy, because it contains the same milk proteins that trigger allergic reactions, like casein and whey.
Some research has linked dairy consumption to worsened acne and eczema flares. But it isn’t known if A2 milk affects these conditions differently.
Is A2 milk lactose-free?
Most A2 milk isn’t lactose-free. Standard A2 milk contains lactose, just like regular cow’s milk. But some brands offer lactose-free A2 milk.
If you have lactose intolerance, you can drink a lactose-free version of A2 milk. Or you can try taking a lactase supplement before drinking it.
A1 intolerance vs. lactose intolerance
Lactose intolerance occurs when your body doesn’t make enough lactase — the enzyme that digests lactose. It can cause uncomfortable symptoms after drinking milk or other foods with lactose.
Some people report similar symptoms after drinking milk even when lactose doesn’t seem to be the cause. Researchers are studying whether A1 casein plays a role in symptoms. But A1 intolerance or sensitivity isn’t a well-established diagnosis, and there’s no standard clinical test for it.
Possible symptoms include:
Gas
Bloating
Stomach ache
Cramps
Diarrhea
Frequently asked questions
There’s limited research on A2 milk and inflammation. For most people, regular milk isn’t inflammatory. Some small studies suggest that in people who feel discomfort with regular milk, the A1 protein may trigger more gut inflammation than A2 milk. But this research is limited. If milk seems to bother you, switching to A2 milk is a low-risk option, but there’s no strong proof that it will change how it affects inflammation.
A2 milk isn’t a treatment for irritable bowel syndrome (IBS). And there’s very little research looking at A2 milk in people with IBS. Remember, milk-related discomfort is often driven by lactose, not the A1 or A2 proteins. Certain foods and lactose can trigger symptoms in some people with IBS.
You shouldn’t drink A2 milk if you have a lactose intolerance, milk protein allergy, or galactosemia, a rare genetic disorder in which you can’t digest milk sugar.
There’s limited research on A2 milk and inflammation. For most people, regular milk isn’t inflammatory. Some small studies suggest that in people who feel discomfort with regular milk, the A1 protein may trigger more gut inflammation than A2 milk. But this research is limited. If milk seems to bother you, switching to A2 milk is a low-risk option, but there’s no strong proof that it will change how it affects inflammation.
A2 milk isn’t a treatment for irritable bowel syndrome (IBS). And there’s very little research looking at A2 milk in people with IBS. Remember, milk-related discomfort is often driven by lactose, not the A1 or A2 proteins. Certain foods and lactose can trigger symptoms in some people with IBS.
You shouldn’t drink A2 milk if you have a lactose intolerance, milk protein allergy, or galactosemia, a rare genetic disorder in which you can’t digest milk sugar.
The bottom line
A2 milk is cow’s milk that contains only A2 casein. Most regular milk contains both A1 and A2 casein. The two have similar taste and nutritional value, and A2 milk contains lactose unless it’s labeled lactose-free.
If you get gas and bloating from drinking regular milk, talk with a healthcare professional to rule out lactose intolerance, a milk allergy, or another digestive condition. If those are ruled out, you can try A2 milk to see if it helps with your symptoms.
Why trust our experts?
References
Barrubés, L., et al. (2019). Association between dairy product consumption and colorectal cancer risk in adults: A systematic review and meta-analysis of epidemiologic studies. Advances in Nutrition.
Dehghan, M., et al. (2018). Association of dairy intake with cardiovascular disease and mortality in 21 countries from five continents (PURE): A prospective cohort study. The Lancet.
FoodData Central. (2023). 2% reduced fat A2 milk. U.S. Department of Agriculture.
FoodData Central. (2019). Milk, reduced fat, fluid, 2% milkfat, with added vitamin A and vitamin D. U.S. Department of Agriculture.
Greenway, F. L., et al. (2026). Comparative effects of conventional cow’s milk versus milk free of A1-type beta-casein on gastrointestinal physiology and symptoms of digestive discomfort in participants intolerant to conventional cow’s milk: a pilot randomised controlled trial. Nutrition Journal.
Jianquin, S., et al. (2016). Effects of milk containing only A2 beta casein versus milk containing both A1 and A2 beta casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cows’ milk. Nutrition Journal.
Kay, S. S., et al. (2021). Beneficial effects of milk having A2 β-casein protein: Myth or reality? The Journal of Nutrition.
Pal, S., et al. (2015). Milk intolerance, beta-casein and lactose. Nutrients.
Song, C. H., et al. (2025). Beneficial effect of consuming milk containing only A2 beta-casein on gut microbiota: A single-center, randomized, double-blind, cross-over study. PLoS One.
Ulven, S. M., et al. (2019). Milk and dairy product consumption and inflammatory biomarkers: An updated systematic review of randomized clinical trials. Advances in Nutrition.
University of Minnesota Extension. (2026). A2 milk and A2 genetics.
