What Happens to Your Body When You Drink A2 Milk

Milk is a nutrient-dense staple for some, but for others, it can trigger digestive symptoms. A2 milk contains a type of protein that may be easier to digest. It’s marketed as an option for people who don’t tolerate conventional milk, though not everyone will notice a difference.

Milk contains two main proteins: whey and casein, with casein accounting for about 80% of total protein. One form of casein called beta-casein exists primarily as A1 or A2. Most conventional
cow’s milk contains a mix of both, while A2 milk contains only A2 beta-casein.

During digestion, A1 beta-casein can break down into a peptide called beta-casomorphin-7 (BCM-7). Research suggests that BCM-7 may slow gastrointestinal motility and influence gastrointestinal signaling, potentially contributing to symptoms such as bloating, gas, and abdominal discomfort.

In contrast, digesting A2 beta-casein does not appear to release BCM-7.

While further studies are needed, some human studies suggest that A2 milk may be easier to tolerate for certain people. In one study funded by the A2 Milk Company, adults who reported milk-related digestive discomfort experienced fewer gastrointestinal symptoms after consuming A2 milk compared with conventional milk containing both A1 and A2 proteins.

Another study found that adults with digestive symptoms associated with milk reported less abdominal pain and urgency after drinking A2 milk, though results were mixed, suggesting A2 milk may be gentler on the digestive system for some individuals.

Cow’s milk and A2 milk both contain protein, calcium, phosphorus, and potassium, and fortified options also include vitamin D. Only the type of protein is different.

Research comparing A2 and conventional milk shows comparable levels of essential nutrients and protein quality. Switching to A2 milk does not alter calcium intake or other nutrients.

The digestive differences are related to protein structure, not nutrient content.

People with lactose intolerance lack the enzyme lactase, which breaks down lactose, the main sugar in milk. Because A2 milk contains the same lactose content as conventional milk, it does not resolve true lactose intolerance, even if some people report fewer symptoms with A2 milk.

Symptoms of lactose intolerance and milk protein sensitivity can overlap. Some individuals who believe they are lactose intolerant may not have confirmed lactase deficiency and may be reacting, at least in part, to A1 beta-casein–related digestion rather than to lactose itself. In some research, participants who self-identified as lactose intolerant reported fewer symptoms with A2 milk, even though both contained the same amount of lactose.

If you know you have lactose intolerance, or if symptoms persist with A2 milk, lactose-free milk, or non-dairy alternatives may be more appropriate.

A2 milk is sometimes promoted for potential anti-inflammatory benefits, but the evidence is inconclusive.

Small studies suggest that A1 beta-casein and BCM-7 may be associated with markers of oxidative stress or low-grade inflammation. However, most are animal or cell-based. Some research also suggests A2 milk may reduce certain inflammatory responses related to digestion, but more research is needed.

A2 milk is not safe for people with a diagnosed milk allergy, which is different from lactose intolerance.

A milk allergy is an immune response to milk proteins that can cause symptoms such as hives, vomiting, or, in severe cases, anaphylaxis. A2 milk still contains these proteins, so it’s unsafe for people with a true milk allergy, regardless of whether the protein is A1 or A2.

A2 milk may be worth trying for people who:

• Experience mild digestive discomfort after drinking regular milk.
• Tolerate yogurt or cheese but not fluid milk.
• Have ruled out lactose intolerance or milk allergy.

If you are concerned about symptoms after drinking milk, a registered dietitian or healthcare provider can help determine whether A2 milk is appropriate.