Milk is a staple in many diets, but for some people it brings more discomfort than nourishment.
Bloating, cramps, and other gut issues often lead people to give up dairy altogether.
A2 milk, which comes from cows that produce only the A2 type of beta-casein protein, has been marketed around the world as a gentler alternative to regular milk.
But new research from Finland suggests that A2 milk may not be the best option for everyone with milk sensitivity.
The study, conducted by the University of Turku’s Food Sciences Unit and published in the Journal of Dairy Science, compared A2 milk with another product: protein-hydrolyzed lactose-free milk.
In this type of milk, not only is the lactose removed, but the proteins are partially broken down, a process called hydrolysis, which may make it easier for the gut to handle.
Researchers recruited 36 adults who reported stomach problems after drinking milk.
Participants were divided into two groups based on whether they were genetically lactose tolerant or lactose intolerant. The study was designed as a randomized crossover trial, meaning every participant tried all of the milk types at different times, with a dairy-free period in between.
During the study, participants drank either A2 milk, A2 milk with added lactase enzyme, or lactose-free protein-hydrolyzed milk. Their gut symptoms were recorded, and blood and stool samples were taken to measure signs of inflammation.
The results revealed a nuanced picture. Among people who were lactose tolerant, both A2 milk and protein-hydrolyzed milk were well tolerated, with no major difference in symptoms. But for those who were lactose intolerant, lactose-free protein-hydrolyzed milk was clearly the best choice.
These participants reported fewer gut problems compared to when they drank A2 milk, which still contains lactose.
“Of the milks investigated in our study, the lactose-free, protein-hydrolyzed A1A2 milk was the best milk choice for lactose-intolerant people, and it was at least as stomach-friendly as A2 milk for those who can tolerate lactose,” explained Professor Kaisa Linderborg, the study’s lead researcher.
Interestingly, some participants experienced gut discomfort during every part of the study—even during the milk-free period. This suggests that milk is not always the sole cause of gastrointestinal issues. Other dietary or environmental factors may play a role in how people perceive and experience gut symptoms.
When it came to inflammation, the researchers found no significant changes across the different milk types. Levels of common inflammatory markers such as C-reactive protein and fecal calprotectin remained stable, indicating that the discomfort reported by participants was not linked to widespread inflammation.
This was the third study from the Turku team on milk-related gut issues, and the findings once again highlight how complex the problem is. While lactose intolerance is a well-known cause of milk sensitivity, not all discomfort can be explained by lactose alone. Protein type and processing methods also appear to play a role, and individual differences make the picture even more complicated.
For consumers, the message is that A2 milk is not a universal solution. While it may be easier to digest for some, those with lactose intolerance are better off choosing lactose-free products—particularly those with protein hydrolysis.
As Professor Linderborg noted, milk remains an important part of diets in many cultures, which makes it essential to continue studying how different types of dairy affect sensitive individuals.
The hope is that this research will lead to better-tailored dairy products that meet the needs of people with diverse digestive systems.
