Same … but different
A2 milk is the same as regular milk except for an amino acid in milk’s second most prevalent protein, beta casein. Regular milk, produced by most cows, contains two forms of the amino acid and thus contains two forms of beta casein: A1 and A2. In A2 milk, only one form of the amino acid is present; it comes from cows bred to produce only the A2 form of beta casein.
That difference has led to claims, largely from the A2 milk industry, that A2 can prevent everything from heart disease and type 1 diabetes to sudden infant death syndrome, autism, psychiatric illnesses, and delayed cognitive development in children.
Proponents say A2 milk has advantages over regular milk because the A2 beta-casein protein stays intact during digestion, whereas the protein with A1 breaks down to form a compound called beta-casomorphin-7. That compound has been associated with various ailments involving an inflammatory response in the gut.
What the science says
To see if the claims about A2’s health benefits are supported by objective scientific evidence, a relatively large number of studies have been conducted. But the research has had significant limitations: generally small numbers of participants, short trial periods, and study designs with endpoints looking at potential markers for disease rather than disease itself.
Even in those small research efforts, results have been less than promising. In fact, in a systematic review of more than 20 studies, published in Nutrition Reviews in 2019, it was clear that no matter what the trial and no matter what disease was being researched, it pretty much did not make a difference which kind of milk the participants drank.
For instance, one study found no difference in people’s insulin levels whether they drank regular milk or A2 milk for 12 weeks. In other trials, A2 milk did not result in lower levels of blood cholesterol, triglycerides, or blood pressure.
For the most part, only large population studies included in that review suggested A2 milk could potentially protect heath. But such studies are observational and can find only associations; they do not prove cause and effect.
And, as noted by the authors of the review, roughly half the studies they examined were funded by companies that profit from the sale of A2 milk, and often “the results of these studies favored the interests of the funder.” Study funding should not always be assumed to represent tainted findings, but the reviewers do state “the possibility that economic interests could have influenced the study results cannot be excluded.”
The notion that autism is linked to milk has fallen apart under scientific scrutiny, as well. It’s been hypothesized that autism results from an excess of compounds called opioid peptides, and beta-casomorphin-7 produced during the digestion of regular milk is one of those compounds. But a study in Developmental Medicine & Child Neurology that examined the urine of children with autism and their non-autistic siblings found that neither group had opioid peptides in their urine.
A2 milk for lactose intolerance?
With all of this research that has come up short, you might say that A2 milk has been a product in search of a disease to prevent. But there does seem to be a little evidence (emphasis on “a little”) that for certain people, A2 milk is more easily digested and does not cause bloating, stomach pain, or other gastrointestinal symptoms that they may experience after drinking milk that contains A1. It’s not about lactose. Both types of milk contain the same amount of this milk sugar.
In one well-controlled study, published in Nutrients in 2020, 25 milk “maldigesters” were given regular and A2 milk at different times and not told which was which (the researchers didn’t know either, making the study “double-blinded”). Abdominal pain was lower after consumption of A2 milk. In a separate controlled pilot study of 41 people that appeared in the European Journal of Clinical Nutrition in 2014, A2 milk also caused less abdominal pain. Similarly, a 2016 study in the Journal of Nutrition showed that A2 milk did not exacerbate gastrointestinal symptoms compared to regular milk.
BOTTOM LINE: There’s no good evidence that A2 milk is particularly better for you than regular milk. But if regular milk leaves you feeling bloated or otherwise uncomfortable—and lactose-free milk or lactase pills don’t help things—there’s no harm (other than to your wallet) in giving A2 milk a try.
