A1 and A2 beta-casein in animal studies
What it found
In animals, A2 beta-casein led to less gut inflammation and better gut transit than A1 beta-casein in some studies, while results for heart and diabetes markers were mixed.
Most of the 42 studies looked at BCM-7, a peptide released from A1 beta-casein, and its opioid-like effects.
What they found
Animal and lab studies
Gut effects
In rats, A2 beta-casein caused less intestinal inflammation and a better gut transit time than A1 beta-casein. In mice, A2 beta-casein led to a better gut immune response than A1 beta-casein.
Heart disease markers
In rabbits, A2 beta-casein led to fewer aortic fatty streaks than A1 beta-casein. In pigs, there was no difference in total cholesterol or triglycerides after either type.
Diabetes markers
In mice, A1 beta-casein increased diabetes incidence in the 3rd and 4th generations but not in earlier ones. Blood glucose showed no difference in mice and pigs, but A2 beta-casein had a favourable effect in rats.
BCM-7 pain relief
BCM-7 gave significant pain relief in rats, cockroaches and broiler chickens. The effect was blocked by naloxone, confirming it acts like an opioid.
BCM-7 and insulin
In dogs, BCM-7 or a mix of BCM fragments stimulated insulin release after a meal. In rats, BCM-7 led to lower blood glucose and higher insulin levels.
BCM-7 other effects
BCM-7 protected against diabetic kidney and heart damage in rats, improved gut immune response in mice, and increased growth in broiler chickens. It also reduced sepsis in rats with kidney injury.
What the authors conclude
“More studies addressing this research question in animal models are needed to provide essential information to inform research gaps.”
Also in their conclusions
- They say that only a few studies compared A1 and A2 milk and that more animal studies are needed to fill research gaps.
- They note that results from future animal studies could eventually complement research for humans, especially when the evidence is uncertain as in the A1 and A2 milk debate.
- They advise that an update of this scoping review or a full systematic review would be fundamental in the near future.
How it was done
The authors wanted to map out all animal studies on A1 beta-casein and BCM-7 because evidence from human studies is limited and could be complemented by animal research.
They searched two databases for animal studies on A1 beta-casein or BCM-7 and found 42 studies. Six compared A1 with A2 beta-casein, and 36 looked at BCM-7 against other interventions. The animals included rats, mice, rabbits, dogs, pigs, cows, broilers, and cockroaches.
What it can’t tell you
- These are animal studies. They cannot show what happens in people.
- The studies used many different animals, doses and outcomes, so results cannot be combined to give a single answer.
- No study measured BCM-7 levels after A1 or A2 beta-casein, so the link between A1 beta-casein and BCM-7 release is not shown.
Who paid
- Conflicts
- The authors have declared that no competing interests exist.
- Authors work at
- Medical Center - University of Freiburg, Germany; University of Pécs, Hungary; Bavarian State Ministry for Food, Germany
The paper
- Title
- A1- and A2 beta-casein on health-related outcomes: a scoping review of animal studies
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Kuellenberg de Gaudry D, Lohner S, Bischoff K, et al (2022). A1- and A2 beta-casein on health-related outcomes: a scoping review of animal studies. European journal of nutrition. doi:10.1007/s00394-021-02551-xFree full textPubMed 34075432DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error