The Study
Post-weaning A1/A2 β-casein milk intake modulates depressive-like behavior, brain μ-opioid receptors, and the metabolome of rats
This study watched what happened to a few rats when they drank different kinds of milk. It found that one kind of milk seemed to make them act differently and changed some stuff in their bodies. But it didn't prove the milk caused those changes — maybe something else in the milk or how they were raised did it.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
Rats that drank milk with a special protein called A1 beta-casein after weaning acted more depressed in a water test, while rats drinking milk with A2 beta-casein acted normal.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 513 / 100
Quality score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This suggests A1 milk might affect mood in rats via gut and brain changes, but it's not proven to work the same way in humans.
- 2Rats drinking A1 milk spent significantly more time floating motionless in water (p < 0.01) compared to those drinking A2 milk or water.
- 3Their guts had more Clostridium bacteria, and their brains showed changes in opioid receptors and choline-related chemicals.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
iScience
Year
2021
Authors
A. Osman, Simone Zuffa, G. Walton, Elizabeth O Fagbodun, P. Zanos, Polymnia Georgiou, I. Kitchen, J. Swann, A. Bailey
Related Content
Claims (6)
Casomorphins from dairy proteins bind to opioid receptors in the body and lead to reduced feelings of fullness and increased food intake.
Male Wistar rats fed milk with A1 β-casein show higher levels of immobility during stress tests than rats fed milk with A2 β-casein.
Post-weaned rats fed milk with A1 β-casein show higher levels of Clostridium histolyticum in the cecum and colon, higher urinary hippurate and allantoin, and more depressive-like behavior.
In post-weaned rats, milk with A1 β-casein changes μ-opioid receptor binding in specific brain regions differently than milk with A2 β-casein or diets without casein.
In rats after weaning, levels of certain microbial byproducts in urine are statistically linked to levels of specific chemicals in the brain.
In post-weaned rats, drinking milk with A1 β-casein is linked to specific changes in brain metabolites: phosphocholine and acetylcholine increase, while S-adenosylhomocysteine decreases.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.