🧪 Supplement
a1 beta-casein
The A1 variant of milk's beta-casein (releases BCM-7). Reliably worsens GI symptoms versus A2 milk in sensitive people; the claimed effect on cognition is contested and thin.
1 well-supported · 0 disputed. This shows how settled each sub-question is, not whether a1 beta-casein is "good." Direction lives in each claim below.
The 2 claims about a1 beta-casein
Each keeps its own verdict — we never average them away.
Does regular (A1) milk upset your stomach more than A2 milk?
Strong support Yes — but much of the supporting evidence comes from A2-milk marketers, so weigh that conflict of interest.
Does A1-type milk really upset digestion and slow your thinking versus A2 milk?
Contested A1 milk reliably worsens GI symptoms and transit versus A2 in sensitive people, but the cognitive-speed benefit is weak, inconsistent, and largely from one research lineage.
Educational only, not medical advice. Hub descriptions are curated for honesty; see the methodology.