A1 β-casein is an allelic variant of bovine beta-casein, a member of the casein family of milk proteins that help form micelles and supply amino acids and mineral carriers in dairy. The “islet cell overlap” component refers to specific peptide sequences within or related to A1 β-casein that show amino-acid similarity to proteins expressed in pancreatic islet cells; such overlapping sequences can be targets for antibody binding in some people. Interest in A1 versus A2 beta-casein and peptide-level cross-reactivity grew from nutritional and immunology research that examines how specific food peptides interact with the immune system. In the Food Zoomer, these peptides are assessed at the IgA and IgG level to map whether immune recognition is primarily mucosal (gut-associated) or systemic, supporting detailed pattern analysis across dairy and related domains.

Elevated antibody binding to these peptides suggests increased immune recognition or sensitization to A1 β-casein–related sequences; an IgA-predominant pattern points toward mucosal or gut-associated activity, while IgG predominance suggests a broader systemic response. Low or undetectable binding suggests little measurable antibody recognition of these peptides at the time of sampling. All results should be interpreted in the context of the full Food Zoomer profile, symptom history, and other laboratory findings to understand broader patterns rather than in isolation.

This marker is included to detect immune responses to a common dairy peptide variant and to identify peptide-level overlap with islet-cell proteins. That peptide-level specificity helps reveal whether dairy-related immune activity clusters with other dairy markers or shows cross-reactivity patterns, improving the panel’s ability to inform personalized dietary planning.