Codfish biomarkers target proteins from cod (commonly Gadus species) used as food. Biochemically, the most studied component is parvalbumin, a small EF‑hand calcium‑binding protein abundant in fast‑twitch fish muscle; other proteins and peptides (including fish collagen fragments) can also be antigenic. Parvalbumin’s stability and high abundance make it a frequent target of immune recognition across many fish species. Historically, research into food‑related immune responses identified parvalbumin as a dominant reactive protein in the late 20th century. Functionally, parvalbumin buffers intracellular calcium to support muscle relaxation; its conserved sequence across species explains why immune responses to one fish may cross‑react with others. Food Zoomer’s peptide-level testing can resolve which protein fragments are driving measurable antibody binding.

Elevated IgA or IgG binding to cod proteins suggests measurable immune recognition of cod-derived antigens. Higher IgA may point toward mucosal (gut‑linked) immune activity, while IgG elevations reflect broader systemic antibody exposure; either pattern can cluster with other food responses and reported symptoms. Low or non‑detectable levels indicate little to no measurable antibody binding to cod proteins, which can reflect tolerance, limited exposure, or immune patterns that do not target these antigens. Interpretation should always consider the full Food Zoomer panel, clinical history, and symptom timing rather than a single marker alone.

Codfish markers are included to evaluate immune responses to fish proteins at both whole‑protein and peptide levels, using IgA and IgG isotypes. This helps providers see whether fish proteins are part of broader immune activity, identify cross‑reactivity across fish species, and place cod responses within a structured pattern to support personalized dietary planning and testing strategies.