warum vertrage ich keinen kaffee mehr — which blood markers matter?

Sudden coffee intolerance can stem from several factors. Genetic variants in CYP1A2 (e.g., rs762551) affect caffeine metabolism; slow metabolizers may experience jitters, reflux, or palpitations. However, CYP1A2 testing is a DNA analysis, not a routine blood marker. Histamine intolerance (DAO deficiency) may also contribute: coffee acts as a histamine liberator and inhibits diamine oxidase (DAO). Blood tests for DAO activity or histamine levels are commercially available but lack robust validation. Increased intestinal permeability ('leaky gut') is another proposed mechanism, with markers like zonulin (stool or serum) being controversial and lacking standardized thresholds. Currently, no blood marker is clinically established for diagnosing coffee intolerance. A more evidence-based approach includes a symptom diary, an elimination trial, and medical evaluation (e.g., endoscopy for reflux, allergy testing). Be cautious of expensive lab panels that promise answers without proven clinical utility. Evidence for specific blood markers remains weak to unclear.