What should I know about leaky gut testen?

The concept of 'leaky gut' (intestinal permeability) is controversial in mainstream medicine. There is no validated, widely accepted diagnostic test for leaky gut syndrome. Commercial tests (e.g., stool zonulin, lactulose-mannitol urine test) are marketed by companies like MyBody-X, but evidence is weak: reference ranges are not established, results are inconsistent, and many factors (diet, medications, stress) affect them. A positive result does not confirm a disease. For persistent digestive issues, consult a gastroenterologist to rule out celiac disease, IBS, or IBD. These consumer tests are best classified as 'marketing' – they provide numbers but no clinical interpretation. Caveat: no pediatric norms, no treatment guidance. Evidence: marketing/unclear.