Zonulin (Stool)
Zonulin is a protein thought to help regulate the junctions between cells lining the gut. It has been promoted as a marker of intestinal permeability, often described as "leaky gut."
In theory, higher zonulin could reflect a more permeable gut barrier, and it appears in many wellness testing panels. In practice, zonulin is an emerging and unvalidated marker: the science is still evolving, testing methods vary in what they actually measure, and it is not an established clinical diagnostic.
A high result is sometimes interpreted as increased intestinal permeability, but this link is not well proven and the tests themselves have questioned reliability. An elevated value should not be taken as evidence of a specific disease.
A low result is often presented as reassuring, but given the uncertainty around what zonulin testing measures, a low value carries limited proven clinical meaning.
Because zonulin is not a validated clinical marker, there's no reliable target to aim for. Treat any result as exploratory and discuss its relevance with a clinician rather than acting on it alone.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.