Elevated fecal levels of a zonulin family protein (ZFP) have been associated with metabolic syndrome and obesity; conditions that have been linked to increased intestinal permeability ("leaky gut"). Elevated serum levels of the ZFP antigen have been correlated with results from the established lactulose mannitol test. Definitive research has yet to be published regarding a correlation between fecal ZFP levels and the results of the lactulose mannitol test.