"To diagnose Intestinal Permeability, we have our patients drink a benign liquid preparation containing Mannitol and Lactulose followed by a 6 hour urine collection. Lactulose is a large molecule that should not be able to pass into the blood stream in large amounts. Its presence and quantity in the urine specimen show the degree of permeability and helps us to establish a baseline for healing the intestine. Mannitol is a small molecule that passes easily through the intestinal wall and into the blood stream. If the level of Mannitol is less than usual, this also tells us that the absorption mechanisms in the intestine are compromised."
Understanding Intestinal Permeability or ‘Leaky Gut Syndrome’ | Bothell Natural Health