The intestinal permeability test which assesses lactulose and mannitol recovery can be used to monitor improvements or deterioration in intestinal permeability as a result of therapy, disease or drug use. Furthermore, the intestinal permeability test has been used to monitor the compliance and effectiveness of a gluten-free diet in patients with Coeliac disease.
The test works on the principle that small molecules (i.e. mannitol) are readily absorbed by the intestinal villi, whilst larger molecules such as disaccharides (i.e. lactulose) are not. These water soluble non-metabolised sugar molecules after penetrating the intestinal tract are excreted into the urine. Under normal circumstances the ratio of lactulose to mannitol in urine is low (i.e lactulose is not absorbed), mannitol is absorbed. When the structure of the intestinal epithelium is jeopardised (‘leaky gut’ is present), the large sugar molecule can permeate the mucosa and is recovered in the urine. In this situation the level of lactulose is increased in the urine and therefore the ratio of lactulose to mannitol is high.
In addition to assessing leaky gut, this test can also help diagnose malabsorption. If a low level of mannitol which normally penetrates the intestinal epithelium is observed, it may indicate malabsorption of small molecules and possible atrophy of the intestinal villi.
- Gut dysbiosis
- Irritable Bowel Syndrome
- Inflammatory Bowel Disease – Ulcerative colitis, Crohn’s disease, Coeliac
- Food allergy and sensitivities
Lactulose (recovery %)
Mannitol (recovery %)