A safe, non invasive and inexpensive methods has been developed to measure small intestinal permeability and also test how well a treatment is working. Claude Andre, the leading French research worker in this area, says that measuring gut permeability is a sensitive and practical screening test for detecting food allergy and responsiveness to treatment (Presse Med, 1986, 15: 105-8).

In Andre's protocol, patients ingest 5 g each of the innocuous sugars lactulose and mannitol. These sugars are not metabolized by humans, and the amount absorbed is fully excreted in the urine within six hours. Mannitol, a monosaccharide, is passively transported through the intestinal cell walls; the average absorption is 14 per cent of the administered dose. In contrast, the intestinal tract blocks lactulose, a dissaccharide; less than 1 per cent of the administered dose is normally absorbed. The level of both lactulose and mannitol recovered in urine is then measured. The normal ratio of lactulose/mannitol recovered in urine is less than 0.03. A higher ratio signifies too much absorption of lactulose and therefore a gut that "leaks".It's also possible to indirectly measure leaky gut by measuring the blood's levels of IgG antibody, which is directed against antigens found in common foods and normal gut bacteria. This test is not as useful as the ordinary permeability test.

Gut permeability tests are performed at Biolab (The Stone House, 9 Weymouth St, London W1N 3FF Tel: 0171 636 5959), or Better Health Corporation (413 Abbey House, 4 Abbey Orchard Street, London SW1P 2JJ Tel: 0171 976 0966).