About the leaky gut test (intestinal permeability test)

Intestinal permeability lactulose/mannitol urine test

lactulose : big molecule : not absorbed (much)

mannitol : small molecule : absorbedThere is some interest in the 'intestinal permeability' ("leaky gut") urine test in connection to fecal body odor syndrome. It is hoped this post explains the test to some degree. It is not known if 'leaky gut' is a factor at all in fecal body odor, or if it is typical but not an issue. At this stage of understanding fecal body odor, like many things it is an unknown factor. However, it cannot be good to have 'leaky gut' at all.

Originally the 'leaky gut' test was one of the tests chosen for the MeBO-Biolab gut dysbiosis study, but was dropped to keep the price under £100. However, since the volunteers are paying for their own tests, it was thought sensible to add it as an option. The Biolab 'leaky gut' test uses a different molecule from other testers of 'leaky gut', who normally use lactulose and mannitol as the test molecules. However they all have the same principle.

Someone recently did the lactulose/mannitol intestinal permeability test, and we will look at their results to explain the test. Although people think of the test as the 'leaky gut' test, it does in fact test both for leaky gut and how well mannitol is absorbed as well. This is why it is officially known as the 'intestinal permeability' test.

The 2 test molecules for most 'intestinal permeability' tests are lactulose and mannitol. Lactulose is a large sugar, and should not be absorbed (much) in a normal gut. Mannitol is a small sugar, and should be absorbed in a controlled manner. Neither are changed by the body (i.e. metabolized). The person takes a liquid with both sugars and then over the course of a few hours collects their urine.

Leaky gut : normally the gut lining acts as a filter, allowing only molecules of a certain size to be absorbed into the bloodstream. Molecules of a larger size should not get through (unless they are broken down further in the intestine to smaller molecules). The theory about leaky gut is, the cells lining the intestine normally have a tight junction between them, and if for any reason this junction becomes split, then large molecules can slip into the bloodstream through the gap. These molecules will be regarded as 'aliens' by the body, and may trigger immune responses. The body will not recognise them as normal. In most 'leaky gut' tests, lactulose is used as the test molecule, and a raised amount in the urine constitutes 'leaky gut'.

Mannitol absorption : Normally molecules small enough to be absorbed into the bloodstream are absorbed through the gut lining in various ways. Some by simple diffusion. Many by a complex 'active transport' system. They go through the cell lining directly (not the juction). Mannitol should be relatively well absorbed, in a controlled manner. If absorption is too low, then there is an issue with mannitol absorption (and so probably with most type of gut absorption). If it is too high, it implies some issue in the controlled method of absorption.

Now to look at the test results of someone :

Intestinal permeability lactulose/mannitol urine test results:
analytical-chemistry
intestinal permeability
lactulose recovery 2.37 *H (normal range less than 0.30)
mannitol recovery 69.2 *H (normal range 9.5-25.0)
lactulose:mannitol ratio 0.034 (normal range less than 0.035)
6 hour urine volume 1.700 litres

In this case, both the lactulose and mannitol absorption are too high. Both by quite a bit. Ironically, this makes the 'ratio' almost normal, but this is because both are so high. So there seems to be leaky gut for sure, and also possibly an absorption issue. More about the lactulose/mannitol intestinal permeability test can be seen in these links from Genova Diagnostic website:

Genova intestinal permeability test explanation (PDF document)
Genova intestineal permeability test sample report (PDF document)

So, in summary, it is not known if intestinal permeability is a factor in fecal body odor syndrome, but at this early stage of understanding the problem, it may be worth ruling out as a potential factor.

The Biolab intestinal permeability test is one of the test options in the MeBO-Biolab gut dysbiosis study.

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More about leaky gut :
'About Medicine' article on intestinal permeability test by Liz Lipski
Genova Diagnostic intestinal permeability test through Crohns.net for $90
Leaky gut syndrome : Leo Galland 1995 article
1999 Pubmed paper : Leaky gut in alcoholic cirrhosis: a possible mechanism for alcohol-induced liver damage