SIBO : Testing Options & Recommendations

Today we are following on with the SIBO series of videos covering different ways to test for small intestinal bacterial overgrowth. Don’t forget there is a free Ebook download available to go along with this series which can be downloaded here – The Complete Guide To SIBO.

SIBO testing options

Digging into the different testing options can get a bit complex and a little bit convoluted but I’m going to try and keep it nice and basic and quite simple.

First off you’ve got the aspirate and culture testing for SIBO. This is considered the gold standard. It’s not a great gold standard and they only really use this form of testing in research settings. It’s not applicable to you as a patient who may have SIBO and wants to test for it as it is far to invasive and expensive, especially when there are good alternatives.

In my clinical practice I often recommend SIBO breath-testing so what is SIBO breath testing anyway?

SIBO breath testing 101

Basically with SIBO breath testing you want to starve the possible bacterial overgrowth, then feed the bacteria (or archea as the case may be with methane SIBO) a sugar and test to see if these bacteria in your small bowel produce a gas over a period of time. If there is a spike in gas (hydrogen or methane) then we know that bacteria have overgrown in the small bowel.

Lactulose or glucose are the two main options in regards to sugars used in SIBO breath testing. Fructose is a third sugar that can be used if you really want to cover all the bases. 

Lactulose vs Glucose Which is Better for SIBO?

So the lactulose glucose debate and which one is better?

You are going to get different opinions depending on who you speak to. There are reasons for lactulose being a better sugar to test for SIBO and there are reasons why glucose is better. 

Lactulose is a particular sugar that we can’t actually digest. It is a disaccharide which makes its way down to a large bowel where our resident microbiota can ferment the sugar and produce gas. Glucose on the other hand is absorbed in the small bowel. This means that if the bacterial overgrowth is further on down the small intestine then glucose may miss it. This is one reason why many clinicians prefer lactulose over glucose. 

On the other hand lactulose tends to increase gut transit time so when you consume it and you’re looking for that spike in the gas that signifies SIBO if it happens a little bit later on – say between the 80 to 100 minute mark – then it could be your large bowel microbiome and not SIBO after all. This is one of the real downsides of lactulose.

Finally fructose can be saved and run as a third test or all three can be used to really rule out suspected SIBO.

In my practice I tend to run both lactulose and glucose (on separate days) and if the results are still a bit unclear (all the symptoms of SIBO are there and the SIBO tests say all is clear) then I might follow it up with fructose. It really depends on you, your digestive symptoms, how long you’ve been unwell for how much money you are happy to spend and how quickly you want to get better. These are all factors we have to take into account.

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