Q.How do I find out if I have SIBO?
A.Accurate identification of SIBO requires thorough sampling along a 500-cm length of the small intestine and the ability to grow the bacteria that are present in the gut.
The challenge however, is that an upper gastrointestinal endoscope cannot reach further than about 60-cm of length into the proximal small intestine and a lower gastrointestinal endoscope cannot reach past the terminal ileum. As such, the majority of the 500-cm length of the small intestine cannot be sampled.
The next option is direct aspiration and culture of the small intestinal bacteria, but the challenge is that only a single or very few locations along the entire gut are being sampled and so the results are not representative of the entire small intestine. Additionally, aside from the technical challenges, less than 20% of the bacteria can be grown in laboratory culture, making the results potentially unrevealing.
To bypass these barriers, the most commonly utilized procedure for SIBO testing is a non-invasive Lactulose Breath Test, which is effective because abnormal fermentation of the small intestinal food content leads to gas production, which is a hallmark of SIBO.
The breath test relies on fermentation of a carbohydrate substrate (generally lactulose) and provides an indirect approach to the diagnosis of SIBO that is not limited by the aforementioned difficulties of aspiration and culture.
Ideally, both hydrogen and methane gasses will be tested over a 3-hour time period to fully capture the activity of the bacteria along the full length of the small intestine.
Q.Should I take Probiotics?
A.This is a very common question that unfortunately doesn’t have a clear answer, but I will do my best to add some context.
First, what are probiotics and what do they do?
Probiotics are cultures of a normally benign or beneficial species of gut bacteria that are taken orally in an attempt to re-establish ‘normal’ gut ecology in IBS, inflammatory bowel disease and SIBO.
Prebiotics and probiotics have been found to exert various beneficial effects including strengthening of the barrier function of the gut, inhibit several pathogens, modify the inflammatory response of the bowel and reduce visceral hypersensitivity.
This approach of repopulation however, is limited because we are unaware of the numbers and distribution of species within the complex gut.
One beneficial bacterial species is Bifidobacterium infantis, which has been found to reduce symptoms of IBS in some patients and is associated with a normalization of the ratio between the level of anti-inflammatory and pro-inflammatory cytokines.
Of note, many of these probiotic supplements also contain prebiotics, which are designed to ‘feed’ the beneficial bacteria. However, in SIBO, the bacteria that are producing the methane and/or hydrogen gas can also feed on these prebiotics and exacerbate symptoms. So in this case, it is generally best to avoid probiotics until following successful eradication of the bacterial overgrowth.
In summary: We are taking a shot in the dark as far as what probiotics may be beneficial and based on the research available some strains are showing real promise in the treatment of IBS and inflammatory bowel disease. When it comes to SIBO, studies dealing with the therapeutic use of pre/probiotics are limited and as such it is generally best to wait until successful eradication of the overgrowth before supplementing. Upon successful eradication it is generally advisable to choose a probiotic that has no prebiotics (ie. inulin, FOS, galactans).