*EMBARGOED All research presented at the 2018 ACG Annual Scientific Meeting and Postgraduate Course is strictly embargoed until Monday, October 8, 2018, at 8:00 am EDT.

Emilie Mitten, MD
Emilie Mitten, MD

P0779 Recent Probiotic Use Is Independently Associated With Methane-Positive Breath Test for Small Intestinal Bacterial Overgrowth

Author Insight from Emilie Mitten, MD, Walter Chan, MD, MPH (Senior Author), Brigham & Women’s Hospital/Harvard Medical School

What’s new here and important for clinicians?

Probiotics are often regarded as beneficial or at least neutral in the prevention or treatment of a variety of gastrointestinal conditions. It has been proposed that patients with small intestinal bacterial overgrowth (SIBO), which consists of symptoms including bloating, gas, diarrhea and/or constipation, may also benefit from probiotics. We did a retrospective study to examine the association between probiotic use and diagnosis of SIBO via lactulose breath test (LBT), which is the most widely used method for diagnosis of SIBO. LBT involves the ingestion of lactulose, which is then metabolized by intestinal bacteria to release hydrogen and/or methane gases. Measurement of the exhaled hydrogen and/or methane allow the diagnosis of SIBO. We reviewed patients with symptoms suggestive of SIBO, about one-third of whom were already on probiotics, who underwent a LBT to evaluate for SIBO. We found that probiotic use was significantly associated with a positive LBT for SIBO, specifically a methane-positive LBT but not hydrogen-positive LBT. This association remained significant even after controlling for other factors that modulate the risk of SIBO. While prior studies have demonstrated an association between probiotic use and decreased likelihood of a hydrogen-positive LBT, our study suggests that probiotic use may not be universally beneficial among all cases of SIBO. Rather, this association between probiotic use and increased methane-positive LBT suggests that these two variants of SIBO may warrant different management.

For clinicians, our study highlights the importance of judicial use of probiotics and the role of LBT when evaluating patients with symptoms suggestive of SIBO or irritable bowel syndrome (IBS). Probiotics may need to be avoided in patients with symptoms more commonly associated with methanogenic SIBO i.e., constipation-predominant or those with methane-positive LBT. Careful history-taking is also vital, as patients may not always proactively report probiotics use.

What do patients need to know?

The health of our gut is dependent on the bacteria that live there. Probiotics are living bacteria and yeasts that can be taken as a supplement (such as a pill or capsule) or can be found in some food products (such as yogurt). Some studies suggest that probiotics can help to prevent or treat a variety of gastrointestinal conditions, such as irritable bowel syndrome (IBS). In the condition called small intestinal bacterial overgrowth, or SIBO, which is often associated with IBS, there is a change in and overpopulation of the gut bacteria. This may lead to symptoms such as diarrhea, constipation, bloating, gas and abdominal pain. Probiotics have been proposed and used by many patients for treatment or “prevention” of SIBO. However, the role of probiotics in SIBO remains unclear. In our study, we found that patients with symptoms suspicious for SIBO who were taking probiotics were more likely to test positive for SIBO (in particular, the methane-positive variant of SIBO) than patients who were not taking probiotics. This could mean that probiotics may not be beneficial in patients with certain types of SIBO.  The use of probiotics may actually raise the risk of the methane-positive variant of SIBO, which is often associated with constipation-predominant symptoms.  Patients should exercise caution in the use of probiotics and should consult with their physicians begore initiation, including consideration for breath testing for SIBO.

Read the Abstract

Author Contacts
Emilie Mitten, MD, Walter Chan, MD, MPH (Senior Author), Brigham & Women’s Hospital/
Harvard Medical School

Media Interview Requests
To arrange an interview with any ACG experts or abstract authors, please contact Brian Davis of ACG via email at bdavis@gi.org or by phone at 301-263-9000.