Is there a link between SIBO and symptoms of reflux?
Is there a link between SIBO and symptoms of reflux?

Is there a link between SIBO and symptoms of reflux?

By Jordan Haworth, Clinical GI Physiologist

A new study from our team at Functional Gut Diagnostics has shown that small intestinal bacterial overgrowth (SIBO) could be contributing to symptoms of gastroesophageal reflux disease (GERD). The prevalence of intestinal dysbiosis in patients referred for antireflux surgery was published in this month’s medical journal Surgical Endoscopy.

The study retrospectively looked at a group of patients who were being reviewed for antireflux surgery because their symptoms of reflux were unresponsive to medications. A large proportion of them – around 60% – had intestinal dysbiosis diagnosed by hydrogen and methane breath testing (HMBT). These patients were more likely to report troublesome belching and abdominal bloating.

Intestinal dysbiosis relates to an imbalance in the gut microbiota, which is associated with the medications used to treat GERD called proton pump inhibitors (PPIs). While PPIs are generally very safe medications, they have been shown to moderately increase the risk of SIBO. Our researchers found that SIBO may be contributing to PPI-refractory symptoms of reflux, namely regurgitation.

SIBO is a type of dysbiosis relating to the excessive colonisation of bacteria in the small bowel. The study showed that patients with SIBO were more likely to have a positive reflux-symptom association for regurgitation. This means that the patient’s symptoms were statistically correlated to reflux episodes. A positive-reflux symptom association for regurgitation is often enough evidence for antireflux surgery, but according to the research, this may in part be brought about by SIBO.

Interestingly, another type of dysbiosis known as intestinal methanogen overgrowth (IMO) was not associated with regurgitation. IMO describes the overgrowth of microorganisms that produce methane gas. Hydrogen gas production was greater during HMBT in patients with reflux-associated regurgitation, but methane production was not different. Our researchers think this is because methanogens, the microbes that produce methane, predominantly overgrow in the large bowel whereas hydrogen gas produced in the small bowel (i.e., SIBO) may contribute to regurgitation.

Intestinal gas production by SIBO and IMO can lead to gas-related symptoms, such as bloating and belching, as shown in this study. For those who undergo antireflux surgery, gas-related symptoms are the most common complaint in around 40% of patients after surgery. The exact reason for this is unknown, but this study showed that a similar proportion of patients suitable for antireflux surgery had SIBO.

This is one of the first studies to show a link between SIBO and PPI-refractory symptoms, especially regurgitation. HMBT could play an important role in patients with GERD who also report gas-related symptoms. Further research is now needed to determine if treating SIBO may ultimately reduce symptoms like regurgitation and belching.


  1. Haworth, J.J., Boyle, N., Vales, A. et al. The prevalence of intestinal dysbiosis in patients referred for antireflux surgery. Surg Endosc (2021).