Small intestine/upper GI Critical appraisal of the SIBO hypothesis and breath testing: A clinical practice update endorsed by the European society of neurogastroenterology and motility (ESNM) and the American neurogastroenterology and motility society (ANMS) (May 2024)

Michael Harrop

Active member
Jul 6, 2023

Key points​

  • The SIBO-IBS hypothesis has stimulated significant research into the role of the microbiota in symptoms of DBGI but remains unproven.
  • This hypothesis has resulted in serious unintended consequences, namely the use of poorly validated breath tests to diagnose SIBO and the resulting injudicious use of antibiotics.
  • The lactulose breath test (LBT) is primarily a measure of intestinal transit and has very low sensitivity and specificity to diagnose SIBO.
  • The glucose breath test (GBT) has better performance characteristics if the pre-test probability is high, as found in conditions underlying classical SIBO, but also has a high false-positive rate in DGBI.
  • Future studies in DGBI are needed to better understand the impact of bacterial communities, their metabolites, and diet-host interactions in the small and large intestine on DGBI symptoms and move away from the sole focus on absolute numbers of bacteria.



There is compelling evidence that microbe-host interactions in the intestinal tract underlie many human disorders, including disorders of gut-brain interactions (previously termed functional bowel disorders), such as irritable bowel syndrome (IBS). Small intestinal bacterial overgrowth (SIBO) has been recognized for over a century in patients with predisposing conditions causing intestinal stasis, such as surgical alteration of the small bowel or chronic diseases, including scleroderma and is associated with diarrhea and signs of malabsorption. Over 20 years ago, it was hypothesized that increased numbers of small intestine bacteria might also account for symptoms in the absence of malabsorption in IBS and related disorders. This SIBO-IBS hypothesis stimulated significant research and helped focus the profession's attention on the importance of microbe-host interactions as a potential pathophysiological mechanism in IBS.


However, after two decades, this hypothesis remains unproven. Moreover, it has led to serious unintended consequences, namely the widespread use of unreliable and unvalidated breath tests as a diagnostic test for SIBO and a resultant injudicious use of antibiotics.

In this review, we examine why the SIBO hypothesis remains unproven and, given the unintended consequences, discuss why it is time to reject this hypothesis and its reliance on breath testing. We also examine recent IBS studies of bacterial communities in the GI tract, their composition and functions, and their interactions with the host. While these studies provide important insights to guide future research, they highlight the need for further mechanistic studies of microbe-host interactions in IBS patients before we can understand their possible role in diagnosis and treatment of patient with IBS and related disorders.

It seemed like I was one of the few people pushing back on this hypothesis, and there is/was massive support for it in patient communities and other "online" and "alternative health" practitioners since it's "an answer" they can sell to patients with a course of action, etc. And patients seem to eat it up for the same reason, and because it appears more simple and easy to treat than "gut dysbiosis".

It's nice to see papers like this that help push back on this tidal wave of flawed and harmful information.
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This article has additional quotes from one of the authors of the paper:

The Microbiome and Chronic Disease: The SIBO Hypothesis "Hope, Deception, and Transformation"

Dr. Stephen Vanner, MD, MSc is the co-founder of the Translational Institute of Medicine (TIME) at Queen's University, director of the Gastrointestinal Disease Research Unit (GIDRU) at KGH and a practicing clinician scientist.

Dr. Vanner further discussed how clinicians endorsing the use of rifaximin are highly motivated by their relationships with pharmaceutical companies that directly benefit from rifaximin drug-sales.

Dr. Vanner explained that this theory has sparked debate amongst researchers and clinicians as the hypothesis is largely based on unvalidated breath tests.

Dr. Vanner emphasized that the use of breath tests for SIBO in GI disorders should be abandoned completely.

Further complicating clinical management is the unfounded use of the antibiotic rifaximin in patients with IBS

He indicated that this transformation should include no longer using the term SIBO, as well as discontinuing the use of breath tests for IBS, and other GI disorders.

Dr. Vanner also emphasized how guidelines should be improved by medical societies and regulatory bodies to prevent conflicts of interest from influencing research that has potential to guide clinical practice.

Further, he explained the low FODMAP diet as a safe and effective alternative to antibiotic use that shows greater promise in improving patient’s GI symptoms (6).

he explained how social media has impacted patient perceptions of GI disorders
Holy shit. This is so nice to see. I've been saying this for years, and I'm an IBS patient who was severely harmed by Rifaximin. I'm not a participant in any SIBO communities so I feel that I don't have any impact on this topic. So that makes it extra nice that professionals in the field are taking a stance against this.

Thank you so much Dr. Stephen Vanner!