Methane-Producing Gut Bacteria as a Cause of SIBO? What Can Be Done About It
Content
1. What is SIBO?
1.1 SIBO Diagnosis
1.2 SIBO Treatment
2. Types of SIBO
2.1 Hydrogen SIBO
2.2 Methane SIBO
2.3 Hydrogen Sulfide SIBO
3. Effects of Methane on the Gut
4. What to Do in Case of IMO?
1. What is SIBO?
SIBO stands for “Small Intestinal Bacterial Overgrowth,” describing the abnormal overgrowth of bacteria in the small intestine. Unlike the large intestine, a healthy small intestine has only a sparse bacterial presence. When bacteria multiply excessively in the wrong place, the small intestine becomes overwhelmed, unable to manage the gases and toxins they produce. This leads to symptoms such as abdominal pain, bloating, flatulence, diarrhea, constipation, belching, a feeling of fullness, and heartburn.
1.1 SIBO Diagnosis
SIBO is typically diagnosed using a breath test. Various test substances, each with its own advantages and disadvantages, can be used for this test, including lactulose, lactose, glucose, and fructose (1). These are consumed in liquid as part of the test. The variety of test substrates is necessary because not all bacteria metabolize every type of sugar.
The breath test works based on the fact that human cells do not produce hydrogen or methane. An increase in these gases after carbohydrate ingestion must therefore originate from bacterial fermentation. The produced gas is absorbed into the bloodstream and exhaled in the breath.
1.2 SIBO Treatment
If a SIBO diagnosis is confirmed, several treatment options are available. These include a specialized SIBO diet, herbal or conventional antibiotics (2), and probiotics. Treatment is tailored based on the type and severity of symptoms, as well as the predominant bacterial strains present.
2. Types of SIBO
There are three main types of SIBO, classified based on the primary gases produced by the bacteria: hydrogen (H2), methane (CH4), and hydrogen sulfide (H2S).
2.1 Hydrogen SIBO
Individuals with hydrogen-dominant SIBO often experience diarrhea, bloating, and flatulence. Hydrogen is a byproduct of various metabolic processes and is produced by numerous bacterial species, the most common being E. coli and Klebsiella.
2.2 Methane SIBO
People with methane-dominant SIBO typically suffer from constipation. Methane gas is mainly produced by archaea rather than bacteria, making the term “SIBO” technically inaccurate in this case. As a result, methane-dominant SIBO is also referred to as IMO (Intestinal Methanogen Overgrowth) (3).
Unlike bacteria, archaea can colonize both the small and large intestines, which is an important factor when interpreting breath test results. Archaea and bacteria both belong to the prokaryotes, meaning they lack a nucleus, but they differ in cell structure and metabolic processes.
The primary methanogen species responsible for methane-dominant SIBO are Methanobrevibacter smithii (4), Methanomassiliicoccus, and Methanosphaera stadtmanae.
2.3 Hydrogen Sulfide SIBO
As the name suggests, hydrogen sulfide-dominant SIBO is characterized by bacteria that produce hydrogen sulfide. These include Enterobacteriaceae such as Escherichia coli and Klebsiella. Hydrogen sulfide is the chemical name for the gas commonly known as sulfurous gas. Symptoms of this form of SIBO can include either diarrhea (5) or constipation (6), along with bloating that often has a characteristic rotten egg smell.
3. Effects of Methane on the Gut
As previously mentioned, individuals with IMO frequently suffer from constipation. This is because methane produced by methanogenic microorganisms can slow down intestinal transit time (7). The amount of methane detectable in breath tests correlates with the severity of constipation (8).
A slower gut transit reduces its ability to regulate microbial populations through natural cleansing movements, potentially leading to further overgrowth of archaea—creating a vicious cycle.
Methanogenic microorganisms can convert hydrogen produced by gut bacteria into methane. Compared to hydrogen, methane molecules are much smaller and cause less bloating. It was long believed that methane-SIBO/IMO always coexists with hydrogen-SIBO. However, newer research suggests that the presence of hydrogen-producing commensal bacteria is sufficient, meaning IMO can occur independently of hydrogen-SIBO.
4. What to Do in Case of IMO?
Archaea are particularly difficult to eliminate, making medical supervision essential for IMO treatment. As with SIBO, treatment options include specialized diets, antibiotics, as well as probiotics and prebiotics.
References
- Rezaie A, Buresi M, Lembo A, Lin H, McCallum R, Rao S, Schmulson M, Valdovinos M, Zakko S, Pimentel M. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Am J Gastroenterol. 2017 May;112(5):775-784. doi: 10.1038/ajg.2017.46. Epub 2017 Mar 21. PMID: 28323273; PMCID: PMC5418558.
- Ginnebaugh B, Chey WD, Saad R. Small Intestinal Bacterial Overgrowth: How to Diagnose and Treat (and Then Treat Again). Gastroenterol Clin North Am. 2020 Sep;49(3):571-587. doi: 10.1016/j.gtc.2020.04.010. Epub 2020 Jun 14. PMID: 32718571.
- Takakura W, Pimentel M. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome – An Update. Front Psychiatry. 2020 Jul 10;11:664. doi: 10.3389/fpsyt.2020.00664. PMID: 32754068; PMCID: PMC7366247.
- Takakura W, Pimentel M. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome – An Update. Front Psychiatry. 2020 Jul 10;11:664. doi: 10.3389/fpsyt.2020.00664. PMID: 32754068; PMCID: PMC7366247.
- Pimentel M, Hosseini A, Chang C, Mathur R, Rashid M, Sedighi R, et al. Fr248 EXHALED HYDROGEN SULFIDE IS INCREASED IN PATIENTS WITH DIARRHEA: RESULTS OF A NOVEL COLLECTION AND BREATH TESTING DEVICE. Gastroenterology. 2021 May;160(6):S-278. DOI: 10.1016/S0016-5085(21)01391-3.
- Guo HZ, Dong WX, Zhang X, Zhu SW, Liu ZJ, Duan LP. [The diagnostic value of hydrogen sulfide breath test for small intestinal bacterial overgrowth]. Zhonghua Nei Ke Za Zhi. 2021 Apr 1;60(4):356-361. Chinese. doi: 10.3760/cma.j.cn112138-20200731-00725. PMID: 33765706.
- Pimentel M, Lin HC, Enayati P, van den Burg B, Lee HR, Chen JH, Park S, Kong Y, Conklin J. Methane, a gas produced by enteric bacteria, slows intestinal transit and augments small intestinal contractile activity. Am J Physiol Gastrointest Liver Physiol. 2006 Jun;290(6):G1089-95. doi: 10.1152/ajpgi.00574.2004. Epub 2005 Nov 17. PMID: 16293652.
- Chatterjee S, Park S, Low K, Kong Y, Pimentel M. The degree of breath methane production in IBS correlates with the severity of constipation. Am J Gastroenterol. 2007 Apr;102(4):837-41. doi: 10.1111/j.1572-0241.2007.01072.x. PMID: 17397408.
