It’s possible to have no symptoms at all, but SIBO often occurs with other GI diseases that have overlapping symptoms, which can complicate diagnosing either accurately.[1] For example, antibiotics are more effective in cases of people who have both irritable bowel syndrome (IBS) and SIBO compared with IBS alone, which suggests that SIBO may play a direct role in some IBS symptoms.[2] It could also explain the persistent GI symptoms in people with chronic pancreatitis who don’t respond to pancreatic enzyme replacement therapy.
Bloating, flatulence, nausea, abdominal pain, and diarrhea are some of the most common symptoms, but constipation may also occur in certain types of SIBO.[3][4] Some theories suggest that SIBO may affect gut motility and induce constipation by altering the serotonin pathway that coordinates intestinal contractions or producing excess methane, which slows intestinal transit (the speed at which food moves through the intestines).[4]
Anemia isn’t a primary symptom, but it has been identified as a predictor of SIBO. This may reflect a reduction in vitamin B12 absorption and could explain the fatigue people with SIBO sometimes have. SIBO is also associated with reduced nutritional status (the levels of nutrients in the body) in people with inflammatory bowel disease (IBD).
SIBO may contribute to malnutrition in IBD, Parkinson’s disease, and cirrhosis. It could also exacerbate liver disease by making the intestinal wall more permeable, which could allow bacterial contents to enter the bloodstream and cause inflammation.[5][6] SIBO also has the potential to increase the risk of bacterial translocation — bacteria moving from inside the intestine to outside tissue — in susceptible individuals, such as people with chronic liver disease, who would then be at risk of life-threatening infection.[7]
References
- ^George B Saffouri, Robin R Shields-Cutler, Jun Chen, Yi Yang, Heather R Lekatz, Vanessa L Hale, Janice M Cho, Eric J Battaglioli, Yogesh Bhattarai, Kevin J Thompson, Krishna K Kalari, Gaurav Behera, Jonathan C Berry, Stephanie A Peters, Robin Patel, Audrey N Schuetz, Jeremiah J Faith, Michael Camilleri, Justin L Sonnenburg, Gianrico Farrugia, Jonathan R Swann, Madhusudan Grover, Dan Knights, Purna C KashyapSmall intestinal microbial dysbiosis underlies symptoms associated with functional gastrointestinal disordersNat Commun.(2019 May 1)
- ^Uday C Ghoshal, Deepakshi Srivastava, Asha Misra, Ujjala GhoshalA proof-of-concept study showing antibiotics to be more effective in irritable bowel syndrome with than without small-intestinal bacterial overgrowth: a randomized, double-blind, placebo-controlled trialEur J Gastroenterol Hepatol.(2016 Mar)
- ^Y A Kucheryavyy, D N Andreev, I V MaevPrevalence of small bowel bacterial overgrowth in patients with functional dyspepsia: a meta-analysisTer Arkh.(2020 Dec 15)
- ^Arjun Gandhi, Ayesha Shah, Michael P Jones, Natasha Koloski, Nicholas J Talley, Mark Morrison, Gerald HoltmannMethane positive small intestinal bacterial overgrowth in inflammatory bowel disease and irritable bowel syndrome: A systematic review and meta-analysisGut Microbes.(Jan-Dec 2021)
- ^Karn Wijarnpreecha, Susan Lou, Kanramon Watthanasuntorn, Paul T Kroner, Wisit Cheungpasitporn, Frank J Lukens, Surakit Pungpapong, Andrew P Keaveny, Patompong UngprasertSmall intestinal bacterial overgrowth and nonalcoholic fatty liver disease: a systematic review and meta-analysisEur J Gastroenterol Hepatol.(2020 May)
- ^Roman Maslennikov, Chavdar Pavlov, Vladimir IvashkinSmall intestinal bacterial overgrowth in cirrhosis: systematic review and meta-analysisHepatol Int.(2018 Nov)
- ^Ayesha Shah, Erin Shanahan, Graeme A Macdonald, Linda Fletcher, Pegah Ghasemi, Mark Morrison, Mike Jones, Gerald HoltmannSystematic Review and Meta-Analysis: Prevalence of Small Intestinal Bacterial Overgrowth in Chronic Liver DiseaseSemin Liver Dis.(2017 Nov)