Inside: what exactly is SIBO ( Small Intestinal Bacterial Overgrowth). And how SIBO is the real reason behind IBS symptoms. How SIBO treatment can actually improve your IBS symptoms.
SIBO or small intestinal bacterial overgrowth is not a new condition and we have known about it for a long time.
Now a lot of people will have this question that, aren’t we supposed to have bacteria in our intestines, so the answer is that we are supposed to have all those bacteria in our large intestine and not so much in the small intestine.

In SIBO we have overgrowth or overabundance of wrong bacteria in the small intestine.
The medical definition of SIBO is the presence of more than 100,000 bacteria per ml in jejunal aspirate( part of the small intestine )[1,2,3].
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Diagnosis of SIBO
The older way of diagnoses which was also the gold standard was to perform open surgeries to collect this aspirate; later on, this aspirate was collected through an endoscope.
But now we have new non-invasive tests to test for SIBO. Like Breath Tests to test for overgrowth od bacteria in the small intestine, or SIBO.
The basis of these breath tests is understanding that the colonic bacteria ferments the carbohydrates and produces gases like hydrogen and methane[4]. This breath test involves giving you a carbohydrate drink, most commonly lactulose and measure the hydrogen and methane gas levels in your breath.

SIBO at that time was considered to be the cause of malabsorption and typical symptoms that were associated with SIBO were weight loss, fatty stools, nutritional deficiencies.
Newer understanding is — SIBO can give you symptoms of bloating, diarrhoea, constipation, foul-smelling gas, stomach gurgling or cramping and sometimes can also cause chronic fatigue.
So as you will see SIBO is not a fake diagnosis but it is very real and we have known about it for so long and our understanding about it is constantly growing.
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Is SIBO your cause for IBS ( Irritable Bowel syndrome)
In our quest to know more about SIBO we have also realised that there is a strong correlation between SIBO and IBS ( Irritable Bowel Syndrome), and now SIBO is recognised as one of the causes of IBS[ 5,6,7].
IBS is a very common condition and it was shown in a study that 11% of the world population have IBS related symptoms[8]. Typical symptoms of IBS are diarrhoea, constipation or alternating constipation and diarrhoea, abdominal pain, gas and bloating. And SIBO also can give you similar symptoms.
This meta-analysis or study that was done to look for incidence of SIBO in IBS patients showed that — 38% of IBS patients had SIBO, which was much higher than the healthy control population[9].
They also noticed that the incidence of SIBO was higher in females and elderly, as compared to males with IBS. Typical treatment for SIBO is to use rifaximin and a study was done to evaluate the improvement in IBS symptoms after rifaximin treatment in people with SIBO[10]. There was a significant improvement in IBS symptoms after treatment, and simultaneously it got rid of SIBO also.
These studies point that the real cause of your IBS could actually be underlying SIBO. Especially in females and elderly patients who have been diagnosed with IBS also have higher chances of SIBO. And especially now we know that treating SIBO does improve IBS symptoms, it makes sense to get evaluated for it and get treated.
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Summary
So this post explores the question of Is SIBO real? And can SIBO be the cause of IBS symptoms in people and also talks about the improvement in IBS symptoms following treatment of SIBO.
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References:
- Quigley EMM. Small intestinal bacterial overgrowth: what it is and what it is not. Curr Opin Gastroenterol. 2014;30:141–6.
- Sachdev, A. H., & Pimentel, M. (2013). Gastrointestinal bacterial overgrowth: pathogenesis and clinical significance. Therapeutic Advances in Chronic Disease, 4(5), 223–231
- Gorbach SL. Microbiology of the Gastrointestinal Tract. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 95.
- Rezaie A, Buresi M, Lembo A, Lin H, McCallum R, Rao S, et al. Hydrogen and methane-based breath testing in gastrointestinal disorders: the North American consensus. Am J Gastroenterol. 2017;112:775–8 A detailed examination of current criteria for the diagnosis of SIBO together with consensus-based recommendations for the performance and interpretation of breath tests.
- Reddymasu SC, Sostarich S, McCallum RW. Small intestinal bacterial overgrowth in irritable bowel syndrome: are there any predictors? BMC Gastroenterol. 2010;10:23.
- Chu H, Fox M, Zheng X, et al. Small intestinal bacterial overgrowth in patients with irritable bowel syndrome: clinical characteristics, psychological factors, and peripheral cytokines. Gastroenterol Res Pract. 2016;2016:3230859.
- Ford AC, Spiegel BM, Talley NJ, et al. Small intestinal bacterial overgrowth in irritable bowel syndrome: systematic review and meta-analysis. Clin Gastroenterol Hepatol. 2009;7(12):1279–86.
- Lovell RM, Ford AC. Global prevalence of and risk factors for irritable bowel syndrome: a meta-analysis. Clin Gastroenterol Hepatol. 2012;10(7):712–721.e714.
- Chen B, Kim JJ, Zhang Y, Du L, Dai N. Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis. J Gastroenterol. 2018
- Pimentel M. Review of rifaximin as treatment for SIBO and IBS. Expert Opin Investig Drugs. 2009;18(3):349–58.
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