Thank you the post. I maintain a large library of research papers FGID. Over the past 2-3 years there have been some very interesting papers published on the topic. In the paper that Drossman and colleagues published (see reference below) they say "more recent reports using jejunal cultures found SIBO in only 4% of the IBS population and detected no differences from a HC (healthy controls)population." This seems to be a fairly good indication that SIBO is not the cause of IBS. But as you say it possible for SIBO and IBS to co-exist.
Reference
Grover, M., Kanazawa, M., Palsson, O., Chitkara, D., Gangarosa, L., Drossman, D., et al. (2008). Small intestinal bacterial overgrowth in irritable bowel syndrome: association with colon motility, bowel symptoms, and psychological distress. Neurogastroenterology Motility, 20
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