The evidence suggesting that irritable bowel syndrome, IBS, overlaps considerably with small intestinal bacterial overgrowth, SIBO, is growing. Some even speculate that IBS = SIB—that they are one and the same condition. The likelihood of someone with IBS of also having SIBO is around 10-fold higher than in people without IBS. At the very least, some factor operating in people with IBS (I would propose that grain and sugar consumption be put at the top of the list) encourages the development of SIBO.
For instance, this Chinese series showed that 72% of people with IBS tested positive for breath H2 and/or methane consistent with SIBO, compared to 38% (!!!) of normal controls. (Note the worrisome number of SIBO-positive controls suggesting that SIBO is common even in people without IBS.)
There are also several clinical trials of rifaximin, the conventional antibiotic of choice for treating SIBO, vs. placebo in people diagnosed with IBS: 40-50% of people with IBS treated with rifaximin obtain significant relief of their symptoms, further bolstering the idea that IBS and SIBO overlap.
This is no small matter. About 10% of the U.S. population has IBS, meaning around 30-35 million people, children included. Putting aside its practical struggles, such as the inconvenience and embarrassment of bowel urgency, unpleasant discomfort, gas, bloating, etc., there is even potential for increased risk for autoimmune diseases, diverticular disease, and cancers of the colon, pancreas, liver, biliary tract, and kidney.
Even if someone with IBS does not meet quantitative criteria for SIBO (e.g., numbers of microorganisms in a duodenal aspirate), there can still be shifts in microbial species, i.e., dysbiosis, with an excess of organisms such as E. coli and Enterobacter and a lack of other species, as illustrated by this graphic from Giamarellos-Bourboulis et al 2015 (control on left, IBS on right):
We also have to recognize that breath testing for SIBO is plagued by low sensitivity, i.e., it fails to identify many people who do indeed have the disease but have negative breath tests. Breath testing in people with IBS may therefore underestimate the proportion who have SIBO and could benefit from efforts to eradicate it.
Looking for evidence of SIBO is causing many diseases to be rethought and redefined. Look at this study of people with acute diverticulitis, for example, with 59% of participants proving to be positive (H2 and/or methane) for SIBO. Does this mean that SIBO is the precursor to diverticular disease, i.e., is the severe dysbiosis of SIBO among the factors that weaken the colonic wall that allows outpouching, or diverticuli, to form and rupture?
We still have plenty of unanswered questions in IBS and SIBO, but we have been having more and more success dealing with these issues, tackled in our discussion in the Undoctored Inner Circle. The Inner Circle conversations have exposed the fact that many mainstream doctors and gastroenterologists don’t know anything about SIBO, dismiss it as inconsequential (because they don’t read the science), or simply don’t see it as a revenue-producing activity. This means that more and more people are making the diagnosis themselves (even obtaining their own H2 and methane breath tests), then treating it themselves with herbal antibiotic regiments like Candibactin AR/BR and FC Cidal + Dysbiocide, followed by a vigorous program of bowel flora restoration.