SIBO – is the name misleading?

“Small intestinal bacterial overgrowth (SIBO) is defined as the presence of excessive bacteria in the small intestine. SIBO is frequently implicated as the cause of chronic diarrhea and malabsorption. Patients with SIBO may also suffer from unintentional weight loss, nutritional deficiencies, and osteoporosis.” [2007]


A 2017 study reports: ” Between 4% and 78% of patients with IBS and 1% and 40% of controls have SIBO; such wide variations in prevalence might result from population differences, IBS diagnostic criteria, and, most importantly, methods to diagnose SIBO.

To put it simply, a healthy person walks into a MD’s office. The odds that they will get a SIBO diagnosis is 1 in 100 for some MDs and 4 out of 10 with other MDs. Is this diagnosis meaningful when there is such extreme differences between MDs in diagnosing it?

My first question on SIBO, looking backwards from 10 years later:

What are theses? these are the first level (phyla) that bacteria is classified as. In other words what is overgrown — “bacteria” is an extremely broad term equivalent to “transportation”. Transportation can be broken down to ships, planes, trains, cars, horses, bicycle and even foot. For CFS/IBS/FM there is a distinctive pattern of what bacteria are overgrown and reduced that research from 1998 on wards have confirmed. While there is no official test for CFS — research reports have constantly found similar patterns in the microbiome shifts with over 80% reliable prediction of CFS from a microbiome sample alone.

The official definition appears to be ” growth of bacteria more than 105 colony forming unit (CFU) per milliliter in culture of upper gut aspirate is used to diagnosis small intestinal bacterial overgrowth (SIBO), ” [2017] – which bacteria are over-represented is the critical question.

Looking on pub-med for “Small intestinal bacterial overgrowth phyla” – there were just two hits – none useful.

We read “A variety of antibiotics have been used in the treatment of SIBO, most with little supporting evidence. Ideally, antibiotic therapy would be based on bacterial culture and sensitivity data. ” [2007] – in other words, the bacteria phyla at least should be determined before any treatment. I suspect the shifts will be all over the place for a SIBO diagnosis unless you group into tight symptom groups.

Current status of testing for SIBO

“Case-control studies evaluating the prevalence of SIBO in IBS and healthy individuals have shown conflicting results. Moreover, the tests available in routine clinical practice to diagnose SIBO are not valid and lack both sensitivity and specificity… The SIBO-IBS hypothesis lacks convincing evidence but remains under scrutiny. ” [2017]

Treatment Success

“One hundred and four patients who tested positive for newly diagnosed SIBO by lactulose breath testing (LBT) were offered either rifaximin 1200 mg daily vs herbal therapy for 4 weeks with repeat LBT post-treatment….  Of the 37 patients who received herbal therapy, 17 (46%) had a negative follow-up LBT compared to 23/67 (34%) of rifaximin users (P=.24). ” [2014]

  • Note: other tests may have been positive or negative before or after. There was no report on those who were not treated. They may also have had 40% with a negative followup….  — poor study design…

“Evidence is also increasing on the poor intra-individual reproducibility in breath responses with repeated testing for fructose and lactulose. On the basis of these limitations, it is not surprising that the diagnosis of small intestinal bacterial overgrowth based on a lactulose breath test yields a wide prevalence rate and is unreliable.” [2017]

  • In other words, you may be positive today and negative next week without doing anything. The meal you had last night could be the sole difference of results.
  • If I sell water with a pinch of mint (“proprietary herbal blend“), I will likely get 50% of people who tried it saying and writing glowing “this saved me” testimonials with medical reports backing it!!) – excellent way to make a living!

Bottom Line

SIBO appears to be a very last century definition of a condition. A condition that is too often diagnosis without the critical testing of upper gut aspirate. Even if that is tested, without knowing the profile of the overgrowth (i.e. which bacteria phyla (and finer breakdowns)), the diagnosis almost becomes meaningless for determining appropriate treatment. Which bacterias needs to be reduced?

“Digestive issues” may be as meaningful as SIBO – SIBO appears to give a cause, a very vague cause — “Jack has an infection – is it flu? Ebola? Tuberculous? Common cold? Leprosy?  Salmonella? etc”