Small intestinal bacterial overgrowth, or SIBO, is often the reason for gut symptoms such as bloating, gas, abdominal pain, spasm, constipation, diarrhea, and poor digestion.
These symptoms have always been attributed to irritable bowel syndrome (IBS) and treatment was limited to symptom control.
But now we know that eradicating the bacteria (and fungus) of SIBO, and improving gut motility, is the best treatment for many people with IBS.
Our current knowledge is due to some intrepid researchers who brought an end to old myths about IBS and how to treat it.
How the IBS and SIBO evolution started
My own journey of finding a solution for my own IBS, and severe food and chemical environmental sensitivities, started with the work of Dr. Leo Galland, a New York University School of Medicine-Bellevue Medial Center trained internist.
Having become frustrated with the single diagnosis emphasis of conventional medicine, he was one of the first clinicians to practice what we now call functional medicine.
Putting together his observations with the work of others before him, he started working in the 1980 with the idea that a wide variety of symptoms, from IBS to allergies, originated in the complex system of the gut and its microbial balance.
In the early 1990's, he advanced the idea of "dysbiosis", or an imbalance of bacteria in the gut, as stemming from four potential patterns: putrefaction, excess fermentation, deficiency of normal bacteria, and sensitization. He came up with a systemized approach for diagnosing and treating dysbiosis and leaky gut [1,2,3,4].
Meanwhile, in conventional medicine, doctors Henry Lin and Mark Pimentel started an evolution in thinking about IBS and SIBO, noting that IBS and SIBO symptoms were similar, and set out to see if the two conditions were related, and to see if treating for SIBO resolved the symptoms of IBS.
They published their results in the American Journal of Gastroenterology in 2000 (5). Their conclusion was that IBS and SIBO were actually related and that treating the SIBO resolved symptoms in 48% of their IBS patient subjects.
Then, in 2004, Dr. Henry Lin, at USC Medical Center, published a clinical review paper in JAMA (The Journal of the American Medical Association), summarizing the research so far on IBS and the possible relationship to SIBO (6).
This was a landmark because he put the idea out in a prominent respected medical journal where it could not be ignored.
For the first time, there was a chance that the myth could be put to rest that people with IBS, mostly women, just needed to take an anti-depressant and symptom control medications.
He outlined how IBS was found in 14% of the population, with 92% with IBS having bloating. He explained how SIBO (small intestinal bacterial overgrowth) might explain the bloating.
Furthermore, from his earlier study, 84% of IBS patients had a positive breath test for excess hydrogen production. And 75% had improvement of their IBS symptoms after being treated to resolve their SIBO.
In addition, Dr. Lin explained how bacteria from SIBO could move across the gut barrier activating the immune system. He thought this could explain the immune response that is often seen in IBS patients.
He also reported on the increased intestinal permeability and "leaky gut syndrome" seen in SIBO patients, as well as mast cell degranulation and enteric nervous system activation thought to be behind gut irritability and cramping.
Hyper irritability can even carry over into other conditions such as fibromyalgia, interstitial cystitis, and chronic fatigue syndrome.
He explained that the major migrating complex, known as the MMC, dictates the motility of the gut. That proper motility is imperative in preventing SIBO, and how methane gas reduces motility and contributes to constipation.
While the antibiotic Xifaxan could be used for hydrogen predominant SIBO, Neomycin could be added when there is methane gas.
The Paradigm switch from IBS to SIBO
Dr. Lin's review paper was a big awareness event, in a widely read medical journal, broadcasting the paradigm switch from thinking of IBS as a functional disorder defined by a set of symptoms, to a condition that frequently had an underlying treatable bacterial overgrowth, SIBO.
In their earlier 2000 study (5), doctors Lin and Pimentel had found that 78% of IBS patients had SIBO upon breath testing in a study of 202 patients. After treatment with antibiotics, breath testing became normal and only 50% of the patients still met criteria for having IBS.
In a 2003 study, they followed up on the IBS and SIBO connection.(7) Their controlled double-blind, placebo-controlled study showed that IBS patients had positive breath tests 84% of the time vs. only 20% in the control patients that did not have IBS.
Symptoms resolved in 36.7% of patients who got antibiotics (Neomycin) but still had abnormal breath tests, and in 75.0% of patients who got antibiotics and achieved normal breath tests.
Treating IBS patients with antibiotics for SIBO worked, especially if the breath test normalized.
In 2010 Dr. Pimentel published an evidence-based treatment algorithm for IBS based on the bacterial SIBO hypothesis that outlined how to use breath testing for diagnosis, and Xifaxan and Neomycin antibiotics for treatment, along with motility agents .
Fast forward to today, and Dr. Pimentel's current research leads him to believe that a bout of food poisoning may start off a cascade that results in IBS and SIBO.
He has developed a blood test, the IBSCheck test, for the toxin that he believes is associated with diarrhea predominant IBS. This new blood panel tests for antibodies to cytolethal distending toxin B and anti-vinculin .
Strategies for diagnosing and treating SIBO
Today, people are becoming more aware of SIBO, but it is still, after all these years, not at all routine for physicians to recognize, diagnose, and treat SIBO.
It is even less routine for physicians to automatically think of SIBO when treating a patient with IBS.
Patients must be proactive about finding physicians familiar with diagnosing and treating SIBO. Fungal small bowel overgrowth may also be present (SIFO) and must be addressed .
Fortunately, there are several tools we can use to help guide us in SIBO and SIFO (small intestinal fungal overgrowth) diagnosis.
In addition to the hydrogen and methane breath test, there are stool GI profiles, and organic acid testing, that look at organic acids that are produced by bacteria and fungus.
Some of the treatment options include dietary change or elemental diet, including low FODMAPs and low fermentable diets, herbal antibiotics (herbals with antibacterial properties), antibiotics such as Xifaxan and Neomycin, anti-fungals (both herbal and pharmaceutical), and gut motility agents.
Probiotics are very popular and can be very important in achieving gut balance. However, care must be taken with them because they can make things worse in some people until the underlying condition is improved.
Hope for SIBO and IBS
With increased understanding of the gut microbiome and post infection toxins, there is more hope than ever in identifying and treating IBS and SIBO. Up to 15% of the population has IBS.
IBS is not a psychological disorder and antidepressants are not the answer.
What is needed is diagnostic investigation, then treatment, to get rid of harmful SIBO bacteria and fungus, restore good bacteria, restore the gut barrier, encourage the hyperactive immune and neurologic responses to calm down, and restore proper gut motility.
Better solutions are needed to help patients who have IBS that is not SIBO or SIFO related, but many patients test positive for SIBO and respond to treatment.
There is now a toxin antibody blood test to diagnose post infectious diarrhea predominant IBS, so that patients can have a diagnosis, and so that invasive testing such as colonoscopy and endoscopy can be safely avoided .
Most importantly, there are clinicians who have experience with testing for and treating SIBO and fungal overgrowth. It is well worth your time to seek them out.
1) Galland Leo. An Integrated Approach to Gastrointestinal Disorders. http://mdheal.org/articles/word2/gastrointestinalisorder2.htm
2) Galland Leo. Intestinal Parasites, Bacterial Dysbiosis and Leaky Gut. Excerpts from Power Healing (Random House, 1998). http://mdheal.org/parasites.htm
3) Galland Leo. Leaky Gut Syndromes: Breaking the Vicious Cycle. http://mdheal.org/leakygut.htm
4) Galland lea, Barrie Stephen. Digestive System: Intestinal Dysbiosis annd the Causes of Disease. http://www.healthy.net/Health/Article/Intestinal_Dysbiosis_and_the_Causes_of_Disease/423/1
5) Pimentel M, Chow E, Lin H. Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome. The American Journal of Gastroenterology. 2000;95:3503-3406. www.nature.com/doifinder/10.1111/j.1572-0241.2000.03368
6) Lin H. Small Intestinal Bacterial Overgrowth. Journal of the American Medical Association. 2004;292:852. jama.jamanetwork.com/article.aspx?doi=10.1001/jama.292.7.852
7) Pimentel M, Chow E, Lin H. Normalization of lactulose breath testing correlates with symptom improvement in irritable bowel syndrome: a double-blind, randomized, placebo-controlled study. The American Journal of Gastroenterology. 2003;98:412-419. www.ncbi.nlm.nih.gov/pubmed/12591062
8) Pimentel M. An Evidence-Based Treatment Algorithm for IBS Based on a Bacterial/SIBO Hypothesis: Part 2. The American Journal of Gastroenterology. 2010;105:1227-1230. www.nature.com/doifinder/10.1038/ajg.2010.125
9) Erdogan A, Rao S. Small Intestinal Fungal Overgrowth. Current Gastroenterology Reports. 2015;17:16. link.springer.com/10.1007/s11894-015-0436-2
10) Pimentel M, Purdy C, Magar R, Rezaie A. A Predictive Model to Estimate Cost Savings of a Novel Diagnostic Blood Panel for Diagnosis of Diarrhea-predominant Irritable Bowel Syndrome. Clinical Therapeutics. 2016;38:1638-1652. www.ncbi.nlm.nih.gov/pubmed/27261204
Dr Ann Haiden DO is an internal medicine physician and functional medicine specialist, two time breast cancer survivor, multiple other things survivor, and advocate of a low carb, plentiful produce, Paleo Ancestral eating and living lifestyle.
If you would like to work with Dr Haiden for personalized medical care, we invite you to find out more about her clinic and how to become a patient.
Dr. Haiden's clinic is in Los Gatos, California, in the greater San Jose and San Francisco Silicon Valley area.