By Dr. Carla Cashin, ND
Irritable bowel syndrome (IBS) is a chronic disorder of the gastrointestinal tract, presenting with symptoms of abdominal pain and altered bowel habits in the absence of an overt disease process. This condition is very common, with approximately 10 to 15 percent of adults and adolescents experiencing symptoms consistent with IBS. Unfortunately, standard treatments often provide little relief and those with IBS are left with symptoms that negatively affect their quality of life. The good news is new treatment protocols from leading hospitals in North America are being developed and combined with naturopathic approaches that focus on addressing a common root cause of IBS, small intestinal bacterial overgrowth (SIBO).
What is SIBO? For the most part, intestinal bacteria reside in the large intestine with smaller populations inhabiting the small intestine. In the condition of small intestinal bacterial overgrowth (SIBO), bacteria inundate the small intestine and cause a series of problems. These bacteria produce gases as they digest carbohydrates from our food. Hydrogen, methane and occasionally hydrogen sulfide gases are produced by the bacteria, contributing to the core symptoms of SIBO - abdominal bloating and/or distension, abdominal pain (as gas is trapped in the small intestine), diarrhea from hydrogen-producing bacteria, and constipation from methane-producing microbes. Interestingly, the microbes that produce methane are in fact not bacteria at all, but a different class of organism called archaea. Little is yet understood about the microbes that produce hydrogen sulfide. Additionally, the overgrowth of bacteria in the small intestine can contribute to nutrient deficiencies, as the bacteria diminish the absorptive capacity of the small intestine or consume the nutrients themselves. In SIBO, nutrient deficiencies such as iron and B12 deficiency are common, which can cause anemia and subsequently fatigue.
Why does SIBO occur? The main reason SIBO occurs is abnormal gastrointestinal motility from impaired gut nerves. In a healthy gut, undigested material as well as bacteria are swept through the digestive tract to the colon. One of the main physiological mechanisms responsible for this sweeping action is the migrating motor complex (MMC): waves of electrical activity that propel digestive contents through the intestines during fasting. In many individuals with IBS, the MMC is impaired causing an overabundance of undigested food and bacteria to remain in the small intestine and triggering SIBO.
How can I find out if my IBS symptoms are from SIBO? The mainstay of SIBO testing is lactulose breath testing, which measures levels of hydrogen and methane gases in breath samples. A prep diet that limits certain carbohydrates is followed for 1-2 days prior to testing. The morning of testing a baseline sample is collected, followed by drinking a sugary solution (lactulose) with repeated samples collected every 20 minutes for 2-3 hours. Testing can be completed at home and samples are sent to the lab; results are usually expected within 1-2 weeks following testing. Testing is important to confirm a diagnosis of SIBO, establish whether hydrogen, methane or both gases are present, and to determine which antibiotic or herbal antimicrobial agents will be most appropriate for treatment. Testing can also help predict how an individual may respond to treatment; for example, if gas levels are quite elevated, the bacterial overgrowth may be more severe and require repeated rounds of treatment. In most cases, breath testing is preferred for the above reasons, however, empirical treatment without prior breath testing may be appropriate for some individuals suspected of having SIBO.
How is SIBO treated? Naturopathic treatment of SIBO involves several stages: 1) Antibiotics or herbal antimicrobials are used to modify bowel flora, with different agents prescribed depending on whether you have hydrogen or methane dominant SIBO. A round of antibiotics is typically administered for 2 weeks, while antimicrobial herbs take a little longer to work and require a 4 week course. Occasionally multiple rounds of antibiotics or herbal antimicrobials are needed in more severe cases of SIBO. 2) Prokinetic agents are used to stimulate normal functioning of the migrating motor complex (MMC). This is a key element of treatment, as failure to re-establish the MMC will allow bacteria to repopulate the small intestine, causing a relapse of SIBO. Typically prokinetic agents are taken for at least 12 weeks. 3) Therapeutic diets which limit certain carbohydrates, the food source for these bacteria, are implemented to further modify bowel flora and prevent recurrence. Most patients feel dramatically better when they stick within the parameters of their diet and choose to follow these dietary changes long term. Therapeutic diets are most effective when individualized for the patient, and adjusted throughout treatment as needed.
- Wald, Arnold. “Clinical Manifestations of and diagnosis of irritable bowel syndrome.” UpToDate. Jan 2017.
- Wald, Arnold. “Pathophysiology of irritable bowel syndrome,” UpToDate. Jan 2017.
- SIBO Symposium. Hosted at the National University of Natural Medicine in Portland, Oregon. June, 2015.
- Pimentel, Mark et al. “Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome.” American Journal of Gastroenterology. 2000; 95(12): 3503.
- Pimentel, Mark et al. “Rifaximin therapy for patients with irritable bowel syndrome without constipation. New England Journal of Medicine. 2011; 364 (1): 22-32.