SIBO Overview & Its Relation to IBS

SIBO, or small intestinal bowel overgrowth, is a condition that often overlaps with irritable bowel syndrome (IBS). Both conditions share similar symptoms, including abdominal pain and distension, and changes in bowel motility (constipation or diarrhea). Many times SIBO can be misdiagnosed as IBS, and SIBO can also increase risk for IBS. Because of these overlaps, these conditions are further misunderstood and leave those living with them confused.

SIBO is a condition where there is an overgrowth of both aerobic and anaerobic bacteria in the small intestine. Usually, the small intestine has very low levels of microbes, while the large intestine is home to the majority of our important microbes. The overgrowth of bacteria are not all “bad” bacteria. We still have a lot to learn about SIBO, but it seems that the microbes are just in the wrong place, finding their home in the small intestine instead of the large intestine. Dysbiosis, on the other hand, is the imbalance of microbes, where the “bad” outweigh the “good.” This can be present in both the small and large intestine, and will have its own effect on the body. For dysbiosis, the goal is to increase the “good” bacteria through different lifestyle and nutrition interventions. For SIBO, the goal is to clear the small intestine of the bacterial overgrowth, then prevent reoccurence.

SIBO and IBS can be present together or separately. Since symptoms overlap, it’s hard to know for sure whether both are actually present. It’s important to ask for a SIBO breath test when you are getting an IBS diagnosis. Once you treat SIBO, you can monitor symptoms. If IBS-like symptoms still occur after SIBO is treated, then you may also receive a clear IBS diagnosis.

IBS is diagnosed according to Rome criteria, based on symptoms and duration, in the absence of other conditions, including celiac, allergies, and irritable bowel disease (Crohn’s or colitis). SIBO is diagnosed using a glucose or lactulose breath test. Many studies support the glucose test, which may be more ideal for those with severe symptoms. The lactulose test may be able to detect distal SIBO, but it can lead to diarrhea, which may not be ideal. The results of the tests can either be negative, or will be positive for two potential types of SIBO: hydrogen dominant or methane dominant. Breath tests may not 100% accurate, but they are the most non-invasive option we currently have.

The good news is that there are treatments for SIBO that have shown to be fairly effective. The conventional treatment method is to use non-absorbable antibiotics that target the overgrowth, without having a broad spectrum effect. Rifaximin is used for hydrogen dominant, and a combination of rifaximin and neomycin is used for methane dominant. The alternative treatment option is to use herbal therapy, which has still shown a lot of great success. This method uses a combination berberine herbs, allicin (for methane dominant), oregano, and neem to have an antibiotic effect. It’s important to work with a knowledgeable practitioner if you are considering this option.

After treating with antibiotics or herbal therapy, following a low FODMAP diet or other low fermentable carbohydrate diet can help control symptoms and prevent reoccurence. There is very little research to recommend a clear nutritional approach, but practitioners agree that modifying fermentable carbohydrates is effective. Options include low FODMAP, low fermentable diet, GAPS, or paleo. Some practitioners may also recommend a reduction of sugar and resistant starches. The low FODMAP diet is what I use in my practice because it can allow for more variety and less restriction after the reintroduction phase. After treatment, a prokinetic, like erythromycin, may also be used to to enhance intestinal motility. Alternatives include prucalopride or cisapride.

During antibiotic or herbal therapy, the consensus is to avoid complete restriction low fermentable carbohydrates, to allow bacteria to flourish in order to be removed. There are mixed reviews on the use of probiotics during treatment. A 2017 study shows a benefic to probiotic therapy. Align or Culturelle would be good options to consider with your doctor during treatment.

With SIBO, it’s important to find and treat the underlying cause of the bacterial overgrowth to prevent reoccurance. The problem is that the cause can be tricky to identify. Potential causes, include:

  • Foodborne illness - prokinetic therapy or herbal supplement Iberogast can help with this

  • Long-term PPi (proton pump inhibitor) use - can alter the pH of the small intestine and reduce motility - work with a doctor to reduce or discontinue use

  • Chronic constipation - work with a dietitian to alter diet, lifestyle habits, and body positioning to improve

  • Decrease in bile acids - work with doctor

  • Chronic stress - work with therapist to implement habits and practices to reduce stress

  • Migrating motor complex (MMC) deficiency - can be stimulated with a prokinetic

Other conditions can increase your risk of SIBO. If these are present, it’s important to work with your doctor to treat or manage them. Conditions include scleroderma, small intestinal pseudo-obstruction, intestinal adhesions, pancreatic insufficiency, small intestinal diverticulosis, low stomach acid (achlorhydria), diabetes, radiation enteritis, immunodeficiency, and ileocecal valve resection. SIBO, or its underlying cause, could also lead to malabsorption, so it’s important to check nutrient levels in your blood so you can supplement, if necessary.

If you’re looking for personalized care through your SIBO journey, my IBS Management Program can be adapted for you! We will use a low FODMAP approach to decrease symptoms, then talk about how to take care of the underlying cause of your SIBO so you can move forward with more food freedom and less risk for recurrence. If you’re interested, apply for a free consult here.