What is Small Intestinal Bacterial Overgrowth (SIBO)? 

SIBO occurs when more bacteria (or other microorganisms) than normal begin to grow in the small intestine. The types of bacteria that overgrow are usually already found in the small intestine or migrate up from the large intestine. 

What causes SIBO?  

Bacteria and other microorganisms in your GI tract can potentially overgrow if they are given opportunity to do so. Imbalances in the gut can result from:   

• Food poisoning  
• Irritable Bowel Syndrome (IBS) or Inflammatory Bowel Disease (IBD) 
• Low levels of stomach acid or chronic proton pump inhibitor (PPI) use  
• Prolonged antibiotic use  
• Chronic constipation 
• Anatomical changes to the small intestine from surgery, strictures, obstructions, etc.  
• Dysfunction of the Migrating Motor Complex (MMC), the system of “cleansing waves” in the GI tract that moves bacteria into the large intestine that occurs during fasting  

Changes to the types and amounts of bacteria in your gut from SIBO can impact communication along the gut-brain axis, contributing to IBS symptoms. Having IBS also puts you at higher risk for developing SIBO. Gut motility changes or changes in the MMC can occur from stress, other conditions such as hypothyroidism, history of eating disorder, or medications. 

What are the symptoms of SIBO? 

For some people with SIBO, they may be asymptomatic, meaning that they don’t experience any symptoms.  

For others with SIBO, they may experience symptoms that are common with IBS such as abdominal pain or cramping, bloating, diarrhea, constipation, or gas. 

How is SIBO diagnosed?  

The easiest test for diagnosing SIBO right now is a breath test. The test typically involves drinking a sugar solution (that has glucose, lactulose, or both) and then breathing into a tube periodically. Levels of hydrogen and methane gases are measured to see if there is an increase, showing that the bacteria in the small intestine are fermenting sugars. If there is an increase in either gas, SIBO is likely to be diagnosed. This test is non-invasive but you do have to follow a special diet the day before taking it. 

How is SIBO treated? 

There are many treatment options for SIBO, depending on an individual’s symptoms, medical history, and preferences. Some treatments that work well for some people may not be as effective in others.  

Treatment can include: 

• Antibiotics like rifaximin, neomycin, or metronidazole  
• Elemental diet for 2–3 weeks  
  • Involves eating only special shakes with nutrients broken down into the smallest parts  
• Diet changes  
  • Low FODMAP diet or low fermentation diet as needed  

How do prevent SIBO from coming back? 

SIBO is a tricky condition as one can relapse very quickly once treatment is finished. Prevention of relapse includes: 

• Prokinetic medication that helps stimulate the Migrating Motor Complex 
• Addressing underlying causes (treating conditions, changing medications, etc.) 
• Continue any recommended diet changes 

Due to the interconnected nature of IBS and SIBO for many cases, incorporating additional therapies for IBS such as stress management or gut directed hypnotherapy may be helpful.