Understanding SIBO: A Complete Guide to Small Intestinal Bacterial Overgrowth

What is SIBO?

Small Intestinal Bacterial Overgrowth (SIBO) is a condition characterized by an abnormal increase in the bacterial population of the small intestine. Unlike the large intestine, which naturally contains trillions of bacteria, the small intestine normally has relatively few microorganisms.

When bacteria from the colon migrate upward or when normal clearing mechanisms fail, these bacteria can proliferate in the small intestine, leading to a range of digestive symptoms.

Common Symptoms

The most common symptoms of SIBO include:

• Bloating and abdominal distension, especially after meals
• Excessive gas and flatulence
• Abdominal pain or cramping
• Diarrhea, constipation, or alternating between both
• Nausea and acid reflux
• Fatigue and brain fog
• Nutrient malabsorption (B12, iron, fat-soluble vitamins)

Causes and Risk Factors

Several factors can contribute to the development of SIBO:

• Impaired motility: The migrating motor complex (MMC) normally sweeps bacteria out of the small intestine between meals. Conditions that impair this function increase SIBO risk.
• Structural abnormalities: Adhesions, strictures, or surgical alterations can create areas where bacteria accumulate.
• Low stomach acid: Stomach acid serves as a natural barrier against bacterial overgrowth.
• Immune deficiency: The gut immune system plays a crucial role in controlling bacterial populations.

Diagnosis

The most common non-invasive test for SIBO is the lactulose or glucose breath test. Patients consume a sugar solution, and the gases produced by bacterial fermentation (hydrogen and methane) are measured over several hours.

A positive test typically shows elevated hydrogen or methane levels within the first 90-120 minutes, indicating bacterial fermentation occurring in the small intestine.

Evidence-Based Treatments

Treatment for SIBO typically follows a multi-phase approach:

• Antibiotics: Rifaximin is the most studied antibiotic for SIBO, with success rates of 40-70% after a single course. For methane-dominant SIBO, neomycin is often added.
• Herbal antimicrobials: Studies show that herbal protocols using berberine, oregano oil, and neem can be as effective as rifaximin in some patients.
• Dietary modifications: The low FODMAP diet, elemental diet, or specific carbohydrate diet can help reduce bacterial fermentation.
• Prokinetics: Medications or supplements that improve motility help prevent SIBO recurrence.

Preventing Recurrence

SIBO has a high recurrence rate, estimated at 40-50% within one year. Strategies to prevent recurrence include:

• Meal spacing (4-5 hours between meals to allow MMC function)
• Prokinetic agents
• Stress management
• Addressing underlying causes