The Pathology of SIBO
Normally, the large intestine houses trillions of bacteria, while the small intestine (where most nutrient absorption occurs) has relatively few. In SIBO, bacteria overpopulate the small intestine. When you eat carbohydrates, these bacteria ferment them prematurely, producing massive amounts of gas (hydrogen or methane) right where your body is trying to absorb food.
This causes severe, objective distension (the classic "six months pregnant" look), bloating, pain, and in severe cases, malabsorption of nutrients like Vitamin B12 and Iron.
Types of SIBO
SIBO is classified by the type of gas produced by the overgrown organisms. This is determined via a Lactulose or Glucose Breath Test.
| Gas Type | Primary Symptom | Clinical Name / Organism |
|---|---|---|
| Hydrogen (H2) | Diarrhea (Bristol 6-7) | Hydrogen-dominant SIBO (Bacteria) |
| Methane (CH4) | Constipation (Bristol 1-2) | Intestinal Methanogen Overgrowth (IMO) - *Technically Archaea, not bacteria.* |
| Hydrogen Sulfide (H2S) | Diarrhea / "Rotten egg" smelling gas | H2S SIBO (Often missed on standard breath tests) |
Why Does It Happen? (The Root Cause)
SIBO is rarely a primary disease; it is almost always a secondary consequence of a failure in the gut's "housekeeping" mechanisms. If you kill the bacteria without fixing the root cause, relapse rates are extremely high (up to 44% within 9 months).
- Migrating Motor Complex (MMC) Failure: The MMC is a sweeping wave of muscular contractions that clears debris from the small intestine during fasting (between meals and overnight). If this fails (often due to nerve damage from food poisoning), bacteria stagnate.
- Low Stomach Acid (Hypochlorhydria): Stomach acid kills incoming bacteria. Prolonged use of PPIs (acid blockers) can increase SIBO risk.
- Structural Issues: Adhesions from surgeries (e.g., appendectomy, C-section), endometriosis, or a faulty ileocecal valve.
Treatment Protocols
Effective SIBO treatment requires a three-pronged approach:
- Eradicate: Reduce the overgrowth using targeted non-absorbable antibiotics (e.g., Rifaximin) or herbal antimicrobials (e.g., Allicin, Oregano oil). Alternatively, the Elemental Diet is used for severe cases.
- Restore Motility: Prokinetics (medications or supplements like ginger/artichoke extract) are taken at night to stimulate the MMC and prevent the bacteria from returning.
- Dietary Management: A Low FODMAP or Bi-Phasic diet is used post-treatment to manage symptoms and slowly reintroduce fermentable fibers.