SIBO: Small Intestinal Bacterial Overgrowth
When beneficial colon bacteria migrate to the small intestine, fermentation happens in the wrong place. Understanding diagnosis, motility, and eradication protocols.
Approximately 60-80% of patients diagnosed with IBS (Irritable Bowel Syndrome) actually have SIBO. It is a structural and functional issue, not just a dietary one.
The Anatomy of SIBO
The large intestine (colon) is designed to house trillions of bacteria that ferment fiber. The small intestine, however, should be relatively sterile, designed for nutrient absorption.
SIBO occurs when bacteria normally found in the colon proliferate in the small intestine. When you eat carbohydrates, these misplaced bacteria rapidly ferment them, producing gases (hydrogen, methane, or hydrogen sulfide) right where nutrient absorption should occur. This causes immediate bloating, pain, and altered bowel habits.
Diagnosis: The Breath Test
Stool testing (like ZOE or Viome) cannot diagnose SIBO, as stool reflects the colon, not the small intestine. The standard non-invasive diagnostic tool is the lactulose or glucose breath test.
Hydrogen-Dominant SIBO
Typically correlates with diarrhea (SIBO-D). Caused by bacteria producing hydrogen gas. Often faster to eradicate.
Methane-Dominant (IMO)
Typically correlates with severe constipation (SIBO-C). Caused by archaea (Methanobrevibacter smithii). Requires different, often harsher, antimicrobial protocols.
The Root Cause: The Migrating Motor Complex
SIBO rarely happens in a vacuum; it is usually secondary to a failure of the Migrating Motor Complex (MMC). The MMC is an electromechanical sweep of the gastrointestinal tract that occurs every 90-120 minutes during fasting to clear out residual debris and bacteria.
If you graze on food all day, the MMC is constantly interrupted. If you had food poisoning (post-infectious IBS), antibodies may have damaged the vinculin proteins that govern the MMC. Without resolving the MMC dysfunction, SIBO will almost certainly relapse post-treatment.
MMC Cycle Calculator
The Migrating Motor Complex requires roughly 90 minutes of fasting to initiate, and completes a sweep every 90 minutes thereafter. Calculate your overnight MMC cycles.
Target: 4+ full cycles per night.
MMC Cycle Targets
The Migrating Motor Complex requires roughly 90 minutes of fasting to initiate, and completes a sweep every 90 minutes thereafter. To achieve the target of 4+ full sweeps per night to prevent SIBO recurrence, a minimum fasting window of 12-14 hours between dinner and breakfast is clinically recommended.
Treatment Protocols
Treatment is highly individualized but generally falls into three phases:
- Eradication: Utilizing localized antibiotics like Rifaximin (which stays primarily in the gut without systemic absorption) or targeted herbal antimicrobials (e.g., Allicin, Berberine, Oregano oil).
- Prokinetics: Immediately following eradication, prokinetic agents (low-dose Naltrexone, Prucalopride, or ginger/artichoke extracts) must be used to stimulate the MMC and prevent relapse.
- Dietary Management: Implementing a Low FODMAP diet temporarily to starve the remaining bacteria, followed by gradual reintroduction to rebuild diversity using prebiotics safely.