Medically Reviewedby Vadim Doroshenko • 19. juli 2026
Sources:
Small Intestinal Bacterial Overgrowth in Irritable Bowel Syndrome

Key takeaways

  • Up to 60-80% of patients diagnosed with IBS may have underlying SIBO.
  • Diagnosis is established using lactulose breath testing for hydrogen and methane.
  • Impaired migrating motor complex (MMC) motility is the leading cause of relapse.

Medical disclaimer: Content is for informational purposes and does not replace medical advice.

What is SIBO and Why Does Small Intestinal Bacterial Overgrowth Occur?

Small Intestinal Bacterial Overgrowth (SIBO) is defined as an excessive accumulation of colonic-type bacteria in the small intestine, exceeding 10^3 CFU/mL. PMID 32467262

Unlike the colon, which harbors trillions of fermentative microbes, the healthy small intestine maintains a low bacterial density due to stomach acid, bile salts, pancreatic enzymes, and intestinal motility. PMID 32467262

When these protective clearing mechanisms fail, bacteria ferment swallowed dietary carbohydrates prematurely, leading to gas, mucosal inflammation, and malabsorption. PMID 32467262

Three Types of SIBO: Hydrogen, Methane (IMO), and Hydrogen Sulfide

Modern breath testing identifies three distinct subtypes of small intestinal microbial overgrowth: PMID 32467262

1. **Hydrogen-Dominant SIBO**: Caused by fermentative bacteria (e.g., E. coli, Klebsiella), presenting primarily with watery diarrhea and hypermotility. PMID 32467262

2. **Intestinal Methanogen Overgrowth (IMO)**: Caused by Methanobrevibacter smithii archaea converting hydrogen into methane gas, associated with severe constipation and slowed transit time. PMID 32467262

3. **Hydrogen Sulfide (H2S) SIBO**: Characterized by sulfate-reducing bacteria (e.g., Desulfovibrio), presenting with rotten-egg odor gas, visceral hypersensitivity, and persistent fatigue. PMID 32467262

The Migrating Motor Complex (MMC) — The Gut's Automatic Sweeper

The Migrating Motor Complex (MMC) is an electro-mechanical wave of electrical activity sweeping through the stomach and small intestine during interdigestive fasting periods (every 90–120 minutes). PMID 32467262

Acting as an automatic sweeper, the MMC clears undigested food debris and bacteria downstream into the colon. PMID 32467262

Disruption of the MMC—often caused by post-infectious gastroenteritis (anti-CdtB / anti-vinculin antibodies), chronic stress, diabetes, or frequent snacking—is the primary root cause of recurrent SIBO. PMID 32467262

Diagnosis via Breath Testing and the 3-Step Treatment Protocol

Comprehensive management of SIBO involves a structured clinical framework: PMID 32467262

1. **Non-Invasive Breath Test**: Lactulose or glucose 3-hour breath test measuring H2, CH4, and H2S concentrations. PMID 32467262

2. **Targeted Antimicrobial Therapy**: Non-absorbable targeted antibiotics (Rifaximin for Hydrogen; Rifaximin + Neomycin/Metronidazole for Methane) or botanical antimicrobials (oregano oil, berberine, neem). PMID 32467262

3. **Motility Support & Root Cause Resolution**: Administering prokinetic agents (e.g., low-dose naltrexone, ginger extract) to restore MMC function and prevent relapse. PMID 32467262

Internal Further Reading

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FAQ

Where can one obtain a SIBO breath test?

SIBO breath testing kits are available through gastroenterology departments and private functional medicine practitioners internationally.

Can SIBO be treated without prescription antibiotics?

Yes, herbal antimicrobial protocols (utilizing berberine, oregano oil, and garlic-derived allicin) have demonstrated equivalent efficacy to Rifaximin in clinical trials for bacterial reduction.

What is a prokinetic agent?

A prokinetic is an agent (botanical or pharmaceutical) that stimulates the Migrating Motor Complex (MMC) between meals to sweep the small intestine and prevent bacterial recurrence.

Sources and References

  1. [1]
    Small Intestinal Bacterial Overgrowth in Irritable Bowel Syndrome
    Chen et al., J Gastroenterol Hepatol 2020SIBO meta-analysis

Editorial History

19. juli 2026

Første publicering

Første version blev publiceret som del af metabolic health med intro, takeaways, FAQ og referenceblok.

19. juli 2026

Faglig gennemgang

Formuleringer, forbehold og interne links blev gennemgået for klarhed, konsistens og YMYL-tydelighed.

19. juli 2026

Seneste opdatering

SIBO (Small Intestinal Bacterial Overgrowth) fik opdaterede metadata, referenceoutput og forbedret beslutningsnær struktur.

Vadim Doroshenko, medical reviewer

Medical Review

Medical Review and Update Process

This article has been medically reviewed by Vadim Doroshenko with a focus on clinical accuracy, sources, disclaimers, and whether the conclusions still align with current scientific evidence.

Medical background from Dnipro State Medical University. Reviews articles for medical precision, strength of evidence, and clinical relevance.

Published

19. juli 2026

Medically Reviewed

19. juli 2026

Last Updated

19. juli 2026

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