SIBO and IBS: Symptoms, Causes, and the 3 Types You Need to Know

• Hydrogen SIBO
  Causes diarrhea, urgency, bloating, and cramps. Strongly linked to IBS-D in clinical studies.

• Methane SIBO (IMO)
  Caused by methane-producing archaea. Leads to constipation, hard stools, and slower gut transit - confirmed by Neurogastroenterology & Motility research.

• Hydrogen Sulfide SIBO
  Produces rotten egg-smelling gas, diarrhea, abdominal pain, and sometimes brain fog or anxiety. Harder to test — only a few labs, such as the Trio-Smart breath test, measure hydrogen sulfide directly.

Some people have mixed SIBO, with more than one gas type.

That’s why symptoms sometimes swing between constipation and diarrhea.

Both IBS and SIBO often develop from overlapping root causes:

• Slowed motility: Research in the World Journal of Gastroenterology shows that when gut movement slows due to stress, age, or medication, bacteria have more time to accumulate and overgrow.

• Stress: The American Journal of Gastroenterology highlights how stress hormones like cortisol alter gut contractions and sensitivity, making flare-ups worse.

• Low stomach acid: Acid-blocking medications reduce stomach acid, which normally helps prevent bacteria from colonizing the small intestine.

• Microbiome imbalance: A study in Nature Microbiology found that transferring microbiota from IBS patients into mice caused IBS-like symptoms, showing just how much microbial balance drives gut health.

Here are signs that suggest SIBO instead of IBS:

• Bloating after most meals → fermentation in the small intestine

• Chronic constipation and distension → methane SIBO

• Frequent diarrhea or foul-smelling gas → hydrogen or hydrogen sulfide SIBO

The most reliable test is a lactulose or glucose breath test. The North American Consensus sets positive cutoffs at ≥20 ppm hydrogen or ≥10 ppm methane.

For background on gut healing, revisit IBS in Women: What Really Causes It and How to Finally Heal Your Gut Naturally.

Fiber or probiotic supplements, stress management, or standard medications may ease symptoms, but they don’t address bacterial imbalance.

That’s why so many people with “IBS” continue to struggle — the true culprit may be SIBO.

Diet plays an important role in managing symptoms and preventing flare-ups, but it won’t clear SIBO by itself.

To heal fully, the bacterial overgrowth needs to be removed — otherwise the symptoms keep coming back or will persist, no matter how carefully you eat.

Telling people to “eat more fiber” or “reduce stress” rarely fixes root causes.

IBS and SIBO require a sequence:

• Calm inflammation

• Heal the gut barrier

• Eradicate overgrowth

• Prevent further fermentation/growth

• Rebuild microbial diversity

That’s why I developed the 28 Day Gut Reset — a complete program designed to restore balance step by step.

And with new updates, it now includes options to naturally target and support the eradication of different types of SIBO, making it more effective than ever.

Even after treatment, daily habits are key:

• Stress management — cortisol spikes can worsen gut issues.

• Sleep — restores the gut microbiome.

• Exercise — movement improves motility and supports microbial balance.

• Diet variety — diversity of plants feeds beneficial bacteria once symptoms calm.