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The Three Subtypes of SIBO
Dec 12, 2023
✦ Digestive Health · SIBO ✦
The Three Subtypes of SIBO
A single bout of food poisoning can be the tipping point. Each subtype of SIBO needs a tailored approach — here's how to tell them apart, and how to restore the terrain underneath.
By Brehan Crawford, MAcOM, LAc
Watch the Clinical Summary
Start Here
Why the subtype changes everything
In a healthy gut, the small intestine stays relatively free of bacteria — stomach acid and steady motility keep it that way. SIBO happens when those defenses falter and microbes overgrow where they shouldn't. As they ferment undigested carbohydrates, they produce gas — and the type of gas largely determines your symptoms.
That's why naming the subtype matters so much. Hydrogen, methane, and hydrogen sulfide each behave differently, cause different symptoms, and respond to different strategies. Treat the wrong one and you spin your wheels. Below, I'll walk through all three — and the three-stage approach I use to address not just the overgrowth, but the terrain that allowed it.
"SIBO isn't one condition. It's three different gases, three different symptom pictures, and three different terrains — which is exactly why a one-size protocol so often fails."
— Brehan Crawford, MAcOM, LAc
The Three Subtypes at a Glance
Which gas is driving your symptoms?
Hydrogen
Speeds transit through the colon. Typically linked to diarrhea-predominant IBS.
Methane (IMO)
Slows motility. Associated with constipation-predominant IBS and bloating.
Hydrogen Sulfide
Mixed diarrhea and constipation, with telltale sulfur-smelling gas and breath.
Subtype 01
Hydrogen-dominant SIBO
Marked by excess hydrogen production, this subtype tends to speed up gut motility. Hydrogen shortens transit time through the colon — especially the proximal section — which drives diarrhea and abdominal discomfort. It also tends to respond better to the antibiotic rifaximin than the methane-dominant type does.
Subtype 02
Methane-dominant SIBO (IMO)
The American College of Gastroenterology now calls this intestinal methanogen overgrowth (IMO), because the culprits — archaea such as Methanobrevibacter smithii — aren't strictly bacteria and can extend beyond the small intestine. Methane is produced by anaerobic fermentation of carbohydrates, and the body doesn't use it.
Crucially, methane slows gastrointestinal motility — likely by acting on the cholinergic pathway of the enteric nervous system. That sluggishness leads to constipation, bloating, belching, and flatulence, and has even been linked to weight regulation and reduced weight loss after bariatric surgery.
Subtype 03
Hydrogen sulfide-dominant SIBO
The newest and least common variant involves overgrowth of H2S-producing microbes like Desulfovibrio, Citrobacter, and Clostridium. Hydrogen sulfide is a gasotransmitter with real roles in the body — inflammation control, mucosal repair — but in excess it's been associated with serious conditions, and it's notoriously hard to diagnose since there's no accurate breath test yet.
Tell-tale signs: very pungent, sulfur-smelling gas and unexplained bad breath, alongside abdominal pain, bloating, and fatigue. People with autoimmune conditions like rheumatoid arthritis, ankylosing spondylitis, or Sjögren's may be more susceptible.
🔬 Clinical Context
Subtyping is now standard of care
The American College of Gastroenterology's clinical guideline formalized breath-test-based diagnosis and introduced the term IMO for methane overgrowth — recognizing that the gas profile should shape the treatment plan. It's the conventional-medicine version of a principle TCM has held for centuries: identify the pattern before you treat it.
Ref: Pimentel et al., ACG Clinical Guideline: SIBO, Am J Gastroenterol, 2020 — DOI: 10.14309/ajg.0000000000000501
Preventing & Treating SIBO
A three-stage approach
Healthy guts keep the small intestine clear through stomach acidity and steady motility. SIBO sets in when those break down — so durable treatment has to do more than kill bacteria. It has to rebuild the defenses. Here's the staged approach, and where Chorus fits in alongside conventional care.
Stage 01
Clear the overgrowth
The conventional first step is reducing the bacterial overgrowth — often with rifaximin, a non-absorbed antibiotic that acts locally in the small intestine. Rifaximin is less reliable against methanogens, so clinicians frequently pair it with antimicrobial herbs for fuller coverage. The goal isn't just to kill the bad actors — it's to clear the way for rebalancing and to start addressing what caused the overgrowth.
How the herbs in Chorus complement this stage:
- Bai Zhi — documented antibacterial activity (including against Staphylococcus aureus), working through different mechanisms than antibiotics.
- Peppermint — essential oils rich in menthol show broad antibacterial activity, helping create an environment less friendly to overgrowth.
Diet's supporting role (short-term):
- Low-FODMAP starves bacteria of preferred fuels — effective for symptoms, but best kept short, since long-term it can reduce microbial diversity.
- Low-sulfur (easing back on cruciferous veg, red meat, eggs, dried fruit, beer, wine) helps specifically with H2S-dominant SIBO.
- Low-fat moderates bile release, easing digestive strain during healing.
- The contrarian tip: whatever you've been eating most may be feeding the overgrowth — so try the opposite for a short stretch.
One Formula, All Three Drivers
The herbal formula designed to support all three causes of SIBO
Chorus brings together antimicrobial, prokinetic, and bile-supporting herbs in one formula — built to work alongside your treatment plan, not against it.
Subscribe or order a single bottle.
Stage 02
Reintroduce balance — carefully
Adding beneficial bacteria seems like the logical next move, and certain probiotics — like Lactobacillus acidophilus and Bifidobacterium lactis — have shown promise, particularly for reducing methane. But the research is genuinely mixed. Probiotics often help short-term without solving the root issue, and certain Lactobacillus strains accumulating in the small intestine can actually make SIBO worse. This is a stage to approach with a clinician, not guesswork.
Stage 03
Fix the underlying cause
This is the stage that prevents recurrence — and the one most often skipped. It comes down to two things: restoring gut motility and regulating acid and bile production.
Restoring motility:
- Movement — regular activity helps move gas through and reduces bloating.
- Heat — a warm pad on the abdomen relaxes gut muscles and eases passage.
- Abdominal massage — gentle, directed massage helps relax the belly and move contents along.
- Warm water & ginger — soothing, and ginger is a well-known prokinetic. (Why warm water matters.)
Regulating bile & the gut-liver axis:
- Citrus peel — a traditional prokinetic; research shows dried citrus peel extract increased GI transit and fecal output in animal models.
- Hawthorn fruit (Fructus Crataegi) — promotes healthy bile secretion, supporting the gut-liver axis.
- Bismuth (e.g., Pepto-Bismol) — binds H2S into insoluble bismuth sulfide and can curb sulfate-reducing bacteria; useful short-term for H2S SIBO, but limit duration due to neurotoxicity risk, and only under professional guidance. Zinc and certain B12 analogs are gentler long-term options worth discussing with your provider.
🔬 Research Spotlight
Citrus peel as a natural prokinetic
In a study of dried citrus peel (the TCM herb chen pi), an ethanolic extract given orally to mice increased intestinal transit rate and fecal output without significant toxicity — supporting its traditional use for sluggish digestion, the exact motility problem at the root of so many SIBO cases.
Ref: Lee, H.-T., Journal of Life Science, 2014 — DOI: 10.5352/JLS.2014.24.3.260
Why Choose Chorus
Built for all three stages
Most SIBO tools do one job. Chorus was formulated to support the whole arc — antimicrobial herbs like Bai Zhi and Peppermint for the clearing stage, prokinetics like citrus peel and ginger for motility, and bile-supporting herbs like hawthorn for the gut-liver axis. It supports your gut's natural environment so beneficial bacteria can recover while keeping the harmful ones in check.
"Killing the overgrowth is the easy part. Keeping it from coming back means restoring motility and the terrain — and that's where most SIBO treatment quietly falls apart."
— Brehan Crawford, MAcOM, LAc
Keep Reading
More on Chorus & gut health
Start Here
What Is Chorus?
The formula bridging the gap between antibiotics and probiotics.
The Mechanisms
What Does Chorus Actually Do?
How it supports secretion, motility, and a healthier microbiome.
Self-Assessment
Is Chorus Right for You?
A few questions to tell whether Chorus fits your pattern.
Gut Brain Synchrony — Skool Community
SIBO rarely travels alone.
Bloating, irregularity, fatigue, and brain fog live in a nervous system shaped by your gut. The Gut Brain Synchrony community is where I teach the terrain-first approach behind beating recurrence — free.
Free Gut Brain Classes
Structured modules mapping the path from gut to brain.
EEG & HRV Training
Live sessions working both gut-to-brain and brain-to-gut.
A Community That Gets It
MCAS, POTS, fibromyalgia, long COVID, Lyme — people who understand.
Join Gut Brain Synchrony — Free
Gut to brain, brain to gut — your reset begins here.
Your Next Step
Treat the subtype. Restore the terrain.
Work with your provider on the right plan for your subtype — and give your gut the herbal support to clear, rebalance, and keep moving.
References
- Pimentel, M., et al. (2020). ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. American Journal of Gastroenterology, 115(2), 165–178. doi:10.14309/ajg.0000000000000501
- Lee, H.-T. (2014). Prokinetic Activity of Ethanolic Extracts from Dried Citrus unshiu Peels in Mice. Journal of Life Science, 24(3), 260–266. doi:10.5352/JLS.2014.24.3.260
This content is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. SIBO and its treatment — including antibiotics, probiotics, and bismuth — should be managed with a qualified healthcare provider. This post contains affiliate links — if you purchase or join through our link, we may receive a commission at no additional cost to you. Individual results vary and are not guaranteed. · Join the Community · © Crawford Wellness
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