SIBO: When Bacteria Grow in the Wrong Place 🦠
- Feb 19
- 3 min read
But when growth expands into the wrong territory, harmony turns into dysfunction.
If you feel bloated after nearly every meal…If your abdomen becomes visibly distended as the day goes on…If you’ve been told it’s “just IBS”…
You might be dealing with SIBO — Small Intestinal Bacterial Overgrowth.
And it’s more common than most people realize.
🦠 What Is SIBO?
SIBO (Small Intestinal Bacterial Overgrowth) happens when bacteria that belong primarily in the colon migrate upward and overgrow in the small intestine.
The small intestine is designed for:
Enzyme activity
Nutrient absorption
Relatively low bacterial counts
When bacteria overgrow there, they ferment carbohydrates too early, producing hydrogen, methane, or hydrogen sulfide gas.
That gas = your symptoms.
🚩 Common SIBO Symptoms
Bloating
Excess gas or burping
Constipation (especially methane-type)
Diarrhea (more common in hydrogen-type)
Brain fog
Fatigue after meals
Food sensitivities that seem to multiply
Iron or B12 deficiency
Reflux that doesn’t fully respond to acid reducers
If you’ve tried probiotics, elimination diets, or random supplements without lasting improvement, SIBO may be the missing layer.
🔬 Why Does SIBO Happen?
SIBO is rarely “just bad luck.” It’s usually a motility problem.
The small intestine has a built-in cleaning wave called the Migrating Motor Complex (MMC). It activates between meals and sweeps bacteria downward.
If that system slows, bacteria accumulate.
Common root contributors:
Post-food poisoning (anti-vinculin antibodies)
Chronic stress (sympathetic dominance)
Hypothyroidism
Low stomach acid
Adhesions or prior abdominal surgery
Chronic constipation
Long-term PPI use
🧪 How Is SIBO Diagnosed?
The most common test is a breath test measuring hydrogen and methane gas after ingesting lactulose or glucose.
Important nuance:
Hydrogen-dominant → often diarrhea
Methane-dominant (technically IMO) → constipation
Mixed patterns exist
Interpretation matters. Over-diagnosis and under-diagnosis both happen.
💊 Why Quick Fixes Often Fail
Many patients are prescribed:
Rifaximin
Herbal antimicrobials
Low-FODMAP diet
These can help.
But if motility isn’t addressed, relapse rates are high.
SIBO is not just an infection. It’s a functional imbalance.
Long-term resolution often requires:
Motility support
Nervous system regulation
Strategic antimicrobial rotation (if needed)
Digestive optimization
Addressing underlying drivers (thyroid, stress physiology, post-infectious autoimmunity)
🧠 SIBO and the Nervous System
The gut is heavily innervated by the vagus nerve.
Chronic stress shifts you into sympathetic dominance. Sympathetic dominance slows digestion.
Slower digestion = higher risk of overgrowth.
If your symptoms keep cycling — bloating, food reactions, fatigue — it’s usually because the underlying drivers haven’t been addressed.
SIBO is rarely random.It reflects altered motility, stress signaling, or structural factors.
When we correct those upstream patterns, the gut becomes more resilient — and relapse becomes less likely. Understanding that framework changes everything.
❓FAQ: SIBO
Is SIBO the same as IBS?
Not exactly. Many IBS cases have underlying SIBO, but not all IBS is SIBO.
Can probiotics make SIBO worse?
Sometimes. In certain patients, adding bacteria before correcting motility and microbiome increases bloating.
Do I need to stay on Low-FODMAP forever?
No. It’s a short-term symptom management tool, not a lifelong diet.
Is SIBO permanent?
No — but recurrence is common if root causes aren’t addressed.
Can SIBO cause anxiety or brain fog?
Yes. Bacterial metabolites and nutrient malabsorption can affect cognition and mood.
Dr. Kseniya Zvereva (ND) is a licensed naturopathic doctor in Washington, California, and Minnesota and founder of Xenia Integrative. She specializes in hormone imbalance, fatigue, gut dysfunction, pain, and stress-related conditions using personalized, evidence-informed naturopathic medicine.
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