Small Intestinal Bacterial Overgrowth (SIBO): Symptoms, Causes, and Treatment

Written By Samar Shadly

Small Intestinal Bacterial Overgrowth (SIBO) is one of the most common yet overlooked causes of chronic digestive symptoms such as bloating, gas, abdominal pain, diarrhea, or constipation.

Many patients diagnosed with Irritable Bowel Syndrome (IBS) may actually be suffering from SIBO.

In functional medicine, SIBO is not just viewed as a bacterial imbalance but as a sign of deeper dysfunction in gut motility, immunity, or microbiome balance.

What is SIBO?

Normally, the small intestine contains relatively few bacteria compared with the colon.

In SIBO, excessive bacteria colonize the small intestine.

These bacteria ferment carbohydrates before absorption, producing gases such as:

  • Hydrogen

  • Methane

  • Hydrogen sulfide

These gases are responsible for many symptoms.

Symptoms of SIBO

Common symptoms include:

Digestive symptoms:

  • Severe bloating after meals

  • Excess gas

  • Abdominal pain

  • Diarrhea

  • Constipation (common in methane SIBO)

  • Frequent belching

  • Early satiety

Systemic symptoms:

  • Brain fog

  • Chronic fatigue

  • Vitamin deficiencies

  • Iron deficiency anemia

  • Vitamin B12 deficiency

  • Skin issues

  • Headaches

  • Anxiety or depression

Types of SIBO

Hydrogen SIBO
Often associated with diarrhea.

Methane SIBO (Intestinal Methanogen Overgrowth – IMO)
Often associated with constipation.

Hydrogen sulfide SIBO
Less common but associated with diarrhea and food sensitivities.

Causes of SIBO

SIBO usually develops due to an underlying dysfunction.

Common causes include:

  • Impaired gut motility

  • Low stomach acid

  • Chronic stress

  • Autoimmune diseases

  • Prior food poisoning

  • Abdominal surgeries

  • Structural intestinal abnormalities

Diagnosis

The most common diagnostic tool is:

Breath testing

Patients ingest lactulose or glucose, and breath samples are collected over 2–3 hours to measure hydrogen and methane gases.

Functional Medicine Approach to Treatment

Treatment usually includes four steps:

  1. Reduce bacterial overgrowth

  2. Modify diet

  3. Restore gut motility

  4. Repair intestinal lining

Phase 1: Reduce Bacterial Overgrowth

Options include:

Antibiotics such as Rifaximin

Herbal antimicrobials including:

  • Berberine

  • Oregano oil

  • Allicin

  • Neem

Some studies show herbal therapies may be as effective as antibiotics in certain cases.

Phase 2: Dietary Strategy

Low FODMAP diet is commonly used to reduce fermentable carbohydrates.

However, long-term restriction is not recommended.

Phase 3: Improve Gut Motility

Key strategies include:

  • Prokinetic agents

  • Spacing meals 4–5 hours apart

  • Stress reduction

  • Adequate sleep

Phase 4: Gut Healing

Nutrients that may support gut repair include:

  • L-glutamine

  • Zinc carnosine

  • Collagen

  • Omega-3 fatty acids

Final Thoughts

SIBO is a common but underdiagnosed condition that can significantly affect digestive and overall health.

A comprehensive functional medicine approach focusing on root causes often leads to better long-term outcomes.

If you suffer from persistent bloating, digestive symptoms, or unexplained fatigue, SIBO may be an underlying cause.

You can book a consultation to evaluate your case and develop a personalized treatment plan.

Dr. Samar Shadly
Functional & Integrative Medicine

🌐 Website
https://www.drsamarshadly.com

📱 WhatsApp
https://wa.me/966558837786

Samar Shadly
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