SIBO Symptoms, Causes, and Diagnosis: A Complete Guide

If you've been feeling bloated, dealing with irregular bowel movements, or experiencing unexplained digestive discomfort, you may be suffering from Small Intestinal Bacterial Overgrowth (SIBO). With over 70 million Americans experiencing gut-related issues, SIBO is a leading cause of Irritable Bowel Syndrome (IBS) and other digestive problems.

In this guide, we'll break down the symptoms, causes, and diagnosis of SIBO, along with the steps you can take to reclaim your gut health.

What is SIBO?

Small Intestinal Bacterial Overgrowth (SIBO) happens when bacteria that typically reside in the large intestine migrate to the small intestine, where they don't belong. The small intestine normally has a low concentration of bacteria, but when this balance is disrupted, it can lead to fermentation of food, gas production, and a host of uncomfortable symptoms.

SIBO is also closely linked to Irritable Bowel Syndrome (IBS), with studies showing that up to 60% of IBS cases are caused by SIBO.

Common Symptoms of SIBO

SIBO symptoms can vary depending on the type of gas produced by the bacteria: hydrogen, methane, or hydrogen sulfide. Here's what to watch for:

Digestive Symptoms

• Bloating after meals (the most common symptom)
• Diarrhea (more common in hydrogen-dominant SIBO)
• Constipation (associated with methane-dominant SIBO)
• Flatulence, often malodorous
• Floating stools, a sign of fat malabsorption

Systemic Symptoms

• Brain fog, anxiety, and depression
• Nutrient deficiencies, including Vitamin B12 and fat-soluble vitamins (A, D, E, K)
• Unexplained weight loss or difficulty gaining weight
• Skin conditions like rosacea or eczema

If left untreated, SIBO can lead to more severe complications such as leaky gut, nonalcoholic fatty liver disease, or D-lactic acidosis.

What Causes SIBO?

Several factors can disrupt the balance of bacteria in your small intestine, leading to SIBO:

• Food Poisoning: Toxins from bacteria like Salmonella or E. coli can damage the nerves in your gut, impairing its ability to clear bacteria effectively.
• Autoimmune Reactions: Food poisoning can trigger autoantibodies (e.g., anti-vinculin), leading to slowed gut motility and bacterial overgrowth.
• Gut Motility Issues: Conditions like gastroparesis or nerve damage can cause stagnation in the small intestine, creating a breeding ground for bacteria.
• Low Stomach Acid: Stomach acid kills harmful bacteria; reduced levels can increase your risk of SIBO.
• Diet and Lifestyle: Frequent snacking, stress, and modern diets high in fermentable carbohydrates can contribute to bacterial overgrowth.

Types of SIBO

The type of gas produced by the bacteria determines the symptoms and treatment approach:

Hydrogen-Dominant SIBO:

• Symptoms: Diarrhea, bloating, and abdominal pain.
• Common bacteria: E. coli and Klebsiella pneumoniae.

Methane-Dominant SIBO (Intestinal Methanogen Overgrowth or IMO):

• Symptoms: Constipation, bloating, and gas retention.
• Caused by archaea (not bacteria), which produce methane.

Hydrogen Sulfide SIBO:

• Symptoms: Diarrhea and "rotten egg" smelling gas.
• A newer subtype with promising treatment outcomes.

How is SIBO Diagnosed?

Diagnosing SIBO involves ruling out other conditions and using specific tests to measure bacterial overgrowth.

Step 1: Rule Out Other Conditions

Doctors may first conduct:

• Physical exams.
• Colonoscopy or endoscopy.
• Stool tests to check for parasites or infections.

Step 2: Breath Testing

Breath tests are the most common diagnostic tool for SIBO. Patients drink a sugar solution (glucose or lactulose), and their breath is analyzed for hydrogen, methane, and hydrogen sulfide gases.

Positive Test Results Include:

• Hydrogen increase ≥20ppm above baseline.
• Methane levels ≥10ppm at any point.
• Flat-line hydrogen and methane levels with symptoms suggest hydrogen sulfide SIBO.

Step 3: Blood Tests

Tests for anti-vinculin and anti-CDT antibodies can confirm post-infectious IBS caused by food poisoning.

Treating SIBO

Effective treatment for SIBO depends on the type of gas produced and focuses on reducing bacterial overgrowth, improving gut motility, and preventing recurrence.

1. Antibiotics

• Hydrogen-Dominant SIBO: Rifaximin (550mg, 3x daily for 10-14 days). Combining Rifaximin with Partially Hydrolyzed Guar Gum (PHGG) improves success rates.
• Methane-Dominant SIBO: Rifaximin + Neomycin or Metronidazole.
• Hydrogen Sulfide SIBO: Rifaximin + Bismuth (e.g., Pepto-Bismol).

2. Herbal Therapies

Herbal treatments can be just as effective as antibiotics. Popular options include:

• Dysbiocide and FC-Cidal.
• Candibactin-AR and Candibactin-BR.
• Garlic-derived allicin (for methane-dominant SIBO).

3. Diet and Lifestyle Changes

• Low FODMAP Diet: Reduces fermentable carbohydrates to starve bacteria.
• Low Fermentation Diet: A less restrictive alternative that avoids fiber, dairy, and artificial sweeteners.
• Meal Spacing: Allow at least 5 hours between meals to activate the gut's natural cleaning waves.

4. Prokinetics

Medications or supplements like low-dose naltrexone, erythromycin, or Iberogast can improve gut motility and prevent recurrence.

Preventing SIBO Recurrence

SIBO has a high recurrence rate due to underlying motility issues. Long-term strategies include:

• Prokinetics to support gut motility.
• Periodic breath testing to monitor for relapse.
• Supporting gut health with probiotics (e.g., bifidobacteria) and prebiotics after treatment.

Take Control of Your Gut Health

Don't let SIBO symptoms disrupt your life. Early diagnosis and personalized treatment can help you regain control of your digestive health.