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Decoding SIBO: Causes and Symptoms Explained

Small Intestinal Bacterial Overgrowth (SIBO) is a condition characterized by an excessive number of bacteria in the small intestine.

This can lead to various digestive issues such as stomach pain, bloating, and altered bowel habits. Since the symptoms of SIBO, like stomach pain, bloating, and diarrhea, can be vague, it's often not diagnosed properly. This makes it hard to figure out how common it is.

Understanding the Causes of SIBO

Dislocation of Bacteria

A key factor in the development of SIBO is the dislocation of bacteria that are normally confined to the colon. When these bacteria move up into the small intestine, they can cause significant problems because the small intestine is primarily responsible for nutrient absorption.

The presence of excess bacteria here can lead to:

  • Nutrient Competition: Bacteria consume nutrients meant for our body, leading to deficiencies.

  • Fermentation of Food: Bacteria ferment undigested food, producing gas and causing bloating and discomfort.

  • Impaired Digestion: Overgrowth can interfere with the absorption of essential vitamins and minerals, leading to malnutrition.

Gut Motility

The migrating motor complex (MMC) is a series of muscle contractions that help move food and bacteria through the digestive tract when we are not eating. If the MMC is impaired, bacteria can accumulate in the small intestine, leading to SIBO.

Factors affecting gut motility include:

  • Nerve or Muscle Damage: Conditions such as diabetes or Parkinson’s disease can slow gut motility, increasing the risk of SIBO.

  • Medications: Opioids and anticholinergics can impair gut movement, contributing to bacterial overgrowth.

Changes in Digestive Fluids

The acidic environment of the stomach helps kill bacteria, but reduced acid production can lead to bacterial growth.

Factors influencing this include:

  • Proton Pump Inhibitors (PPIs): These medications reduce stomach acid and are often prescribed for temporary relief of acid-related conditions. However, long-term use without addressing the underlying cause can increase the risk of SIBO. It’s important to discuss with a primary care provider about gradually weaning off PPIs. Some common PPIs that are prescribed include medications like Pantoprazole, tecta or Nexium 

  • Pancreatic Insufficiency: The pancreas releases enzymes essential for digestion. Conditions like chronic pancreatitis reduce enzyme production, increasing the risk of SIBO.

Structural Changes in the Intestines

Structural abnormalities in the intestines can provide an environment conducive to bacterial overgrowth:

  • Diverticulitis: Small pouches in the intestine can trap bacteria.

  • Surgical Interventions: Surgeries such as gastric bypass or bowel resection create areas where bacteria can accumulate.

  • Inflammatory Bowel Diseases (IBD): Conditions like Crohn’s disease can cause blockages or damage intestinal valves, increasing SIBO risk.

Weakened Immune System

The immune system in the gut helps regulate bacterial populations. Conditions that weaken the immune system, such as common variable immunodeficiency or IgA deficiency, can make SIBO more likely.

Symptoms and Complications of SIBO

The symptoms of SIBO are often nonspecific and include:

  • Stomach pain

  • Bloating

  • Diarrhea

  • Feeling full quickly

  • Excessive gas

  • Indigestion

These symptoms can vary in frequency and severity. Chronic SIBO can lead to serious complications such as:

  • Unintentional Weight Loss: Due to poor nutrient absorption.

  • Nutrient Deficiencies: Malabsorption can lead to deficiencies in essential vitamins and minerals, affecting overall health and quality of life.

Recognizing and treating SIBO early is crucial to prevent long-term health issues and ensure proper digestion and nutrient absorption.

If you experience persistent digestive symptoms, it's important to consult a healthcare provider to explore the possibility of SIBO and discuss appropriate diagnostic and treatment options.

If you suspect you might have SIBO or are struggling with persistent digestive issues, book a FREE discovery call HERE

With virtual consultations available throughout BC, Canada, take the step today to address digestive concerns and establish a harmonious relationship with food. 

Schedule an appointment for lasting relief and improved well-being.

Written by: Matthew Riccardi, 4th Year UBC Dietetic Student 


Ahmed, J. F., Padam, P., & Ruban, A. (2023). Aetiology, diagnosis and management of small intestinal bacterial overgrowth. Frontline Gastroenterology, 14(2), 149-154.

Rao, S. S. C., & Bhagatwala, J. (2019). Small intestinal bacterial overgrowth: Clinical features and therapeutic management. Clinical and Translational Gastroenterology, 10(10), e00078-e00078.

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