Small Intestinal Bacterial Overgrowth – Symptoms and Causes

ByJanis Updated

Overview

Small intestinal bacterial overgrowth (SIBO) is a condition where bacteria grow excessively in the small intestine. These bacteria are typically not found in this part of the digestive system. Some people call this condition blind loop syndrome.

SIBO often develops when food and waste move too slowly through the digestive tract. This slow movement creates an environment where bacteria can multiply rapidly.

Common causes include:

  • Surgery on the abdomen
  • Structural problems in the digestive tract
  • Certain diseases that affect digestion

The symptoms of SIBO can be uncomfortable and sometimes serious. Most people experience:

  • Diarrhea
  • Weight loss
  • Malnutrition

Doctors typically treat SIBO with antibiotics to reduce the bacterial overgrowth. In some cases, surgery might be needed to fix underlying structural issues that cause the condition. Early treatment helps prevent long-term complications.

What to Look For

People with SIBO may experience:

  • Loss of appetite
  • Stomach pain
  • Feeling sick
  • Bloating
  • Fullness after meals
  • Diarrhea
  • Weight loss without trying
  • Poor nutrition

These signs can range from mild to severe, and may come and go over time.

When to See a Doctor

If you have ongoing digestive issues, it’s important to get medical help. Contact your doctor if you experience:

  • Diarrhea that doesn’t go away
  • Unexplained weight loss
  • Stomach pain lasting several days

Seek emergency care immediately for severe abdominal pain.

These symptoms might indicate a serious condition, especially if you have had stomach surgery before. Early medical attention can prevent complications.

Root Causes

The digestive system runs from your mouth to your anus. It contains all the organs needed to process food, take in nutrients, and remove waste.

Your small intestine is about 20 feet long, making it the longest part of your digestive tract. Food mixes with digestive juices here, and nutrients enter your bloodstream.

Usually, the small intestine has few bacteria because:

  • Food moves through quickly
  • Bile is present, which limits bacterial growth

When these normal processes change, problems can develop.

How Bacterial Imbalance Occurs

Small intestinal bacterial overgrowth happens when too many bacteria grow in your small intestine. This can happen for several reasons:

After Surgery

  • Gastric bypass operations
  • Stomach removal surgery (for ulcers or cancer)

Structural Problems

  • Scar tissue wrapping around the intestine
  • Small pouches forming in the intestinal wall

Medical Conditions

  • Digestive disorders:
    • Crohn’s disease
    • Celiac disease
    • Radiation damage to intestines
  • Other conditions:
    • Scleroderma
    • Diabetes
    • Any disease that slows food movement

When food moves too slowly through your small intestine, it creates an ideal environment for bacteria to multiply. These excess bacteria can:

  1. Produce harmful toxins
  2. Block nutrient absorption
  3. Break down food in ways that cause diarrhea

Risk Factors

Several factors can raise your chances of getting small intestinal bacterial overgrowth (SIBO). These include:

  • Weight loss surgery or operations for stomach ulcers
  • Structural problems in the small intestine
  • Small intestine injuries
  • Abnormal connections between bowel segments (fistulas)
  • Certain diseases affecting the small intestine, like Crohn’s disease, intestinal lymphoma, or scleroderma

Diabetes increases risk, as do small intestine diverticula (pouches). Previous stomach radiation therapy and scar tissue from abdominal surgeries can also lead to SIBO.

Complications

SIBO can lead to several serious health issues if left untreated. These complications often develop gradually as the condition persists.

Nutrient Absorption Problems

When too many bacteria grow in the small intestine, they interfere with normal digestion. The bacteria break down bile salts needed for fat digestion, leading to:

  • Incomplete fat digestion
  • Diarrhea
  • Poor absorption of carbohydrates and proteins
  • Weight loss
  • Malnutrition

Bacteria can also compete with your body for available nutrients in food. The waste products these bacteria create can trigger diarrhea, making the absorption problems worse.

Vitamin Deficiencies

SIBO commonly causes vitamin shortages, particularly:

  • Fat-soluble vitamins (A, D, E, and K): These cannot be properly absorbed when fat digestion is compromised.
  • Vitamin B-12: Excess bacteria both use and produce this vitamin, often leading to a B-12 deficiency. This can cause:
    • Weakness and fatigue
    • Tingling or numbness in hands and feet
    • Mental confusion in severe cases

The nerve damage from B-12 deficiency may become permanent if not treated promptly.

Bone and Kidney Problems

Long-term SIBO can affect your bones and kidneys.

  • Bone weakening: Poor calcium absorption due to intestinal damage can lead to osteoporosis over time.
  • Kidney stones: The same calcium absorption issues may increase the risk of developing painful kidney stones.

These complications highlight why proper diagnosis and treatment of SIBO are important. Many of these health problems can be prevented or improved when bacterial overgrowth is effectively addressed.

Health Writer

Janis's areas of expertise include nutrition, exercise, stress management, and mental health. She is passionate about educating and empowering people to take control of their health and make positive changes that can last a lifetime. Janis believes that small, sustainable changes are the key to long-term success, and she works with her clients to develop personalized plans that fit their individual needs and lifestyles.