Small Intestinal Bacterial Overgrowth (SIBO) is a very common condition that causes chronic abdominal pain, gas/bloating, diarrhea, or constipation. Here’s a visual that can help you understand what causes SIBO: picture the small intestine as a creek. In a clean creek, the water flows smoothly down the stream. When the water is stagnated, it breeds bacteria, like the many things that grow up from stilled pond.
The cause of SIBO can be grouped into the following three categories:
Slowed Motility in the Small Intestine
This is the most common cause of SIBO. In the small intestine, there is a periodic cleansing wave operated by the migrating motor complex (MMC). This cleansing wave helps move foods, water, digestive juices, bacteria, and cell debris down into the colon. Many factors can affect this cleansing wave:
- Connective Tissue Defect: Ehlers-Danlos Syndrome, Scleroderma
- A Damaged Nerve That Leads Deficient MMC: Post-infectious, Parkinson’s, Diabetes
- Infection: Parasite, Lyme or other Co-Infections
- Lifestyle: Stress, Small Frequency Meals Through the Day
- Medication: Opiates and Antibiotics
- Injury: Traumatic Brain or Spine Injury, Whiplash
Structural Defect in the Small Intestine
The stagnation can also be caused by a blockage in the small intestine.
- Obstruction: inflammation (appendicitis or endometriosis), adhesion from past surgeries, tumors, twisted small intestine, and structure seen in Crohn’s disease.
- Back Migration:
- A fistula from the colon to the small intestine seen in Crohn’s disease
- Ileocecal valve absence/dysfunction. Ileocecal valve is a muscular gate between the small intestine and the colon. When the gate is not closed properly, bacteria in the colon can easily migrate into the small intestine.
Weakened Defense in the Upper Gastrointestinal (GI) Tract
Our stomach acid, bile, and digestive enzymes not only help digest foods but also kill bacteria and fungus. When the body lacks this digestive juice, more bacteria can survive and reach the end of the small intestine. If you have a healthy MMC, this weakened defense can be compensated, but if you don’t, the combination of deficient MMC and digestion leads to more severe SIBO.