It’s near impossible to pinpoint the exact causes of SIBO because everyone’s internal environment is so different. However, studies suggest SIBO is caused by a structural change in the GI tract. It could also be caused by disordered peristalsis of the gastrointestinal tract, or a disruption of the normal mucosal defenses of the small intestine. In other words, anything that causes the regular function of the GI tract to go haywire, especially valve and muscle function, can cause SIBO.

Here are the most common causes of SIBO:

  1. Low Stomach Acid – Stomach acid activates digestive enzymes and kills pathogenic bacteria. Low stomach acid, which can be caused by frequent antibiotic use, a diet of processed foods, or a natural decline with age, can lead to microbial overgrowth and therefore becomes a greater risk for bacteria entering the small intestine.
  2. Pre-existing Medical Conditions – Any medical condition that affects the gut’s muscle function can lead to SIBO. Type 2 diabetes, prior bowel surgeries, leaky gut syndrome, Crohn’s disease, and long-term Celiac disease can all increase your risk of developing SIBO.
  3. Dietary Factors (including Alcohol, Gluten, and Refined Sugar) – Studies show a much higher rate of SIBO with moderate alcohol consumption compared to people who don’t drink at all. Moderate alcohol consumption is considered one alcoholic beverage per day for women, and two per day for men. Alcohol has been shown to damage small bowel mucosal cells, which can decrease the muscular contractions of the ileocecal valve, which keeps the contents of the large and small intestine separated. Damaged bowel mucosal cells can cause impaired muscle function, thereby a greater risk for SIBO. Both alcohol and refined sugar feed certain types of “bad bacteria” in your system such as yeast, which is harmful when it overgrows and outnumbers your healthy gut bacteria. Eating gluten may also increase your risk for SIBO, as it’s one of the main contributors to leaky gut syndrome.
  4. Small Intestine Dysmotility – This occurs when your small intestine is functioning at a slower rate than it should be. It can be caused by genetics, autoimmune conditions, and any illness that causes inflammation in the GI tract.
  5. Slow Bowel Transit Time – A sluggish bowel transit time means it takes longer than 72 hours for food to move through your digestive tract from the time it’s been eaten to the time it’s eliminated. It’s a risk factor for SIBO because it allows more time for harmful bacteria to accumulate.
  6. Prescription Use – Prescription medications such an antibiotics, antidepressants, and birth control can deplete healthy gut flora and damage bowel mucosal cells.


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