Small Intestinal Bacterial Overgrowth (SIBO): What You Should Know

Posted on September 10, 2019 by M. Elizabeth Swenor, D.O.

Suffering from bellyaches? Gas? Bloating? You may have an overgrowth of bacteria in your small intestine. Called small intestinal bacterial overgrowth, or SIBO, this condition may affect up to 80% of people with irritable bowel syndrome (IBS). Yet many don’t realize bacteria is to blame for their bothersome symptoms.

Bacteria in the bowel makes sense. After all, that’s where our bodies process and eliminate toxins. The trouble starts when bacteria that normally grow in other parts of the gut become trapped in the small bowel, ferment and produce gas. That gas leads to bloating, pain, belching, nausea, diarrhea and constipation.

FAQ: Small Intestinal Bacterial Overgrowth

Beyond the bloat, gas and cramping, SIBO may interfere with your body’s ability to absorb food, leading to nutrient deficiencies or imbalances, weight loss and other troubling symptoms. The questions people ask me regularly:

Q: What is SIBO?

A: SIBO reflects a change in the bacteria in the small intestine. The condition results when there’s an increase in the number of bacteria that end up trapped in the small bowel or an alteration in the type of bacteria that reside there.

Q: What causes it?

A: There are plenty of potential culprits. Factors that increase your risk of developing SIBO include:

  • Lack of barriers: Natural antimicrobial barriers like stomach acid and pancreatic enzymes prevent bacteria from hanging out in the small bowel. When these barriers are weakened because of inflammatory bowel disease (IBD), pancreatic insufficiency or other issues, bacteria can seep into the small intestine. Medications that change the pH level of stomach acid (like proton pump inhibitors used to treat acid reflux) can also weaken your body’s natural barriers.
  • Immune deficiencies: Part of your immune system’s job is to crowd out unhealthy bacteria. So if you have a health condition that compromises your immune system, you’re at greater risk of developing SIBO. People who have weakened immune systems, including the elderly and people who have HIV, cancer and celiac disease, have a greater risk of developing SIBO.
  • Anatomical abnormalities: Ever had bariatric surgery or a procedure to resect part of your intestine? These procedures could result in anatomical changes to the intestines that create an ideal environment for bacteria to grow. Bowel adhesions and scar tissue can also cause obstructions that lead to SIBO. Women are more likely to suffer from SIBO in part because they are more likely to have IBS, which increases the risk.
  • Constipating conditions: Health conditions, such as hypothyroidism, scleroderma and nervous system disorders that interfere with your body’s ability to move waste through the digestive tract increase the risk of SIBO. Medications such as narcotics can also slow down the gut and increase your risk.

Q: How do you know if you have SIBO?

A: The most definitive way to determine whether someone has SIBO is to examine microbes from the small intestine. Since that requires an invasive procedure, most doctors diagnose SIBO with a lactulose or glucose breath test. This simple, noninvasive test involves drinking a solution of either glucose or lactulose (both types of sugar). Bacteria in the small bowel ferment the sugars, producing hydrogen and/or methane gas. When levels of those gases are above normal, chances are good you have SIBO.

Q: What can you do about the condition?

A: Treatment for SIBO is highly individualized and complex. Doctors strive to address every identifiable cause of the bacterial overgrowth, including diet, lifestyle habits and underlying conditions such as Parkinson’s disease. Often patients follow a diet that is lower in fermentable carbohydrates to control symptoms. Called a low FODMAP diet (FODMAP is an acronym for molecules in food that are difficult for some people’s bodies to absorb: fermentable oligosaccharides, disaccharides, monosaccharides, and polyols), the plan isn’t proven to control bacterial growth. Elemental diets, which are processed liquid formulas that replace food and drink for a set time period, have a higher cure rate than a low-FODMAP diet. Other treatment approaches include antimicrobial herbs (like oregano and berberine), antibiotics such as ciprofloxacin (Cipro), metronidazole (Flagyl) or rifaximin (Xifaxan), and restoring balance in the gut with probiotics (good bacteria).

Related video: What Is Gut Health?

Taking Care of SIBO

SIBO often occurs due to some underlying condition, particularly bowel-compromising conditions such as Crohn’s disease, celiac disease and inflammatory bowel disease (IBD). For example, research suggests that more than one-third of people with IBD also have SIBO.

Many people who have SIBO don’t realize their symptoms are caused by bacterial overgrowth. Left untreated, SIBO can lead to serious complications including nutrient deficiencies, dehydration and malnutrition.

The condition is treatable, but it can also recur. If you suspect you have SIBO, it’s important to work with an experienced physician. Once treatment begins, any underlying illness also needs to be addressed. Some people will feel better within a few weeks. Others require several months of treatment. It all depends on the amount of bacterial overgrowth in the small bowel.

To find a doctor at Henry Ford, visit or call 1-800-HENRYFORD (436-7936).

Dr. M. Elizabeth Swenor is a family medicine physician seeing patients at Henry Ford Medical Center - Bloomfield Township. She has been practicing functional medicine for more than 15 years and leads the Functional Medicine program at the Henry Ford Center for Integrative Medicine. Read more LiveWell articles by Dr. Swenor.

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