• SIBO is a common complication of celiac disease that produces persistent symptoms of gas, bloating and diarrhea, and damages the intestinal lining. 
    If these symptoms persist, the IgA-tTG levels remain elevated, and/or biopsies reveal mildly increased numbers of white blood cells in the lining of the small intestine and patchy damage to the villi in the ABSENCE of gluten exposure, SIBO testing should be considered. 1
  • SIBO is a clinical diagnosis usually based on the standard breath test using lactulose or glucose, or culturing (growing) the bacteria from a sample of fluid from the small intestine, the traditional "gold standard." 
    The hydrogen (lactulose) breath test is considered the most accurate way to diagnose SIBO currently. To do this, you drink a specific sugar solution and then breathe into a bag. Measurements of hydrogen and methane gas production are collected at baseline and then at 15- to 20- minute intervals. As bacteria feed off the lactulose and produce gas, the gas is expelled through the lungs and measured. Since bacteria produce different gases, it is preferred to measure both hydrogen and methane. 

    A lactulose breath test is positive if the patient produces at least 20 ppm (parts per million) of hydrogen and/or methane within the first two hours. However, the breath test with lactulose may be able to diagnose only 60% of patients with SIBO. 

    A lactulose breath test is preferred over glucose since the glucose breath test only measures overgrowth of the proximal (upper part) small intestine, thereby, possibly missing disease in the lower parts of the small intestine. 

    Culturing requires a long flexible tube to be passed through the nose, down the throat and esophagus, and through the stomach under x-ray guidance so that the fluid can be obtained from the small intestine. Since only one, or very few locations, can be sampled, the overgrowth may be overlooked if it is in a part of the small intestines that is not tested. 3 For this reason, culturing for intestinal bacteria is used mainly for research purposes and not in the clinical setting.
  • Bacteria and other organisms cause symptoms by digesting nutrients before your body can. 
    Although the reasons that SIBO occurs in some people are unclear, for some it appears that abnormal intestinal motion and lowered immune defenses allow large numbers of bacteria to grow in the upper small intestine (duodenum and/or jejunum), which normally contain very few bacteria. 1
  • If it goes untreated, SIBO can lead to persistent damage to villi, elevated celiac blood tests, and vitamin deficiencies (especially vitamin B-12). 
    The bacteria that normally live in the small intestines stimulate growth of the intestinal lining and the immune system of the intestine. In this way, they prevent the growth of unhealthy bacteria within the intestine. They produce vitamin K which is absorbed and used by the body for different purposes including blood clotting. In fact, the bacteria that normally live in the small intestines are important even for the muscular activity of the small intestine. 

    In SIBO, this overgrowth of bacteria and other organisms in the small intestine competes with your body for the digestion of nutrients, such as vitamins (especially Vitamin B-12). There is also malabsorption of sugars and carbohydrates, which are then passed to the colon where greater amounts of gas are produced, causing bloating, abdominal discomfort and loose stool.
  • Antibiotics and probiotics can be the used alone or in combination to treat SIBO. 
    Treatment success, based on symptom improvement or by normalization of the hydrogen breath test, ranges from 40-70%.3 When one antibiotic fails, the doctor may add another antibiotic, change to a different antibiotic, or replace and/or add probiotics. Probiotics are different strains of healthy bacteria.
  • Following a balanced, healthy diet that corrects nutrient deficiencies and limits foods that are commonly poorly digested, such as FODMAPS (fermentable carbohydrates) 2,4 can be useful when you are diagnosed with SIBO. 
    FODMAPs stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. FODMAPs are good sources of food for bad bacteria. They include fructose (found in apples, pears, honey and products sweetened with fruit juice which can contain fructose), fructans (wheat, rye, garlic, onions), galactans (cabbage, peaches, plums, apricots, nectarines, cherries), lactose (the natural sugar in dairy products), and sugar alcohols such as xylitol, mannitol (cauliflower, mushrooms), and isomalt, which are also found in many sugar-free products. 4,5,6


  • A dietitian can also recommend foods that are easily digested so that the body can absorb most of the nutrients before they are used as a fuel source by the bad bacteria. 
    A diet that has modest amounts of fiber (rather than high fiber which may make symptoms worse) and adequate fluid is generally recommended. 4,

    Spacing meals several hours apart will allow time for the small intestine to get rid of food by-products, bacteria and waste, which can only happen when a person is not eating. 2,4


  • Similar to celiac disease, SIBO can damage the villi of the small intestine, elevate celiac antibody levels, and lead to vitamin deficiencies.
  • SIBO is treated with antibiotics and certain dietary changes that help "starve" the bad bacteria. Probiotics are often used, as well.
  • To ensure adequate nutrition, please visit a dietitian when making dietary changes to manage SIBO.


Visit these links for more information on FODMAPs:


  1. Dennis M, Leffler D. Small Intestinal Bacterial Overgrowth. In Real Life with Celiac Disease: Troubleshooting and Thriving Gluten-Free . AGA Press. Bethesda, MD, 2010.
  2. Scarlata K. Small intestinal bacterial overgrowth- what to do when unwelcome microbes invade. Today's Dietitian, April 2011,13(4):46.
  3. Small Intestinal Bacterial Overgrowth. Accessed April 13, 2011.
  4. Diet for IBS and SIBO. Specialists in Gastroenterology. . Accessed April 13, 2011.
  5. Dennis M, Barrett J. Malabsorption of Fructose, Lactose, and Related Carbohydrates. In Real Life with Celiac Disease: Troubleshooting and Thriving Gluten-Free . AGA Press. Bethesda, MD, 2010.

Revision Date: 8-28-12 
Author: Melinda Dennis, MS, RD, LDN and Annie Peer 
Editors: Suzanne Simpson, RD and Rupa Mukherjee, MD

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