• Most people naturally have between 300 - 500 different bacterial species in their gastrointestinal tracts. These are primarily in the middle and the last parts of the small intestine and colon because fewer bacteria can survive the muscular contractions and acidic environment of the stomach and the first part of the small intestine of a healthy person. 1
  • Small intestinal bacterial overgrowth 
  • In some people, SIBO appears to be caused by abnormal intestinal motion and lowered immune defenses which allow large numbers of bacteria to grow in the FIRST part of the small intestine. 1
  • SIBO is a common complication of celiac disease that produces persistent symptoms of gas, bloating, and diarrhea, and damages the intestinal lining. 1 A combination of these symptoms, an elevated celiac antibody level (specifically, the IgA-tTG level) and abnormal biopsy results (WITHOUT apparent gluten exposure), should lead to further testing for SIBO.
  • "SIBO is a clinical diagnosis usually based on breath testing for excess hydrogen and/or methane using lactulose or glucose. The traditional "gold standard" test was culturing (growing) the bacteria from a sample of fluid from the small intestine. However, this test is rarely performed because it is invasive and time-consuming.
  • Bacteria and other organisms cause symptoms by digesting nutrients before the body can. If left untreated, SIBO can lead to persistent damage to villi, elevated celiac blood tests, 2,3,4 and vitamin deficiencies (especially vitamin B-12).
  • Antibiotics and probiotics can be used alone or in combination to treat SIBO. 5
  • Following a balanced, healthy diet that corrects nutrient deficiencies and limits foods that are commonly poorly digested, such as FODMAPs (fermentable carbohydrates) 6,7 can be particularly useful when you are diagnosed with SIBO. See Level 3 for more information on FODMAPs.
  • Consuming easily digested foods that have modest (not high) amounts of fiber, and adequate fluid is generally recommended for SIBO 3 . Spacing meals several hours apart is also recommended. 6,7
  • Your doctor or dietitian may also recommend certain vitamins and minerals to help you resolve any nutritional deficiencies caused by SIBO.


  • Since the symptoms of SIBO can mimic those of celiac disease, talk to your doctor about getting tested if you are experiencing any of the above symptoms.
  • It is highly recommended that the above dietary changes be made under the supervision of a dietitian to ensure that you receive adequate nutrition.


  1. Leffler D. Small Intestinal Bacterial Overgrowth. In Real Life with Celiac Disease: Troubleshooting and Thriving Gluten-Free. Eds. Dennis M, Leffler D. AGA Press. Bethesda, MD, 2010.
  2. Ghoshal UC, Ghoshal U, Misra A, Choudhuri G. Partially responsive celiac disease resulting from small intestinal bacterial overgrowth and lactose intolerance. BMC Gastroenterol 2004;4:10.
  3. Tursi A, Brandimarte G, Giorgetti G. High prevalence of small intestinal bacterial overgrowth in celiac patients with persistence of gastrointestinal symptoms after gluten withdrawal. Am J Gastroenterol2003;98:839-43.
  4. Leffler DA, Dennis M, Hyett B, Kelly E, Schuppan D, Kelly CP. Etiologies and predicators of diagnosis in nonresponsive celiac disease. Clin Gastroenterol Hepatol 2007;5:445-50.
  5. Small Intestinal Bacterial Overgrowth.
  6. Diet for IBS and SIBO. Specialists in Gastroenterology. . Accessed April 13, 2011.
  7. Scarlata K. Small intestinal bacterial overgrowth- what to do when unwelcome microbes invade. Today's Dietitian, April 2011,13(4):46.

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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