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A healthy intestinal microbiome is essential for optimal immune function and wellness. Microbial overgrowth in the small intestine has been associated with several health issues and may be caused by many factors. Small intestinal bacterial overgrowth (SIBO), specifically, is a condition that presents with a range of detrimental gastrointestinal (GI) and non-GI-related symptoms and is associated with diverse comorbid conditions.

Studies suggest links between SIBO and diseases such as irritable bowel syndrome (IBS) and other disorders of gut-brain interaction, inflammatory bowel disease (IBD), motility disorders, chronic pancreatitis, cirrhosis, and various immunodeficiency syndromes.^1-4 Specific to IBS, a 2020 systematic review and meta-analysis examined 25 case-controlled studies with a total of 3,192 IBS patients and 3,320 controls and found that SIBO prevalence in patients with IBS was significantly increased compared to controls.⁵

Additional studies have found that SIBO is frequently present in populations with active H. pylori infection,⁶ celiac disease,⁷ and diabetes⁸ and may also be associated with obesity,⁹ rosacea,¹⁰ and nonalcoholic fatty liver disease (NAFLD) at a higher rate than controls. For children, a 2021 meta-analysis (n=205 total patients) reported a significant association between SIBO and NAFLD.¹¹ Those children who had NAFLD showed a two-fold increased relative risk of developing SIBO.¹¹ In adults, a 2022 meta-analysis of 18 studies (n=1,263 total participants) found that among patients with chronic non-alcoholic fatty liver diseases, the prevalence of SIBO was as high as 35%.¹²

Clinical Diagnosis, Root Cause, and Treatment Considerations

SIBO can be a challenge to diagnose. According to the American College of Gastroenterology clinical guidelines, small bowel aspirate and culture is often considered appropriate for the diagnosis of SIBO, as well as the use of breath testing for those patients with IBS; however, the guidelines acknowledge ongoing efforts for re-evaluating the criteria for a SIBO diagnosis and the optimal methods for diagnostic testing.¹

For a potential SIBO diagnosis, the identification and treatment of the underlying conditions causing the microbial imbalances in the small intestine is important. Common treatments for SIBO may include antibiotics, and dietary modifications may also be beneficial.^1,13 In the following video, IFM educator Thomas Sult, MD, IFMCP, discusses nutritional therapies and modifiable food plans that may be appropriate for patients with SIBO.

To read more about augmenting SIBO interventions with nutritional therapies, please read IFM’s article Managing SIBO Through Dietary Interventions by guest authors Kara Fitzgerald, ND, IFMCP, and Lara Zakaria, RPh, MSc, CNS, CDN, IFMCP.

Functional medicine tools help organize a patient’s clinical imbalances and develop a personalized treatment strategy to improve gut health. A wide range of GI health issues, including SIBO, can be addressed using IFM’s 5R framework that uses specific steps—remove, replace, repopulate, repair, and rebalance—to help restore a natural balance to the GI system.³ Join IFM at the GI Advanced Practice Module (APM) to learn clinically useful techniques such as the 5R framework for addressing all types of gastrointestinal issues. In addition to the latest research, you’ll also learn about how to develop individualized treatment protocols using lifestyle-based approaches.

Related Articles

Managing SIBO Through Dietary Interventions

IBS Development: Primary Causes and Triggers

References

1. Pimentel M, Saad RJ, Long MD, Rao SSC. ACG clinical guideline: small intestinal bacterial overgrowth. Am J Gastroenterol. 2020;115(2):165-178. doi:14309/ajg.0000000000000501
2. El Kurdi B, Babar S, El Iskandarani M, et al. Factors that affect prevalence of small intestinal bacterial overgrowth in chronic pancreatitis: a systematic review, meta-analysis, and meta-regression. Clin Transl Gastroenterol. 2019;10(9):e00072. doi:14309/ctg.0000000000000072
3. Patel SM, Young MC. The identification and management of small intestinal bacterial overgrowth: a functional medicine approach. Phys Med Rehabil Clin N Am. 2022;33(3):587-603. doi:1016/j.pmr.2022.04.003
4. Tziatzios G, Gkolfakis P, Papanikolaou IS, et al. High prevalence of small intestinal bacterial overgrowth among functional dyspepsia patients. Dig Dis. 2021;39(4):382-390. doi:1159/000511944
5. Shah A, Talley NJ, Jones M, et al. Small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis of case-control studies. Am J Gastroenterol. 2020;115(2):190-201. doi:14309/ajg.0000000000000504
6. Liao L, Su BB, Xu SP. Helicobacter pylori infection and small intestinal bacterial overgrowth: a systematic review and meta-analysis. BMC Microbiol. 2023;23(1):386. doi:1186/s12866-023-03063-w
7. Shah A, Thite P, Hansen T, et al. Links between celiac disease and small intestinal bacterial overgrowth: a systematic review and meta-analysis. J Gastroenterol Hepatol. 2022;37(10):1844-1852. doi:1111/jgh.15920
8. Feng X, Li XQ. The prevalence of small intestinal bacterial overgrowth in diabetes mellitus: a systematic review and meta-analysis. Aging (Albany NY). 2022;14(2):975-988. doi:18632/aging.203854
9. Wijarnpreecha K, Werlang ME, Watthanasuntorn K, et al. Obesity and risk of small intestine bacterial overgrowth: a systematic review and meta-analysis. Dig Dis Sci. 2020;65(5):1414-1422. doi:1007/s10620-019-05887-x
10. Wang FY, Chi CC. Rosacea, germs, and bowels: a review on gastrointestinal comorbidities and gut-skin axis of rosacea. Adv Ther. 2021;38(3):1415-1424. doi:1007/s12325-021-01624-x
11. Kuang L, Zhou W, Jiang Y. Association of small intestinal bacterial overgrowth with nonalcoholic fatty liver disease in children: a meta-analysis. PLoS One. 2021;16(12):e0260479. doi:1371/journal.pone.0260479
12. Gudan A, Jamioł-Milc D, Hawryłkowicz V, Skonieczna-Żydecka K, Stachowska E. The prevalence of small intestinal bacterial overgrowth in patients with non-alcoholic liver diseases: NAFLD, NASH, fibrosis, cirrhosis—a systematic review, meta-analysis and meta-regression. Nutrients. 2022;14(24):5261. doi:3390/nu14245261
13. Redondo-Cuevas L, Belloch L, Martín-Carbonell V, et al. Do herbal supplements and probiotics complement antibiotics and diet in the management of SIBO? A randomized clinical trial. Nutrients. 2024;16(7):1083. doi:3390/nu16071083