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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. Restoring balance to gut flora through individualized interventions and tailored treatments that address lifestyle factors and nutritional needs may dramatically improve health.
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.
Research results have suggested links between SIBO and diseases such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), motility disorders, chronic pancreatitis, cirrhosis, and various immunodeficiency syndromes.1-3 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.4
In addition, smaller studies have found that SIBO is more frequently present in populations with active H. pylori infection5 and spinal cord injury with deep vein thrombosis6 and is also associated with pediatric obesity,7 papulopustular rosacea,8 and nonalcoholic fatty liver disease (NAFLD) at a higher rate than controls. In a small study of obese children with SIBO, researchers found an increased risk for developing NAFLD.9 The study concluded that the relationship between intestinal dysbiosis and diet can influence the gut-liver axis.9 In an interesting contrast, researchers found a lower prevalence of SIBO in patients with type 1 diabetes and suggested this may be due to nutritional interventions in the management of the disease.10
Considering the Fungal Component
Within a healthy GI tract, bacterial and fungal organisms most heavily colonize the colon, while these microbial communities appear less in the small intestine. As with SIBO, small intestinal fungal overgrowth (SIFO) may lead to various systemic symptoms such as migraines, fatigue, depression, bloating, and more.11 Also like SIBO, intestinal dysmotility and reduced amounts of stomach acid resulting from PPI use are potential risk factors specifically for SIFO.1,12-14
While treatment for SIBO may include antibiotics and probiotics,1,15 antifungal therapy may be effective in improving symptoms for SIFO.14 Dietary modifications may also be beneficial for both conditions. A pilot study evaluated the effectiveness of a dietary intervention in combination with antifungals for patients with a chronic form of intestinal Candida overgrowth.16 Ten days after the diet and control groups received an antifungal treatment, both showed satisfactory antifungal and symptomatic effect with no statistically significant difference; however, at the second examination three months later, the diet intervention group showed a significantly higher percentage of patients without symptoms (85%) compared to the control group (42.5%).16
Clinical Diagnosis and Root Cause
SIBO can be a challenge to diagnose, and with overlapping symptoms, SIFO may also be a contributor to GI imbalance and an important factor to consider when identifying root causes and selecting optimal treatment strategies. Recent literature suggests that there is no gold standard for the diagnosis of SIBO.17 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 potential SIBO and SIFO diagnoses, the identification and treatment of the underlying conditions causing the microbial imbalances in the small intestine is important, and the restoration of gut flora populations may dramatically improve health and ameliorate a range of symptoms.18,19 IFM’s 5R framework addresses a range of GI health issues, including SIBO and SIFO, and uses specific steps—remove, replace, re-inoculate, repair, and rebalance—to help restore a natural balance to the GI system.3 Functional medicine approaches to improve gut health may include nutritional interventions that reduce the fermentation of carbohydrates in the gut to help address bacterial and fungal overgrowth or an elimination diet that removes trigger foods to potentially reduce inflammation and improve symptoms.
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, diet, nutraceuticals, pharmaceuticals, and botanicals to help restore gut health.
- Pimentel M, Saad RJ, Long MD, Rao SSC. ACG clinical guideline: small intestinal bacterial overgrowth. Am J Gastroenterol. 2020;115(2):165-178. doi:10.14309/ajg.0000000000000501
- Lee AA, Baker JR, Wamsteker EJ, Saad R, DiMagno MJ. Small intestinal bacterial overgrowth is common in chronic pancreatitis and associates with diabetes, chronic pancreatitis severity, low zinc levels, and opiate use. Am J Gastroenterol. 2019;114(7):1163-1171. doi:10.14309/ajg.0000000000000200
- 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:10.1016/j.pmr.2022.04.003
- 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:10.14309/ajg.0000000000000504
- Enko D, Kriegshäuser G. Functional (13)C-urea and glucose hydrogen/methane breath tests reveal significant association of small intestinal bacterial overgrowth in individuals with active Helicobacter pylori infection. Clin Biochem. 2017;50(1-2):46-49. doi:10.1016/j.clinbiochem.2016.08.017
- Cheng X, Zhang L, Xie NC, Xu HL, Lian YJ. Association between small-intestinal bacterial overgrowth and deep vein thrombosis in patients with spinal cord injuries. J Thromb Haemost. 2017;15(2):304-311. doi:10.1111/jth.13583
- Guercio Nuzio S, Di Stasi M, Pierri L, et al. Multiple gut-liver axis abnormalities in children with obesity with and without hepatic involvement. Pediatr Obes. 2017;12(6):446-452. doi:10.1111/ijpo.12164
- Agnoletti AF, DE Col E, Parodi A, et al. Etiopathogenesis of rosacea: a prospective study with a three-year follow-up. G Ital Dermatol Venereol. 2017;152(5):418-423. doi:10.23736/S0392-0488.16.05315-3
- Belei O, Olariu L, Dobrescu A, Marcovici T, Marginean O. The relationship between non-alcoholic fatty liver disease and small intestinal bacterial overgrowth among overweight and obese children and adolescents. J Pediatr Endocrinol Metab. 2017;30(11):1161-1168. doi:10.1515/jpem-2017-0252
- Adamska A, Nowak M, Pilacinski S, et al. Small intestinal bacterial overgrowth in adult patients with type 1 diabetes: its prevalence and relationship with metabolic control and the presence of chronic complications of the disease. Pol Arch Med Wewn. 2016;126(9):628-634. doi:10.20452/pamw.3501
- Singh R, Mullin GE. A wasting syndrome and malnutrition caused by small intestine fungal overgrowth: case report and review of the literature. Integr Med (Encinitas). 2017;16(3):48-51.
- Su T, Lai S, Lee A, He X, Chen S. Meta-analysis: proton pump inhibitors moderately increase the risk of small intestinal bacterial overgrowth. J Gastroenterol. 2018;53(1):27-36. doi:10.1007/s00535-017-1371-9
- Jacobs C, Coss Adame E, Attaluri A, Valestin J, Rao SS. Dysmotility and proton pump inhibitor use are independent risk factors for small intestinal bacterial and/or fungal overgrowth. Aliment Pharmacol Ther. 2013;37(11):1103-1111. doi:10.1111/apt.12304
- Erdogan A, Rao SSC. Small intestinal fungal overgrowth. Curr Gastroenterol Rep. 2015;17(4):16. doi:10.1007/s11894-015-0436-2
- Avelar Rodriguez D, Ryan PM, Toro Monjaraz EM, Ramirez Mayans JA, Quigley EM. Small intestinal bacterial overgrowth in children: a state-of-the-art review. Front Pediatr. 2019;7:363. doi:10.3389/fped.2019.00363
- Otaševic S, Momcilovic S, Petrovic M, Radulovic O, Stojanovic NM, Arsic-Arsenijevic V. The dietary modification and treatment of intestinal Candida overgrowth – a pilot study. J Mycol Med. 2018;28(4):623-627. doi:10.1016/j.mycmed.2018.08.002
- Adike A, DiBaise JK. Small intestinal bacterial overgrowth: nutritional implications, diagnosis, and management. Gastroenterol Clin North Am. 2018;47(1):193-208. doi:10.1016/j.gtc.2017.09.008
- Leventogiannis K, Gkolfakis P, Spithakis G, et al. Effect of a preparation of four probiotics on symptoms of patients with irritable bowel syndrome: association with intestinal bacterial overgrowth. Probiotics Antimicrob Proteins. 2019;11(2):627-634. doi:10.1007/s12602-018-9401-3
- Krajicek EJ, Hansel SL. Small intestinal bacterial overgrowth: a primary care review. Mayo Clin Proc. 2016;91(12):1828-1833. doi:10.1016/j.mayocp.2016.07.025