SIBO: Comorbidities, SIFO, and Diagnosis

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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.

(Video Time: 1 minute) Dr. Sult has been practicing functional medicine for nearly 30 years. He is a fellow of the American Academy of Family Physicians, a diplomate of both the American Board of Family Medicine and the American Board of Physician Specialties in Integrative Medicine, and is board certified by the American Board of Integrative Holistic Medicine.

SIBO Comorbidities

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.

Learn More About gut Dysfunction and Chronic Conditions

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  2. 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
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