possible causes of SIBO
Content
1. Impaired Motility
2. Impaired Digestion
3. Anatomic Problems
4. Medication
SIBO (small intestinal bacterial overgrowth) describes an excessive growth of bacteria in the small intestine which is normally not that densely populated by microorganism compared to the large intestine. SIBO diagnosis is based on breath testing. SIBO treatment options are manyfold: diet, antibiotics, stress management, …
The causes of SIBO are diverse and can be categorized into several groups. These include reduced motility of the small intestine (1), impaired digestion, organic or anatomical problems (1), and medication use.
1. Impaired Motility
Small intestinal motility may be reduced, for example, due to gastrointestinal infections. A post-infectious irritable bowel syndrome (IBS) may develop following an infectious gastrointestinal illness, which is often associated with small intestinal bacterial overgrowth (SIBO) (2).
Other causes of reduced motility include dysautonomia (conditions affecting the autonomic nervous system), diabetes (3,4), or hypothyroidism (4), all of which can negatively impact small intestinal motility. A reduction in motility can impair the gut’s natural cleansing mechanism, slowing down transit and facilitating bacterial colonization (4). But there are further causes for a reduced motility.
2. Impaired Digestion
Impaired digestion is often the result of a deficiency in essential digestive juices or enzymes, which are crucial for breaking down food and absorbing nutrients. These include stomach acid (3,4), pancreatic enzymes (3), and bile acids, each playing a vital role in the digestive process. Chronic stress is a significant contributing factor to these digestive enzyme deficiencies. When the body is under stress, it enters a “fight or flight” response, diverting resources away from processes like digestion. Stomach acid, for example, is necessary for protein breakdown and the activation of digestive enzymes. A deficiency in stomach acid can lead to incomplete digestion, causing symptoms like bloating, heartburn, and indigestion. Pancreatic enzymes, which are produced by the pancreas, help break down fats, proteins, and carbohydrates. When there is a shortage of these enzymes, it can lead to malabsorption, which may cause diarrhea, weight loss, and nutrient deficiencies. Similarly, bile acids, produced by the liver and stored in the gallbladder, are essential for the emulsification and absorption of fats. A lack of bile acids can result in difficulty digesting fatty foods, leading to diarrhea or fatty stools (steatorrhea).
3. Anatomic Problems
Organic or anatomical problems may include adhesions following abdominal surgery, diverticula (3), or fistulas (3). These conditions may further impair small intestinal motility. Moreover, patients who have undergone stomach resection are frequently affected by SIBO (5).
4. Medication
Medications that may influence the development of SIBO include antibiotics, opioids, and hormonal therapies. Antibiotics and hormonal medications can alter the composition of the gut microbiome, while opioids can reduce intestinal motility.
References
- 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 Sep 4;7:363. doi: 10.3389/fped.2019.00363 . PMID: 31552207; PMCID: PMC6737284.
- Pyleris E, Giamarellos-Bourboulis EJ, Tzivras D, Koussoulas V, Barbatzas C, Pimentel M. The prevalence of overgrowth by aerobic bacteria in the small intestine by small bowel culture: relationship with irritable bowel syndrome. Dig Dis Sci. 2012 May;57(5):1321-9. doi: 10.1007/s10620-012-2033-7. Epub 2012 Jan 20. PMID: 22262197.
- Bures J, Cyrany J, Kohoutova D, Förstl M, Rejchrt S, Kvetina J, Vorisek V, Kopacova M. Small intestinal bacterial overgrowth syndrome. World J Gastroenterol. 2010 Jun 28;16(24):2978-90. doi: 10.3748/wjg.v16.i24.2978. PMID: 20572300; PMCID: PMC2890937.
- Bushyhead D, Quigley EMM. Small Intestinal Bacterial Overgrowth-Pathophysiology and Its Implications for Definition and Management. Gastroenterology.2022Sep; 163(3):593-607.doi: 10.1053/j.gastro.2022.04.002. Epub 2022 Apr 7. PMID: 35398346.
- Paik CN, Choi MG, Lim CH, et al. The role of small intestinal bacterial overgrowth in postgastrectomy patients. Neurogastroenterol Motil 2011; 23:e191–e196. https://doi.org/10.1111/j.1365-2982.2011.01686.x
