top of page
Writer's pictureKate Sweeney

What is SIBO?

How SIBO is connected to Eating Disorders

Bubbles under water
Photo credit: https://lymemexico.com/sibo-testing-the-process-the-connection-to-lyme-disease-and-treatment/
 

by Kate Sweeney


SIBO, or small intestinal bacterial overgrowth, is a condition in which someone has “excessive numbers of bacteria in the small bowel, causing gastrointestinal symptoms” (ACG Guidelines, 2020).  The criteria to meet diagnosis are >/= 10^5 colony forming units (CFU)/milliliter (ml) in the proximal jejunum or >/= 10^3 CFU/ml based on duodenal aspirates.


There are currently two types of SIBO - hydrogen or hydrogen sulfide. This means that the bacteria in the gut either give off hydrogen or hydrogen sulfide as gas. 


Methane-predominant SIBO was changed to IMO, or Intestinal Methanogen Overgrowth, in 2022.  This is because methanogens are not bacteria, can reside in the colon and cause different symptoms.



 

What are the symptoms of SIBO and IMO?


One of the hallmarks in SIBO is a change in bowel habits. If someone was constipated, they may have more frequent bowel movements. If someone was having regular bowel movements, they may have diarrhea.


Clients who have methane-predominant IMO are typically constipated and not having regular bowel movements. 


Most people with SIBO have pain with eating and often start to avoid eating over time. This is because when someone eats food, the bacteria in the small intestine will ferment (this is normal!) and use this food, giving off gasses that cause some symptoms.


Symptoms of SIBO include:

  • Bloating

  • Abdominal distention

  • Abdominal pain, sometimes radiating to the back

  • Diarrhea

  • Constipation


In severe SIBO cases, individuals cannot absorb dietary fat well and have vitamin and mineral deficiencies due to low-grade inflammation in the small bowel. Deficiencies in fat soluble vitamins like A and D along with anemia and weight loss may occur. 


For those who start to eat less due to symptoms, they can struggle with malnutrition, leading to more issues with their gut and to poor muscle tone of the pelvic floor, affecting the ability to have a bowel movement.


What are the risk factors?


SIBO does not occur without other pre-existing conditions being present. 


When immune function, motility or the pH of the gut are changed, bacteria are more prone to overgrow. So far, the following risk factors have been associated with SIBO.


  • Irritable Bowel Syndrome (IBS) and gastroparesis (stomach empties too slowly), which affects motility of the gut 

  • Foodborne illness, which can cause dysfunction of nervous and muscular systems leading to changes in motility

  • Poorly controlled diabetes, scleroderma, hypothyroidism and inflammatory bowel disease and undiagnosed/poorly controlled Celiac disease, which affect the immune system and can result in inflammation

  • Low stomach pH due to use of proton-pump inhibitors (PPIs) or aging

  • Ehlers-Danlos Syndrome, a genetic connective tissue disorder

  • Diverticula (pockets in the intestinal wall, which can fill with food and bacteria)

  • Chronic pancreatitis, affecting digestive enzyme production

  • Prior abdominal surgeries like a gastric bypass or bowel resection can lead to scar tissue formation and affect motility and openness of the bowel.


SIBO and Eating Disorders


There is not much research on SIBO/IMO and Eating Disorders (EDs). However, as me and my colleagues can attest, it is very important to consider the connection.


We know gastrointestinal distress and diagnoses are high in individuals with eating disorders. The prevalence of GI distress varies between 60-95% of participants with an ED across studies. Since IBS, constipation, gastroparesis and other conditions that are risk factors for SIBO/IMO are present in those with eating disorders, it makes sense that SIBO/IMO may also be present at higher numbers in the ED population than the general population (0-20% prevalance of SIBO/IMO).


We are starting to learn how the gut microbiome changes during eating disorder challenges. This is a relatively new area of research. I can imagine that if the bacteria in the gut change, this may affect motility and immune function.


I’ve witnessed clients with eating disorders/disordered eating being put on restrictive diets to ‘cure’ or ‘help’ their SIBO/IMO. Unfortunately, because the provider has not fully assessed or understanding of eating disorders, this results in increased dietary restriction, fixation on food and a loss of weight. This restriction and weight loss can exacerbate their eating disorder, mental health and make the SIBO symptoms worse.


How do you get tested for SIBO?


The goal standard of treatment is to do an endoscopy and sample duodenal aspirates. However, this is expensive, invasive and not practical.


Most people get tested for SIBO or IMO through a breath test. These tests involve drinking a substrate of glucose or lactulose and then breathing into a device that will measure the amount of hydrogen, hydrogen sulfide and/or methane on your breath. 


If you have SIBO or IMO, you will either or both of the following:

  • A rise in exhaled hydrogen of at least 20 parts per million (ppm) above baseline within 90 minutes of oral ingestion of either 75 g of glucose or 10 g of lactulose.

  • A concentration of ≥10 ppm of methane at any point during the test.


For hydrogen sulfide SIBO, the baseline is still being negotiated. So far, a concentration of ≥5 ppm of hydrogen sulfide is considered positive and associated with diarrhea.


The test you take will determine what your doctor thinks is appropriate, and what you have access to. There are home tests that can be helpful for people. You need to ensure the home test is validated.


It is very important to note that these tests are not 100% accurate and have a risk of false positive results. Also, many people with chronic constipation or those full of stool may test as a false positive. Strategies to improve constipation may be warranted before testing.


It is highly recommended to consult with a skilled GI doctor or dietitian before considering getting a home test.


What is the treatment?


The treatment for SIBO or IMO are antibiotics. There are no dietary interventions that ‘treat’ or ‘cure’ SIBO. Diet will only help, if at all, with symptom management. 


Commonly prescribed antibiotics are Rifaximin, Neomycin, Ciproflaxin, Doxycycline and others. The dosage and length of use depend on the antibiotic. It is typical for people to need a 10-14 day course.


Some people need multiple rounds of antibiotics, and sometimes different ones each time. 


It is important to determine, with the help of a doctor, the underlying issue causing SIBO and treat that. If it is Crohn's disease, treat that. If it is slow motility causing chronic constipation and IMO, getting on a bowel regimen and trying to do meal spacing so that our migrating motor complex (cleansing waves of our gut every 90 minutes) helps move things along.


From a dietary perspective, there is some literature to support a low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) diet to help with symptom management before taking antibiotics.


However, this is not appropriate for clients with disordered eating, and does not always help.


The Specific Carbohydrate Diet and Elemental Diet are often touted as even ‘curing’ SIBO. I do not recommend them, as they are very restrictive and there is not enough data to support their use. I also do not recommend probiotics, as this introduces more bacteria into the gut.


What don’t we know yet about SIBO?


There is still a lot we do not know about SIBO. 


We are learning that a particular organism/bacteria that is overgrowing may dictate what symptoms are present. Therefore, in the future, we may have many more specific diagnoses depending on the actual bacteria overgrowing, as assessed with indirect microbiome testing.


We also are learning more about hydrogen sulfide producing bacteria and the symptoms this overgrowth causes, and realizing that testing for H2S is important because hydrogen and methane only is an incomplete picture.


There are no validated questionnaires for SIBO, so this is being studied now so providers have something to use to help determine if a client needs a breath test.


In the future, the definition of SIBO will likely change as our knowledge of specific microorganisms in the gut, intestinal permeability, motility and immune function grows. We will be screening for SIBO/IMO more, given more awareness of the condition.


Closing Thoughts


SIBO and IMO are both increasingly common diagnoses that can occur because of a wide range of underlying conditions. They are present in individuals with eating disorders. While they can cause a lot of distress and discomfort, they are treatable. However, dietary restriction, especially for those with eating disorders is not recommended.


If you think you may be struggling with SIBO/IMO, I encourage you to reach out to a professional like your doctor or dietitian to do some investigative work to determine testing and treatment. 


With hope, 

Kate


Resources:

  1. Duker Freuman, T. The Bloated Belly Whisperer.

  2. Duker Freuman, T. Bloating: Dietary Management Based on Etiology. Presented September 19, 2024. Available: https://fodzyme.com/resources/ceu-webinars-for-clinicians.

  3. Ghoshal UC et al. irritable bowel syndrome and small intestinal bacterial overgrowth: Meaningful association or unnecessary hype. World J Gastroenterol. 2014; 20(10): 2482–2491.

  4. Jaffee, N. SIBO: Evidence and Nutrition Interventions. Available: https://fodzyme.com/resources/ceu-webinars-for-clinicians.

  5. Murray, Helen B. BA1; Thomas, Jennifer J. PhD2; Kuo, Braden MD3; Eddy, Kamryn T. PhD2; Staller, Kyle D. MD2. The Frequency of Gastrointestinal Symptom Complaints and Functional Gastrointestinal Disorders in Patients Presenting for Eating Disorder Treatment: 447. American Journal of Gastroenterology 113():p S260-S261, October 2018.

  6. Pimentel, Mark MD, FRCP(C), FACG1; Saad, Richard J. MD, FACG2; Long, Millie D. MD, MPH, FACG (GRADE Methodologist)3; Rao, Satish S. C. MD, PhD, FRCP, FACG4. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. The American Journal of Gastroenterology 115(2):p 165-178, February 2020. | DOI: 10.14309/ajg.0000000000000501

  7. Pimentel M, Soffer EE, Chow EJ, Kong Y, Lin HC. Lower frequency of MMC is found in IBS subjects with abnormal lactulose breath test, suggesting bacterial overgrowth. Dig Dis Sci. 2002;47(12):2639-43.

  8. Rao SSC, Bhagatwala J. Small Intestinal Bacterial Overgrowth: Clinical Features and Therapeutic Management. Clin Transl Gastroenterol. 2019;10(10): e00078.

  9. Scarlata, K. 2022. Fact Sheet: Small Intestinal Bacterial Overgrowth Update + Overview Treatments, Testing and Current Approaches to Managing Symptoms. Available: katescarlata.com

  10. Terry, S.M., Barnett, J.A. & Gibson, D.L. A critical analysis of eating disorders and the gut microbiome. J Eat Disord 10, 154 (2022). https://doi.org/10.1186/s40337-022-00681-z



Recent Posts

See All

Comments


bottom of page