What is Small Intestinal Bacterial Overgrowth (SIBO)?

by

Introduction

I used to believe that SIBO was a condition that only alternative medicine practitioners, such as naturopaths, identified and treated. I thought it wasn’t a real diagnosis at all, and it seems I was not alone in this belief. This is the first article about SIBO, outlining what it is, its symptoms, and its risk factors. Subsequent articles will explore how SIBO is diagnosed and the various treatment options available.

When I asked on Twitter whether people believed SIBO was a credible diagnosis, only 15% thought it wasn’t legitimate. The majority (62%) felt it was a credible diagnosis that many doctors simply don’t know about yet. My own interest began when a rheumatologist suggested SIBO might be underlying an increase in joint pain I was experiencing. To my surprise, I found that SIBO is not only well-researched but is being studied by academics at prestigious universities.

What is SIBO?

Small Intestinal Bacterial Overgrowth (SIBO) is an increase in the types of bacteria in the small intestine that are normally only found in the large intestine (the colon). The small intestine consists of the duodenum, the jejunum, and the ileum. While it is longer than the large intestine, its diameter is smaller. Normally, the small intestine contains very few bacteria. When the bacteria that normally populate the large intestine “spill over” into the small intestine, it is classified as SIBO.

The body has several mechanisms to prevent this, including high stomach acid which kills most bacteria and the ileocaecal valve, which acts as a barrier between the small and large intestines. Secretions from the pancreas and bile also help keep bacteria from reproducing in the wrong areas.

Risk Factors and Causes

SIBO can occur for several reasons, including low stomach acid (achlorhydria), pancreatic insufficiency, anatomical abnormalities like obstructions or diverticula, and motility disorders common in conditions like diabetes mellitus. Interestingly, while heavy alcohol consumption has long been a known risk factor, recent studies have found an association between moderate alcohol consumption (one drink per day for women) and SIBO, likely due to injury to mucosal cells and slowed intestinal contractions.

How Common is SIBO?

The prevalence of SIBO in young and middle-aged adults appears to be between 6% and 15%. However, this rises to nearly 16% in older adults. This increase may be due to the natural decrease in stomach acid associated with aging, as well as the higher prevalence of type 2 diabetes and diverticulosis in older populations.

Symptoms of SIBO

Many symptoms of SIBO overlap with Irritable Bowel Syndrome (IBS), including abdominal pain, bloating, gas, and alternating bouts of diarrhea or constipation. As I discovered personally, there are also lesser-known symptoms, such as significant joint pain, that can be associated with the condition.

Final Thoughts

If you have been diagnosed with IBS but find that your symptoms do not improve despite appropriate dietary changes, it may be worth investigating SIBO. Understanding the underlying mechanisms—from stomach acid to intestinal motility—is the first step toward effective treatment and recovery.

More Info?

If you would like to know more, you can learn about me and the Small Intestinal Bacterial Overgrowth (SIBO) Package that I offer.

To your good health!

Joy

You can follow me on:

Twitter: https://twitter.com/jyerdile
Facebook: https://www.facebook.com/BetterByDesignNutrition/

Quick Clinical Summary

Q: What is Small Intestinal Bacterial Overgrowth (SIBO)?

A: SIBO is a clinical condition characterized by an abnormal increase in the number and/or type of bacteria in the small intestine. Specifically, it involves bacteria that are normally found in the large intestine migrating or ‘spilling over’ into the small intestine, where they do not belong.

Q: What are the risk factors for developing SIBO?

A: Primary risk factors include low stomach acid (achlorhydria), which fails to kill bacteria; pancreatic insufficiency; anatomical abnormalities like diverticula; and motility disorders often seen in diabetes. Moderate alcohol consumption has also been identified as a significant risk factor.

Q: Can SIBO cause symptoms outside of the digestive tract?

A: Yes. While the most common symptoms are bloating, gas, and abdominal pain, SIBO has been clinically associated with systemic symptoms like joint pain and chronic widespread pain conditions such as fibromyalgia.

References

  1. Bures J, Cyrany J, Kohoutova D, et al. Small intestinal bacterial overgrowth syndrome. World Journal of Gastroenterology. 2010 Jun 28;16(24):2978-90. [https://doi.org/10.3748/wjg.v16.i24.2978]
  2. Medscape. Small Intestine Anatomy. Updated Dec 8, 2017. [https://emedicine.medscape.com/article/1948951-overview]
  3. Hauge T, Persson J, Danielsson D. Mucosal bacterial growth in the upper gastrointestinal tract in alcoholics (heavy drinkers). Digestion. 1997;58(6):591-5. [https://doi.org/10.1159/000201507]
  4. Gabbard SL, Lacy BE, Levine GM, et al. The impact of alcohol consumption and cholecystectomy on small intestinal bacterial overgrowth. Digestive Diseases and Sciences. 2014 Mar;59(3):638-44. [https://doi.org/10.1007/s10620-013-2960-y]
  5. Dukowicz AC, Lacy BE, Levine GM. Small intestinal bacterial overgrowth: a comprehensive review. Gastroenterology & Hepatology. 2007 Feb;3(2):112-22. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3099351/]
Nutrition is BetterByDesign

Privacy Policy | Terms of Use

© 2025 BetterByDesign Nutrition Ltd.

LEGAL NOTICE: The contents of this blog, including text, images, and cited statistics, are for informational purposes only. The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read in this content.