SIBO (Small Intestinal Bacterial Overgrowth) is an increase in the number of bacteria in the small intestine that are normally found in large amounts in the colon, resulting in excessive fermentation, inflammation and malabsorption. It is a microbiome dysbiosis, that is, an imbalance in the bacteria of the digestive system.
Gut bacteria are very important for health. For example, they help to support digestion, the immune system, and the production of certain nutrients. However, if too many bacteria from the colon and/or the “wrong” type of bacteria migrate to the small intestine, this can become problematic. By multiplying in the small intestine, these bacteria produce gases (hydrogen or methane) that can cause various symptoms. These can be digestive symptoms (stomach pain, bloating, gas, constipation, early satiety, nausea, diarrhea, bowel movement urgency, alternating diarrhea and constipation, etc.), but also systemic symptoms (fatigue, foggy brain after meals, weight loss or gain, eczema, joint pain, headaches, mouth ulcers, depression, etc.). SIBO can affect the functioning of the digestive system by altering the intestinal mucosa that prevents bad bacteria and undigested food from inadvertently entering the bloodstream. This can increase inflammation, lead to malabsorption of nutrients and fats, and thus create deficiencies in nutrients, especially vitamin B12 and fat-soluble vitamins (A, D, E, K).
Reading the list of symptoms, everyone could believe that they have SIBO since these symptoms are unfortunately very vague and can be caused by many other health conditions as well. The digestive symptoms of SIBO also closely resemble those of irritable bowel syndrome, making diagnostic delineation difficult. In addition, there is a lot of pseudoscience on the Internet about SIBO, making it easy to be persuaded to spend tons of money, take plenty of supplements, or try very restrictive diets. Research on SIBO has grown in recent years, but there is still much to learn. The following information is based on the most recent scientific data.
It is essential to understand that SIBO is not a disease in itself, but rather the consequence of an underlying problem. The development of SIBO can result from several diseases or problems including chronic pancreatitis, alcohol abuse, diabetes, food poisoning, scleroderma, diverticulitis, celiac disease, inflammatory bowel disease, constipation, and irritable bowel syndrome (IBS). The prevalence of SIBO is higher in people with IBS. It is estimated that SIBO affects up to 78% of people with IBS, as compared to about 9% of the general population.
A common cause of SIBO is slow intestinal motility. Gastroparesis, taking certain medications such as narcotics, as well as gastrointestinal surgery (e.g., bariatric surgery, colectomy, or other bowel resections) are some examples of factors that can contribute to a slow intestinal transit and lead to SIBO.
Gastric acidity plays an important role in preventing the proliferation of bacteria in the upper gastrointestinal tract. Patients with hypochlorhydria or achlorhydria secondary to autoimmune gastritis, or partial or total gastrectomy have an increased risk of developing SIBO. It has also been suggested that frequent use of proton pump inhibitors (PPIs) may contribute to SIBO, but studies remain controversial.
There are 3 types of SIBO:
The first two types tend to cause diarrhea while the third tends to cause constipation.
SIBO is diagnosed by a breath test to analyze the gases exhaled by the patient after ingestion of glucose or lactulose. However, these tests have low sensitivity and specificity. In practice, most clinicians choose glucose because it is more likely to underestimate results whereas lactulose is more likely to cause false positives.
The North American Consensus published in 2017 provides a standardized protocol on indications, preparation, performance and interpretation of breath testing for SIBO. The consensus criterion for diagnosing SIBO is an increase in hydrogen greater than or equal to 20 ppm in 90 minutes. It is also important to test the production of hydrogen sulfide and methane in order to be able to diagnose other types of SIBO. Here are some guidelines to follow in preparation for a SIBO breath test:
It should also be noted that a new type of test using an orally ingested capsule is being developed. It can measure in vivo hydrogen and carbon dioxide after ingestion of a high carbohydrate meal and could be an interesting alternative to breath tests.