Dietary Recommendations for SIBO

December 2, 2021 , ,

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.

Causes of SIBO

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.

Types of SIBO and diagnostics

There are 3 types of SIBO:

  • SIBO linked to excess hydrogen produced by bacteria
  • Excess hydrogen sulfide produced by bacteria
  • An excess of methane produced by archaea (called IMO: Intestinal Methanogen Overgrowth)

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:

  • Do not take antibiotics for four weeks before the test
  • Discontinue taking laxatives, probiotics and prokinetic agents one week before the test
  • Avoid complex carbohydrates (starches) 24 hours before the test
  • Avoid eating 8 to 12 hours before the test (the test should be done fasting)

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.

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Author

Kathryn Adel
Kathryn completed degrees in kinesiology and nutrition, as well as a Masters in Sports Nutrition. She is a member of OPDQ and of the Academy of Nutrition and Dietetics. She ran track and cross-country at a national level. Kathryn specializes in sports nutrition, weight loss, diabetes, as well as heart and gastrointestinal health. Kathryn is experienced with the low FODMAP diet and she completed the Monash University low FODMAP dietitian's training.

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