Decoding SIBO

How to identify and regulate small intestinal bacterial overgrowth.
Buckwheat flour, which can be used to make crepes, helps minimize the symptoms of SIBO.

By Tapp Francke Ingolia, MS

Gut health is the key to good health. The vast network of microbes that call our body home is responsible for everything from digestion, mood and weight to our immune response and ability to handle stress. The microbiome, which exists throughout the digestive tract, requires balance in order to operate correctly. Dysbiosis, or an imbalance of those gut microbes, can wreak havoc on our bodies and minds. Small intestinal bacterial overgrowth, or SIBO, is a condition where too many bacteria that normally grow in the large intestine—including Faecalibacterium, Roseburia, Bifidobacterium, Akkermansia and Lactobacillus— begin to proliferate in the small intestine. A wrong-place/ wrong-time issue, the overgrowth of misplaced bacteria can cause uncomfortable gastric symptoms like bloating, gas, nausea, bowel irregularity, diarrhea, a feeling of being overly full after eating, burping and abdominal pain.

The small intestine is poorly named considering that, though narrower than the large intestine, it is the longest part of the digestive tract. Measuring an average of 22 feet, the small intestine is far longer than the mere 5 feet we have of large intestine. Although the majority of our microbiome exists in the large intestine, a delicate balance of microbes make up the ecosystem of the small intestine. The small intestine’s microbial population tends to be limited compared to ones farther down the digestive tract. This is due to the rapid transit of food through the small intestine, and the presence of bile acids, both of which make it an inhospitable environment for bacterial growth.

The problem occurs when that transit is slowed, as happens with buildup of scar tissue from abdominal surgery, structural issues, scleroderma, and conditions like Crohn’s disease and diabetes. Even stress can interfere with gut motility, increasing a person’s susceptibility to developing SIBO. The slowed transit time creates an optimal environment for bacterial growth.

This growth inhibits the absorption of nutrients due to the change in microbial terrain. Additionally, dysfunction of the ileocecal valve can lead to SIBO. This one-way valve that connects the large and small intestines can allow for a backflow of bacteria into the small intestine. As the small intestine’s primary role is to further break down food from the stomach and absorb the nutrients, the microbial growth can get in the way, leading to poor absorption of nutrients, and, if left untreated, malnutrition.

A good way to check for SIBO is with a breath test. The tests look for the presence of methane or hydrogen in the breath (both gases are produced by microbes in the fermentation of carbohydrates and sugars).

One of the helpful tools in regulating SIBO is the FODMAP diet. This diet can also be helpful in cases of irritable bowel syndrome (IBS), Crohn’s disease and colitis. FODMAP, which stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols, are types of carbohydrates found in certain foods including wheat, beans, most grains and starchy vegetables. In a healthy gut, fermentable carbohydrate will pass through the small intestine largely unchanged. The microbes in the large intestine will then ferment these insoluble fibers.

Think you might have SIBO? Check with a functional- medicine doctor or nutritionist to find out. Though SIBO can be tricky, through reconditioning of the microbiome, regulating stomach acid, controlling stressors and addressing other comorbidities, balance is possible.