SIBO stands for small intestinal bacterial overgrowth. It is defined as an increase in the number of bacteria, and/or changes in the types of bacteria living in the small intestines.
Normally bacteria are present throughout your entire digestive tract. Their existence and harmonious function within the human body is now recognized by science as a multi-tasking organ called the microbiome. These beneficial bacteria assist in thousands of functions in the body from nutrient synthesis to immune system modulation.
In a typical healthy digestive tract the majority of bacteria live in the lower bowel. At least 1,000,000,000 bacteria per milliliter of fluid live in the colon. Fewer bacteria inhabit the small intestines, less than 10,000 bacteria per milliliter of fluid. The species of bacteria that live in the colon differ from the species that live in the small intestines. Imagine these ecosystems as drastically different from one another, as the bottom of the Pacific Ocean to the Sahara Desert.
SIBO occurs when bacteria begin to crowd and colonize the small intestines, often the bacteria that should normally be found in the colon migrate into and populate the small intestines. Rarely is SIBO caused by a single type of bacteria, rather it is an accumulation of various types of bacteria that shouldn't be there.
This means that the process of nutrient breakdown is occurring in the wrong place. This causes all sorts of health issues, such a bloating, heartburn, nausea, not to mention the inability to absorb the nutrients consumed. Over time mineral and nutrient deficiencies develop leading to a whole host of conditions.
Dr. Amy Myers explains,
"The excess bacteria then feed off of the undigested food in your small intestine. In particular, they love to feed on sugar, simple and complex carbohydrates, starches, and alcohol – they’re real carb fiends!
As the bacteria feeds, it causes the carbohydrates to ferment, which produces hydrogen as a byproduct. Hydrogen can in turn feed single-celled organisms in your small intestine called archaea, which then produce methane as a byproduct. So when you have SIBO you have excess levels or hydrogen, methane, or both in your digestive system.
Carbohydrates feed SIBO → SIBO produces hydrogen → hydrogen feeds archaea → archaea produces methane
Depending on which gas is most predominantly produced, you can develop different symptoms and respond better to different treatments. Hydrogen-dominant SIBO typically leads to diarrhea, whereas methane-dominant SIBO is usually associated with constipation."