SIBO is like an infection made up of noninfectious bacteria. A SIBO prob- lem is different from getting food poisoning or dealing with a dangerous strain of Clostridium difficile or Salmonella enterica. It’s not an infection in the traditional sense. Instead, SIBO is an overgrowth of bacteria that is nor- mally found in our digestive tract. As you can see in Figure 6.1, SIBO occurs when the gut bacteria normally found in the colon and ileum grow wildly and end up near the top of the small intestine. Bacteria that are nonpatho- genic, healthy types are very good at pooping out vitamins for our body to use. Though a moderate, balanced amount of healthy bacteria supports optimum health, too much of this bacteria can become a bad thing.
Figure 6.1 –Migration of bacteria from the colon and ileum into the upper small intestine
The SIBO problem is a double-edged sword. On one side are the excess bacteria in the small intestine, which interfere with the process of digestion. Just like people, pets, and plants, bacteria need to eat in order to survive. So when the bacteria populations explode in the small intestine, they also eat much more than normal. If the bacteria are eating too much of the food we consume, there is less food and nutrition available for our body. This is why malabsorption is so common with SIBO problems.
On the other side of the SIBO sword is the fact that these bacterial populations actively poop out vitamins that our bodies absorb. Clearly, this is advantageous in a balanced and healthy gut. But when bacteria levels go through the roof, they can actually excrete too much of one vitamin, blocking the absorption of another. We see this relationship in SIBO all the time, as patients experience elevated levels of certain B vitamins such as folic acid along with low levels of B12, vitamin D, iron, and others. This is a problem because the bacteria down there can produce folic acid while simultaneously causing all kinds of other digestive issues.