SIBO: When gut bacteria create health problems
Our body is in a fascinating interaction with bacteria and in our gastrointestinal tract these can play a decisive role in our health. When an imbalance occurs, this can lead to various health problems. One such imbalance that has received increased attention recently is SIBO, or "Small Intestinal Bacterial Overgrowth."
SIBO means abnormally high amounts of bacteria in the small intestine. Since the small intestine does not have the strong protective mucus layer that the large intestine has, overgrowth of bacteria can damage the wall of the small intestine and cause inflammation both in the intestine and in the rest of the body, as well as contribute to the development of chronic diseases and inflammatory conditions such as in muscles and joints.
Chronic stress is considered a major cause of SIBO. In this article, we will present what SIBO is and how health problems can arise in its wake.
The stomach's workhorses should be in the large intestine
The bacteria in our colon can be said to be real workhorses because they digest fibers from our diet that our own cells cannot use and convert these into health-promoting substances such as B and K vitamins.
Bacteria have surface structures that stabilize the outer bacterial cell wall, so-called lipopolysaccharides (LPS) and lipoteichoic acid (LTA) which contribute to maintaining the integrity of the bacteria. However, LPS and LTA are also some of the most powerful inflammation-inducing toxins we know of. Thanks to the colon's wall acting as an impenetrable barrier to LPS and LTA, these toxins cannot reach the body's immune system and cause inflammation.
This important barrier function comes from the fact that the surface of the large intestine consists of two powerful mucus layers (Figure 1) that keep the bacteria in place inside the intestine and prevent LPS and LTA from passing through the intestinal wall and into the bloodstream (1-5), but still allows salts and water to pass through the colon's two mucus layers and into the blood stream. Absorption of water and salts into the bloodstream is one of the most important functions of the colon.
The small intestine is permeable to a variety of substances which reach the immune cells and the vascular system
The situation is completely different in the small intestine, as it does not have the same protective mucous wall as the large intestine, but only has a thin and loose superficial mucus layer (Figure 1). Since the small intestine is built to be permeable to a variety of nutrients (amino acids, fatty acids, carbohydrates, vitamins, minerals), a too thick mucus layer would have reduced this permeability. The total surface area for absorption in the small intestine is estimated to be 200 square meters, roughly the size of a tennis court, and it is this large surface area that allows a significant amount of nutrients to be transported from the inside of the gut into the bloodstream. If the small intestine would have had a mucus layer corresponding to that seen in the large intestine, the surface for adequate nutrient absorption would have had to be over 400 square meters, that is, our small intestine would then be over 12 meters instead of 6 meters long.
In the case of overgrowth of bacteria in the small intestine, the bacteria will devour and consume the amino acids, vitamins, minerals and other nutrients that should otherwise have benefitted our body. SIBO can actually be likened to a cuckoo chick that takes care of itself at the expense of others.
Figure 1. The small intestine has a superficial thin and loose mucus layer that allows nutrients to pass through the intestinal wall to the bloodstream, but the mucous is not sufficient to protect the cells of the intestinal wall in case of SIBO. Magsäck = stomach, Tunntarm = small intestine, Tjocktarm = colon.