iThei mdcdaelcinfd o c elllllrllll citlhscLarge Intestine
The large intestine is also known as the colon. Resident bacteria of the
colon depend on the host to feed them, especially with carbohydrates
that were not digested/absorbed into the small intestine such as starch-
es, polysaccharides, fiber, sugars, and oligosaccharides. The colon bac-
teria ferment undigested foods, mucous, sloughed epithelial cells, and
pancreatic enzymes for energy to help themselves grow and multiply.
Bacteria from the colon may also creep into the small intestine, where
they can cause an overgrowth. Small intestinal bacterial overgrowth
(SIBO) has been associated with a variety of gastrointestinal conditions
such as Crohn’s disease and IBS. It is also a potential cause of increased
intestinal permeability.
Generally, the small intestine is supposed to have fewer bacteria than
the colon, but in some cases (following food poisoning, for example),
more bacteria may get into the small intestine. Hydrogen breath tests
are available to test for overgrowth of bacteria in the small intestine.
Food and Intestinal Permeability
When people have a leaky gut, the food is never properly digested.
Instead, food particles can cross the intestinal barrier and get into the
circulation. Just like the bacteria, these substances—once in our circula-
tion—are recognized as “invaders” by our immune system, and the im-
mune system launches a white blood cell (WBC) attack. This leads to the
development of food intolerances, which can be measured as IgG anti-
bodies to these foods, similar to the antibodies formed to the endotoxins
produced by bacteria.
Somehow either the bacteria or the foods are cross-linked with thyroid
peroxidase (bystander effect), and the immune system begins to develop
IgG antibodies to TPO. As time goes on, the foods and bacteria act as en-
vironmental triggers that perpetuate the IgG antibodies. (More about this
in the Food Intolerances chapter.)
The Gluten Autoimmune Connection
Certain proteins may induce an immune system response. The most
well-described is the gluten intolerance seen in celiac disease. Gluten is
a protein found in wheat that causes intestinal damage, destroying the
intestine’s ability to absorb nutrients in people with gluten intolerance.
Researchers are now finding gluten intolerance may exist on a spec-
trum, with many people being intolerant but not testing positive when