There are all kinds of intestinal diseases. They can be caused by various factors. For example, some people have a condition caused by gluten. Do you know what that is? It's celiac disease.
Gluten doesn't cause problems in everyone - just those with celiac disease. Gluten can be found in wheat, rye, barley, and oats. For those who don't have celiac disease, these foods are fine to eat. For those with celiac disease, gluten acts almost as a poison. How? The immune system of a person with celiac disease reacts to gluten by damaging the small intestine's lining. The small intestine is where most foods are broken down. The lining has villi, which are small fingerlike growths that absorb nutrients from foods. The damage, though, prevents this absorption. So the body doesn't get all the vitamins, protein, carbohydrates, calcium, and other nutrients it needs and can't work as well.
Celiac disease can cause different problems. Some people show no symptoms. Some show just one. Others have many symptoms. These symptoms include gas, diarrhea, stomach pain, a very itchy skin rash with blisters, weight loss, slowed growth, tiredness, and even changes in mood.