When the small intestine is inflamed — as it often is with Crohn’s disease — the intestine becomes less able to fully digest and absorb the nutrients from food. Such nutrients, as well as unabsorbed bile salts, can escape into the large intestine to varying degrees, depending on how extensively the small intestine has been injured by inflammation. This is one reason why people with Crohn’s disease become malnourished, in addition to just not having much appetite. Furthermore, incompletely digested foods that travel through the large intestine interfere with water conservation, even if the colon itself is not damaged. Thus, when Crohn’s disease affects the small intestine, it may cause diarrhea as well as malnutrition. Should the large intestine also be inflamed, the diarrhea may become even more extreme.
People with Crohn’s disease whose small intestine is affected, are prone to becoming malnourished due to loss of appetite, poor digestion and malabsorption, and the fact that a chronic disease such as Crohn’s tends to increase the caloric needs of the body due to the energy the body consumes during a flare-up.
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