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.

Good nutrition is one of the ways the body restores and heals itself. Therefore, every effort must be made to avoid becoming malnourished. Protein is a key nutritional element in the recovery process. Consume healthy proteins such as lean cuts of chicken and fish. A protein deficiency can lead fatigue, insulin resistance, and loss of muscle mass.

Iron deficiency is fairly common in people with ulcerative colitis and Crohn's colitis and less common in those with small intestine disease. It results from blood loss following inflammation and ulceration of the colon. Try teaming iron-rich foods such as poultry, soy foods, and some fortified foods such as whole grain cereals with fruits and vegetables that are rich in vitamin C like potatoes, broccoli, cauliflower, Brussels sprouts, red and green bell peppers, and cabbage. This food partnership improves the iron absorption rate, and the vitamin C gives the immune system a boost.

Restrict your consumption of certain high-fiber foods such as nuts, seeds, corn. High-fiber foods also provoke contractions once they enter the large intestine and can cause cramping as a result. They may also cause diarrhea, since they are not completely digested by the small intestine. Sometimes a low-fiber diet is necessary minimize abdominal pain and cramping symptoms.

It may also be necessary to supplement your diet with nutritional supplements to ensure your body is getting the proper amount of vitamins and minerals needed.