Nutrition and IBD


Nutrition concerns of patients with living Inflammatory Bowel Disease (IBD) are extremely common, and appropriate. Patients often believe that their disease is caused by, and can be cured by diet. Unfortunately, that seems to be too simplistic an approach, which is not supported by clinical and scientific data. Diet can certainly affect symptoms of these diseases, and may play some role in the underlying inflammatory process, but it appears not to be the major factor in the inflammatory process.

Because Crohn's disease and ulcerative colitis are diseases of the digestive tract, it is only natural that you will have many questions about diet and nutrition if you have been diagnosed with one of these disorders. First of all, you may be surprised to learn that there is no evidence that anything in your diet history caused or contributed to these diseases. Once you develop IBD, however, paying special attention to what you eat may go a long way toward reducing symptoms and promoting healing.

The information provided here and in Part II of this article offers an overall dietary guide for patients and their families. It is based on the results of ongoing studies and the accumulation of knowledge gained in recent years. As this research continues, we will learn even more about the relationship between nutrition and IBD.

How do Crohn's disease and ulcerative colitis interfere with digestion?

To get a better idea of how diet affects people living with IBD, here's a brief explanation of the way in which the body processes the food you put into it.   The real work of the digestive system takes place in the small intestine, which lies just beyond the stomach. In the small intestine, digestive juices (termed bile) from both the liver and the pancreas mix with food. This mixing is powered by the churning action of the intestinal muscle wall. After digested food is broken down into small molecules, it is absorbed through the surface of the small intestine and distributed to the rest of the body by way of the bloodstream. Watery food residue and secretions that are not digested in the small intestine pass on into the large intestine (the colon). The colon reabsorbs much of the water added to food in the small intestine.

This is a kind of water conservation or "recycling" mechanism. Solid, undigested food residue is then passed from the large intestine as a bowel movement. 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 living 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.

In ulcerative colitis, only the colon is inflamed—the small intestine continues to work normally. But because the inflamed colon does not recycle water properly, diarrhea can be severe.

Is nutrition of special importance to IBD patients?

Yes, vitally so. IBD patients, especially people with Crohn's disease whose small intestine is affected, are prone to becoming malnourished for several reasons:

  • Loss of appetite—a result of nausea, abdominal pain, or altered taste sensation—may cause inadequate food intake.
  • Chronic disease tends to increase the caloric or energy needs of the body; this is especially true during disease flares.
  • IBD, particularly Crohn's disease, is often associated with poor digestion and malabsorption of dietary protein, fat, carbohydrates, water, and a wide variety of vitamins and minerals. Thus, much of what a person eats may never truly get into the body.


Good nutrition is one of the ways the body restores itself to health. Therefore, every effort must be made to avoid becoming malnourished. Restoring and maintaining good nutrition is a key principle in the management of IBD for several reasons, including the following:

  • Medications tend to be more effective in people with good nutritional status.
  • When proteins and other nutrients are lost in IBD, more food must be taken in to compensate for these losses; that may be difficult for many patients when intestinal symptoms are active.
  • Lost proteins, calories, and other nutrients may cause growth retardation in children and teenagers.
  • Weight loss in women and girls can have an impact on hormonal levels, resulting in menstrual irregularities or even cessation of menstruation.

How does nutrition affect growth?

In young people with IBD who had onset of their disease before puberty, growth may be delayed. Poor food intake may further contribute to poor growth. As a result, good nutritional habits and adequate caloric intake are very important. Control of the disease with drugs or, less often, surgical removal of a particularly diseased region of intestine, is most successful when appropriate dietary intake is maintained.

Do patients with IBD absorb foods normally?

Most often, yes. Patients who have inflammation only in the large intestine absorb food normally. People with Crohn's disease may have problems with digestion if their disease involves the small intestine. They may eat enough food but cannot absorb it adequately. In fact, up to 40 percent of people with Crohn's do not absorb carbohydrates properly. They may experience bloating, gaseousness, and diarrhea as well as a loss in important nutrients. Fat malabsorption is another problem in Crohn's disease, affecting at least one-third of patients. At particular risk are people who have had terminal ileal resections.

The degree to which digestion is impaired depends on how much of the small intestine is diseased and whether any intestine has been removed during surgery. If only the last foot or two of the ileum is inflamed, the absorption of all nutrients except vitamin B-12 will probably be normal. If more than two or three feet of ileum is diseased, significant malabsorption of fat may occur. If the upper small intestine is also inflamed, the degree of malabsorption in Crohn's disease is apt to be much worse, and deficiencies of many nutrients, minerals, and more vitamins are likely. Some IBD therapies -- especially the 5-ASA medications (e.g., Asacol,® Pentasa®) -- cause interference with the absorption of folate, which is essential in helping to prevent cancer and birth defects, so it should be taken in supplement form.

Should supplemental vitamins be taken? If so, which ones?

Again, that depends on the extent and location of the disease. Vitamin B-12 is absorbed in the lower ileum—that means that people who have ileitis (Crohn's disease that affects the ileum) or those who have undergone small bowel surgery may have a vitamin B-12 deficiency because they are unable to absorb enough of this vitamin from their diet or from oral supplements. To correct this deficiency—which can be determined by measuring the amount of this vitamin in the blood—a monthly intramuscular injection of vitamin B-12 may be required.

Folic acid (another B vitamin) deficiency is also quite common in patients who are on the drug sulfasalazine. For these patients, the recommended dietary allowance for a folate tablet is 1 mg daily, as a supplement. For most people with chronic IBD, it is worthwhile to take a multivitamin preparation regularly. If you suffer from maldigestion or have undergone intestinal surgery, other vitamins-particularly vitamin D-may be required. Affecting as many as 68 percent of people, vitamin D deficiency is one of the most common nutritional deficiencies seen in association with Crohn's disease. Vitamin D is essential for good bone formation and for the metabolism of calcium.

The recommended dietary allowance for supplementation of this vitamin is in the range of 800 I.U./day, especially in the non-sunny areas of the country, and particularly for those with active disease. Together with vitamins A, E, and K, vitamin D is a fat-soluble vitamin; these tend to be less easily absorbed than water-soluble vitamins. Consequently, they may be absorbed better in liquid rather than pill form.

Are any special minerals recommended?

In most IBD patients, there is no obvious lack of minerals. However, 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. Blood iron levels are easily measured, and if a deficiency is found (otherwise known as anemia), oral iron tablets or liquid may be given. The usual dose is between 8 to 27 mg, taken one to three times a day-depending on the extent of the deficiency and the patient's tolerance. Oral iron turns the stool black, which can be mistaken for intestinal bleeding.   Other mineral deficiencies include potassium and magnesium. People may develop potassium deficiencies with diarrhea or vomiting, or as a result of prednisone therapy. Potassium supplements are available in tablet and other forms. Oral supplements of magnesium oxide may prove necessary for people who have magnesium deficiency caused by chronic diarrhea or extensive small intestinal disease, or those who have had substantial lengths of intestine removed through surgery.

Trace elements are nutrients that are absorbed in the body in minute quantities. Still, they are essential for some important biologic functions. Deficiencies in trace elements are noted in people with advanced Crohn's disease-mainly those with poor nutritional intake and extensive small intestine disease.

How can you treat calcium deficiency and bone disease in IBD?

One of the more important deficiencies seen in association with IBD is calcium deficiency-either alone or in conjunction with vitamin D deficiency. People with IBD may have limited intake of calcium in their diet, avoiding dairy products because they have a lactose intolerance or because they think they have one. Other people may consume enough calcium in their diet but do not absorb it properly because of small-intestine disease or resection. Then, too, certain medications used in IBD may have an adverse effect on bone health.

Long-term use of prednisone and other steroids, for example, slows the process of new bone formation and accelerates the breakdown of old bone. It also interferes with calcium absorption. In addition to steroid use, Crohn's disease itself has been shown to be linked with bone thinning and osteoporosis, so screening with bone density studies is suggested for those at risk.

If prednisone cannot be discontinued altogether, a reduction in dosage or an alternate-day dosing may help prevent IBD-related bone loss. Patients should aim for at least 1,500 mg of calcium daily, either in dietary form or as supplements taken in three divided doses during the day. Vitamin D supplements (see above) are also recommended.

Research is currently under way to determine whether other therapies for bone disease-such as those used in people with postmenopausal osteoporosis-might be appropriate for IBD-related bone loss. These include the bisphosphonates (such as Fosamax®), calcitonin, and fluoride.

Part II of our article gives you more an overall dietary guide for patients and their families.



For further information, call CCFA at our Information Resource Center: 888.MY.GUT.PAIN (888.694.8872).

The Crohn’s & Colitis Foundation of America provides information for educational purposes only. We encourage you to review this educational material with your health care professional. The Foundation does not provide medical or other health care opinions or services. The inclusion of another organization’s resources or referral to another organization does not represent an endorsement of a particular individual, group, company or product.

About this resource

By: CCFA
Published: May 31, 2012