The Dietary Treatment of Crohn’s Disease

In many ways the best treatment for Crohn’s disease (CD) is diet. This can lead to long remissions without the risk of the side effects produced by so many drugs and may reduce the need for surgery. However the diet varies from one patient to another and must be tailored to each individual carefully and conscientiously under the supervision of a qualified dietitian. 

How do diets work?

Food residues which have not been digested and absorbed in the small intestine pass down into the lower bowel and are fermented by the bacteria that live there. It is believed that an immune reaction against the bacteria living in the bowel is a very important factor in the cause of CD and that the activity of these bacteria can be modulated by diet. Diet does not work in Ulcerative Colitis (UC), probably because the bacteria involved rely not on food residues but on substances which naturally occur in the bowel, such as mucus, for their energy requirements.

The reaction to foods is quite different to allergy where special antibodies are circulating in the blood. This means that skin prick and blood tests for allergy are of no help in deciding which foods need to be avoided, and medication which may help allergic reactions such as anti-histamines are of no value in preventing foods causing difficulty in CD.

How is a diet for Crohn’s disease constructed?

There are 3 stages in dietary treatment: 

1. The patient stops eating normal food stuffs and is given a liquid feed as the sole source of nutrition. Symptoms normally disappear after 2-3 weeks. This is discussed in further detail in the following section ‘Which dietary treatment should I choose?
2. When all symptoms have cleared normal foods are reintroduced to see which ones cause symptoms and which ones may be eaten without difficulty. Those provoking symptoms are subsequently excluded.
3. When all foods have been reintroduced those irritating the bowel are tried again to make certain they genuinely cause difficulties and the dietitian checks the resulting diet to make sure it is nutritionally adequate and advises on any supplements needed.

Advantages of diet

The development of CD is a cascade starting with the bacteria in the lumen of the bowel, which lead to the triggering of complex inflammatory reactions in the gut wall and tissues beyond. Diet targets the inflammatory cycle at the very beginning, thus can be more effective than treatments such as corticosteroids or Infliximab, which interrupt the inflammatory cascade at a lower level. 

Furthermore, the patient has control over the disease and its treatment. If mild relapses occur they can be controlled quickly without medical intervention. Patients understand how to avoid running into difficulties at times of holidays, celebrations and other major events when they particularly wish to be well. 

Diet allows long remissions of CD. Once the process of food testing is complete it is unusual for patients to relapse. After a year of successful dietary treatment most patients remain completely well and find after 5-10 years their diet has returned to normal, CD having apparently burnt itself out completely. 

The diet does not have the side effects associated with drug treatment. In particular there is a very much reduced risk of osteoporosis. In a study of 95 female patients treated by steroids, diet or mainly by surgery, it was found that the diet group’s bone density was similar to that of age matched normal controls, whereas it was significantly reduced in those treated mainly by steroids.

For female patients it is important to know that patients treated by diet can expect to experience a pregnancy comparable to that of a woman who does not have CD.