Nutritional considerations in Crohn's Disease 
OBJECTIVE:  NUTRITION n°62 (March 2002) 
By Prof. Jacques Cosnes 
Hôpital Rothschild, Paris 
 
Of unknown cause, Crohn's disease can result in major nutritional adverse effects. Indeed, artificial nutrition has an immediate beneficial effect but does not affect the long-term progression of this disease. Currently, no avoidance or supplementation diet, effective in Crohn's disease is known. Thus, the practitioner's primary objective, during acute episodes of this disease, is to provide adequate protein caloric intake to prevent malnutrition and the development of dangerous or unreasonable eating patterns. 
 
Crohn's disease is a chronic inflammatory disorder of the gastro-intestinal tract, which most often involves the intestines and whose etiology is unknown. It especially affects young adults, predominantly women. About 60,000 people in France suffer from it. The disease can have major nutritional adverse effects. Its particula r nature is that it is apparently worsened or maintained by oral feeding. And yet, for many years, priority was assigned to treating it with artificial nutrition. The development of new, especially effective anti-inflammatory compounds has somewhat produced major changes in therapeutic indications, but the treatment of its nutritional complications continues to be a topic of current interest. 
 

 
 
Malnutrition in Crohn's disease 
 
The occurrence of an acute episode of this disorder produces rapid adverse effects on the subjects nutritional status, by a decrease in dietary intake (anorexia or eating fear, with symptoms being exacerbated during the post-prandial period), an increase in energy consumption and exudative enteropathy (protein-losing enteropathy). In addition, accelerated protein turnover and increased energy consumption at rest are observed, all the more pronounced when the acute episode is complicated by fever and systemic reactions. In case of a severe episode, protein exudation and hemorrhagic oozing from intestinal ulcerations become dominant and rapidly impact protein metabolism with onset of anemia as with extensive burning (Figure 1). 
 
These acute episodes mainly result in weight loss with a decrease in lean body mass and internal organ proteins. A decrease in serum albumin is a good marker of the severity of gastro-intestinal involvement. 
Outside of acute episodes, protein-energy malnutrition (PEM) is rare. Indeed, a young subject with recent onset of the disease has a sub-normal basic nutritional status and recovers quickly; only a reduction in adipose tissues persists in the aftermath of an acute episode. This is not always the case for an older subject, especially in the following cases: if he has a long-standing disease, follows a restrictive diet, is often treated by steroids and underwent mutilating surgery. 
 
Artificial nutrition 
 
Since the 1970s, replacement of oral feeding by artificial intravenous (parenteral) or liquid enteral nutrition has been demonstrated to make control of acute episodes of Crohn's disease possible. These results have been confirmed by many controlled studies: today, artificial nutrition is considered as an integral part of the treatment of acute episodes of Crohn's Disease, to the same extent as steroid therapy. The effect observed is not only symptomatic (decrease of pain and diarrhea): regression of systemic manifestations and inflammatory syndrome, restoration of intestinal permeability, and an improvement or even healing of intestinal ulcerations. Results obtained with parenteral or enteral nutrition are quite similar, with two minor differences. Parenteral nutrition may perhaps have a faster and more pronounced effect on symptoms, which makes it preferable for treatment of patients with a severe episode. The constraints associated with enteral nutrition (feeding tube, noise of the pump, cessation of all oral feeding) are not always well accepted and up to 40 % of patients abandon such treatment prematurely. Unfortunately, the effectiveness of artificial nutrition is of short duration : the acute episode is controlled but the resumption of normal oral feeding is inevitably followed by a progressive resumption of the disease after a few months, especially in the case of chronic active, steroid-dependent Crohn's disease. 
 
Mechanisms and indications of artificial nutrition 
 
The underlying mechanisms of effectiveness of artificial nutrition are unknown. It can be suggested that giving the gastro-intestinal tract a rest is an essential element. But it is not the only one; the improvement of the patient's nutritional status undoubtedly also plays an important role. The response of Crohn's Disease lesions to artificial nutrition is probably little specific: the interruption (or decrease) in the endoluminal flow in the diseased areas may decrease the food and bacteria-related local immunological stimulation and the release of cytokines (in particular TNFα, IL₂ and interferon γ), while the nutritional improvement may improve tissue repair, shifting the disease process from inflammation to healing. This tentative conclusion does not cast doubt on the usefulness of artificial nutrition but has contributed to stemming the initial enthusiasm of clinical researchers. 
Artificial nutrition is effective especially in steroid-resistant forms of the disease, if no extra-parietal complications are present. Currently the same result may be obtained with a single infusion of Infliximab (anti-TNFα) which is very quickly effective in these forms of the disease. Immunosuppressive agents, for their part, remarkably improve steroid-dependent forms. Thus, artificial nutrition continues to be used in case of rejection or contraindication of immunosuppressive agent use, or if the objective is to exhaust the chances of medical therapy before having recourse to it. In young subjects, enteral nutrition, as first line therapy, may be used to replace steroid therapy, which often is poorly accepted because of its associated cosmetic complications. Nevertheless, their incidence tends to decrease with the use of mainly topically active steroids such as budesonide. 
The nutritional indications, strictly speaking, of artificial nutrition have become rare. Isolated malnutrition can be the consequence of a subacute chronic progression, of a dietary restriction in case of upper, in particular stenotic involvement, or a concomitant disorder (substance abuse, eating disorders). Usually malnutrition responds dramatically to night-time cyclical enteral nutrition continued in the patient's home, in addition to oral feeding. In children, the broad use of immunosuppressive agents tends to limit indications of enteral nutrition, even though its effects on growth are remarkable. 
 
Dietary considerations and Crohn's Disease 
 
The success of artificial nutrition and especially of the elementary diet, have led to the development of various diets whose efficacy has currently not been demonstrated (see insert 1). 
This does not mean that there are no dietary indications for Crohn's Disease. In case of severe acute colitis, intake of fiber should be limited to improve the patient's comfort. If stenosis of the small intestine is present, all foods which may form plugs will be banned (such as coconuts, leeks or peanuts). Outside of severe episodes, a residue-free regimen should not be indicated: the physician can simply advise the patient to limit intake of "hard" fibers (salads and cruciferous). In case of cessation of smoking, (this is the most effective lifestyle change by far for this disease), a low calorie diet sometimes is necessary to limit weight gain. Generally speaking, unauthorized foods will be limited, with the primary objective being to ensure long term protein energy intake which is adequate to prevent malnutrition. Lastly, salt intake should be restricted only in case of steroid therapy with Prednisone, at high dosage and for long term use, and only in this context. 
 
Conclusion 
 
Malnutrition is a complication of severe episodes of Crohn's Disease. Artificial nutrition and the discontinuation of oral feeding have an immediate beneficial effect. Nevertheless in the long term, daily feeding may have some effect on the course of this disease. In spite of many studies, the nature of these dietary factors, i.e., beneficial or harmful, is not known. The physician's role, above all, should be to prevent the development of dangerous or unreasonable patterns of eating behavior.

 
Pr. Jacques COSNES 
Hôpital Rothschild, Paris

 
 
REFERENCES 
 
Carbonnel F, Cosnes J. Thérapeutiques nutritionnelles dans les maladies inflammatoires chroniques de l'intestin: Bilan et perspectives. Gastroenterol Clin Biol. 1999 ; 23 (supplt) : B195-9 
Griffiths AM, Ohlsson A, Sherman PM, Sutherland LR. Meta-analysis of enteral nutrition as a primary treatment of active Crohn's disease. Gastroenterology 1995 ; 108 : 1056-1067 
Kelly DG, Fleming CR. Nutritional considerations in inflammatory bowel diseases. Gastroenterol Clin N Amer 1995 ; 24 : 597-611. 
King TS, Woolner JT, Hunter JO. Review article: the dietary management of Crohn's disease. Aliment Pharmacol Ther 1997 ; 11 : 17-31. 
 
Insert 1.

 
Insert 2.

 
 
Figure 1: the main ideological factors of malnutrition in Crohn's Disease