[Diet therapy in chronic inflammatory bowel disease: results from meta-analysis and randomized controlled trials]

Crohn's disease and ulcerative colitis are chronic inflammatory bowel diseases of unknown etiology. Unspecific immunosuppressive therapy represents current standard treatment and is often associated with severe side effects. Several treatment regimens have been evaluated to identify alternative therapeutic options. Among these different diet therapies were investigated. Objective of this paper is to review the results of diet therapy in chronic inflammatory bowel disease on the basis of randomised controlled trials and meta-analysis of randomised controlled trials.

Medline and Cochrane Library were searched for meta-analysis and randomised controlled trials investigating this question. Additionally reference lists of identified articles and text books were checked for further trials.

Four meta-analyses investigated the treatment of acute Crohn's disease with elemental-, semi-elemental-, and polymeric diets in comparison to corticosteroids or to another form of enteral diet. All meta-analyses show a superiority of corticosteroids and no difference in the effect of the compared enteral diets. Randomised controlled trials investigating diet therapy in ulcerative colitis have not been summarised in a meta-analysis yet. Eleven randomised trials were identified which evaluated diets in ulcerative colitis patients: Dietary supplementation with n-3-fatty acids (6 trials), elemental diet [2], dietary supplementation with dietary fiber [1], elimination diet [1], and dietary supplementation with olestra [1]. Only for the elimination diet a significant positive effect on the course of disease was found in one trial which investigated only 18 patients.

Enteral nutritional therapy of acute Crohn's disease is less effective than treatment with corticosteroids. In case of severe steroid induced side effects diet treatment can present a promising alternative. Superiority of one of the investigated different formulations was not found. Meta-analyses of randomised trials provide a clear and easy to understand presentation of the effect of this intervention. Eleven published trials investigating the effect of diets in ulcerative colitis show only for elimination diet a positive treatment effect. The trials do find a positive effect of one of the other interventions but the trials are very small and cannot exclude a treatment effect. Meta-analysis of these trials would be helpful for a better presentation and understanding of these results.