Review article: nutrition and adult inflammatory bowel disease

Major advances in the understanding of the aetio-pathogenesis and genetics of inflammatory bowel disease have been accompanied by an escalation in the sophistication of immunomodulatory inflammatory bowel disease therapeutics. However, the basic 'triple' therapy (5-aminosalicylates, corticosteroids, azathioprine) and nutrition have maintained their central role in the management of patients with inflammatory bowel disease over recent decades. This review provides an overview of the supportive and therapeutic perspectives of nutrition in adult inflammatory bowel disease. The objective of supportive nutrition is to correct malnutrition in terms of calorie intake or specific macro- or micronutrients. Of particular clinical relevance is deficiency in calcium, vitamin D, folate, vitamin B12 and zinc. There is justifiably a growing sense of unease amongst clinicians and patients with regard to the long-term use of corticosteroids in inflammatory bowel disease. This, rather than arguments about efficacy, should be the catalyst for revisiting the use of enteral nutrition as primary treatment in Crohn's disease. Treatment failure is usually related to a failure to comply with enteral nutrition. Potential factors that militate against successful completion of enteral nutrition are feed palatability, inability to stay on a solid-free diet for weeks, social inconvenience and transient feed-related adverse reactions. Actions that can be taken to improve treatment outcome include the provision of good support from dietitians and clinicians for the duration of treatment and the subsequent 'weaning' period. There is evidence to support a gradual return to a normal diet through exclusion-re-introduction or other dietary regimen following the completion of enteral nutrition to increase remission rates. We also review the evidence for emerging therapies, such as glutamine, growth factors and short-chain fatty acids. The future may see the evolution of enteral nutrition into an important therapeutic strategy, and the design of a 'Crohn's disease-specific formulation' that is individually tailored, acceptable to patients, cost-effective, free from adverse side-effects and combines enteral nutrition with novel pre- and pro-biotics and other factors.