Fibre and enteral nutrition

Clinical experience during the last decade has confirmed that enteral nutrition is an efficient and cost effective means of providing nutritional support to patients with normal or near normal gastrointestinal function.' Before and during this period the knowledge gained of the processes involved in the physiology of nutrient absorption has been applied to the formulation of enteral diets and if comparisons are made of the composition of present day diets with those used 10 to 15 years ago several differences can be seen. These relate mainly to the nitrogen and energy concentrations of polymeric diets and the sources of nitrogen and energy and electrolyte compositions of predigested chemically defined elemental diets.2 Until recently all the commercially produced liquid enteral diets continued to have one thing in common, namely that they contained a low 'residue' or 'fibre' content. Historically it must be remembered that the very earliest low residue enteral diets were specifically designed not only to provide balanced nutrition to astronauts in space but also to reduce their stool weight and stool frequency.3 Subsequently it was realised that one clinical advantage of low residue diets was that they had a low viscosity and could be administered easily through 'fine bore' nasogastric or nasoenteric feeding tubes. Furthermore as it became clear that there could even be a number of therapeutic advantages in administering low residue diets4 their widespread use became accepted without question. Although the 1970s and early 1980s has been the time when advances have been achieved in the field of enteral nutrition the same period has seen also significant advances in the field of fibre research and as a consequence there has developed a belief that many of the diseases of Western civilisation such as atherosclerosis, obesity, appendicitis, constipation, irritable bowel syndrome, colon cancer, diverticular disease, diabetes mellitus, and gall stones were related to a deficiency in dietary fibre and that supplementing the diet with fibre would prevent and might even cure these conditions.5 Although not all recent studies6 have been in complete agreement the observations made by Heaton and colleagues over 10 years ago78 that ingestion of bran accelerated slow intestinal transit and delayed rapid intestinal transit lead to suggestions that the ingestion of fibre produces a more regular bowel habit.9 Based largely on this premise, as well as on the above doctrine that dietary fibre is good overall, suggestions are beginning to be made that there could be benefits to supplementing commercially produced liquid enteral diets with fibre. This article seeks to critically examine the premises on which the proposed use of fibre supplemented enteral diets are based. In the ensuing text, attempts have been made to determine whether there is any substantive evidence to support the use of fibre supplemented enteral diets clinically. Finally, potential areas of interest requiring further research have been highlighted. A proper understanding of the potential applications of fibre to