HORIZONS IN NUTRITION
CSNS
LA NUTRITION DE DEMAIN
N
Canadian Society for Nutritional Sciences/La Societe Canadienne des Sciences de la Nutrition SCSN
Liquid formula diets: Does fibre make a difference? Alison M. Stephen, PhD
D iarrhea occurs in up to 25% of patients receiving enteral nutrition.' Why it occurs is not clear, but large volumes or high osmotic loads and concomitant antibiotic therapy may be factors.' Frank and Green2 reported the first use of fibre in enteral feeds in 1979. They successfully used the bulk laxative Metamucil (psyllium hydrophilic mucilloid) to eliminate diarrhea in critically burned patients.2 Since then, inclusion of fibre has become increasingly popular. Several enteral feeding products are available in Canada, each having as its fibre source soy polysaccharide, which, unlike Metamucil, does not clog the narrow-bore tubes used for enteral feeding. The daily dose of fibre (18 to 25 g/ 1800 mL) is considerably higher than the typical Canadian intake (12 to 15 g/d) but in keeping with that recommended for good health. The rationale for using fibre in enteral feeds is based on recent knowledge about fermentation of fibre in the large intestine, with the production of short-chain fatty acids (SCFA), particularly acetate, propionate and butyrate. Acetate and propionate are readily absorbed from the colon, along with water and sodium, in a concentration-dependent process. However, butyrate is not absorbed; it is used by the colonic mucosa as a fuel, preferred even to glucose. Butyrate helps maintain and restore mucosal integrity, and colonic irrigation of SCFA has recently been shown to be beneficial in colitis.3 Thus, the antidiarrheal effect of added fibre in enteral feeds is thought to be due to the increased water and sodium absorption plus the enhanced repair and maintenance of the colonic mucosa. The extent of fibre fermentation in the human colon is not yet well studied, partly because methods for analysing fibre are inadequate and because the
studies take a long time and require controlled diets and complete collections of feces. However, soluble types of fibre are more readily fermented than insoluble. The soy polysaccharide in most enteral feeds consists mainly of insoluble fibre; this may facilitate delivery but limit effectiveness.4 Few well-controlled studies of fibre in enteral feeds have been conducted; so far, no significant effects on fecal weight have been observed.5 There have not yet been any investigations of SCFA production or fibre fermentation in humans to support the antidiarrheal hypothesis. As well, little is known about possible negative effects - such as impairment of absorption of minerals, vitamins or medications - of this amount of fibre received daily by tube-fed patients. Clearly, further studies are needed to justify the widespread use of fibre in enteral feeds. Although preliminary trials are promising, studies must determine the optimum dose and type of fibre, the expected effectiveness in controlling diarrhea, and the time required to achieve control.
References 1. Silk DBA: Fibre and enteral nutrition. Gut 1989; 30: 246-264 2. Frank HA, Green LC: Successful use of a bulk laxative to control the diarrhea of tube feeding. Scand J Plast Reconstr Surg 1979; 13: 193-194 3. Harig JM, Soergel KH, Komorowski RA et al: Treatment of diversion colitis with short-chain-fatty-acid irrigation. N Engl J Med 1989; 320: 23-29 4. Elia M: Artificial enteral nutrition. Patient profiles and the use of fiber. In Cummings JH (ed): The Role of Dietary Fiber in Enteral Nutrition, Abbott International, Abbott Park, Ill, 1989 5. Scheppach W, Burghardt W, Bartram P et al: Addition of dietary fiber to liquid formula diets: the pros and cons. JPEN 1990; 14: 204-209
This article was made possible by an educational grant to the Canadian Societyfor Nutritional Sciences (CSNS) from Clintec Nutrition Company, but the author and the content of the article were determined solely by the CSNS. The opinions expressed herein are those of the author and not necessarily those of the CSNS. Reprint requests to: Dr. Alison M. Stephen, Head, Division ofNutrition and Dietetics, College of Pharmacy, University of Saskatchewan, Saskatoon, SK 57N OWO JUNE 1,1991
CAN MED ASSOC J 1991; 144 (11)
1483
CSNS
LA NUTRITION DE DEMAIN
N
Canadian Society for Nutritional Sciences/La Societe Canadienne des Sciences de la Nutrition SCSN
Liquid formula diets: Does fibre make a difference? Alison M. Stephen, PhD
D iarrhea occurs in up to 25% of patients receiving enteral nutrition.' Why it occurs is not clear, but large volumes or high osmotic loads and concomitant antibiotic therapy may be factors.' Frank and Green2 reported the first use of fibre in enteral feeds in 1979. They successfully used the bulk laxative Metamucil (psyllium hydrophilic mucilloid) to eliminate diarrhea in critically burned patients.2 Since then, inclusion of fibre has become increasingly popular. Several enteral feeding products are available in Canada, each having as its fibre source soy polysaccharide, which, unlike Metamucil, does not clog the narrow-bore tubes used for enteral feeding. The daily dose of fibre (18 to 25 g/ 1800 mL) is considerably higher than the typical Canadian intake (12 to 15 g/d) but in keeping with that recommended for good health. The rationale for using fibre in enteral feeds is based on recent knowledge about fermentation of fibre in the large intestine, with the production of short-chain fatty acids (SCFA), particularly acetate, propionate and butyrate. Acetate and propionate are readily absorbed from the colon, along with water and sodium, in a concentration-dependent process. However, butyrate is not absorbed; it is used by the colonic mucosa as a fuel, preferred even to glucose. Butyrate helps maintain and restore mucosal integrity, and colonic irrigation of SCFA has recently been shown to be beneficial in colitis.3 Thus, the antidiarrheal effect of added fibre in enteral feeds is thought to be due to the increased water and sodium absorption plus the enhanced repair and maintenance of the colonic mucosa. The extent of fibre fermentation in the human colon is not yet well studied, partly because methods for analysing fibre are inadequate and because the
studies take a long time and require controlled diets and complete collections of feces. However, soluble types of fibre are more readily fermented than insoluble. The soy polysaccharide in most enteral feeds consists mainly of insoluble fibre; this may facilitate delivery but limit effectiveness.4 Few well-controlled studies of fibre in enteral feeds have been conducted; so far, no significant effects on fecal weight have been observed.5 There have not yet been any investigations of SCFA production or fibre fermentation in humans to support the antidiarrheal hypothesis. As well, little is known about possible negative effects - such as impairment of absorption of minerals, vitamins or medications - of this amount of fibre received daily by tube-fed patients. Clearly, further studies are needed to justify the widespread use of fibre in enteral feeds. Although preliminary trials are promising, studies must determine the optimum dose and type of fibre, the expected effectiveness in controlling diarrhea, and the time required to achieve control.
References 1. Silk DBA: Fibre and enteral nutrition. Gut 1989; 30: 246-264 2. Frank HA, Green LC: Successful use of a bulk laxative to control the diarrhea of tube feeding. Scand J Plast Reconstr Surg 1979; 13: 193-194 3. Harig JM, Soergel KH, Komorowski RA et al: Treatment of diversion colitis with short-chain-fatty-acid irrigation. N Engl J Med 1989; 320: 23-29 4. Elia M: Artificial enteral nutrition. Patient profiles and the use of fiber. In Cummings JH (ed): The Role of Dietary Fiber in Enteral Nutrition, Abbott International, Abbott Park, Ill, 1989 5. Scheppach W, Burghardt W, Bartram P et al: Addition of dietary fiber to liquid formula diets: the pros and cons. JPEN 1990; 14: 204-209
This article was made possible by an educational grant to the Canadian Societyfor Nutritional Sciences (CSNS) from Clintec Nutrition Company, but the author and the content of the article were determined solely by the CSNS. The opinions expressed herein are those of the author and not necessarily those of the CSNS. Reprint requests to: Dr. Alison M. Stephen, Head, Division ofNutrition and Dietetics, College of Pharmacy, University of Saskatchewan, Saskatoon, SK 57N OWO JUNE 1,1991
CAN MED ASSOC J 1991; 144 (11)
1483
