• S A Kapadia, A H Raimundo, G K Grimble, P Aimer, and D B Silk.
• Department of Gastroenterology and Nutrition, Central Middlesex Hospital, London.
• Jpen Parenter Enter. 1995 Jan 1; 19 (1): 63-8.

BackgroundDietary fiber is known to influence bowel habit and gastrointestinal mucosal cell morphology and function. large-bowel function is particularly influenced by insoluble, poorly fermentable fiber sources, whereas mucosal function is affected by fiber sources that are soluble and highly fermentable. The aim of the present study was to compare bowel function during consumption of a self-selected diet, a fiber-free enteral diet, and three polymeric enteral diets, each supplemented with a fiber with different fermentation characteristics. The fiber sources used were oat, soy oligosaccharide, and soy polysaccharide.MethodsSeven healthy subjects consumed four diets in random order for 4 to 7 days. These were a self-selected diet, a 2-L polymeric enteral diet, and a 2-L polymeric enteral diet supplemented with 15 g of total dietary fiber per liter derived from either soy oligosaccharide fiber (75 g/L) or oat fiber (15 g/L). An additional six healthy subjects were randomly assigned to three diets (4 to 7 days): a self-selected diet, a 2-L polymeric enteral diet, or the same 2-L polymeric enteral diet supplemented with 20 g of soy polysaccharide fiber per liter (15 g of total dietary fiber per liter). Bowel function was assessed by measuring whole-gut transit time, mean daily stool wet weights, and bowel movement frequency per day. Fermentation characteristics of the different fiber sources were determined quantitatively and qualitatively by measuring short-chain fatty acids produced during in vitro stool culture.ResultsTotal short-chain fatty acid and butyric acid production with soy oligosaccharide fiber were significantly higher compared with values observed for soy polysaccharide fiber (p < .003), oat fiber (p < .005), and self-selected (control) diet (p < .003). Compared with the fiber-free diet, consumption of the soy polysaccharide, oat, and soy oligosaccharide-fiber-supplemented enteral diets did not significantly (p > .05) alter whole-gut transit time or stool wet weight. However, bowel frequency was significantly improved by consumption of the soy polysaccharide-fiber-supplemented diet but not the oat fiber or soy oligosaccharide-fiber-supplemented diets.ConclusionCompared with a fiber-free polymeric enteral diet, the daily consumption of an enteral diet supplemented with 30 g of total dietary fiber per day derived from a poorly fermentable oat fiber, a highly fermentable soy oligosaccharide fiber, or a moderately fermentable soy polysaccharide fiber has little impact, if any, on bowel function.

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