Potential water-holding capacity and short-chain fatty acid production from purified fiber sources in a fecal incubation system.

Liquid enteral diets supplemented with dietary fiber, typically soy fiber, are in widespread use to increase stool bulking and maintain gastrointestinal function. Yeast cells, containing beta-glucans, represent another commercially available fiber source that could be added to enteral diets. The objective of this study was to compare commercially available purified fiber sources, i.e., mixed fiber (Fibrad), psyllium hydrocolloid (Metamucil), and yeast cell walls (Fibercel), for potential use in liquid diets in terms of potential water-holding capacity (PWHC) and SCFA production (mmol SCFA/g organic matter [OM]). Fiber samples were fermented in vitro with human fecal microbiota from three donors for 24 h, and SCFA production was greatest from beta-glucan (8.24 mmol/g OM), followed by psyllium (5.57 mmol/g OM) and mixed fiber (4.50 mmol/g OM) (p less than 0.0001). WHCs of the original materials (g H2O/g OM) differed (p less than 0.02) at 4.59, 5.79, and 8.63 for beta-glucan, mixed fiber, and psyllium, respectively. PWHC (g H2O/g OM), an in vitro measure of stool bulking, differed (p less than 0.0001) with psyllium (4.48) greater than mixed fiber (3.52) greater than beta-glucan (2.22). These three fiber systems appear to have distinctly different physiological effects in vivo. Of the three products, mixed fiber was the most inert. Psyllium seems to enhance both SCFA production and stool bulk relative to mixed fiber, whereas beta-glucan most significantly increases SCFA production with a minimal effect on stool bulk.