Dietary Fiber's Contribution to the Energy Needs of the Microbiota

Abstract

The objective of this research is to address the amount of energy resulting from the total fermentation of an oligosaccharide, resistant maltodextrin (RM), used for the growth of the microbiota (MB). The metabolizable energy (ME) of RM has been previously reported (J. Nutr. 144:1, 2014). Dietary Fiber (DF), intrinsic and intact in plant foods, and Added Fiber, isolated or modified from plant foods or chemically synthesized are now defined (FDA, 2014) as having “beneficial physiological effects for human health (BPEFHH)”. The microbiota (MB) is considered to have strong associations with BPEFHH, but evidence to confirm this association has not been established. While DF can contribute to health benefits, its quintessential properties are to promote laxation and serve as the primary energy source for the MB. However, the energy contribution of DF for MB growth is not known. A randomized placebo controlled double blind crossover study was conducted and all participants were provided all foods for replicated intakes and fed to maintain body weight. As part of the controlled diet, men (n=14) were fed, in in random order, sequence 3‐treatments, of 0 g RM and 50 g digestible dextrin (DD), 25 g RM and 25 g DD, and 50 g RM and 0 g DD. In addition to a MB analysis of feces, total MB counts were accomplished by appropriate dilution of wet fecal samples and MB stained for FISH (counts) cell counting with a light microscope. Total wet and dry fecal weights (g), increased with 25g RM (148,32‐NS) and 50g RM (161,39‐P ≤0.02) compared to the control treatment, 0g RM (118,27), respectively. Total MB counts in wet fecal samples, in counts per g for 0, 25 and 50 g RM/day were 8.6a, 10.1a,b and 10.3b × 109, and for the total feces, total MB counts would be 1.0, 1.5 and 1.2 × 1012, respectively. The ME values for RM fed 25g and 50g/d were 8.2 kJ and 10.4 kJ levels, and net energy (NE) values were 8.2 kJ and 2.0 kJ/g, respectively. It is suggested that totally fermentable DF even in diets currently providing 18–20 g total DF/d, provide approximately 5 to 7 kJ/g for MB growth. Increased total MB in wet fecal weight, increased mass, and with increased MB concentration per g feces is considered as contributing to DF ability to improve BPEFHH, and initially via better laxation.Support or Funding InformationSupport, Matsutani, Co, LTD, USDA, ARS