Abstract/Summary

Dietary intake of resistant dextrin may alter gut microbial composition, appetite regulation, glucose homeostasis, and anthropometric measures. To date, much of the research has been conducted on overweight Asian individuals and there is a lack of information on the in vitro and in vivo effects in Western populations. The research presented in this PhD thesis consists of an in vitro, pilot, and human intervention study. The in vitro study utilised a three-stage gut model system, to which 14g/day resistant dextrin, NUTRIOSE® FB0G, was administered for 18 days. The pilot study was undertaken to determine feasibility, and optimise methods, for the main human intervention study. In the main human intervention study, 36 normal weight or overweight participants consumed 14g/day of NUTRIOSE® FB0G or control for 28 days in a crossover design. Resistant dextrin increased total bacteria, Clostridium cluster XIVa, Roseburia genus, and short chain fatty acid production in the gut model system (P<O.Ol). In vivo, resistant dextrin intake increased faecal Clostridium cluster IX (P=O.OOl) and propionate (P=O.049), in both normal weight and overweight individuals, and increased ß-glucosidase activity in normal weight participants (P=O.OOl). Resistant dextrin intake increased fasting satiety ratings (P=O.036), and responses to a morning preload, but resulted in a transient reduction following lunch and evening meals (P<O.05). Moreover, glucose and glucose-dependent insulinotropic peptide (GIP) responses to a morning preload were reduced (P<O.05). Effects on satiety were found in normal weight but not overweight participants. No differences in energy intake or body composition were found, however, resistant dextrin intake lowered systolic blood pressure in normal weight participants (P=O.030). In conclusion, resistant dextrin favourably modified gut microbiology, including elevated propionate production in vitro, and in normal weight and overweight humans. Furthermore, resistant dextrin intake altered satiety, glucose and hormone responses in vivo, however, specific effects differed between BMI groups.