A high fat diet attenuates fermentation effects of resistant starches and fructans

Abstract

In our previous studies, ingestion of prebiotics in low fat diets resulted in decreased cecal pH from 8 to about 6 and increases in short chain fatty acids indicating robust fermentation. However, in some preliminary studies this effect on fermentation was not seen when rodents were obese and/or fed a high-fat diet. This comprehensive high-fat diet study was conducted to determine which sources and combinations of prebiotics would enhance fermentation despite a high dietary fat content. The effects of prebiotics in a high-fat diet (44% energy) on pH, cecal weights, abdominal fat, and body weight were studied in mature male C57Bl/6 mice fed one of 9 diets of similar energy (4.0 ± 0.2 kcal/g) for 12 weeks. A control (C) diet was compared to 4 prebiotics: Hi-Maize® RS2 (R), Novelose® RS3 (N), Nutraflora® fructooligosaccharide (F), BENEO-Orafti HP gel® inulin (I), which were fed individually and combined (F+I, R+F, R+I, and R+N). Results were significant at p<0.05. Fermentation, indicated by lower pH values, occurred with all F and I diets and combination diets. However, none of the groups had reduced abdominal fat compared to control as has been observed in previous studies with consumption of RS in low fat diets. All prebiotic diets had larger empty ceca, but only F and I had greater full ceca than the RS groups. It is proposed that diets with high concentrations of fat affect monogastric fermentation and microbial populations in a manner similar to ruminants. It is possible that the beneficial health effects of prebiotic ingestion may be most effective if consumed with a low-fat diet.