Effects of Dietary Fat on Resistant Starch Fermentation in Mice

Previous studies have demonstrated health benefits of resistant starch fermentation in rodents, with some evidence that a high fat diet may reduce this fermentation. In a current study, 39 mature male C57Bl/6 mice were fed 4 diets (n=9–10): high fat resistant starch (HFRS), low fat resistant starch (LFRS), high fat energy control (HFEC), and low fat energy control (LFEC) for 13 weeks. The mice were fed a purified Western diet for 7 weeks prior to the treatment diets to induce obesity. A 2×2 factorial design with diet type (RS and EC) and diet fat level (HF and LF) was used and results were considered significant at p< 0.05. Fermentation was indicated by the weight of the empty cecum and was significantly affected by diet type (RS greater than EC), but not by fat level. Both diet type and fat level had a significant effect on weight of cecum contents, with an interaction between diet type and fat level, with values lower for HFRS than LFRS. An assay was performed to determine amount of RS present in the cecum contents. Diet type had a significant effect, and fat level and interaction approached significance at p=0.09. Results indicate that while fermentation occurred in both HFRS and LFRS mice, the weight of cecal contents was significantly lower, and the amount of RS in cecal contents was numerically less in HFRS mice. It appears that more RS was digested in the small intestine of mice fed the HF diet. Funding: LSU AgCenter and National Starch.