Increasing the Impact of Dietary Fiber from Grains on Human Health through Gut Microbiome

The relationship between dietary fiber intake and human health has gained significant attention due to its potential in preventing chronic diseases and promoting gut health. Grains are a primary source of dietary fiber; however, the health impact of grain fibers is often limited because they are incompletely metabolized by gut bacteria. This dissertation explores innovative strategies to enhance the concentration and of dietary fiber from grains and its utilization by gut bacteria. By investigating various treatments, this research aims to maximize the health benefits of grain-derived dietary fibers, thereby contributing to a healthier society. This dissertation is organized into four chapters. Chapter 1 presents an overview of the current methods to increase dietary fiber content in the diet, emphasizing the importance of dietary fibers in promoting gut health and practical strategies to integrate more dietary fiber into daily diets. Chapter 2 investigates the effect of alkali treatment on maize bran, specifically its influence on the fermentability of arabinoxylan by the human gut microbiota. While alkali treatment increased the solubility and fermentability of arabinoxylan, it also negatively impacted the utilization of insoluble arabinoxylan and non-digestible carbohydrates, reducing butyrate production due to declines in Butyricicoccus and some Lachnospiraceae. Chapter 3 examines the role of phenolic compounds in dietary fiber utilization by gut microbiota. The results suggest that the impact of phenolic compounds on dietary fiber utilization varies depending on the solubility of the fiber; certain levels of phenolics can enhance microbial fermentation, while higher concentrations may inhibit it. Chapter 4 focuses on the impact of high-fiber wheat varieties on the gut microbiota, showing that both insoluble and soluble wheat fibers are strongly propiogenic, but impart different effects on the gut microbiota depending on source. Overall, this dissertation advances our understanding of how targeted treatments and breeding can enhance the fermentation of dietary fibers from grains. Advisor: Devin J. Rose