Promoting Gastrointestinal Health and Decreasing Inflammation with Whole Grains in Comparison to Fruit and Vegetables through Clinical Interventions and in vitro Tests

The incidence of metabolic syndrome and its side effects are increasing throughout the world. Diet plays a key role in reducing the risk of metabolic syndrome, possibly mediated by metabolic activity of the gut microbiota. Whole grains (WG) and fruits and vegetables (FV) are two food groups that are commonly promoted for their ability to reduce the risk of metabolic syndrome. However, these two food groups provide vastly different nutrients that likely impact health via different mechanisms. Therefore, the primary objective of this research was to determine the impact of consuming recommended amounts of whole grains and fruit and vegetables against a background of their typical diet on inflammatory makers and gut microbiota composition in overweight or obese individuals that have low intakes of these food groups. The WG treatment significantly reduced tumor necrosis factor and lipopolysaccharide binding protein (TNF-α and LBP), while the FV treatment reduced IL-6 and LBP. Both treatments induced individualized changes in microbiota composition, with the FV treatment causing a significant increase in α-diversity. Thus, WG and FV both have the capability of decreasing inflammation associated with metabolic syndrome, but by different mechanisms. A follow-up in vitro study was performed using the fecal microbiota collected from subjects in the WG and refined grain (control) treatment groups to gain insight into changes in metabolic activity of the microbiota that may help explain the reduction in inflammatory markers identified in the feeding trial. Microbiota collected at the end of the WG intervention tended to increase the fermentation of carbohydrates from WG compared with before the intervention. Correlation analysis suggested that changes in Corpococcus may be related to increased short chain fatty acids production by the microbiota and subsequent reduction in inflammatory markers. Thus, this in vitro approach enabled possible insight into the relationship between WG intake, changes in the gut microbiota, and reduced inflammation. Advisor: Devin Ros