Effects of oat phenolic acids and avenanthramides on gut microbiota

High consumption of wholegrains is related to positive health effects, including reduced risk of cardiovascular disease. Oat β-glucans have been considered to be partly responsible for these effects; furthermore, dietary phenolic acids and avenanthramides, are natural phenolic components in oats, which may also contribute to health benefits, whilst mechanisms for these effects remain unclear. Dietary components are well known to impact on the gut microbiome (GM), this consortium of bacteria are becoming increasingly associated with health effects, as such some of the health effects attributed by oats could be driven by the microbiota. This thesis investigates the potential interaction between of the gut microbiota, β-glucans, polyphenols and oats, to explore if this is a potential route for positive health outcomes. In vitro batch culture fermentations identified oats as a food matrix that significantly increased the abundance of Proteobacteria and Bacteroidetes, the lower dose resulted a bifidogenic effect and influenced microbial production of short chain fatty acids (SCFA). This is mediated by the synergy of all oat compounds within the complex food matrix, rather than its main bioactive β-glucan or polyphenols. During in vitro microbial fermentation, bound phenolic fractions largely remained intact up to 4h, following a significant increase in total free phenolic metabolites at 24 h and reached the same levels as control, pure free phenolic acids of microbial metabolites. 28 healthy adults enrolled on a randomised cross-over trial with three 4-week dietary intervention periods, comprising of a high (68.1 mg of phenolic acids) or moderate (38.9 mg of phenolic acids) avenanthramide and phenolic acid rich-wholegrain oat diet, or fibre matched control diet. The high avenanthramides and phenolic acids rich-wholegrain oat diet significantly increased the relative abundance of Proteobacteria phyla and Sutterella genus, without the alteration of the serum inflammatory markers. These data suggest that daily consumption of oats may beneficially modificate of the microbiota and metabolic activity.