The purpose of this project was to determine the impact of β-glucan on the composition of gut microbiota in mildly hypercholesterolemic individuals and to identify if the altered microbiota are associated with bioactivity of β-glucan in improving risk factors of cardiovascular disease (CVD). Using a randomized, controlled crossover study design, individuals received for 5 wk either a treatment breakfast containing 3g high molecular weight (HMW), 3g low molecular weight (LMW), 5g LMW barley β-glucan or wheat and rice (WR). The American Heart Association (AHA) diet served as the background diet for all treatment groups. Phases were separated by 4 wk washout periods. Fecal samples were collected at the end of each intervention phase and subjected to Illumina sequencing of 16S rRNA genes.