Pearson T, et al. - In view of the previous reports suggesting the efficacy of ursodeoxycholic acid (UDCA), a therapeutic bile acid, in reducing the risk for advanced colorectal adenoma in men but not women, researchers sought to validate if the gut microbiome interact with fecal bile acid composition as a factor in colorectal cancer neoplasia. Researchers analyzed banked stool samples collected as part of a phase III randomized clinical trial of UDCA for the prevention of colorectal adenomatous polyps to compare change in the microbiome composition after a 3-year intervention in a subset of participants randomized to oral UDCA at 8-10 mg/kg of body weight per day (n = 198) or placebo (n = 203). Outcomes suggest modest influences of daily UDCA use on the relative abundance of microbial species in stool. The microbial network composition was affected in a way that suggested sex-specific effects of UDCA on stool microbial community composition as a modifier of colorectal adenoma risk.