MUC5AC and irritable bowel syndrome: Abnormal bile acid metabolism with increased fecal primary bile acids or idiopathic bile acid malabsorption (BAM) has been reported in about 30% of patients with IBS-D.226–228 These patients have a significantly faster colonic transit and an altered microbiome with decreased dihydroxylation capacity and sulfatases that distinguish them from other IBS patients.199,200,228 They also present with an upregulation of barrier, immune, and inflammatory markers in the colon, as well as a loss of mucin, pointing toward the detergent and proinflammatory effects of bile acids.228