In an open-label study of 29 men, including patients with ulcerative colitis and Crohn’s disease in remission, 6 g per day of curcumin for eight weeks led to modest, transient shifts in gut microbiota composition without sustained restructuring. Despite achieving high fecal concentrations and minimal systemic bioavailability, curcumin did not produce durable microbiome changes, and disease activity scores remained stable.