Effect of curcumin on the gut microbiota of patients with ulcerative colitis, Crohn’s disease and healthy participants

Curcumin exhibits anti-inflammatory properties, but clinical evidence is limited, in part because of its low systemic bioavailability. Nevertheless, its limited absorption may favor local activity in the gut, where it could influence inflammatory bowel disease via microbiota modulation. This study assesses the impact of curcumin on gut microbiota diversity, as well as clinical and biochemical parameters in patients with ulcerative colitis, and Crohn’s disease in remission and healthy individuals. In a single-center, open-label, single-arm study, 29 male participants aged 18–65 were included. Participants received 3 g of curcumin twice daily for 8 weeks. Blood, urine, and fecal samples were collected at baseline, 4 weeks, and 8 weeks. Clinical and biochemical parameters, along with curcumin plasma, urine, and fecal concentrations, were assessed. Microbiome diversity was analysed using 16 S rRNA amplicon sequencing. The study was registered in the Dutch Clinical Trial Register with ID NL8770. Twenty-nine participants completed the study. Curcumin was well tolerated with stable clinical scores (SSCAI ≤ 2, HBI ≤ 5). Plasma levels were near the lower limit of quantification, while fecal levels were markedly higher. No significant changes in alpha-diversity were found. A temporary shift in beta-diversity appeared at 4 weeks but reversed by week 8. Curcumin caused only transient microbiota changes and slight alterations in taxa abundance, suggesting limited potential for sustained microbiota modulation in IBD management. Clinical trial registration: The study was registered in the Dutch Clinical Trial Register with ID NL8770.