Sucralose and the Gut-Immune Axis: Emerging Evidence Linking Dysbiosis, Barrier Alterations, and Implications for Colitis and Colorectal Cancer Immunotherapy

Sucralose is one of the most widely used non-nutritive sweeteners and has long been considered metabolically inert and safe within established acceptable daily intake levels. However, emerging evidence suggests that chronic exposure to sucralose may alter gut microbial composition, epithelial barrier function, mucosal inflammation, and immune responses. This review examines current experimental and clinical evidence on the effects of sucralose on the gut-immune axis, with particular attention to its potential implications for colitis and colorectal cancer (CRC). Preclinical studies indicate that sucralose may reduce beneficial short-chain fatty acid-producing taxa, alter microbial metabolic pathways, disrupt epithelial barrier-related molecules, and promote inflammatory and immune changes associated with colitis severity and inflammation-driven tumorigenesis. Experimental evidence also suggests that sucralose may impair CD8⁺ T-cell fitness and reduce responsiveness to immune checkpoint inhibitors through microbiome-dependent mechanisms involving altered arginine and citrulline metabolism. Human studies further indicate that sucralose can modify gut and oral microbiome composition and influence metabolic responses, although these effects appear heterogeneous and context-dependent. Overall, the current literature suggests that sucralose may act as a modifier of microbiome-immune interactions in susceptible settings, but most mechanistic evidence remains preclinical, and human data are still insufficient to establish causality. These findings highlight the need for prospective studies to determine whether sucralose-associated microbial and immune alterations translate into clinically meaningful effects in colitis, CRC, and immunotherapy response.