For the millions of adults who routinely consume zero-calorie sweeteners while managing weight or blood sugar, the assumption that sucralose is biologically neutral is now under serious scientific scrutiny. If confirmed in humans, the mechanisms described in this review would reframe sucralose not as an inert substitute, but as an active modifier of the gut-immune environment — with particular relevance for cancer patients and people with inflammatory bowel conditions.
This comprehensive review in Biomedicines synthesizes preclinical and emerging clinical data on sucralose's effects along the gut-immune axis. The central concern is not acute toxicity but chronic low-level disruption. Experimental models indicate sucralose reduces short-chain fatty acid (SCFA)-producing bacterial taxa — organisms critical for maintaining epithelial integrity and anti-inflammatory signaling. Beyond microbial composition shifts, sucralose appears to alter arginine and citrulline metabolism in ways that impair CD8+ cytotoxic T-cell fitness, the very immune cells that immune checkpoint inhibitor (ICI) therapies depend on to attack tumors. This mechanistic chain — sweetener intake → dysbiosis → disrupted amino acid metabolism → blunted anti-tumor immunity — represents a potentially significant and underappreciated variable in oncology care.
Putting this in broader context, the gut microbiome's role as a determinant of ICI therapy efficacy is now well-established; studies have demonstrated that antibiotic-induced dysbiosis meaningfully reduces immunotherapy response rates. Sucralose's potential to selectively suppress beneficial taxa adds a new dietary variable clinicians and patients are not yet accounting for. That said, critical limitations must be acknowledged: the most mechanistic evidence comes from animal and cell-culture models, human studies show heterogeneous and context-dependent effects, and no randomized controlled trial has yet linked sucralose consumption to demonstrably worse cancer outcomes. The findings are hypothesis-generating rather than conclusive. Still, for immunotherapy patients or those with colitis, voluntarily removing sucralose from the diet carries essentially no risk and may carry meaningful benefit — making this an area warranting urgent human clinical investigation.
