Aspartame promotes intestinal tumor progression via Akkermansia muciniphila -mediated 5-hydroxytryptophan production

Aspartame, one of the most widely consumed artificial sweeteners globally, has been associated with increased cancer risk in epidemiological studies, yet the underlying mechanisms remain poorly understood. This study investigated the effects of subchronic aspartame exposure on intestinal tumorigenesis using the Apc^min/+ spontaneous intestinal tumor mouse model and elucidated the mechanistic pathways involved. Mice were exposed to physiologically relevant doses of aspartame (0.07 and 0.2 mg/mL) in drinking water for 3 months, followed by comprehensive analysis of tumor development, gut microbiota composition, and intestinal metabolomics. The results revealed that aspartame exposure significantly promoted tumor progression, as evidenced by increased proportions of medium-sized tumors in the small intestine. Microbiota analysis using 16S rRNA sequencing revealed selective enrichment of Akkermansia muciniphila (A. muciniphila) and increased microbial dysbiosis following aspartame treatment. Metabolomic profiling identified tryptophan metabolism as the most significantly altered pathway, with enhanced production of serotonin pathway metabolites. Mechanistic validation through in vitro experiments demonstrated that aspartame directly stimulated A. muciniphila growth and increased bacterial production of 5-hydroxytryptophan (5-HTP), which was subsequently converted to serotonin (5-HT) in tumor tissues. Culture supernatants from aspartame-treated A. muciniphila promoted colorectal cancer cell proliferation, an effect that was specifically blocked by carbidopa, an inhibitor of 5-HTP to 5-HT conversion. These findings reveal a novel aspartame-microbiota-serotonin axis that promotes intestinal tumor progression, challenging the perceived safety of long-term aspartame consumption and highlighting the need for reevaluation of current safety guidelines.