Dietary Influences on Upper Gastrointestinal Cancers: Mechanisms, Prevention, and Therapeutic Implications

Upper gastrointestinal cancers, including malignancies of the esophagus, stomach, and gastroesophageal junction, constitute a major global health burden, with approximately 1.7 million new cases and 1.3 million deaths annually. This narrative review synthesizes current evidence on the dual role of dietary factors in the etiology, prevention, and treatment of these cancers. Non-modifiable risk factors, such as Helicobacter pylori infection and genetic susceptibility, interact with modifiable dietary exposures—including high salt intake, processed meat consumption, and antioxidant deficiencies—to promote carcinogenesis. In contrast, functional foods (for example, sulforaphane-rich broccoli and probiotics) and public health interventions (for example, dietary salt reduction and sugar-sweetened beverage taxation) show preventive potential by attenuating oxidative stress, modulating the gut microbiome, and reducing obesity-related risk. Nutritional interventions, such as glutamine and omega-3 fatty acid supplementation, improve treatment tolerance and mitigate cancer-associated cachexia, while emerging approaches like precision nutrition and engineered probiotics aim to address genetic and microbial heterogeneity. Observational evidence predominates, limiting causal inference; regional disparities bias the literature toward high-income settings, and genetic polymorphisms complicate universal recommendations. Nutrient supplementation is constrained by narrow therapeutic windows. Future research should prioritize longitudinal and interventional studies, standardized dietary assessments, and equitable policy frameworks.