Nutrient-derived metabolic signals in tumor immune regulation: bioavailability, compartmental allocation, and translational boundaries

The relationship between dietary factors and antitumor immunity has attracted growing attention, but dietary intake, circulating biomarkers, and biological activity within tumor-associated tissues occupy different positions along the path from exposure to function. Nutrient signals are continually reshaped by host processing and local delivery. Their effects depend less on the nutrient label itself than on the molecular form that reaches a given cell and the function that is actually limiting in that cell. This review integrates mechanistic and clinical evidence to explain why the same nutritional change may preserve effector-cell function or support tumor adaptation, with opposing compartment-specific effects most clearly demonstrated for lipid-related pathways. We also distinguish interventions that directly act on tumor-immune processes from nutritional support strategies designed mainly to maintain patient reserve and treatment tolerance. Claims of immune regulation should match the level of measurement. When tumor cells and immune cells may respond differently, paired compartment-specific readouts are needed. Nutritional strategies have translational value only when they target a defined and reversible limitation in a specific patient group and treatment window.