Natural Mineral Water and Metabolic Regulation in Type 2 Diabetes: Current Evidence, Mechanistic Insights, and Future Directions

Natural mineral water (NMW) represents a heterogeneous hydrochemical exposure whose metabolic effects may depend on its complete mineral and physicochemical profile. This critical review evaluates human evidence on NMW consumption in relation to glucose regulation and metabolic pathways relevant to type 2 diabetes mellitus (T2DM), while distinguishing clinical findings from mechanistic plausibility. Controlled studies have not demonstrated a consistent glucose-lowering effect: oral glucose tolerance and postprandial glucose responses were generally unchanged, while longer-term reductions in fasting glucose were not clearly attributable to water composition. Conversely, selected studies identified potentially relevant intermediate responses, including altered postprandial insulin dynamics, reduced glycoalbumin, changes in oxidative status, gastrointestinal and microbiota-related variables, and favourable intestinal, inflammatory, and liver-related outcomes in metabolic dysfunction-associated steatotic liver disease. Human studies also establish mineral water as a bioavailable source of magnesium and calcium, although bioavailability does not imply metabolic efficacy. Interpretation remains limited by small samples, heterogeneous hydrochemical profiles, short interventions, and comparator design. We propose a hydrochemical–phenotypic framework in which metabolic responses may depend on water composition, dose, exposure duration, and host phenotype. Current evidence does not support NMW as a treatment for T2DM but identifies specific metabolic pathways warranting rigorous clinical investigation.