Zinc and Type 2 Diabetes: A Systematic Review with a Narrative Synthesis of Their Bidirectional Relationship and Clinical Perspectives for Personalized Nutritional Support

Background: Type 2 diabetes mellitus (T2DM) remains one of the most significant public health problems, and its incidence rate is steadily increasing worldwide despite scientific and technological progress in the field of medicine. The focus of research in this area is gradually shifting from classic risk factors—such as obesity, sedentary lifestyle and genetic predisposition—toward additional, potentially modifiable contributors such as micronutrient imbalances; among them are disturbances in zinc homeostasis that may influence glucose metabolism and oxidative stress. Objective: This systematic review with narrative synthesis aims to examine the bidirectional relationship between zinc status and T2DM and to evaluate whether zinc screening and personalized nutritional support could contribute to comprehensive metabolic management. Methods: A literature search was conducted in the PubMed database and the Cochrane library for studies published between 2010 and 2024. Studies assessing zinc status or supplementation in relation to the risk, progression, or management of T2DM were included. Data were synthesized narratively, focusing on clinical and mechanistic evidence. Results: Thirty studies met the inclusion criteria. Evidence indicates that zinc imbalance (both deficiency and excess) is associated with T2DM risk and outcomes. Zinc deficiency may impair insulin synthesis and signaling, promote oxidative stress and inflammation, while excessive zinc intake may induce metabolic disturbances. T2DM itself may lead to reduced zinc status via altered absorption and increased excretion. While some studies suggest modest improvements in glycemic or lipid parameters following zinc supplementation, findings remain inconsistent and context-dependent. The prevalence of suboptimal zinc status in certain populations supports the rationale for targeted screening rather than routine supplementation. Conclusions: Zinc is mechanistically involved in insulin synthesis, antioxidant defense, and inflammation control, but current clinical evidence does not justify its use as a therapeutic agent in T2DM. Instead, assessment of zinc status and individualized correction of deficiency may represent a component of personalized nutritional support, particularly for patients with long disease duration, poor dietary quality, or genetic predispositions affecting zinc metabolism.