Effects of Zinc Supplementation on Glycemic Control, Insulin Resistance, Inflammation and Oxidative Stress in Diabetes: A Systematic Review and Meta‐Analysis of Randomized Controlled Trials

OBJECTIVES: Diabetes mellitus (DM) is a chronic metabolic disorder characterized by insulin resistance, impaired insulin secretion, and increased cardiometabolic and inflammatory burden. Zinc plays a key biological role in insulin synthesis, storage, signalling and antioxidant defence; however, the clinical relevance and consistency of zinc supplementation effects in diabetes remain uncertain. METHODS: A systematic search of PubMed/MEDLINE, Web of Science, Scopus, CINAHL and Google Scholar was conducted to identify randomized controlled trials (RCTs) assessing zinc supplementation in individuals with diabetes, gestational diabetes or prediabetes. RESULTS: Eighteen RCTs involving 1023 participants met the eligibility criteria. Zinc supplementation significantly increased plasma zinc concentrations (MD = 7.80; 95% CI 4.33 to 11.26) and improved insulin resistance, as reflected by reductions in serum insulin (MD = -2.50; 95% CI -4.69 to -0.31) and HOMA-IR (MD = -1.10; 95% CI -2.05 to -0.15). Total cholesterol decreased modestly but significantly (MD = -5.70; 95% CI -7.50 to -3.89), representing a relatively small absolute reduction, while LDL cholesterol showed a modest increase (MD = 3.46; 95% CI 1.48 to 5.43), although the clinical relevance of this finding remains uncertain. Inflammatory and oxidative stress markers improved, including reductions in C-reactive protein (SMD = -0.91; 95% CI -1.43 to -0.38) and malondialdehyde (SMD = -0.76; 95% CI -1.34 to -0.18), alongside an increase in total antioxidant capacity (SMD = 1.79; 95% CI 0.68 to 2.91). CONCLUSIONS: Zinc supplementation was associated with improvements in insulin resistance, inflammatory status and oxidative stress markers in individuals with diabetes. TRIAL REGISTRATION: International Prospective Register of Systematic Reviews (PROSPERO) registration number: CRD42025638646.