Vitamin D supplementation associated with improved metabolic markers in patients with Metabolic-Associated Fatty Liver Disease.

BACKGROUND: Vitamin D supplementation has been proposed as a therapeutic strategy for metabolic dysfunction-associated fatty liver disease (MAFLD); however, clinical evidence remains conflicting. OBJECTIVE: The aim of this investigation was to ascertain the efficacy of vitamin D treatment in managing MAFLD. METHODS: We searched PubMed, EMBASE, Web of Science, and the Cochrane Library, extending until April 2025. After analyzing and screening 2123 studies, 21 studies meeting the eligibility criteria for meta-analysis were selected. A random-effects model was used to determine the mean change in the standard mean difference for various variables, including insulin, fasting blood glucose (FBG), homeostasis model assessment of insulin resistance (HOMA-IR), high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, total cholesterol (TC), triglycerides (TG), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Heterogeneity was assessed using I in the analysis, and subgroup analysis was conducted to identify the sources of heterogeneity. RESULTS: Pooled analysis demonstrated that vitamin D supplementation significantly reduced: FBG concentrations [-0.21; 95% confidence interval (CI): -0.41, -0.02], insulin (-0.60, 95% CI: -1.15, -0.05), HOMA-IR (-0.70; 95% CI: -1.23, -0.17), TG (-0.32; 95% CI: -0.60, -0.05), and ALT (-0.50; 95% CI: -0.90, -0.11), whereas increasing HDL cholesterol (0.30; 95% CI: 0.01, 0.59). However, vitamin D supplementation did not show a significant effect on TC (-0.28; 95% CI: -0.61, 0.05), AST (-0.29; 95% CI: -0.60, 0.02), or LDL cholesterol (-0.17; 95% CI: -0.41, 0.07). CONCLUSIONS: The findings of this study indicate that vitamin D supplementation exerts a positive impact on carbohydrate and lipid metabolism, specifically in terms of FBG, insulin, HOMA-IR, TG, HDL cholesterol, and ALT concentrations among patients with MAFLD. Therefore, vitamin D could serve as an adjunctive therapy for fatty liver management in this patient population. The protocol for this study has been registered with PROSPERO as CRD42023457081.