Impact of vitamin D-fortified foods and beverages on growth, bone mineralization, and nutritional biomarkers in children: insights from a comprehensive meta-analysis and meta-regression

Abstract Background Vitamin D deficiency remains highly prevalent among children worldwide. Although vitamin D food fortification is an established strategy for improving serum 25-hydroxyvitamin D [25(OH)D] concentrations, its effects on child growth, mineral metabolism, and hematological outcomes remain uncertain and inconsistently reported. Objectives To systematically evaluate the effects of vitamin D fortified foods and beverages on growth indicators and biochemical outcomes related to mineral metabolism and nutritional status in children. Methods A systematic review, meta-analysis, and meta-regression were conducted in accordance with PRISMA 2020 guidelines and registered in PROSPERO (CRD420261278423). PubMed, Scopus, Web of Science, and Epistemonikos were searched up to August 2025. Randomized controlled trials involving children (< 18 years) comparing vitamin D fortified foods or beverages with non-fortified controls were included. Quality was performed using RoB 2.0. Pooled mean differences (MDs) with 95% confidence intervals (CIs) were calculated using random-effects models. Heterogeneity, sensitivity analyses, publication bias, and meta-regression were performed. Results Twelve randomized controlled trials involving 2,676 children were included. Vitamin D fortified foods significantly increased serum 25(OH)D concentrations (MD 12.84 ng/mL; 95% CI 7.65–18.02; p < 0.001) and reduced PTH levels (MD − 9.02 pg/mL; 95% CI − 15.31 to − 2.73; p < 0.01), although heterogeneity was high. Hemoglobin levels increased significantly (MD 3.22 g/L; 95% CI 1.84–4.60; p < 0.001), although this estimate was derived from only three trials, at least one of which involved co-fortification with iron or other micronutrients, and should be interpreted cautiously rather than attributed solely to vitamin D. No significant effects were observed for height, weight, ferritin, or serum calcium. Conclusions Vitamin D fortified foods and beverages substantially improve vitamin D status and suppress secondary hyperparathyroidism in children, without significantly affecting linear growth or body weight. A significant increase in hemoglobin was also observed, although this finding was based on only three trials, may be influenced by co-fortification with iron or other micronutrients, and should be interpreted cautiously rather than as an isolated effect of vitamin D. No apparent safety concerns were identified in the included trials; however, the available evidence regarding safety outcomes remains limited. Longer-term, adequately powered trials with standardized safety reporting are needed to clarify growth-related, hematological, and functional outcomes.