Yuxin Hou, Qitong Zhang, X Xu, 赵光燃
Background: The association between vitamin D levels/supplementation and the risk of allergic diseases has been extensively studied. However, the strength and consistency of the existing evidence remain unclear, and most reviews have focused on single diseases. This umbrella review aims to systematically evaluate the current meta-analytic evidence on the associations between vitamin D and allergic diseases, in order to establish a hierarchy of evidence and identify research gaps. Methods: -value of the largest study, and excess significance bias were recalculated. The methodological quality of included studies was appraised using AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews 2). Results: A total of 14 eligible articles were included, yielding 16 associations (total population: 66,387). The credibility of evidence assessment revealed the following: the association between serum 25(OH)D levels and urticaria was graded as highly suggestive evidence (MD -9.35, -12.27 to -6.44, class II); the associations between serum 25(OH)D levels and allergic rhinitis and between vitamin D supplementation and urticaria were graded as suggestive evidence (SMD -1.29, -1.92 to -0.65, class III). Vitamin D supplementation significantly alleviated symptoms in allergic rhinitis (SMD -2.25, -3.05 to -1.43, class Ⅳ), reduced disease severity in atopic dermatitis (SMD -0.41, -0.65 to -0.17, class Ⅳ), and decreased clinical scores in urticaria (SMD -3.63, -5.72 to -1.54, class III). However, no significant effect was observed for vitamin D supplementation on asthma or food allergy. Prenatal vitamin D supplementation showed no significant preventive effect on the risk of offspring allergic rhinitis, atopic dermatitis, or asthma. Conclusions: Lower vitamin D levels are consistently associated with several allergic diseases. The available evidence suggests that vitamin D supplementation demonstrates beneficial effects on symptom improvement for specific diseases (allergic rhinitis, atopic dermatitis, urticaria), but its efficacy is disease-specific. Future research requires greater standardization and precision to clarify the exact role and clinical utility of vitamin D in the prevention and management of different allergic diseases. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/.