Impact of polymorphisms in genes related to vitamin d metabolism on serum response to supplementation in adults and elderly: a systematic review and meta-analysis protocol

Abstract

Background and Aims: Vitamin D deficiency is a major public health issue, with varying individual responses to supple-mentation. Genetic factors, especially single‐nucleotide polymorphisms (SNPs) in Vitamin D metabolism genes, likely play akey role. This protocol proposes a systematic review to explore how genetic variability affects serum 25‐hydroxyvitamin D[25(OH)D] levels after supplementation.Methods: This protocol adheres to the Preferred Reporting Items for Systematic Review and Meta‐Analysis Protocols(PRISMA‐P). The literature search will be conducted across MEDLINE, Scopus, Web of Science, and Embase, withoutrestrictions on publication date or language. The study selection will be guided by Population, Exposure, Comparator, Out-comes, Study Design (PECOS) framework, focusing on randomized clinical trials that report pre‐ and post‐supplementationserum 25(OH)D levels alongside genotype data. Inclusion criteria comprise adults and elderly individuals, from both sexes andany ethnicity, who received Vitamin D supplementation and have SNPs data, while exclusion criteria reject studies withconfounding factors such as pre‐existing conditions or use of medications affecting Vitamin D status. Data extraction willinclude study characteristics, participant demographics, intervention details, SNPs, and serum 25(OH)D data. Inter‐raterreliability will be assessed using Cohen's kappa coefficient. A descriptive synthesis will summarize the findings, and if feasible, ameta‐analysis will be conducted. The primary outcome will be changes in serum 25(OH)D concentrations. Heterogeneityamong studies will be quantified using the I² statistic. The methodological quality of studies will be assessed using the JoannaBriggs Institute checklist, and the overall certainty of evidence will be evaluated using the Grading of Recommendations,Assessment, Development, and Evaluations (GRADE) approach.Conclusion: By identifying genetic subgroups with differential responses to vitamin D supplementation, the findings areexpected to contribute to the development of personalized supplementation strategies. These insights may enhance healthinterventions by optimizing supplementation protocols based on genetic predispositions, ultimately improving health outcomes.