The effect of vitamin D2 supplementation on vitamin D levels in humans: A time and dose–response meta-analysis of randomized controlled trials

Background Inconsistencies exist regarding the influence of vitamin D2 (ergocalciferol) supplementation on serum vitamin D levels. These inconsistencies could be attributed to numerous factors, such as dosage, baseline vitamin D levels, and duration of intervention. Hence, this dose–response meta-analysis of randomized controlled trials was conducted to assess the efficacy of vitamin D2 supplementation on vitamin D levels. Methods Relevant studies were searched in PubMed/Medline, Web of Science, Embase, and Scopus, from their inception to 3 January 2023. Variable alterations were considered to calculate the pooled weighted mean difference (WMD) with 95% confidence interval (CI) using the random effects model. Results Pooled results from 33 study arms demonstrated that Vitamin D2 treatment significantly increases total vitamin D concentrations (WMD: 11.47 ng/mL, 95 %CI: 9.29 to 13.64, p < 0.001), 25(OH)D2 concentrations (WMD: 11.40 ng/mL, 95 %CI: 4.72 to 18.09, p = 0.001), and 1,25(OH)D concentrations (WMD: 5.61 ng/mL, 95 %CI: 0.74 to 10.48, p = 0.024), but decreases 25(OH)D3 concentrations (WMD: −4.63 ng/mL, 95 %CI: −6.46 to −2.81, p < 0.001). In subgroup analyses, increase in total vitamin D concentrations was more significant in vitamin D2 doses >2000 IU/day (WMD: 13.82 ng/mL), studies with duration ≤12 weeks (WMD: 12.53 ng/mL), participants aged ≥60 years (WMD: 14.40 ng/mL), and trials with basal 25(OH)D concentrations <20 ng/mL (WMD: 11.47 ng/mL). Conclusions This meta-analysis indicates that the supplementation of vitamin D2 significantly increases the serum concentrations of total vitamin D, 25(OH)D2, and 1,25(OH)D, but decreases 25(OH)D3 concentrations. Careful consideration of patient characteristics, dosage, and treatment duration is recommended for vitamin D2 supplementation.