A systematic review and meta-analysis of the response of serum 25-hydroxyvitamin D concentration to vitamin D supplementation from RCTs from around the globe

Optimal doses of vitamin D (VitD) supplement in different populations are unclear. We aim to evaluate the relationship between VitD supplementation and post-intervention serum 25-hydroxyvitamin D [25(OH)D] concentration, to provide a recommended dosage of VitD for achieving an optimal 25(OH)D concentration for different populations. Literature search was conducted in Embase, etc. Randomized controlled trials about VitD supplemental intakes and their effect on 25(OH)D concentration were enrolled. The effect on 25(OH)D concentration between different supplementation doses in each population group was compared by meta-analysis. Multivariate meta-regression model is utilized to establish reference intake dosage of VitD. A total of 136 articles were included about children (3–17 years), adults (18–64 years), postmenopausal women, the elderly ( >64 years), pregnant, or lactating women. Overall, intervention groups obtained higher 25(OH)D concentration than controls and there was obvious dose–response effect between intake dose and 25(OH)D concentration. Baseline 25(OH)D concentration and age were significant indicators for 25(OH)D concentration. To reach sufficient 25(OH)D concentration (75 nmol/L), the recommended VitD supplemental intakes was 1340 and 2250 IU/day for children and pregnant women, 2519 and 797 IU/day for European adults aged 18–64 and 65–85 years, 729, 2026, and 1229 IU/day for adults in North America, Asia and Middle East and Africa, respectively. Regional- and age-specific recommended dosages of VitD supplements for population to achieve optimal 25(OH)D concentrations have been suggested.