Both doses led to sufficiency concentrations during winter months .
Among athletes with baseline vitamin D suggesting sufficiency , serum 25(OH)D sufficiency was maintained from different doses at both latitudes .
Conclusion Despite achieving sufficiency in vitamin D concentrations from ≥3000 IU supplementation , physical performance did not significantly improve .
Background There is currently no systematic review examining the effects of vitamin D supplementation  among athletes .
A rigorous systematic review and meta- analysis is important to provide a balanced view of current knowledge on the effect of vitamin D on serum 25-hydroxyvitamin D [ 25(OH)D ] concentrations and physical performance .
Objectives This systematic review of r and omized controlled trials ( RCTs ) evaluated the effects of oral vitamin D supplementation on serum 25(OH)D concentrations and physical performance in athletes .
A positive dose-response effect of vitamin D supplementation on site-specific bone mineral augmentation in adolescent girls: a double-blinded randomized placebo-controlled 1-year intervention.
UNLABELLED The effect of vitamin D supplementation on bone mineral augmentation in 212 adolescent girls with adequate calcium intake was studied in a r and omized placebo-controlled setting . Bone mineral augmentation determined by DXA increased with supplementation both in the femur and the lumbar vertebrae in a dose-responsive manner . Supplementation decreased the urinary excretion of resorption markers , but had no impact on formation markers . INTRODUCTION Adequate vitamin D intake protects the elderly against osteoporosis , but there exists no indisputable evidence that vitamin D supplementation would benefit bone mineral augmentation . The aim of this 1-year study was to determine in a r and omized double-blinded trial the effect of 5 and 10 microg vitamin D3 supplementation on bone mineral augmentation in adolescent girls with adequate dietary calcium intake . MATERIAL S AND METHODS Altogether , 228 girls ( mean age , 11.4 + /- 0.4 years ) participated . Their BMC was measured by DXA from the femur and lumbar spine . Serum 25-hydroxyvitamin D [ S-25(OH)D ] , intact PTH ( S-iPTH ) , osteocalcin ( S-OC ) , and urinary pyridinoline ( U-Pyr ) and deoxypyridinoline ( U-Dpyr ) were measured . Statistical analysis was performed both with the intention-to-treat ( IT ) and compliance-based ( CB ) method . RESULTS In the CB analysis , vitamin D supplementation increased femoral BMC augmentation by 14.3 % with 5 microg and by 17.2 % with 10 microg compared with the placebo group ( ANCOVA , p = 0.012 ) . A dose-response effect was observed in the vertebrae ( ANCOVA , p = 0.039 ) , although only with the highest dose . The mean concentration of S-25(OH)D increased ( p < 0.001 ) in the 5-microg group by 5.7 + /- 15.7 nM and in the 10-microg group by 12.4 + /- 13.7 nM , whereas it decreased by 6.7 + /- 11.3 nM in the placebo group . Supplementation had no effect on S-iPTH or S-OC , but it decreased U-DPyr ( p = 0.042 ) . CONCLUSIONS Bone mineral augmentation in the femur was 14.3 % and 17.2 % higher in the groups receiving 5 and 10 microg of vitamin D , respectively , compared with the placebo group , but only 10 mug increased lumbar spine BMC augmentation significantly . Vitamin D supplementation decreased the concentration of bone resorption markers , but had no impact on bone formation markers , thus explaining increased bone mineral augmentation . However , the positive effects were noted with the CB method but not with IT
Both doses led to sufficiency concentrations during winter months .
Among athletes with baseline vitamin D suggesting sufficiency , serum 25(OH)D sufficiency was maintained from different doses at both latitudes .
Conclusion Despite achieving sufficiency in vitamin D concentrations from ≥3000 IU supplementation , physical performance did not significantly improve .
Background There is currently no systematic review examining the effects of vitamin D supplementation  among athletes .
A rigorous systematic review and meta- analysis is important to provide a balanced view of current knowledge on the effect of vitamin D on serum 25-hydroxyvitamin D [ 25(OH)D ] concentrations and physical performance .
Objectives This systematic review of r and omized controlled trials ( RCTs ) evaluated the effects of oral vitamin D supplementation on serum 25(OH)D concentrations and physical performance in athletes .