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 .
Conclusions Regional- and age-specific recommended dosages of VitD supplements for population to achieve optimal 25(OH)D concentrations have been suggested
Background / Objectives Optimal doses of vitamin D ( VitD ) supplement in different population s 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 population s .
Vitamin D supplementation has no effect on insulin sensitivity or secretion in vitamin D-deficient, overweight or obese adults: a randomized placebo-controlled trial.
Background : Vitamin D supplementation has been proposed as a potential strategy to prevent  type 2 diabetes .  Existing clinical trials have been limited by short duration , low doses of vitamin D , variability in participants ' vitamin D-deficiency status , and the use of surrogate measures of body composition , insulin sensitivity , and insulin secretion . Objective : To address existing knowledge gaps , we conducted a double-blind , r and omized , placebo-controlled trial to investigate whether vitamin D supplementation that is provided in a sufficient dose and duration to vitamin D-deficient individuals would improve insulin sensitivity or secretion as measured with the use of gold-st and ard methods . We hypothesized that vitamin D supplementation would improve insulin sensitivity and secretion compared with placebo . Design : Sixty-five overweight or obese , vitamin D-deficient ( 25-hydroxyvitamin D [ 25(OH)D ] concentration ≤50 nmol/L ) adults were r and omly assigned to receive either a bolus oral dose of 100,000 IU cholecalciferol followed by 4000 IU cholecalciferol/d or a matching placebo for 16 wk . Before and after the intervention , participants received gold-st and ard assessment s of body composition ( via dual X-ray absorptiometry ) , insulin sensitivity ( via hyperinsulinemic-euglycemic clamps ) , and insulin secretion [ via intravenous-glucose-tolerance tests ( IVGTTs ) ] . Results : Fifty-four participants completed the study [ 35 men and 19 women ; mean ± SD age : 31.9 ± 8.5 y ; body mass index ( in kg/m2 ) : 30.9 ± 4.4 ] . 25(OH)D increased with vitamin D supplementation compared with placebo ( 57.0 ± 21.3 compared with 1.9 ± 15.1 nmol/L , respectively ; P = 0.02 ) . Vitamin D and placebo groups did not differ in change in insulin sensitivity ( 0.02 ± 2.0 compared with -0.03 ± 2.8 mg · kg-1 · min-1 , respectively ; P = 0.9 ) or first-phase insulin secretion ( -21 ± 212 compared with 24 ± 184 mU/L , respectively ; P = 0.9 ) . Results remained nonsignificant after adjustment for age , sex , percentage of body fat , sun exposure , physical activity , and dietary vitamin D intake ( P > 0.1 ) . Conclusions : Vitamin D supplementation does not improve insulin sensitivity or secretion in vitamin D-deficient , overweight or obese adults , despite using high-dose vitamin D supplementation and robust endpoint measures . Therefore , it is unlikely that vitamin D supplementation would be an effective strategy for reducing diabetes risk even in vitamin D-deficient population s. This trial was registered at clinical trials.gov as NCT02112721
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 .
Conclusions Regional- and age-specific recommended dosages of VitD supplements for population to achieve optimal 25(OH)D concentrations have been suggested
Background / Objectives Optimal doses of vitamin D ( VitD ) supplement in different population s 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 population s .