Vitamin D supplementation reduces insulin resistance in Japanese adults: a secondary analysis of a double-blind, randomized, placebo-controlled trial. Effect of vitamin D supplementation on glycemic control in patients with type 2 diabetes: a systematic review of interventional studies The effect of different doses of vitamin D supplementation on insulin resistance during pregnancy A double-blind, randomized, placebo-controlled trial of the short-term effect of vitamin D3 supplementation on insulin sensitivity in apparently healthy, middle-aged, centrally obese men. Effect of short-term vitamin D supplementation on markers of vascular health in South Asian women living in the UK--a randomised controlled trial. Effect of Vitamin K Supplementation on Insulin Resistance in Older Men and Women Effects of a 1-year supplementation with cholecalciferol on interleukin-6, tumor necrosis factor-alpha and insulin resistance in overweight and obese subjects. Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and vitamin D deficient - a randomised, placebo-controlled trial.
Higher circulating 25-hydroxyvitamin D ( 25[OH]D ) concentration has been linked to a lower prevalence of insulin resistance and type 2 diabetes mellitus . However , r and omized controlled trials have not clarified the effect of vitamin D supplementation on insulin resistance in healthy adults . The objective of this study was to assess the effect of vitamin D supplementation for 1 year on insulin resistance ; the study was a secondary analysis of a clinical trial . We hypothesized that increased 25(OH)D concentration after vitamin D supplementation for 1 year would significantly improve insulin resistance .  Ninety-six healthy adults participated in this study , of whom 81 completed the study . The participants r and omly received daily either 420 IU vitamin D3 or placebo in a double-blind manner for 1 year . The levels of fasting insulin , glucose , and other parameters were assessed at baseline and after 1 year of intervention . Homeostasis model assessment of insulin resistance index was calculated from insulin and glucose levels . Visceral fat area and physical activity were also investigated . Serum 25(OH)D and 1,25-dihydroxyvitamin D concentrations were significantly increased by approximately 29.5 nmol/L and 7.0 pg/mL , respectively , after 1-year vitamin D supplementation . After vitamin D supplementation , fasting glucose levels and values of homeostasis model assessment of insulin resistance index significantly decreased from 88.3 to 85.3 mg/dL ( P < .01 ) and 1.17 to 0.84 ( P < .01 ) , respectively , and the results were independent of physical activity and visceral fat accumulation . In conclusion , the present study showed that vitamin D supplementation for 1 year effectively improves fasting glucose level and insulin resistance in healthy Japanese adults Background Diabetes and vitamin D deficiency are global epidemics . Research ers have long been exploring the role of potentially modifiable factors to manage type 2 diabetes . We conducted a systematic review of prospect i ve studies and r and omized controlled trials that involved vitamin D supplementation and specifically intended to study glycemic outcomes related to type 2 diabetes . Methods Two authors independently search ed Medline and PubMed for longitudinal studies that had assessed the effect of vitamin D supplements on glycemic control , insulin resistance and beta-cell dysfunction in patients with diabetes . Results Seventeen r and omized control trials and seven longitudinal studies with a minimum follow-up of one month were included . Results of the various short-term studies ( follow up ≤ 3 months ) suggested that vitamin D supplementation had a positive impact on glycemic control and metabolic parameters such as insulin resistance and beta cell dysfunction . However , the evidence was weak due to the low method ological quality of the studies . There was no significant effect on HbA1c , beta cell function and insulin resistance in the long-term studies ( follow up > 3 months ) . There existed heterogeneity in the methodology of the studies , inclusion criteria , mode of supplementation of vitamin D and the duration of follow up . Conclusions Current evidence based on r and omized controlled trials and longitudinal studies do not support the notion that vitamin D supplementation can improve hyperglycemia , beta cell secretion or insulin sensitivity in patients with type 2 diabetes . Large-scale trials with proper study design , optimal vitamin D supplementation and longer follow up need to be conducted Abstract Low serum vitamin D levels are correlated with insulin resistance during pregnancy . We have assessed the effects of different doses of vitamin D on insulin resistance during pregnancy . A r and omized clinical trial was done on 120 women with a gestational age of less than 12 weeks . The women were divided into three groups r and omly . Group A received 200 IU vitamin D daily , group B 50 000 IU vitamin D monthly and group C 50 000 IU vitamin D every 2 weeks from 12 weeks of pregnancy until delivery . The serum levels of fasting blood sugar ( FBS ) , insulin , calcium and 25-hydroxyvitamin D were measured before and after intervention . We used the homeostatic model assessment of insulin resistance ( HOMA-IR ) as a surrogate measure of insulin resistance . The mean ± st and ard deviation of serum 25-hydroxyvitamin D increased in group C from 7.3 ± 5.9 to 34.1 ± 11.5 ng/ml and in group B it increased from 7.3 ± 5.3 to 27.23 ± 10.7 ng/ml , but the level of vitamin D in group A increased from 8.3 ± 7.8 to 17.7 ± 9.3 ng/ml ( p < 0.001 ) . The mean differences of insulin and HOMA-IR before and after intervention in groups A and C were significant ( p = 0.01 , p = 0.02 ) . This study has shown that supplementation of pregnant women with 50 000 IU vitamin D every 2 weeks improved insulin resistance significantly AIM To determine the short-term effect of vitamin D(3 ) supplementation on insulin sensitivity in apparently healthy , middle-aged , central ly obese men . SUBJECTS AND METHODS A double-blind r and omized controlled trial was conducted at a tertiary care facility in which 100 male volunteers aged > or = 35 years received three doses of vitamin D(3 ) ( 120,000 IU each ; supplemented group ) fortnightly or placebo ( control group ) . Hepatic fasting insulin sensitivity [ homeostasis model assessment ( HOMA ) , quantitative insulin-sensitivity check index , HOMA-2 ] , postpr and ial insulin sensitivity [ oral glucose insulin sensitivity ( OGIS ) ] , insulin secretion ( HOMA%B , HOMA2-%B ) , lipid profile and blood pressure were measured at baseline and at 6 weeks ' follow-up . RESULTS Seventy-one of the recruited subjects completed the study ( 35 in supplemented group , 36 in control group ) . There was an increase in OGIS with supplementation by per protocol analysis ( P = 0.038 ; intention-to-treat analysis P = 0.055 ) . The age- and baseline 25-hydroxyvitamin D level-adjusted difference in change in OGIS was highly significant ( mean difference 41.1 + /- 15.5 ; P = 0.01 ) . No changes in secondary outcome measures ( insulin secretion , basal indices of insulin sensitivity , blood pressure or lipid profile ) were found with supplementation . CONCLUSION The trial indicates that vitamin D(3 ) supplementation improves postpr and ial insulin sensitivity ( OGIS ) in apparently healthy men likely to have insulin resistance ( central ly obese but non-diabetic ) OBJECTIVE Low vitamin D levels and risk factors for vascular disease are both common in South Asian women . This trial evaluated whether vitamin D supplementation could improve markers of vascular health in South Asian women with low 25-hydroxyvitamin D levels . METHODS Parallel-group , double-blind , r and omised placebo-controlled trial . Healthy South Asian women with baseline serum 25-hydroxyvitamin D levels of < 75 nmol/L were r and omised to receive a single dose of 100,000 units oral vitamin D3 or matching placebo . Outcomes were measured at baseline , 4 and 8 weeks . The primary outcome was change in endothelial function measured using brachial artery flow-mediated dilatation . Secondary outcomes included blood pressure , arterial stiffness , microvascular function measured using laser Doppler iontophoresis , insulin resistance , serum lipids , circulating markers of inflammation , thrombosis and adipokines . RESULTS 50 women were r and omised , 25 to each group . Mean age was 41 years ; mean baseline 25-hydroxyvitamin D level was 27 nmol/L.  25-Hydroxyvitamin D levels rose in the vitamin D group relative to the placebo group by 4 weeks ( 16 nmol/L , 95 % CI 11 to 21 , p < 0.001 ) . There was no improvement in flow-mediated dilatation in the vitamin D group relative to placebo at 4 weeks ( 0.1 % , 95 % CI -0.9 to 1.1 , p = 0.84 ) or 8 weeks ( 0.0 % , 95 % CI -1.4 to 1.4 , p = 0.98 ) . There was no improvement in cholesterol , insulin resistance or markers of inflammation . Both platelet activation inhibitor-1 and tissue plasminogen activator levels fell significantly in the vitamin D group relative to placebo at 8 weeks . CONCLUSION A single large dose of vitamin D3 did not improve blood pressure or endothelial function in South Asian women with low baseline 25-hydroxyvitamin D levels . TRIAL REGISTRATION IS RCT N75081811 OBJECTIVE —Vitamin K has a potentially beneficial role in insulin resistance , but evidence is limited in humans . We tested the hypothesis that vitamin K supplementation for 36 months will improve insulin resistance in older men and women . RESEARCH DESIGN AND METHODS —This was an ancillary study of a 36-month , r and omized , double-blind , controlled trial design ed to assess the impact of supplementation with 500 μg/day phylloquinone on bone loss . Study participants were older nondiabetic men and women ( n = 355 ; aged 60–80 years ; 60 % women ) . The primary outcome of this study was insulin resistance as measured by homeostasis model assessment ( HOMA-IR ) at 36 months . Fasting plasma insulin and glucose were examined as the secondary outcomes . RESULTS —The effect of 36-month vitamin K supplementation  on HOMA-IR differed by sex ( sex × treatment interaction P = 0.02 ) . HOMA-IR was statistically significantly lower at the 36-month visit among men in the supplement group versus the men in the control group ( P = 0.01 ) after adjustment for baseline HOMA-IR , BMI , and body weight change . There were no statistically significant differences in outcome measures between intervention groups in women . CONCLUSIONS —Vitamin K supplementation for 36 months at doses attainable in the diet may reduce progression of insulin resistance in older men Insufficient vitamin D status has been linked to autoimmune diseases , cancer and metabolic disorders , like obesity and insulin resistance . In vitro and animal studies suggest that vitamin D may play a crucial role in immune activation and inflammation . The relation between vitamin D and pro-inflammatory cytokines is not completely established . Furthermore , it is not known if the effect of vitamin D on entities of metabolic syndrome is mediated through its effect on cytokines or other biomarkers . The objectives of this study were to investigate if there is a relationship between vitamin D status and such pro-inflammatory cytokines as tumor necrosis factor-alpha ( TNF-α ) , interleukin 6 ( IL-6 ) and high sensitive C-reactive protein ( hs-CRP ) in patients with overweigh and obesity . We also proposed that the intervention with high dose of cholecalciferol may have effect on the cytokine levels and result in corresponding changes in the measures of insulin resistance ( HOMA-IR and QUICKI ) . Serum levels of IL-6 , TNF-α and hs-CRP were measured in 332 overweight and obese subjects who completed a 1-year r and omised intervention with either 40,000 IU vitamin D ( cholecalciferol ) per week or 20,000 IU vitamin D per week  ,  or placebo .  We found significant associations between IL-6 , TNF-α , vitamin D and insulin resistance indices at baseline . One year intervention with vitamin D  decreased serum IL-6 levels ; however hs-CRP levels were significantly increased . Neither measures of insulin resistance , nor TNF-α were influenced by a 1-year vitamin D supplementation Low serum 25-hydroxyvitamin D ( 25(OH)D ) has been shown to correlate with increased risk of type 2 diabetes . Small , observational studies suggest an action for vitamin D in improving insulin sensitivity and /or insulin secretion . The objective of the present study was to investigate the effect of improved vitamin D status on insulin resistance ( IR ) , utilising r and omised , controlled , double-blind intervention administering 100 microg ( 4000 IU ) vitamin D(3 ) ( n 42 ) or placebo ( n 39 ) daily for 6 months to South Asian women , aged 23 - 68 years , living in Auckl and , New Zeal and . Subjects were insulin resistant - homeostasis model assessment 1 (HOMA1)>1.93 and had serum 25(OH)D concentration < 50 nmol/l . Exclusion criteria included diabetes medication and vitamin D supplementation > 25 microg ( 1000 IU)/d . The HOMA2 computer model was used to calculate outcomes . Median ( 25th , 75th percentiles ) serum 25(OH)D(3 ) increased significantly from 21 ( 11 , 40 ) to 75 ( 55 , 84 ) nmol/l with supplementation . Significant improvements were seen in insulin sensitivity and IR ( P = 0.003 and 0.02 , respectively ) , and fasting insulin decreased ( P = 0.02 ) with supplementation compared with placebo . There was no change in C-peptide with supplementation . IR was most improved when endpoint serum 25(OH)D reached > or = 80 nmol/l . Secondary outcome variables ( lipid profile and high sensitivity C-reactive protein ) were not affected by supplementation . In conclusion , improving vitamin D status in insulin resistant women result ed in improved IR and sensitivity , but no change in insulin secretion . Optimal vitamin D concentrations for reducing IR were shown to be 80 - 119 nmol/l , providing further evidence for an increase in the recommended adequate levels . Registered Trial No. ACTRN12607000642482
Conclusions Short-term ( 4–12 weeks ) supplementation with vitamin D is associated with lower fasting glucose levels in ESRD with no change in fasting insulin levels .
Abstract Purpose We tested whether short-term vitamin D supplementation improves insulin resistance in patients with kidney disease , a condition with little intrinsic vitamin D activity .