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. The effect of vitamin K1 supplementation on sensitivity and insulin resistance via osteocalcin in prediabetic women: a double-blind randomized controlled clinical trial Effect of Vitamin D Supplementation on Obesity‐Induced Insulin Resistance: A Double‐Blind, Randomized, Placebo‐Controlled Trial Effect of Vitamin K Supplementation on Insulin Resistance in Older Men and Women Effect of moderate-dose vitamin D supplementation on insulin sensitivity in vitamin D-deficient non-Western immigrants in the Netherlands: a randomized placebo-controlled trial. High-dose vitamin D supplementation and measures of insulin sensitivity in polycystic ovary syndrome: a randomized, controlled pilot trial. 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. Effect of vitamin D supplementation on glycemic control in patients with type 2 diabetes: a systematic review of interventional studies Vitamin D supplementation has no effect on insulin sensitivity or secretion in vitamin D-deficient, overweight or obese adults: a randomized placebo-controlled trial. Vitamin D, Insulin Secretion, Sensitivity, and Lipids Effects of Combined Calcium and Vitamin D Supplementation on Insulin Secretion, Insulin Sensitivity and β-Cell Function in Multi-Ethnic Vitamin D-Deficient Adults at Risk for Type 2 Diabetes: A Pilot Randomized, Placebo-Controlled Trial A randomized, placebo-controlled trial of vitamin D supplementation to improve glycaemia in overweight and obese African Americans. Study of comparative effects of antioxidants on insulin sensitivity in type 2 diabetes mellitus. Vitamin D supplementation affects serum high-sensitivity C-reactive protein, insulin resistance, and biomarkers of oxidative stress in pregnant women. Effect of vitamin D supplementation on insulin kinetics and cardiovascular risk factors in polycystic ovarian syndrome: a pilot study Changes in mineral status are associated with improvements in insulin sensitivity in obese patients following l-arginine supplementation Vitamin D supplementation has no effect on insulin resistance assessment in women with polycystic ovary syndrome and vitamin D deficiency.
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 ) Background / Objectives : A relationship between osteocalcin ( OC ) levels and factors associated with energy metabolism and insulin resistance has been reported recently . The aim of this study was to investigate whether modulation of ostecalcin isoforms via vitamin K1 supplementation would affect glucose metabolism or insulin sensitivity in prediabetic and premenopause women . Subjects/ Methods : Eighty-two prediabetic women were r and omized to consume vitamin K1 supplement ( n=39 ) or placebo ( n=43 ) for 4 weeks . Participants in the vitamin K1 supplement group received one pearl softgel capsule containing 1000 μm of phylloquinone , and the placebo group received one placebo capsule daily for 4 weeks . Blood sample s were collected at baseline and after the 4-week intervention period to quantify carboxylated OC ( cOC ) , undercarboxylated OC ( ucOC ) and relevant variables . Results : Phylloquinone supplementation increased the serum levels of cOC and decreased ucOC , compared with placebo ( 12.53±5.95 compared with 7.43±4.85 ng/ml and 2.47±1.91 compared with 4.79±2.43 ng/ml , respectively ; P<0.001 ) . Furthermore , intake of phylloquinone supplement led to significant decreases in % ucOC ( 17.97±12.24 compared with 43.80±19.86 ) and 2-h post-oral glucose tolerance test ( OGTT ) glucose ( 7.32±1.50 compared with 8.62±1.45 mmol/l ) , and 2- h post-OGTT insulin level ( 80.34±42.24 compared with 112.43±53.19 μIU/ml ) and increased insulin sensitivity index ( 2.46±0.71 compared with 1.75±0.61 ) compared with placebo . Overall , a significant association was found between changes in % ucOC and changes in 2-h post-OGTT glucose ( r=0.308 , P=0.028 ) . Conclusions : The results of this study demonstrated that vitamin K1 supplementation for 4 weeks did not affect insulin resistance in premenopausal and prediabetic women but had beneficial effects on glycemic status and insulin sensitivity Objective The aim was to investigate whether vitamin D supplementation , combined with a hypocaloric diet , could have an independent effect on insulin sensitivity in subjects with both overweight and hypovitaminosis D. Changes from baseline in anthropometric parameters , body composition , glucose tolerance , and insulin secretion were considered as secondary outcomes . Methods Eighteen volunteers who were nondiabetic and vitamin D deficient and had BMI > 25 kg/m2 were r and omized ( 1:1 ) in a double‐blind manner to a hypocaloric diet + either oral cholecalciferol at 25,000 IU/wk or placebo for 3 months . Hyperinsulinemic‐euglycemic clamp to measure insulin sensitivity  was performed at baseline and after intervention . Results Body weight in both groups decreased significantly ( −7.5 % in the vitamin D group and −10 % in the placebo group ; P < 0.05 for both ) , with no between‐group differences . Serum 25‐hydroxyvitamin D levels in the vitamin D group increased considerably ( from 36.7 ± 13.2 nmol/L to 74.8 ± 18.7 nmol/L ; P < 0.001 ) . Insulin sensitivity in the vitamin D group improved ( from 4.6 ± 2.0 to 6.9 ± 3.3 mg·kg−1·min−1 ; P < 0.001 ) , whereas no changes were observed in the placebo group ( from 4.9 ± 1.1 to 5.1 ± 0.3 mg·kg−1·min−1 ; P = 0.84 ) . Conclusions Cholecalciferol supplementation , combined with a weight loss program , significantly improves insulin sensitivity in healthy subjects with obesity and might represent a personalized approach for insulin‐resistant subjects with obesity 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 BACKGROUND Low serum 25-hydroxyvitamin D [ 25(OH)D ] concentrations have been associated with insulin resistance , the metabolic syndrome , and type 2 diabetes . Because many non-Western immigrants in the Netherl and s are vitamin D deficient , obese , and at high risk of diabetes , vitamin D supplementation may contribute to prevent diabetes and insulin resistance . OBJECTIVE We examined the effect of vitamin D supplementation on insulin sensitivity and β cell function in overweight , vitamin D-deficient , non-Western immigrants at high risk of diabetes . DESIGN The study was a 16-wk , r and omized , placebo-controlled trial . A total of 130 non-Western immigrants with prediabetes ( fasting glucose concentration > 5.5 mmol/L or r and om glucose concentration from 7.8 to 11.1 mmol/L ) and vitamin D deficiency ( serum 25[OH]D concentration < 50 nmol/L ) were r and omly assigned after stratification by sex to receive either cholecalciferol ( 1200 IU/d ) or a placebo for 16 wk . All participants received 500 mg Ca/d as calcium carbonate . The primary outcome was the difference in the area under the curve of insulin and glucose after a 75-g oral-glucose-tolerance test after 4 mo of treatment . Secondary outcomes were insulin-sensitivity variables , β cell-function variables , and metabolic syndrome . RESULTS Mean serum 25(OH)D concentrations increased significantly in the vitamin D compared with placebo groups . After 4 mo of therapy , the mean between-group difference was 38 nmol/L ( 95 % CI : 32.1 , 43.9 nmol/L ; P < 0.001 ) . There was no significant effect on insulin sensitivity and β cell function . In a post hoc analysis , when patients with diabetes at baseline were excluded , a significant increase in the insulinogenic index was observed in participants who obtained a 25(OH)D concentration ≥60 nmol/L ( P = 0.040 ) . CONCLUSIONS Vitamin D supplementation in non-Western vitamin D-deficient immigrants with prediabetes did not improve insulin sensitivity or β cell function or change the incidence of metabolic syndrome . However , after the exclusion of diabetic subjects , an improvement in the insulinogenic index was observed in participants who obtained a 25(OH)D concentration ≥60 nmol/L. This trial was registered at trialregister.nl as NTR1827 OBJECTIVE To determine the effects of high-dose vitamin D on insulin sensitivity in polycystic ovary syndrome ( PCOS ) . DESIGN R and omized , placebo-controlled trial . SETTING Academic medical center . PATIENT(S ) Twenty-eight women with PCOS . INTERVENTION(S ) Vitamin D3 , 12,000 IU , or placebo daily for 12 weeks . MAIN OUTCOME MEASURE(S ) The primary outcome was quantitative insulin sensitivity check index . Secondary outcomes included glucose and insulin levels during a 75-g oral glucose tolerance test and blood pressure . RESULT ( S ) Twenty-two women completed the study . Compared with placebo , vitamin D significantly increased 25-hydroxyvitamin D ( mean [ 95 % confidence interval ] in vitamin D group 20.1 [ 15.7 to 24.5 ] ng/mL at baseline and 65.7 [ 52.3 to 79.2 ] ng/mL at 12 weeks ; placebo 22.5 [ 18.1 to 26.8 ] ng/mL at baseline and 23.8 [ 10.4 to 37.2 ] ng/mL at 12 weeks ) . There were no significant differences in quantitative insulin sensitivity check index and other measures of insulin sensitivity ; however , we observed trends toward lower 2-hour insulin and lower 2-hour glucose . We also observed a protective effect of vitamin D on blood pressure . CONCLUSION ( S ) In women with PCOS , insulin sensitivity was unchanged with high-dose vitamin D , but there was a trend toward decreased 2-hour insulin and a protective effect on blood pressure . CLINICAL TRIAL REGISTRATION NUMBER NCT00907153 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 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 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 OBJECTIVE Vitamin D deficiency is associated with an unfavorable metabolic profile in observational studies . The intention was to compare insulin sensitivity ( the primary end point ) and secretion and lipids in subjects with low and high serum 25(OH)D ( 25-hydroxyvitamin D ) levels and to assess the effect of vitamin D supplementation on the same outcomes among the participants with low serum 25(OH)D levels . RESEARCH DESIGN AND METHODS Participants were recruited from a population -based study ( the Tromsø Study ) based on their serum 25(OH)D measurements . A 3-h hyperglycemic clamp was performed , and the participants with low serum 25(OH)D levels were thereafter r and omized to receive capsules of 20,000 IU vitamin D3 or identical-looking placebo twice weekly for 6 months . A final hyperglycemic clamp was then performed . RESULTS The 52 participants with high serum 25(OH)D levels ( 85.6 ± 13.5 nmol/L [ mean ± SD ] ) had significantly higher insulin sensitivity index ( ISI ) and lower HbA1c and triglycerides ( TGs ) than the 108 participants with low serum 25(OH)D ( 40.3 ± 12.8 nmol/L ) , but the differences in ISI and TGs were not significant after adjustments . After supplementation , serum 25(OH)D was 142.7 ± 25.7 and 42.9 ± 17.3 nmol/L in 49 of 51 completing participants r and omized to vitamin D and 45 of 53 r and omized to placebo , respectively . At the end of the study , there were no statistically significant differences in the outcome variables between the two groups . CONCLUSIONS Vitamin D supplementation to apparently healthy subjects with insufficient serum 25(OH)D levels does not improve insulin sensitivity or secretion or serum lipid profile Objectives To examine whether combined vitamin D and calcium supplementation improves insulin sensitivity , insulin secretion , β-cell function , inflammation and metabolic markers . Design 6-month r and omized , placebo-controlled trial . Participants Ninety-five adults with serum 25-hydroxyvitamin D [ 25(OH)D ] ≤55 nmol/L at risk of type 2 diabetes ( with prediabetes or an AUSDRISK score ≥15 ) were r and omized . Analyses included participants who completed the baseline and final visits ( treatment n = 35 ; placebo n = 45 ) . Intervention Daily calcium carbonate ( 1,200 mg ) and cholecalciferol [ 2,000–6,000 IU to target 25(OH)D > 75 nmol/L ] or matching placebos for 6 months .  Measurements Insulin sensitivity ( HOMA2%S , Matsuda index ) , insulin secretion ( insulinogenic index , area under the curve ( AUC ) for C-peptide ) and β-cell function ( Matsuda index x AUC for C-peptide ) derived from a 75 g 2-h OGTT ; anthropometry ; blood pressure ; lipid profile ; hs-CRP ; TNF-α ; IL-6 ; adiponectin ; total and undercarboxylated osteocalcin . Results Participants were middle-aged adults ( mean age 54 years ; 69 % Europid ) at risk of type 2 diabetes ( 48 % with prediabetes ) . Compliance was > 80 % for calcium and vitamin D. Mean serum 25(OH)D concentration increased from 48 to 95 nmol/L in the treatment group ( 91 % achieved > 75 nmol/L ) , but remained unchanged in controls . There were no significant changes in insulin sensitivity , insulin secretion and β-cell function , or in inflammatory and metabolic markers between or within the groups , before or after adjustment for potential confounders including waist circumference and season of recruitment . In a post hoc analysis restricted to participants with prediabetes , a significant beneficial effect of vitamin D and calcium supplementation on insulin sensitivity ( HOMA%S and Matsuda ) was observed . Conclusions Daily vitamin D and calcium supplementation for 6 months may not change OGTT-derived measures of insulin sensitivity , insulin secretion and β-cell function in multi-ethnic adults with low vitamin D status at risk of type 2 diabetes . However , in participants with prediabetes , supplementation with vitamin D and calcium may improve insulin sensitivity . Trial Registration Australian New Zeal and Clinical Trials Registry AIMS Vitamin D deficiency may increase the risk for type 2 diabetes . African Americans tend to have poor vitamin D status and increased risk of diabetes , but effects of vitamin D supplementation on components of diabetes risk have not been tested in this group . This study was conducted to determine whether vitamin D supplementation improves insulin secretion , insulin sensitivity and glycaemia in African Americans with prediabetes or early diabetes . METHODS In this r and omized , placebo-controlled trial , we examined the effect of 4000 IU/day vitamin D(3 , ) on glycaemia and contributing measures including insulin secretion , insulin sensitivity and the disposition index over 12 weeks in 89 overweight or obese African Americans with prediabetes or early diabetes . Outcome measures were derived from oral glucose tolerance testing . RESULTS Mean plasma 25-hydroxyvitamin D was about 40 nmol/l in the placebo and vitamin D groups at baseline and increased to 81 nmol/l with supplementation . Insulin sensitivity decreased by 4 % in the vitamin D group compared with a 12 % increase in the placebo group ( p = 0.034 ) . Insulin secretion increased by 12 % in the vitamin D group compared with a 2 % increase in the placebo group ( p = 0.024 ) , but changes in the disposition index were similar across groups . There was no effect of supplementation on post-load glucose or other measures of glycaemia . CONCLUSIONS Supplementation with 4000 IU/day vitamin D(3 ) successfully corrected vitamin D insufficiency and had divergent effects on insulin secretion and sensitivity with no overall effect on disposition index or glycaemia . In this study , vitamin D supplementation for 3 months did not change the pathophysiology of prediabetes in overweight and obese African Americans OBJECTIVES This study intended to assess the effects of the antioxidants ; Alpha Lipoic Acid ( ALA ) , omega 3 fatty acids and vitamin E on the parameters of insulin sensitivity , oxidative stress , lipid metabolism and glycaemic control in patients of type 2 diabetes mellitus . METHODS This was a prospect i ve , r and omized , double blind , placebo controlled , single centred study . One hundred four patients with type 2 diabetes mellitus with insulin resistance were recruited for the study . They were given ALA , omega 3 fatty acids , vitamin E or placebo . Their weight , Body Mass Index ( BMI ) and Waist circumference were measured . The investigations which were fasting glucose and fasting total cholesterol . The insulin resistance was calculated on the basis of the BMI and the waist circumference . RESULTS In the intra group analysis at the baseline ( V1 ) vs at the end of the treatment period ( V5 ) , we observed a significant decrease in the BMI , waist circumference and the total cholesterol in the three treatment groups . In the intergroup analysis at V5 , ALA , omega 3 fatty acids and vitamin E showed a significant improvement in the total cholesterol as compared to the placebo and vitamin E showed the maximum improvement . CONCLUSION ALA , omega 3 fatty acids and vitamin E showed the improvement in insulin sensitivity . Since they differ in improving different parameters all of these three can be used as an add on therapy in patients with type 2 diabetes mellitus to improve their insulin sensitivity and lipid metabolism Unfavorable metabolic profiles and oxidative stress in pregnancy are associated with several complications . This study was conducted to determine the effects of vitamin D supplementation on serum concentrations of high-sensitivity C-reactive protein ( hs-CRP ) , metabolic profiles , and biomarkers of oxidative stress in healthy pregnant women . This r and omized , double-blind , placebo-controlled clinical trial was conducted in 48 pregnant women aged 18 - 40 y old at 25 wk of gestation . Participants were r and omly assigned to receive either 400 IU/d cholecalciferol supplements ( n = 24 ) or placebo ( n = 24 ) for 9 wk . Fasting blood sample s were taken at study baseline and after 9 wk of intervention to quantify serum concentrations of hs-CRP , lipid concentrations , insulin , and biomarkers of oxidative stress . After 9 wk of intervention , the increases in serum 25-hydroxyvitamin D and calcium concentrations were greater in the vitamin D group ( + 3.7 μg/L and + 0.20 mg/dL , respectively ) than in the placebo group ( -1.2 μg/L and -0.12 mg/dL , respectively ; P < 0.001 for both ) . Vitamin D supplementation result ed in a significant decrease in serum hs-CRP ( vitamin D vs. placebo groups : -1.41 vs. + 1.50 μg/mL ; P-interaction = 0.01 ) and insulin concentrations ( vitamin D vs. placebo groups : -1.0 vs. + 2.6 μIU/mL ; P-interaction = 0.04 ) and a significant increase in the Quantitative Insulin Sensitivity Check Index score ( vitamin D vs. placebo groups : + 0.02 vs. -0.02 ; P-interaction = 0.006 ) , plasma total antioxidant capacity ( vitamin D vs. placebo groups : + 152 vs. -20 mmol/L ; P-interaction = 0.002 ) , and total glutathione concentrations ( vitamin D vs. placebo groups : + 205 vs. -32 μmol/L ; P-interaction = 0.02 ) compared with placebo . Intake of vitamin D supplements led to a significant decrease in fasting plasma glucose ( vitamin D vs. placebo groups : -0.65 vs. -0.12 mmol/L ; P-interaction = 0.01 ) , systolic blood pressure ( vitamin D vs. placebo groups : -0.2 vs. + 5.5 mm Hg ; P-interaction = 0.01 ) , and diastolic blood pressure ( vitamin D vs. placebo groups : -0.4 vs. + 3.1 mm Hg ; P-interaction = 0.01 ) compared with placebo . In conclusion , vitamin D supplementation for 9 wk among pregnant women has beneficial effects on metabolic status To assess the effect of vitamin D supplementation on parameters of insulin sensitivity/resistance ( IS/IR ) and insulin secretion in subjects with polycystic ovarian syndrome ( PCOS ) . A prospect i ve double-blind r and omized control trial was conducted to assess the effect of vitamin D on insulin kinetics in women with PCOS . The trial was conducted in a tertiary care research hospital . A total of 36 subjects with PCOS , aged 18–35 years , were included in this study . Vitamin D3 4000 IU/day versus placebo was given once a month for 6 months and both groups received metformin .  IS ( by whole-body IS index or Matsuda index ) , IR ( by homeostasis model assessment IR ( HOMA-IR ) ) , and insulin secretion ( by insulinogenic index ; II30 ) were the main outcome measures . Secondary outcome included blood pressure ( BP ) , lipid profile , disposition index ( DI ) , and vascular stiffness . Out of 36 subjects who consented , 32 completed the study . Subjects were r and omized into two groups : group A ( n=15 ; metformin and vitamin D 4000 IU/day ) or group B ( n=17 ; metformin and placebo ) . Oral glucose tolerance tests with 75 g glucose were carried out at baseline and 6 months after supplementation . Hypovitaminosis D was observed in 93.8 % of all subjects with mean serum 25 hydroxy vitamin D level of 7.30±4.45 ng/ml . After 6 months of vitamin D supplementation , there was no significant difference in any of the parameters of IS/IR ( area under curve (AUC)–glucose , AUC – insulin , insulin : glucose ratio , HOMA-IR , Matsuda index , insulinogenic index , and DI ) , II30 , and cardiovascular risk factors between the two groups . Supplementation of vitamin D , at a dose of 4000 IU/day for 6 months , did not have any significant effect on parameters of IS/IR and insulin secretion in subjects with PCOS Purpose The aim of this study is to evaluate the long-term influence of l-arginine intake on mineral concentration in patients with obesity and to assess the changes in lipid serum levels , fat content , and insulin resistance that result . Methods A r and omized double-blind placebo-controlled study was conducted . 88 obese patients were r and omly assigned to receive either 9 g of l-arginine or placebo daily , for 6 months . At baseline and after 6 months , selected anthropometrical measurements and blood biochemical analyses were performed and mineral levels were assessed . To assess insulin sensitivity , the gold-st and ard euglycemic clamp methodology was used . Results We found that 6 months of l-arginine supplementation result ed in significant increases in insulin sensitivity ( Δ1.1 mg/kg/min , P < 0.01 ) and zinc levels ( Δ1.5 μmol/L , P < 0.001 ) . Moreover , a positive correlation between the change in zinc concentration in serum and the change in insulin sensitivity was observed ( R = 0.80 , P < 0.01 ) . In the group of patients treated with l-arginine , a negative correlation between the change in zinc concentration in serum and the change in body fat content was noted ( R = −0.38 , P < 0.05 ) . Conclusions l-Arginine supplementation affects zinc status in obese patients . One beneficial influence is related to the improvements in insulin sensitivity Insulin resistance is one of the most common features of polycystic ovary syndrome ( PCOS ) . Some studies suggest that vitamin D deficiency may have a role in insulin resistance ; thus , the aim of the current study was to determine the effect of vitamin D supplementation on insulin resistance in women with PCOS and a vitamin D deficiency . We hypothesized that vitamin D supplementation would lower the glucose level and insulin resistance in women with PCOS and a vitamin D deficiency . The current study was a r and omized , placebo-controlled , double-blinded trial with 50 women with PCOS and a vitamin D deficiency , 20 to 40 years old , assigned to receive 3 oral treatments consisting of 50,000 IU of vitamin D₃ or a placebo ( 1 every 20 days ) for 2 months ( vitamin D , n = 24 ; placebo , n = 26 ) . The fasting blood glucose , insulin , 25-hydroxyvitamin D , and parathyroid hormone levels , as well as the homeostasis model assessment of insulin resistance and quantitative insulin sensitivity check index were measured at baseline and after treatment . In the vitamin D group , the serum level of 25-hydroxyvitamin D increased ( 6.9 ± 2.8 to 23.4 ± 6.1 ng/mL , P < .0001 ) , and the parathyroid hormone level decreased ( 70.02 ± 43.04 to 50.33 ± 21.99 μ IU/mL , P = .02 ) . There were no significant changes in the placebo group . There was a significant increase in insulin secretion in the vitamin D group ( P = .01 ) , but this was not significant compared with the placebo group . The fasting serum insulin and glucose levels and the insulin sensitivity and homeostasis model assessment of insulin resistance did not change significantly by the end of the study . We were not able to demonstrate the effect of vitamin D supplementation on insulin sensitivity and insulin resistance in women with PCOS and vitamin D deficiency
Vitamin K supplementation did not affect insulin sensitivity as measured by homeostasis model assessment of insulin resistance , fasting plasma glucose , fasting plasma insulin , C-reactive protein , adiponectin , leptin , and interleukin-6 levels .
Our analysis suggests no effect of vitamin K supplementation on insulin sensitivity
OBJECTIVE To perform a systematic review and meta- analysis of r and omized , placebo-controlled trials to assess the effect of vitamin K supplementation on insulin sensitivity .