Role of vitamin D in the development of insulin resistance and type 2 diabetes

Dysfunctional immunometabolic effects of vitamin D deficiency, increased cardiometabolic risk. Potential epidemiological alert in America?

Vitamin D deficiency is a serious public health problem worldwide that affects not only skeletal health, but also a wide range of acute and chronic diseases. However, there is still skepticism because of the lack of randomized, controlled trials to support association studies on the benefits of vitamin D for non-skeletal health. This review was based on articles published during the 1980-2015 obtained from the Cochrane Central Register of controlled trials, MEDLINE and PubMed, and focuses on recent challenges with regard to the definition of vitamin D deficiency and how to achieve optimal serum 25-hydroxyvitamin D levels from dietary sources, supplements, and sun exposure. The effect of vitamin D on epigenetic fetal programming and regulation of genes that may potentially explain why vitamin D could have such lifelong comprehensive health benefits is reviewed. Optimization of vitamin D levels in children and adults around the world has potential benefits to improve skeletal health and to reduce the risk of chronic diseases, including some types of cancer, autoimmune diseases, infectious diseases, type 2 diabetes mellitus, and severe cardiovascular disorders such as atherothrombosis, neurocognitive disorders, and mortality.

Association between tuberculosis, diabetes and 25 hydroxyvitamin D in Tanzania: a longitudinal case control study

Background

Vitamin D level is inversely associated with tuberculosis (TB) and diabetes (DM). Vitamin D could be a mediator in the association between TB and DM. We examined the associations between vitamin D, TB and DM.

Methods

Consecutive adults with TB and sex- and age-matched volunteers were included in a case-control study in Dar es Salaam, Tanzania. Glycemia and total vitamin D (25(OH)D) were measured at enrolment and after TB treatment in cases. The association between low 25(OH)D (<75 nmol/l) and TB was evaluated by logistic regression adjusted for age, sex, body mass index, socioeconomic status, sunshine hours, HIV and an interaction between low 25(OH)D and hyperglycemia.

Results

The prevalence of low 25(OH)D was similar in TB patients and controls (25.8 % versus 31.0 %; p = 0.22). In the subgroup of patients with persistent hyperglycemia (i.e. likely true diabetic patients), the proportion of patients with low 25(OH)D tended to be greater in TB patients (50 % versus 29.7 %; p = 0.20). The effect modification by persistent hyperglycemia persisted in the multivariate analysis (p_interaction = 0.01).

Conclusions

Low 25(OH)D may increase TB risk in patients with underlying DM. Trials should examine if this association is causal and whether adjunct vitamin D therapy is beneficial in this population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1960-x) contains supplementary material, which is available to authorized users.

Pleiotropic protective effects of Vitamin D against high fat diet-induced metabolic syndrome in rats: One for all

Several lines of evidence point to the association of vitamin D deficiency with the different components of metabolic syndrome. Yet, the effect of vitamin D supplementation on metabolic syndrome is not clearly elucidated. Herein, we tested the hypothesis that administration of vitamin D, either alone or in combination of metformin can improve metabolic and structural derangements associated with metabolic syndrome. Fifty wistar rats were randomly assigned to serve either as normal control (10 rats) or metabolic syndrome rats, by feeding them with a standard or a high fat diet (HFD), respectively. Metabolic syndrome rats were further assigned to receive either vehicle, Metformin (100mg/Kg orally), vitamin D (6ng/Kg SC.) or both, daily for 8 weeks. Body weight, blood pressure, serum glucose, insulin, insulin resistance, lipid profile, oxidative stress, serum uric acid and Ca⁺² were assessed at the end of the study. Histopathological examination of hepatic, renal and cardiac tissues were also performed. Treatment with vitamin D was associated with a significant improvement of the key features of metabolic syndrome namely obesity, hypertension and dyslipidaemia with a neutral effect on Ca⁺² level. When combined with metformin, most of the other metabolic abnormalities were ameliorated. Furthermore, a significant attenuation of the associated hepatic steatosis was observed with vitamin D as well as vitamin D/metformin combination. In conclusion, vitamin D can improve hypertension, metabolic and structural abnormalities induced by HFD, and it provides additional benefits when combined with metformin. Therefore, vitamin D could represent a feasible therapeutic option for prevention of metabolic syndrome.

1,25(OH)2 D3 improves cardiac dysfunction, hypertrophy, and fibrosis through PARP1/SIRT1/mTOR-related mechanisms in type 1 diabetes

SCOPE

Diabetic cardiomyopathy is one of the most important cardiac complications associated with diabetes. However, the mechanisms underlying diabetic cardiomyopathy remain unclear. The PARP1, SIRT1, and mTOR pathways have been implicated in cardiac diseases, and they are also associated with diabetes. 1,25(OH)₂ D₃ was recently recognized as a potential PARP1inhibitor in a macrophage cell line. The aim of our study was to investigate whether 1,25(OH)₂ D₃ can improve diabetic cardiomyopathy through a vitamin D receptor (VDR)-dependent mechanism associated with the PARP1/SIRT1/mTOR pathway.

METHODS AND RESULTS

1,25(OH)₂ D₃ -treated diabetic rats displayed improved left ventricular wall thickness and end-diastolic/systolic diameter, end-diastolic/systolic volume, left ventricular ejection fraction, fractional shortening, atrial natriuretic peptide, and brain natriuretic peptide gene expression, and interstitial fibrosis compared with untreated diabetic rats, while silencing the VDR gene in DM rats blocked the above results. 1,25(OH)₂ D₃ treatment also decreased PARP1 and increased SIRT1 expression levels and repressed the phosphorylation of mTOR. Treating neonatal cardiomyocytes with 1,25(OH)₂ D₃ and a PARP1 inhibitor decreased PARP1 and increased SIRT1 protein expression.

CONCLUSION

The present study demonstrates that 1,25(OH)₂ D₃ treatment has the potential to improve diabetic cardiomyopathy in rats and suggests that VD-VDR signaling induces this protective effect against diabetic cardiomyopathy might partly through the PARP1/SIRT1/mTOR pathway.

Effects of vitamin D supplementation on glycated haemoglobin and fasting glucose levels in hypertensive patients: a randomized controlled trial

AIM

To investigate the efficacy of vitamin D supplementation on glycaemic control.

METHODS

The Styrian Vitamin D Hypertension Trial was a single-centre, double-blind, placebo-controlled study conducted between 2011 and 2014 at the Medical University of Graz, Austria. We enrolled 200 people with arterial hypertension and 25-hydroxyvitamin D [25(OH)D] concentrations <30 ng/mL. Study participants were randomized to receive either 2800 IU of vitamin D or placebo per day for 8 weeks. The present study was a post hoc analysis that incorporated an analysis of covariance (ancova) approach, while adjusting for baseline differences.

RESULTS

A total of 185 participants [mean ± standard deviation age, 60.1 ± 11.3 years; 47% women; mean 25(OH)D 21.2 ± 5.6 ng/mL, mean glycated haemoglobin (HbA1c) 44.8 ± 11.8 mmol/mol and mean body mass index 30.4 ± 5.4 kg/m(2) ] completed the trial. ancova showed a mean treatment effect [95% confidence interval (CI)] on HbA1c of -3.52 (-6.7 to -0.34) mmol/mol (p = .045). There was no difference in fasting glucose -4.7 mg/dL (95% CI -16.3 to 6.9; p = .426).

CONCLUSIONS

Vitamin D supplementation in obese hypertensive patients with low 25(OH)D reduces HbA1c levels. This finding warrants further investigation into potential vitamin D effects on glucose homeostasis.

Influence of Vitamin D and Parathyroid Hormone on Bone and Metabolic Risk in Women with Previous Gestational Diabetes

The purpose of this study was to compare plasma 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH), VO2max, bone (by DXA), and metabolic outcomes across age and race-matched postmenopausal women (54±1 years; mean±SEM): 1) with previous gestational diabetes (GDM) (32±1 kg/m(2); n=17), 2) without previous GDM, but with a similar BMI to GDM (32±1 kg/m(2); n=17), and 3) without previous GDM, but with a higher BMI than GDM (36±1 kg/m(2); n=17; p<0.01). The prevalence of 25(OH)D insufficiency and deficiency was high (~80%), but not different across groups, while PTH tended to be ~30% lower in women with a history of GDM (p=0.09). Women with a history of GDM had lower HDL cholesterol and higher diastolic blood pressure and fasting and 2-h glucose levels (by oral glucose tolerance test) (vs. groups 2 and 3; p<0.05). Bone mineral density (BMD) tended to be slightly higher in women with prior GDM than the BMI matched women with no prior GDM (p=0.09). Overall, higher PTH was associated with lower femoral neck (r=- 0.33) and (r=- 0.38) (p <0.05), while lower 25(OH)D was associated with lower VO2max (r=0.25, p=0.05) and higher fasting glucose (r=- 0.14) and insulin (r=- 0.29 (p <0.05). We observed that the poor metabolic profiles of postmenopausal women with a history of GDM are independent of 25(OH)D and PTH. However, due to associations between 25(OH)D and PTH with bone and metabolic outcomes, maintaining recommended 25(OH)D and PTH concentrations is important regardless of a previous history of GDM.

Rationale and design of Diabetes Prevention with active Vitamin D (DPVD): a randomised, double-blind, placebo-controlled study

INTRODUCTION

Recent research suggests that vitamin D deficiency may cause both bone diseases and a range of non-skeletal diseases. However, most of these data come from observational studies, and clinical trial data on the effects of vitamin D supplementation on individuals with pre-diabetes are scarce and inconsistent. The aim of the Diabetes Prevention with active Vitamin D (DPVD) study is to assess the effect of eldecalcitol, active vitamin D analogue, on the incidence of type 2 diabetes among individuals with pre-diabetes.

METHODS AND ANALYSIS

DPVD is an ongoing, prospective, multicentre, randomised, double-blind and placebo-controlled outcome study in individuals with impaired glucose tolerance. Participants, men and women aged ≥30 years, will be randomised to receive eldecalcitol or placebo. They will also be given a brief (5-10 min long) talk about appropriate calorie intake from diet and exercise at each 12-week visit. The primary end point is the cumulative incidence of type 2 diabetes. Secondary endpoint is the number of participants who achieve normoglycaemia at 48, 96 and 144 weeks. Follow-up is estimated to span 144 weeks.

ETHICS AND DISSEMINATION

All protocols and an informed consent form comply with the Ethics Guideline for Clinical Research (Japan Ministry of Health, Labour and Welfare). The study protocol has been approved by the Institutional Review Board at Kokura Medical Association and University of Occupational and Environmental Health. The study will be implemented in line with the CONSORT statement.

TRIAL REGISTRATION NUMBER

UMIN000010758; Pre-results.

Relationship between HOMA-IR and serum vitamin D in Chinese children and adolescents

BACKGROUND

The objective of this study was to examine the cross-sectional relationship between homeostasis model assessment for insulin resistance (HOMA-IR) and serum 25-hydroxyvitamin D (25-OHD) level in Chinese children and adolescents.

METHODS

Anthropometric indices, lipid metabolic profile, and serum levels of glucose, insulin and 25-OHD were determined among 278 healthy prepubertal and pubertal, normal and overweight/obese children and adolescents aged 8-18 years between March 2014 and February 2015.

RESULTS

HOMA-IR was significantly different across vitamin D statuses (p<0.001), even after adjusting for body mass index (BMI) (p=0.035) and waist-to-height ratio (p=0.044); the difference was not significant between the vitamin D deficient and insufficient groups (p=0.120). HOMA-IR negatively correlated with serum 25-OHD level for all subjects (R2=0.148, p<0.001). Furthermore, they negatively correlated in the normal (R2=0.160, p<0.001) and overweight/obese (R2=0.086, p<0.001) groups, respectively. The regression lines of the two groups were parallel (p=0.669) but had a significantly different intercept (p<0.001). An association between HOMA-IR and BMI and serum 25-OHD level (R2=0.654, p<0.001) was demonstrated based on the stepwise multiple linear regression analysis of age, sex, pubertal maturation, BMI, waist-to-height ratio, triglyceride, cholesterol, high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), 25-OHD and HOMA-IR.

CONCLUSIONS

Our findings supported that lower vitamin D status is strongly associated with worse HOMA-IR.

The associations of vitamin D status and dietary calcium with the metabolic syndrome: an analysis of the Victorian Health Monitor survey

OBJECTIVE

To examine the associations between serum 25-hydroxyvitamin D (25(OH)D), dietary Ca intake and presence of the metabolic syndrome (MetS).

DESIGN

A stratified cluster sample of a population aged 18-75 years from the Victorian Health Monitor survey.

SETTING

Non-institutionalized adults living in private dwellings in Victoria, Australia.

SUBJECTS

Adults (n 3404) with complete data and without type 1 or type 2 diabetes.

RESULTS

Adjusted for sociodemographic factors, physical characteristics and dietary covariates including Ca intake, every 10 nmol/l increase in serum 25(OH)D was significantly associated with decreased odds of MetS (adjusted odds ratio (AOR)=0·85, 95 % CI 0·80, 0·89; P<0·001). Relative to the low 25(OH)D tertile (median 33 nmol/l), there was a progressive decrease in odds of MetS that reached significance with the high 25(OH)D tertile (median 77 nmol/l; AOR=0·35, 95 % CI 0·26, 0·48; P<0·001). Every 500 mg/d increase in Ca intake adjusted for 25(OH)D did not reduce odds of MetS (AOR=0·81, 95 % CI 0·66, 1·06; P=0·141) but approached significance if unadjusted for 25(OH)D in the final model (AOR=0·81, 95 % CI 0·64, 1·02; P=0·073). No significant effect was obtained for tertiles of Ca intake. However, Ca and vitamin D tertile combinations suggested a beneficial effect of high Ca (median 1233 mg/d) only at low and medium 25(OH)D. The high 25(OH)D tertile was associated with significantly decreased odds of MetS regardless of Ca intake.

CONCLUSIONS

A high vitamin D status significantly reduced the odds of MetS. A high Ca intake may have a similar favourable outcome but only at lower circulating concentrations of 25(OH)D.

Vitamin D and cardiovascular disease prevention

Vitamin D is a precursor of the steroid hormone calcitriol that is crucial for bone and mineral metabolism. Both the high prevalence of vitamin D deficiency in the general population and the identification of the vitamin D receptor in the heart and blood vessels raised interest in the potential cardiovascular effects of vitamin D. Experimental studies have demonstrated various cardiovascular protective actions of vitamin D, but vitamin D intoxication in animals is known to induce vascular calcification. In meta-analyses of epidemiological studies, vitamin D deficiency is associated with an increased cardiovascular risk. Findings from Mendelian randomization studies and randomized, controlled trials (RCTs) do not indicate significant effects of a general vitamin D supplementation on cardiovascular outcomes. Previous RCTs, however, were not adequately designed to address extraskeletal events, and did not focus on vitamin D-deficient individuals. Therefore, currently available evidence does not support cardiovascular benefits or harms of vitamin D supplementation with the commonly used doses, and whether vitamin D has cardiovascular effects in individuals with overt vitamin D deficiency remains to be evaluated. Here, we provide an update on clinical studies on vitamin D and cardiovascular risk, discuss ongoing vitamin D research, and consider the management of vitamin D deficiency from a cardiovascular health perspective.

Serum 25-Hydroxyvitamin D Status and Longitudinal Changes in Weight and Waist Circumference: Influence of Genetic Predisposition to Adiposity

Studies of the relationship between serum 25-hydroxyvitamin D (25(OH)D) and changes in measures of adiposity have shown inconsistent results, and interaction with genetic predisposition to obesity has rarely been examined. We examined whether 25(OH)D was associated with subsequent annual changes in body weight (ΔBW) or waist circumference (ΔWC), and whether the associations were modified by genetic predisposition to a high BMI, WC or waist-hip ratio adjusted for BMI (WHR_BMI). The study was based on 10,898 individuals from the Danish Inter99, the 1958 British Birth Cohort and the Northern Finland Birth Cohort 1966. We combined 42 adiposity-associated Single Nucleotide Polymorphisms (SNPs) into four scores indicating genetic predisposition to BMI, WC and WHR_BMI, or all three traits combined. Linear regression was used to examine the association between serum 25(OH)D and ΔBW or ΔWC, SNP-score × 25(OH)D interactions were examined, and results from the individual cohorts were meta-analyzed. In the meta-analyses, we found no evidence of an association between 25(OH)D and ΔBW (-9.4 gram/y per 10 nmol/L higher 25(OH)D [95% CI: -23.0, +4.3; P = 0.18]) or ΔWC (-0.06 mm/y per 10 nmol/L higher 25(OH)D [95% CI: -0.17, +0.06; P = 0.33]). Furthermore, we found no statistically significant interactions between the four SNP-scores and 25(OH)D in relation to ΔBW or ΔWC. Thus, in view of the narrow CIs, our results suggest that an association between 25(OH)D and changes in measures of adiposity is absent or marginal. Similarly, the study provided evidence that there is either no or very limited dependence on genetic predisposition to adiposity.

Vitamin D 20,000 IU per Week for Five Years Does Not Prevent Progression From Prediabetes to Diabetes

CONTEXT

Vitamin D deficiency is associated with insulin resistance and risk of future diabetes.

OBJECTIVE

The objective of the study was to test whether supplementation with vitamin D to subjects with prediabetes will prevent progression to type 2 diabetes mellitus (T2DM).

DESIGN

This was a randomized controlled trial performed in 2008 through 2015.

SETTING

The study was conducted at the clinical research unit at a teaching hospital.

PATIENTS

Five hundred eleven subjects (mean age 62 y, 314 males) with prediabetes diagnosed with an oral glucose tolerance test as part of the Tromsø Study 2007–2008 were included. A total of 256 were randomized to vitamin D and 255 to placebo. Twenty-nine subjects in the vitamin D and 24 in the placebo group withdrew because of adverse events.

INTERVENTIONS

Interventions included vitamin D (cholecalciferol) 20 000 IU/wk vs placebo for 5 years. Annual oral glucose tolerance tests were performed.

MAIN OUTCOME MEASURE

Progression to T2DM was the main outcome measure. Secondary outcomes were change in glucose levels, insulin resistance, serum lipids, and blood pressure.

RESULTS

The mean baseline serum 25-hydroxyvitamin D level was 60 nmol/L (24 ng/mL). One hundred three in the vitamin D and 112 in the placebo group developed T2DM (hazard risk 0.90; 95% confidence interval 0.69–1.18, Cox regression, P = .45, intention to treat analysis). No consistent significant effects on the other outcomes were seen. Subgroup analyses in subjects with low baseline 25-hydroxyvitamin D yielded similar results. No serious side effects related to the intervention were recorded.

CONCLUSIONS

In subjects without vitamin D deficiency, vitamin D supplementation is unlikely to prevent progression from prediabetes to diabetes. Very large studies with inclusion of vitamin D-deficient subjects will probably be needed to show such a putative effect. This study tested if supplementation with vitamin D to subjects with prediabetes will prevent progression to type 2 diabetes (T2DM).

Reductions in body weight and percent fat mass increase the vitamin D status of obese subjects: a systematic review and metaregression analysis

The purpose of this review was to confirm a volumetric dilution of vitamin D in obesity. It was based on the hypothesis that weight loss, particularly fat loss, would increase serum 25-hydroxyvitamin D (25OHD) in the obese. We conducted a systematic review of the literature over the last 21 years and included human trials that reported changes in 25OHD, weight, or body composition after weight loss. Study arms were excluded if vitamin D was supplemented, dietary intake exceeded 800 IU/d, or extreme sun exposure was reported. Eighteen of 23 trials that met our criteria documented an increase in vitamin D status with weight loss. Metaregression analyses indicated a marginally significant effect of weight loss on unadjusted weighted mean difference of 25OHD (β = -0.60 [95% confidence interval {CI}, -1.24 to +0.04] nmol/L; P = .06) and after adjustment for study quality (Jadad score ≥3) (β = -0.64 [95% CI, -1.28 to +0.01] nmol/L; P = .05). The effect of percent fat mass on weighted mean difference of 25OHD was also marginally significant before (β = -0.91 [95% CI, -1.96 to +0.15] nmol/L; P = .08) and after adjustment of study quality (β = -1.05 [95% CI, -2.18 to +0.08] nmol/L; P = .06). Collectively, these outcomes support a volumetric dilution of vitamin D. The slopes of the respective regression lines, however, indicate a smaller increase in 25OHD than would be expected from a direct mobilization of stores into the circulation. Hence, sequestration of 25OHD and its conversion to inactive metabolites would also play a role. Future studies could relate changes in body fat compartments to the enzymatic regulation of 25OHD in response to weight loss.

Vitamin D status and health-related quality of life in patients with Type 2 diabetes

AIMS

To test whether vitamin D status was associated with health-related quality of life in people with Type 2 diabetes mellitus.

METHODS

Demographic and clinical characteristics, including health-related quality of life scores, were obtained from 241 adult patients with Type 2 diabetes managed with oral hypoglycaemic agents. Health-related quality of life was assessed using the Short-Form 36 Health Survey. Multiple logistic regression analysis was used to investigate the association between vitamin D status and health-related quality of life, with adjustment for confounders.

RESULTS

The mean age of the patients included in the study was 67 ± 8 years. Their mean HbA1c concentration was 52 ± 8 mmol/mol (6.9 ± 0.7%) and their mean serum 25-hydroxyvitamin D concentration was 59 ± 23 nmol/l. Vitamin D deficiency (serum 25-hydroxyvitamin D < 50 nmol/l) was present in 38% of patients. No significant associations were found between vitamin D status and health-related quality of life.

CONCLUSIONS

Vitamin D status was not associated with health-related quality of life in patients with Type 2 diabetes. This could be explained by the relatively high serum 25-hydroxyvitamin D concentration, good glycaemic control and relatively good health-related quality of life of all patients. A prospective study among patients with vitamin D deficiency and poor glycaemic control would be interesting for future research.

Calcium and Vitamin D in Obesity and Related Chronic Disease

There is a pandemic of lifestyle-related diseases. In both developed and lesser developed countries of the world, an inadequacy of calcium intake and low vitamin D status is common. In this chapter, we explore a mechanistic framework that links calcium and vitamin D status to chronic conditions including obesity, systemic inflammation, endothelial dysfunction, dyslipidemia and cardiovascular disease, and type 2 diabetes mellitus. We also update the available clinical evidence, mainly from randomized controlled trials, to provide a synthesis of evidence in favor or against these hypotheses. There is consistent data to support calcium increasing whole body fat oxidation and increasing fecal fat excretion, while there is good cellular evidence for vitamin D reducing inflammation. Clinical trials support a marginal reduction in circulating lipids and some meta-analysis support an increase in insulin sensitivity following vitamin D. However, these mechanistic pathways and intermediate biomarkers of disease do not consistently transcribe into measurable health outcomes. Cementing the benefits of calcium and vitamin D for extraskeletal health needs a reexamination of the target 25(OH)D level to be achieved and the minimum duration of future trials.

Non-linear contribution of serum vitamin D to symptomatic diabetic neuropathy: A case-control study

AIMS

Vitamin D deficiency has recently been speculated to be associated with increased risk of diabetes neuropathy (DN). The aim of this study was to evaluate the odds of symptomatic DN across serum vitamin D levels.

METHODS

All patients with DM were assessed using diabetic neuropathy symptoms and diabetic neuropathy examination score. Overall, 150 cases with DN and 600 controls were included. Serum 25-hydroxyvitamin D (25-OH-D) was measured to determine vitamin D status.

RESULTS

A non-linear association between 25-OH-D and suffering from symptomatic DN was observed which was extracted after stratifying the ORs across different serum 25-OH-D levels. When compared to individuals with 25-OH-D of 30-40 ng/mL, patients with deficient (<20 ng/mL) vitamin D levels had higher odds of having symptomatic DN (OR: 2.04, 95%CI: 0.99-4.02, P=0.054). Participants with vitamin D values of greater than 40 ng/mL were also more likely to exhibit symptomatic DN (fully adjusted OR: 4.29, 95%CI: 1.59-11.55).

CONCLUSIONS

We hypothesize a non-linear contribution of serum vitamin D to symptomatic DN occurrence, which emphasizes that administration of vitamin D should be monitored and evaluated more carefully, especially in patients with diabetes.

Genetic Variations in the Vitamin D Receptor Predict Type 2 Diabetes and Myocardial Infarction in a Community-Based Population: The Tromsø Study

BACKGROUND

Though the associations between low serum 25-hydroxyvitamin D (25(OH)D) levels and health outcomes such as type 2 diabetes (T2D), myocardial infarction (MI), cancer, and mortality are well-studied, the effect of supplementation with vitamin D is uncertain. This may be related to genetic differences. Thus, rs7968585, a single nucleotide polymorphism (SNP) of the vitamin D receptor (VDR), has recently been reported as a predictor of composite health outcome. We therefore aimed to evaluate whether rs7968585 predicts separate clinical outcomes such as T2D, MI, cancer, and mortality in a community-based Norwegian population.

METHODS AND FINDINGS

Measurements and DNA were obtained from the participants in the Tromsø Study in 1994-1995, registered with the outcomes of interest and a randomly selected control group. The impact of the rs7968585 genotypes was evaluated with Cox proportional hazards. A total of 8,461 subjects were included among whom 1,054 subjects were registered with T2D, 2,287 with MI, 3,166 with cancer, and 4,336 with death. Mean follow-up time from birth was 60.8 years for T2D and MI, 61.2 years for cancer, while mean follow-up time from examination date was 16.5 years for survival. Mean serum 25(OH)D levels did not differ across the rs7968585 genotypes. With the major homozygote genotype as reference, the minor homozygote subjects had hazard ratios of 1.25 (95% CI 1.05-1.49) for T2D and 1.14 (1.02-1.28) for MI (P = 0.011 and 0.023, respectively, without the Bonferroni correction). No significant interaction between serum 25(OH)D status and the rs7968585 genotype was found for any of the endpoints.

CONCLUSIONS

The VDR-related SNP rs7968585 minor allele is a significant and positive predictor for T2D and possibly for MI. Since the functional mechanism of this SNP is not yet understood, and the association with T2D is reported for the first time, confirmatory studies are needed.

Vitamin D Status and the Risk of Anemia in Community-Dwelling Adults: Results from the National Health and Nutrition Examination Survey 2001-2006

Low vitamin D status has been implicated in several chronic medical conditions and unfavorable health outcomes. Our goal was to investigate whether serum 25-hydroxyvitamin D (25OHD) levels are a potentially modifiable risk factor for anemia in a nationally representative cohort of community-dwelling individuals in the United States. We performed a cross-sectional study of 5456 individuals (≥17 years) from the National Health and Nutrition Examination Survey from 2001 to 2006. Locally weighted scatterplot smoothing (LOWESS) was used to graphically depict the relationship between serum 25OHD levels and the cumulative frequency of anemia. Multivariable logistic regression models were then used to assess the independent association of 25OHD levels with anemia, while controlling for age, sex, race, body mass index, chronic kidney disease, as well as serum levels of C-reactive protein, ferritin, iron, vitamin B12, and folic acid. The mean (standard error) 25OHD and hemoglobin levels in the analytic group were 23.5 (0.4) ng/mL and 14.4 (0.1) g/dL, respectively. Prevalence of anemia was 3.9%. Locally weighted scatterplot smoothing analysis demonstrated a near-linear relationship between vitamin D status and cumulative frequency of anemia up to 25OHD levels of approximately 20  ng/mL. With increasing 25OHD levels, the curve flattened out progressively. Multivariable regression analysis demonstrated an inverse association of 25OHD levels with the risk of anemia (adjusted odds ratio 0.97; 95% confidence interval 0.95-0.99 per 1  ng/mL change in 25OHD). Compared to individuals with ≥20  ng/mL, individuals with 25OHD levels <20  ng/mL were more likely to be anemic (adjusted odds ratio 1.64; 95% confidence interval 1.08-2.49). In a nationally representative sample of community-dwelling individuals in the United States, low 25OHD levels were associated with increased risk of anemia. Randomized controlled trials are needed to determine whether optimizing vitamin D status can reduce the burden of anemia in the general population.

The Impact of Vitamin D Levels on Inflammatory Status: A Systematic Review of Immune Cell Studies

Chronic low-grade inflammation accompanies obesity and its related chronic conditions. Both peripheral blood mononuclear cells (PBMCs) and cell lines have been used to study whether vitamin D has immune modulating effects; however, to date a detailed systematic review describing the published evidence has not been completed. We therefore conducted a systematic review on the effect of vitamin D on the protein expression and secretion of inflammatory markers by human-derived immune cells. The review was registered at the International Prospective Register for Systematic Reviews (PROSPERO, Registration number CRD42015023222). A literature search was conducted using Pubmed, Science Direct, Scopus, Web of Science and Medline. The search strategy used the following search terms: Vitamin D or cholecalciferol or 1,25-dihydroxyvitamin or 25-hydroxy-Vitamin D and Inflam* or cytokine* and supplement* or cell*. These terms were searched in the abstract, title and keywords. Inclusion criteria for study selection consisted of human-derived immune cell lines or cellular studies where PBMCs were obtained from humans, reported in the English language, and within the time period of 2000 to 2015. The selection protocol was mapped according to PRISMA guidelines. Twenty three studies (7 cell line and 16 PBMCs studies) met our criteria. All studies selected except one used the active metabolite 1,25(OH)2, with one study using cholecalciferol and two studies also using 25(OH)D. Four out of seven cell line studies showed an anti-inflammatory effect where suppression of key markers such as macrophage chemotactic protein 1, interleukin 6 and interleukin 8 were observed. Fourteen of sixteen PBMC studies also showed a similar anti-inflammatory effect based on common inflammatory endpoints. Mechanisms for such effects included decreased protein expression of toll-like receptor-2 and toll-like receptor-4; lower levels of phosphorylated p38 and p42/42; reduced expression of phosphorylated signal transducer and activator of transcription 5 and decreased reactive oxygen species. This review demonstrates that an anti-inflammatory effect of vitamin D is a consistent observation in studies of cell lines and human derived PBMCs.

Endocrine determinants of incident sarcopenia in middle-aged and elderly European men

BACKGROUND

In men, the long-term consequences of low serum levels of sex steroids, vitamin D metabolites, and insulin-like growth factor 1 (IGF-1) on the evolution of muscle mass, muscle strength, or physical performance are unclear. Moreover, there are no data about the relationship between these hormones and incident sarcopenia defined as low muscle mass and function. The aim of this study was to determine whether the baseline levels of sex hormones, vitamin D metabolites, and IGF-1 predict changes in muscle mass, muscle strength, physical performance, and incident sarcopenia.

METHODS

In 518 men aged 40-79 years, recruited for participation in the European Male Ageing Study, total, free, and bioavailable testosterone (T), oestradiol (E), sex hormone-binding globulin, IGF-1, 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D (1,25(OH)2D), and parathyroid hormone were assessed at baseline. Appendicular lean mass (aLM), gait speed, and grip strength were measured at baseline and after a mean follow-up of 4.3 years. Sarcopenia was defined by the definition of Baumgartner (relative aLM ≤7.26 kg/m(2)), the International Working Group on Sarcopenia (IWGS), and the European Working Group on Sarcopenia in Older People (EWGSOP).

RESULTS

aLM significantly decreased from age 50 years, while gait speed and grip strength significantly decreased from age 70 years. The incidence of sarcopenia by the definitions of Baumgartner, IWGS, and EWGSOP was 8.1%, 3.0%, and 1.6%, respectively. After adjustment for age, centre, body mass index, smoking, and number of comorbidities at baseline, baseline levels of T and vitamin D metabolites were not associated with change in aLM, gait speed, and/or grip strength, while a high baseline level of total E2 was associated with a greater decrease in aLM. In men aged ≥70 years, low IGF-1 was associated with a greater decrease in gait speed. Baseline endocrine variables were not independently associated with an increased risk of incident sarcopenia by any definition.

CONCLUSIONS

Low levels of T and 25OHD do not predict loss of muscle mass, gait speed, or grip strength in middle-aged and elderly community-dwelling European men. Low IGF-1 predicts change in gait speed in men aged ≥70 years.

Circadian rhythm of serum 25 (OH) vitamin D, calcium and phosphorus levels in the treatment and management of type-2 diabetic patients

The circadian time structure of serum 25 (OH) vitamin D (25-OHD), calcium (Ca) and phosphorus (P) may prove to be helpful in prevention, efficacy and management of diabetes mellitus. Ten newly diagnosed patients with type-2 diabetes mellitus (6 men and 4 women), 30-65 years of age, and 10 age-matched clinically healthy volunteers (7 men and 3 women) were synchronized for one week with diurnal activity from about 06:00 to about 22:00 and nocturnal rest. Breakfast was served around 08:00, lunch around 13:30 and dinner around 20:00. Drugs/nutraceuticals known to affect the vitamin D-calcium metabolism and status were not taken. Blood samples were collected at 6-h intervals for 24 h under standardized, 24-h synchronized conditions. Serum 25-OHD, Ca, P, Ca-P product and Ca-P ratio were determined. A marked circadian variation was demonstrated for 25-OHD in healthy volunteers (p = 0.030) and of borderline statistical significance in the diabetic patients (p = 0.083) by population-mean cosinor analysis. Similarly, healthy volunteers showed borderline significance for serum Ca, P and Ca-P ratio. The circadian acrophase of Ca occurred later in the patients as compared to healthy controls. Mapping the circadian rhythm (an important component of the broader time structure or chronome, which includes a.o., trends with age and extra-circadian components) of vitamin D and calcium is needed for exploring their role as markers in the treatment and management of diabetic patients.

The potential regulatory role of vitamin D in the bioenergetics of inflammation

PURPOSE OF REVIEW

The extraskeletal health benefits of vitamin D still need scientific endorsement. Obesity and related chronic diseases are pathogenically linked by inflammation, which carries a considerable energetic cost. Recent techniques for the determination of the bioenergetic demand of inflammation, offer an avenue to cement the regulatory role of vitamin D in this process.

RECENT FINDINGS

Nuclear vitamin D receptors may be translocated into mitochondria of certain cell types, opening up a pathway for direct action on cellular bioenergetics. Classical M1 (inflammatory)/M2(anti-inflammatory) phenotypes can vary with the clinical context. M2 macrophages do not always depend on oxidative metabolism/fatty acid oxidation. Newer methodologies offer real-time bioenergetic measurements that can be used as an index of metabolic health.

SUMMARY

Vitamin D may prove to be a therapeutic agent for inflammation of chronic disease and understanding its role in cellular bioenergetics may offer a diagnostic/prognostic indicator of its action.

Association between circulating 25-hydroxyvitamin D and incident type 2 diabetes: a mendelian randomisation study

BACKGROUND

Low circulating concentrations of 25-hydroxyvitamin D (25[OH]D), a marker of vitamin D status, are associated with an increased risk of type 2 diabetes, but whether this association is causal remains unclear. We aimed to estimate the unconfounded, causal association between 25(OH)D concentration and risk of type 2 diabetes using a mendelian randomisation approach.

METHODS

Using several data sources from populations of European descent, including type 2 diabetes cases and non-cases, we did a mendelian randomisation analysis using single nucleotide polymorphisms (SNPs) within or near four genes related to 25(OH)D synthesis and metabolism: DHCR7 (related to vitamin D synthesis), CYP2R1 (hepatic 25-hydroxylation), DBP (also known as GC; transport), and CYP24A1 (catabolism). We assessed each SNP for an association with circulating 25(OH)D concentration (5449 non-cases; two studies), risk of type 2 diabetes (28 144 cases, 76 344 non-cases; five studies), and glycaemic traits (concentrations of fasting glucose, 2-h glucose, fasting insulin, and HbA1c; 46 368 non-cases; study consortium). We combined these associations in a likelihood-based mendelian randomisation analysis to estimate the causal association of 25(OH)D concentration with type 2 diabetes and the glycaemic traits, and compared them with that from a meta-analysis of data from observational studies (8492 cases, 89 698 non-cases; 22 studies) that assessed the association between 25(OH)D concentration and type 2 diabetes.

FINDINGS

All four SNPs were associated with 25(OH)D concentrations (p<10(-6)). The mendelian randomisation-derived unconfounded odds ratio for type 2 diabetes was 1·01 (95% CI 0·75-1·36; p=0·94) per 25·0 nmol/L (1 SD) lower 25(OH)D concentration. The corresponding (potentially confounded) relative risk from the meta-analysis of data from observational studies was 1·21 (1·16-1·27; p=7·3 × 10(-19)). The mendelian randomisation-derived estimates for glycaemic traits were not significant (p>0·25).

INTERPRETATION

The association between 25(OH)D concentration and type 2 diabetes is unlikely to be causal. Efforts to increase 25(OH)D concentrations might not reduce the risk of type 2 diabetes as would be expected on the basis of observational evidence. These findings warrant further investigations to identify causal factors that might increase 25(OH)D concentration and also reduce the risk of type 2 diabetes.

FUNDING

UK Medical Research Council Epidemiology Unit and European Union Sixth Framework Programme.

No effect of high-dose vitamin D supplementation on glycemic status or cardiovascular risk factors in subjects with prediabetes

OBJECTIVE

In observational studies, low serum 25-hydroxyvitamin D [25(OH)D] concentrations have been associated with insulin resistance and other risk factors for cardiovascular disease.

RESEARCH DESIGN AND METHODS

We present 1-year data from an ongoing 5-year trial in 511 individuals with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) randomly assigned to 20,000 IU/week vitamin D3 or placebo. An oral glucose tolerance test was performed at baseline and after 1 year.

RESULTS

Mean baseline serum 25(OH)D was 59.9 nmol/L and 61.1 nmol/L in the vitamin D and placebo groups, respectively, and increased by 45.8 nmol/L and 3.4 nmol/L, respectively. With adjustment for baseline concentrations, no differences in measures of glucose metabolism, insulin secretion or sensitivity, blood pressure, or hs-CRP were found after 1 year. There was a slight, but significant decrease in total and LDL cholesterol in the vitamin D group compared with the placebo group, but as there was also a decrease in HDL cholesterol, the change in the total/HDL cholesterol ratio did not differ significantly. Only analyzing subjects with 25(OH)D <50 nmol/L did not change the results.

CONCLUSIONS

This study shows that vitamin D supplementation does not improve glycemic indices, blood pressure, or lipid status in subjects with IFG and/or IGT.

Vitamin D: a critical and essential micronutrient for human health

Vitamin D is a micronutrient that is needed for optimal health throughout the whole life. Vitamin D₃ (cholecalciferol) can be either synthesized in the human skin upon exposure to the UV light of the sun, or it is obtained from the diet. If the photoconversion in the skin due to reduced sun exposure (e.g., in wintertime) is insufficient, intake of adequate vitamin D from the diet is essential to health. Severe vitamin D deficiency can lead to a multitude of avoidable illnesses; among them are well-known bone diseases like osteoporosis, a number of autoimmune diseases, many different cancers, and some cardiovascular diseases like hypertension are being discussed. Vitamin D is found naturally in only very few foods. Foods containing vitamin D include some fatty fish, fish liver oils, and eggs from hens that have been fed vitamin D and some fortified foods in countries with respective regulations. Based on geographic location or food availability adequate vitamin D intake might not be sufficient on a global scale. The International Osteoporosis Foundation (IOF) has collected the 25-hydroxy-vitamin D plasma levels in populations of different countries using published data and developed a global vitamin D map. This map illustrates the parts of the world, where vitamin D did not reach adequate 25-hydroxyvitamin D plasma levels: 6.7% of the papers report 25-hydroxyvitamin D plasma levels below 25 nmol/L, which indicates vitamin D deficiency, 37.3% are below 50 nmol/Land only 11.9% found 25-hydroxyvitamin D plasma levels above 75 nmol/L target as suggested by vitamin D experts. The vitamin D map is adding further evidence to the vitamin D insufficiency pandemic debate, which is also an issue in the developed world. Besides malnutrition, a condition where the diet does not match to provide the adequate levels of nutrients including micronutrients for growth and maintenance, we obviously have a situation where enough nutrients were consumed, but lacked to reach sufficient vitamin D micronutrient levels. The latter situation is known as hidden hunger. The inadequate vitamin D status impacts on health care costs, which in turn could result in significant savings, if corrected. Since little is known about the effects on the molecular level that accompany the pandemic like epigenetic imprinting, the insufficiency-triggered gene regulations or the genetic background influence on the body to maintain metabolic resilience, future research will be needed. The nutrition community is highly interested in the molecular mechanism that underlies the vitamin D insufficiency caused effect. In recent years, novel large scale technologies have become available that allow the simultaneous acquisition of transcriptome, epigenome, proteome, or metabolome data in cells of organs. These important methods are now used for nutritional approaches summarized in emerging scientific fields of nutrigenomics, nutrigenetics, or nutriepigenetics. It is believed that with the help of these novel concepts further understanding can be generated to develop future sustainable nutrition solutions to safeguard nutrition security.

Association of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and parathyroid hormone with mortality among middle-aged and older European men

BACKGROUND

vitamin D deficiency has been associated with an increased risk of mortality, but whether this relationship is causal or linked to co-existent comorbidity and adverse life factors remains uncertain. Our objective was to determine whether endogenous 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D) and parathyroid hormone (PTH) levels predicted all-cause, cardiovascular and cancer mortality independently of health and lifestyle factors.

SETTING

: prospective cohort analysis within the European Male Ageing Study.

PARTICIPANTS

: 2,816 community-dwelling men aged 40-79 years at baseline.

METHODS

: Cox regression was used to examine the association of all-cause mortality with 25(OH)D, 1,25(OH)2D and PTH; cardiovascular and cancer mortality were modelled using competing-risks regression. Results were expressed as hazard ratios (HR) and 95% confidence intervals (CIs) for Cox models; sub-hazard ratios (SHR) and 95% CIs for competing-risks models.

RESULTS

: a total of 187 men died during a median of 4.3 years of follow-up. Serum levels of 25(OH)D (per 1 SD decrease: HR = 1.45; 95% CI = 1.16, 1.81) and 1,25(OH)2D (per 1 SD decrease: HR = 1.20; 95% CI = 1.00, 1.44) were associated with an increased risk of all-cause mortality after adjusting for age, centre, smoking, self-reported morbidities, physical activity and functional performance. Only levels of 25(OH)D <25 nmol/l predicted cancer mortality (SHR = 3.33; 95% CI = 1.38, 8.04).

CONCLUSION

: lower 25(OH)D and 1,25(OH)2D levels independently predicted all-cause mortality in middle-aged and older European men. Associations with cancer mortality were only observed among men with very low levels of 25(OH)D. These associations were only partially explained by the range of adverse health and lifestyle factors measured here.

The trials and tribulations of vitamin D: time for the 'sunshine' vitamin to come in out of the cold - or just more broken promises?

We are presently faced with the competing notions of modern life being a 'state of vitamin D depletion', implying a widespread need to supplement with vitamin D, or, the opposite view, which is that the present evidence can only support at best selective targeted vitamin D intervention. This is important as there is evidence that over the last 40-50 years there were downwards global trends in serum 25(OH)D concentrations, while individual consumption of vitamin D as supplements rose. For this reason and many others, a large population-based interventional study, the VITAL trial, was designed to try to establish the health value of vitamin D supplementation. VITAL is a huge primary prevention trial looking at the effects of vitamin D repletion in preventing cancer and cardiovascular disease in a fundamentally healthy population. This may seem an unusual approach given that what we mostly know about vitamin D is that is has some effects on the skeleton. This review looks to explore current knowledge about vitamin D in health and disease, and at how this is now undergoing significant reappraisal and revision. We will carefully critique the VITAL study design to see if it will allow for the construction of the detailed portfolio of clinical evidence so urgently needed to allow us better to understand role of vitamin D supplementation in health and disease.

Relationship between 25-hydroxyvitamin D and newly diagnosed type 2 diabetes mellitus in postmenopausal women with osteoporosis

OBJECTIVE

The aim of the study was to determine a correlation between the level of 25-hydroxivitamin D (25-OHD) and the incidence of diabetes.

SUBJECTS AND METHODS

In this prospective observational study, 97 (out of an initial 100) Caucasian women with osteoporosis (OS) were monitored for 2 years for the incidence of diabetes. Logistic regression analysis was used to establish an association with and prognostic value of vitamin D for the onset of type 2 diabetes mellitus, as well as insulin resistance, body mass index (BMI), total cholesterol and triglyceride levels in the development of diabetes. The serum level of 25-OHD was measured using immunochemiluminescence in March and April 2011.

RESULTS

Of the 97 patients (mean age 51.64 ± 5.86 years, range 36.0-73.0), 21 (21.65%) were diagnosed with diabetes during the observational period. The study showed that the 22 patients with low levels of vitamin D were more susceptible to diabetes (odds ratio = 0.958). The cut-off value of vitamin D using a receiver operating characteristic curve was 62.36 nmol/l with a sensitivity of 39.5% and a specificity of 90.5%. With an increase in BMI and triglyceride levels, women were, respectively, 1,591 and 2,821 times more likely to get diabetes than those without an increase.

CONCLUSION

This study showed that the patients with postmenopausal OS and hypovitaminosis D, besides a high BMI, elevated triglyceride levels and insulin resistance, had an increased risk of developing type 2 diabetes.

The role of vitamin D deficiency in cardiovascular disease: where do we stand in 2013?

The high worldwide prevalence of vitamin D deficiency is largely the result of low sunlight exposure with subsequently limited cutaneous vitamin D production. Classic manifestations of vitamin D deficiency are linked to disturbances in bone and mineral metabolism, but the identification of the vitamin D receptor in almost every human cell suggests a broader role of vitamin D for overall and cardiovascular health. The various cardiovascular protective actions of vitamin D such as anti-diabetic and anti-hypertensive effects including renin suppression as well as protection against atherosclerosis and heart diseases are well defined in previous experimental studies. In line with this, large epidemiological studies have highlighted vitamin D deficiency as a marker of cardiovascular risk. However, randomized controlled trials (RCTs) on vitamin D have largely failed to show its beneficial effects on cardiovascular diseases and its conventional risk factors. While most prior vitamin D RCTs were not designed to assess cardiovascular outcomes, some large RCTs have been initiated to evaluate the efficacy of vitamin D supplementation on cardiovascular events in the general population. When considering the history of previous disappointing vitamin RCTs in general populations, more emphasis should be placed on RCTs among severely vitamin D-deficient populations who would most likely benefit from vitamin D treatment. At present, vitamin D deficiency can only be considered a cardiovascular risk marker, as vitamin D supplementation with doses recommended for osteoporosis treatment is neither proven to be beneficial nor harmful in cardiovascular diseases.

Vitamin D supplementation in patients with diabetes mellitus type 2 on different therapeutic regimens: a one-year prospective study

Background

Little or no research has determined the effect of vitamin D3 supplementation in conjunction with pharmacological and non-pharmacological approaches in the diabetes mellitus type 2 (DMT2) patients. The objective of this study was to determine the effect of vitamin D3 supplementation in a cohort of Saudi DMT2 population on diet, insulin and/or different oral hypoglycemic agents and compare them with a non-DMT2 control cohort.

Methods

A total of 499 randomly selected Saudi subjects divided into 8 groups [Non-DMT2 Control = 151; Rosiglitazone alone = 49; Diet = 15; Insulin alone = 55; Insulin + Orals = 12; Metformin alone = 121; Oral agents combination = 37; Sulphonylurea alone = 59] were included in this 12-month interventional study. All DMT2 patients were given 2000 IU vitamin D3 daily, while the control group received none but were advised to increase sun exposure. Anthropometrics, glucose, lipid profile and 25-hydroxyvitamin D (25-OHVitD) were measured at baseline, 6 and 12 months.

Results

Circulating 25-OHVitD concentrations improved in all patient groups. The metformin group showed the highest change in circulating vitamin D levels both at 6 months (62.6%) and 12 months (50.6%) as compared to baseline (p < 0.001). No significant changes were observed in the BMI and glucose in any of the DMT2 groups. In contrast, the insulin + oral agents group showed more significant improvements in the metabolic profile, which included triglycerides and total cholesterol, as well as systolic blood pressure and HDL-cholesterol in males. Also, significant decreases in triglycerides were observed in the rosiglitazone and insulin + oral hypoglycemic agent groups both at 6 and 12 months of supplementation (both p-values <0.001).

Conclusion

While in all DMT2 groups circulating levels of 25-OHVitD increased after supplementation, in DMT2 patients on insulin in combination with other drugs benefitted the most in improving cardiovascular risk. Metformin improves 25-hydroxyvitamin D levels but did not seem to confer other added cardiometabolic benefits.

Vitamin D and cardiovascular disease

Vitamin D deficiency, as well as cardiovascular diseases (CVD) and related risk factors are highly prevalent worldwide and frequently co-occur. Vitamin D has long been known to be an essential part of bone metabolism, although recent evidence suggests that vitamin D plays a key role in the pathophysiology of other diseases, including CVD, as well. In this review, we aim to summarize the most recent data on the involvement of vitamin D deficiency in the development of major cardiovascular risk factors: hypertension, obesity and dyslipidemia, type 2 diabetes, chronic kidney disease and endothelial dysfunction. In addition, we outline the most recent observational, as well as interventional data on the influence of vitamin D on CVD. Since it is still an unresolved issue whether vitamin D deficiency is causally involved in the pathogenesis of CVD, data from randomized controlled trials (RCTs) designed to assess the impact of vitamin D supplementation on cardiovascular outcomes are awaited with anticipation. At present, we can only conclude that vitamin D deficiency is an independent cardiovascular risk factor, but whether vitamin D supplementation can significantly improve cardiovascular outcomes is still largely unknown.

Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality-a review of recent evidence

BACKGROUND

Optimal vitamin D intake and its status are important not only for bone and calcium-phosphate metabolism, but also for overall health and well-being. Vitamin D deficiency and insufficiency as a global health problem are likely to be a risk for wide spectrum of acute and chronic illnesses.

METHODS

A review of randomized controlled trials, meta-analyses, and other evidence of vitamin D action on various health outcomes.

RESULTS

Adequate vitamin D status seems to be protective against musculoskeletal disorders (muscle weakness, falls, fractures), infectious diseases, autoimmune diseases, cardiovascular disease, type 1 and type 2 diabetes mellitus, several types of cancer, neurocognitive dysfunction and mental illness, and other diseases, as well as infertility and adverse pregnancy and birth outcomes. Vitamin D deficiency/insufficiency is associated with all-cause mortality.

CONCLUSIONS

Adequate vitamin D supplementation and sensible sunlight exposure to reach optimal vitamin D status are among the front line factors of prophylaxis for the spectrum of disorders. Supplementation guidance and population strategies for the eradication of vitamin D deficiency must be included in the priorities of physicians, medical professionals and healthcare policy-makers.