Is high dose vitamin D harmful?

Effects of High Dose Bolus Cholecalciferol on Free Vitamin D Metabolites, Bone Turnover Markers and Physical Function

High dose bolus cholecalciferol supplementation has been associated with falls and fracture, and this does not appear to be due to hypercalcaemia. The primary aim of this study was to determine the change in free vitamin D and metabolites after high dose bolus supplementation. This was a single centre, double-blinded, randomised, controlled trial of three different oral bolus doses of vitamin D3 (50,000 IU, 150,000 IU, and 500,000 IU) in otherwise healthy, vitamin D deficient (total 25-hydroxylated vitamin 25(OH)D < 30 nmol/L) postmenopausal women. Thirty-three women were randomized to one of the three treatment groups. Twenty-seven vitamin D sufficient (25(OH)D > 50 nmol/L) postmenopausal women were recruited as a concurrent control group. Participants attended five study visits over three months. We measured total 25(OH)D3 and free 25(OH)D, total and free 1,25(OH)2D, parathyroid hormone, fibroblast-growth factor-23, serum calcium, ionised calcium, urinary calcium excretion, and bone turnover markers (procollagen I N-propeptide (PINP), serum C-telopeptides of type I collagen (CTX-I) and Osteocalcin (OC)). We assessed muscle strength and function with grip strength and a short physical performance battery. Postural blood pressure and aldosterone:renin ratio (ARR) was also measured. Total 25(OH)D3 and free 25(OH)D increased in response to dose, and there were proportionate increases in total and free metabolites. Treatment did not affect serum calcium, postural blood pressure, ARR, or physical function. Bone turnover markers increased transiently one week after administration of 500,000 IU. High dose bolus cholecalciferol supplementation does not cause disproportionate increases in free vitamin D or metabolites. We did not identify any effect on blood pressure regulation or physical function that would explain increased falls after high dose treatment. A transient increase in bone turnover markers one week after a 500,000 IU bolus suggests that very high doses can have acute effects on bone metabolism, but the clinical significance of this transient increase is uncertain.

Effects of Isoflavonoid and Vitamin D Synergism on Bone Mineral Density-A Systematic and Critical Review

Phytoestrogens are non-steroidal plant compounds, which bind to α and β estrogen receptors, thereby causing specific effects. The best-known group of phytoestrogens are flavonoids, including isoflavonoids-genistein and daidzein. They play a role in the metabolism of bone tissue, improving its density and preventing bone loss, which contributes to reducing the risk of fractures. Vitamin D is found in the form of cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2) and is traditionally recognized as a regulator of bone metabolism. The aim of this review was to evaluate the synergistic effect of isoflavonoids and vitamin D on bone mineral density (BMD). The MEDLINE (PubMed), Scopus and Cochrane databases were searched independently by two authors. The search strategy included controlled vocabulary and keywords. Reference publications did not provide consistent data regarding the synergistic effect of isoflavonoids on BMD. Some studies demonstrated a positive synergistic effect of these compounds, whereas in others, the authors did not observe any significant differences. Therefore, further research on the synergism of isoflavonoids and vitamin D may contribute to a significant progress in the prevention and treatment of osteoporosis.

Effect of vitamin D supplementation on hormones and menstrual cycle regularization in polycystic ovary syndrome women: A systemic review and meta-analysis

AIM

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disease among women of childbearing age. Women with PCOS frequently experience reproductive complications, which are closely associated with the concentration of vitamin D. This systemic review and meta-analysis were conducted to elucidate the possible effect of vitamin D supplementation in PCOS women on hormones, including Luteinizing hormone (LH), follicle-stimulating hormone (FSH), the ratio of LH and FSH (LH/FSH), and the menstrual cycle regularization.

METHODS

We searched PubMed, Web of Science, Ovid MEDLINE, Cochrane Library, and EMBASE for the relevant articles published up to January 2022. The pooled estimates were calculated using RevMan 5.4 software.

RESULTS

Twelve studies involving 849 PCOS patients were included. Our study indicated that vitamin D supplementation could reduce serum LH (standard mean difference [SMD]: -0.41; 95% confidence interval [CI]: -0.54, -0.28; p < 0.01). Subgroup analysis identified that the supplementation of vitamin D ≤4000 IU/day (SMD: -0.69; 95% CI: -1.15, -0.23; p < 0.01), treatment time ≤8 weeks (SMD: -0.61; 95% CI: -0.95, -0.26; p < 0.01), and vitamin D co-supplementation (SMD: -0.37; 95% CI: -0.65, -0.10; p < 0.01) were related to reduce serum LH level. In addition, vitamin D supplementation improved the regularity of menstrual cycle significantly (risk ratio [RR]: 1.35; 95% CI: 1.18, 1.54; p < 0.01). In stratified analysis, the significant effects only existed in dosage of vitamin D >4000 IU (RR: 1.62; 95% CI: 1.02, 2.57; p < 0.01), treatment time >8 weeks (RR: 1.41; 95% CI: 1.06, 1.87; p = 0.02) and vitamin D co-supplementation (RR: 1.18; 95% CI: 1.03, 1.35; p = 0.02). However, vitamin D might have no effects on serum FSH (SMD: -0.05; 95% CI: -0.42, 0.32; p = 0.79) and LH/FSH (SMD: -0.24; 95% CI: -0.55, 0.08; p = 0.14) in PCOS patients.

CONCLUSIONS

Evidence from the existing randomized controlled trials indicated that vitamin D supplementation might improve the LH level and the menstrual cycle regularization but did not have any effect on FSH and LH/FSH levels in PCOS patients.

Very Low and High Levels of Vitamin D Are Associated with Shorter Leukocyte Telomere Length in 148,321 UK Biobank Participants

Background: Shorter leukocyte telomere length (LTL) is observed in multiple age-related diseases, which are also associated with vitamin D deficiency (i.e., osteosarcopenia, neurocognitive disorders, cancer, osteoarthritis, etc.), suggesting a close association between vitamin D and LTL. In this study, we examined the relationship between vitamin D levels and LTL in older participants of the UK Biobank. Methods: Data were collected from the UK Biobank. Participants aged 60 and older (n = 148,321) were included. Baseline LTL was measured using a multiplex qPCR technique and expressed as the ratio of the telomere amplification product (T) to that of a single-copy gene (S) (T/S ratio). Serum 25-hydroxyvitamin D (25OHD) was stratified by z score and linked to LTL in a linear regression model adjusting for covariates. Results: Compared to the medium level, a low (in the range of 16.6 nmol/L, 29.7 nmol/L) or extremely low (≤16.6 nmol/L) level of serum 25OHD was associated with shorter LTL: 0.018 SD (standardized β = -0.018, 95% CI -0.033 to -0.003, p = 0.022) and 0.048 SD (standardized β = -0.048, 95% CI -0.083 to -0.014, p = 0.006), respectively. Additionally, the high serum 25OHD groups (>95.9 nmol/L) had 0.038 SD (standardized β = -0.038, 95% CI -0.072 to -0.004, p = 0.030) shorter mean LTL than the group with medium 25OHD levels. The associations above were adjusted for multiple variables. Conclusions: In this population-based study, we identified an inverted U-shape relationship between LTL and vitamin D status. Our findings could be affected by unmeasured confounders. Whether high or low vitamin D-associated shorter LTL is mechanistically related to age-related conditions remains to be elucidated.

Vitamin D: review of physiology and clinical uses

Interest in vitamin D has increased within the scientific community due to the impact of osteoporosis in the aging population. Vitamin D receptors are present in many tissues and low vitamin D status has been associated with many diseases in observational studies. There was hope that enhanced vitamin D provision might help prevent and treat some widespread disorders. Some of these hopes have been refuted by the results of recent large and well-conducted randomized trials. This review provides an overview of the basic physiology of vitamin D and an update on the evidence base for its clinical applications.

Association between lower serum vitamin D (25-hydroxy-cholecalciferol) concentrations and cognitive impairment in older adults: data from a populational-based cohort study in a middle-income country

OBJECTIVE

To investigate the association between serum vitamin D (25-hydroxy-cholecalciferol) (25(OH)D) concentrations and cognitive impairment in older adults living in Southern Brazil.

DESIGN

Cross-sectional analysis using data from the second follow-up wave of the populational-based EpiFloripa Aging Cohort Study was collected in 2013-2014.

SETTING

Cognitive impairment was evaluated using the Mini-Mental State Examination (MMSE). Blood samples were collected to measure serum vitamin D concentrations using a chemiluminescent microparticle immunoassay. Vitamin D concentrations were distributed in quartiles (Q1: 4·0-20·7 ng/ml; Q2: 20·8-26·6 ng/ml; Q3: 26·7-32·0 ng/ml and Q4: 32·1-60·1 ng/ml), and its association with cognitive impairment was tested by crude and adjusted logistic regression (sociodemographic, behavioural and health aspects) using Q4 as a reference group.

PARTICIPANTS

200 men and 371 women aged 60 years or older participated in this study.

RESULTS

The prevalence of probable cognitive impairment was 21·7 %. Those without cognitive impairment had a higher mean of vitamin D serum concentrations (26·8 v. 24·6, P = 0·014). In the crude analysis, only individuals in Q2 of vitamin D presented an increased risk for probable cognitive impairment compared with Q4 (highest quartile) (OR 2·65, 95 % CI 1·46, 4·81), remaining significant in the adjusted analysis (OR 6·04, 95 % CI 2·78, 13·13). While Q1 (lowest quartile) was not associated in the crude analysis, but when adjusted, an increased risk of cognitive impairment was observed.

CONCLUSION

The lowest quartile of vitamin D was directly associated with probable cognitive impairment in older adults in Southern Brazil. More studies are needed to investigate whether maintaining adequate serum levels may represent a significant factor in preventing age-related neurological disorders as well as to verify the need for new cutoff points for this age group.

High-Dose Vitamin D Supplementation Can Correct Hypovitaminosis D Prior to Total Knee Arthroplasty

BACKGROUND

Vitamin D deficiency in the perioperative surgical period is associated with inferior surgical outcomes. There are no established preoperative supplementation regimens in the orthopedic literature. The purpose of this study is to compare the efficacy between 2 different supplementation regimens of vitamin D prior to total knee arthroplasty.

METHODS

We conducted a retrospective analysis of 174 patients identified as vitamin D deficient (25(OH)D < 30 ng/mL) who received one of 2 vitamin D supplementation protocols: (1) daily supplementation with D3 on a sliding scale from 1000 to 6000 IU or (2) a loading dose of 50,000 IU D3 weekly for 4 weeks then 2000 IU/d. Serum vitamin D levels were measured at 3 months and 1 month preoperatively.

RESULTS

Mean patient age was 65.5(±8.6) years, and 54.6% were female. Deficiency was corrected in 73.3% of patients in the loading dose group and 42.4% of patients in the daily, low-dose group [χ² (1, N = 174) = 16.53, P < .001]. Patients in the loading dose group also achieved a greater average correction in vitamin D levels.

CONCLUSION

This is the first study to compare preoperative vitamin D supplementation protocols. A loading dose regimen of 50,000 IU weekly for 4 weeks followed by a maintenance dose of 2000 IU/d more effectively corrects vitamin D deficiency compared to a low-dose, daily regimen among total knee arthroplasty patients. We recommend this regimen for deficiency correction in patients who have been screened to be deficient in vitamin D preoperatively.

Vitamin D and its' role in Parkinson's disease patients with SARS-CoV-2 infection. A review article

A novel coronavirus reportedly called 2019-nCoV started to spread around the world at the end of 2019. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was later renamed after links with SARS were observed. Multiple studies have reported possible connections between the COVID-19 virus and neurodegenerative diseases, including Parkinson's disease. Theories support that vitamin D deficiency plays a part in the pathogenicity of Parkinson's disease or the credibility of the associated dopamine system. Administration of vitamin D3 was shown to significantly enhance the motor and non-motor manifestations of Parkinson's disease and enhance the quality of life. Also, multiple recent reviews have shown specific ways in which vitamin D reduces the risk of pathogenic infections. Recent studies supported the potential role of vitamin D in reducing the risk of COVID-19 infections and mortality. On the immunological level, immune response regulation remains one of the well-recognized actions of vitamin D. Vitamin D deficiency has been linked to complications in patients with SARS-CoV-2 infection and Parkinson's disease. Whereas more studies are required, Vitamin D supplementation with a moderate and well-calculated dosage of vitamin D3 in patients with Parkinson's disease can help minimize the risk and burden of COVID-19 complications.

Vitamin D supplementation and risk of falling: outcomes from the randomized, placebo-controlled D-Health Trial

BACKGROUND

Falls cause considerable morbidity and mortality in older people. It is unclear how vitamin D supplementation affects falls risk, particularly when taken at high doses. We sought to determine whether monthly high-dose vitamin D supplementation reduces risk and incidence of falls.

METHODS

We used data from the randomized, double-blind, placebo-controlled D-Health Trial conducted in Australia. Between February 2014 and May 2015, 21 315 participants aged 60-84 years were randomized (1:1) to monthly doses of either 60 000 IU of colecalciferol or placebo for a maximum of 5 years. People who reported a history of osteomalacia, sarcoidosis, hyperparathyroidism, hypercalcaemia or kidney stones or who were taking >500 IU/day supplementary vitamin D were ineligible. Each year, we collected blood samples from ~450 randomly sampled participants from each trial arm and measured 25-hydroxyvitamin D [25(OH)D]. Falls, a prespecified tertiary outcome, were ascertained using annual surveys and, for a subset of participants, 3-month falls diaries. The primary outcome for this analysis was any fall in the month before completing an annual survey. As part of our process to maintain blinding, we used random samples of participants (surveys, n = 16 000; diaries, n = 2400), with equal numbers per group. Participants with no outcome data were excluded. Following an intention-to-treat approach, we analysed outcomes using logistic, ordinal and negative binomial regression. Registration: Australian New Zealand Clinical Trials Registry (ACTRN12613000743763); registered 4 July 2013.

RESULTS

Mean treatment duration was 4.3 years (standard deviation [SD] = 1.4 years). Mean serum 25(OH)D concentrations during the trial were 114.8 (SD 30.3) nmol/L and 77.5 (SD 25.2) nmol/L in the vitamin D and placebo groups, respectively. Survey and diary analytic sets included 15 416 and 2200 participants, respectively; approximately half were randomized to vitamin D (surveys: 50.1%; diaries: 50.4%). Vitamin D had no effect on falling in the past month (odds ratio [OR] 1.02, 95% confidence interval [CI] 0.95-1.10). There was an interaction with body mass index (BMI) (P-interaction = 0.001); vitamin D increased risk in participants with BMI < 25 kg/m² (OR 1.25, 95% CI 1.09-1.43), but there was no effect in those with BMI ≥ 25 kg/m² (OR 0.95, 95% CI 0.87-1.04). Analyses of diary data were consistent with these findings. The incidence of hypercalcaemia and kidney stones did not differ between groups.

CONCLUSIONS

Monthly high-dose vitamin D supplementation did not reduce risk of falling. A possible increased risk of falling with vitamin D supplementation in people with normal BMI warrants further investigation.

Vitamin D Supplementation for Prevention of Type 2 Diabetes Mellitus: To D or Not to D?

CONTEXT

Over the last decade, vitamin D has emerged as a risk determinant for type 2 diabetes and vitamin D supplementation has been hypothesized as a potential intervention to lower diabetes risk. Recently, several trials have reported on the effect of vitamin D supplementation on diabetes prevention in people with prediabetes.

EVIDENCE ACQUISITION

A comprehensive literature review was performed using PubMed, Embase, and ClinicalTrials.gov to identify: (1) recent meta-analyses of longitudinal observational studies that report on the association between blood 25-hydroxyvitamin D (25[OH]D) level and incident diabetes, and (2) clinical trials of adults with prediabetes that have reported on the effect of vitamin D supplementation on incident diabetes.

EVIDENCE SYNTHESIS

Longitudinal observational studies report highly consistent associations between higher blood 25(OH)D levels and a lower risk of incident diabetes in diverse populations, including populations with prediabetes. Trials in persons with prediabetes show risk reduction in incident diabetes with vitamin D supplementation. In the 3 large trials that were specifically designed and conducted for the prevention of diabetes, vitamin D supplementation, when compared with placebo, reduced the risk of developing diabetes by 10% to 13% in persons with prediabetes not selected for vitamin D deficiency.

CONCLUSIONS

Results from recent trials are congruent with a large body of evidence from observational studies indicating that vitamin D has a role in modulating diabetes risk. Participant-level meta-analysis of the 3 largest trials should provide a more refined estimate of risk reduction and identify patient populations that are likely to benefit the most from vitamin D supplementation.

Intratrial Exposure to Vitamin D and New-Onset Diabetes Among Adults With Prediabetes: A Secondary Analysis From the Vitamin D and Type 2 Diabetes (D2d) Study

OBJECTIVE

Postrandomization biases may influence the estimate of efficacy of supplemental vitamin D in diabetes prevention trials. In the Vitamin D and Type 2 Diabetes (D2d) study, repeated measures of serum 25-hydroxyvitamin D [25(OH)D] level provided an opportunity to test whether intratrial vitamin D exposure affected diabetes risk and whether the effect was modified by trial assignment (vitamin D vs. placebo).

RESEARCH DESIGN AND METHODS

The D2d study compared the effect of daily supplementation with 100 μg (4,000 units) of vitamin D₃ versus placebo on new-onset diabetes in adults with prediabetes. Intratrial vitamin D exposure was calculated as the cumulative rolling mean of annual serum 25(OH)D measurements. Hazard ratios for diabetes among participants who had intratrial 25(OH)D levels of <50, 75-99, 100-124, and ≥125 nmol/L were compared with those with levels of 50-74 nmol/L (the range considered adequate by the National Academy of Medicine) in the entire cohort and by trial assignment.

RESULTS

There was an interaction of trial assignment with intratrial 25(OH)D level in predicting diabetes risk (interaction P = 0.018). The hazard ratio for diabetes for an increase of 25 nmol/L in intratrial 25(OH)D level was 0.75 (95% CI 0.68-0.82) among those assigned to vitamin D and 0.90 (0.80-1.02) among those assigned to placebo. The hazard ratios for diabetes among participants treated with vitamin D who maintained intratrial 25(OH)D levels of 100-124 and ≥125 nmol/L were 0.48 (0.29-0.80) and 0.29 (0.17-0.50), respectively, compared with those who maintained a level of 50-74 nmol/L.

CONCLUSIONS

Daily vitamin D supplementation to maintain a serum 25(OH)D level ≥100 nmol/L is a promising approach to reducing the risk of diabetes in adults with prediabetes.

The possible double-edged sword effects of vitamin D on COVID-19: A hypothesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) gains access to host cells by attaching to angiotensin-converting enzyme 2 (ACE2). Vitamin D (VitD) can upregulate ACE2 and has an antagonistic effect on Renin, which exerts a vasodilatation and anti-inflammatory effect against coronavirus disease (COVID-19). However, it may also facilitate viral entry by increasing ACE2 as the main SARS-CoV-2 receptor and mediates ROS production through NADPH oxidase, as a double-edged sword effect. Lung function and the immune system are also influenced by VitD through several mechanisms, including increased natural antibiotics (Defensin and Cathelicidin) and upregulated transforming growth factor-β. A higher IgA, Th2/Th1 ratio, and T-regulatory cells are attributable to VitD effects on the immune cells, while these changes may also be a double-edged sword in COVID-19. Although VitD supplementation might be highly recommended in COVID-19, the administration's dosage and route could be challenging. Furthermore, this issue has not been mentioned in various studies so far. So, the report aimed to explain the current challenges with the application of VitD in COVID-19.

Vitamin D and Autoimmune Thyroid Disease-Cause, Consequence, or a Vicious Cycle?

Vitamin D is a steroid hormone traditionally connected to phosphocalcium metabolism. The discovery of pleiotropic expression of its receptor and of the enzymes involved in its metabolism has led to the exploration of the other roles of this vitamin. The influence of vitamin D on autoimmune disease-namely, on autoimmune thyroid disease-has been widely studied. Most of the existing data support a relationship between vitamin D deficiency and a greater tendency for development and/or higher titers of antibodies linked to Hashimoto's thyroiditis, Graves' disease, and/or postpartum thyroiditis. However, there have also been some reports contradicting such relationships, thus making it difficult to establish a unanimous conclusion. Even if the existence of an association between vitamin D and autoimmune thyroid disease is assumed, it is still unclear whether it reflects a pathological mechanism, a causal relationship, or a consequence of the autoimmune process. The relationship between vitamin D's polymorphisms and this group of diseases has also been the subject of study, often with divergent results. This text presents a review of the recent literature on the relationship between vitamin D and autoimmune thyroid disease, providing an analysis of the likely involved mechanisms. Our thesis is that, due to its immunoregulatory role, vitamin D plays a minor role in conjunction with myriad other factors. In some cases, a vicious cycle is generated, thus contributing to the deficiency and aggravating the autoimmune process.

Vitamin D supplement on prevention of fall and fracture: A Meta-analysis of Randomized Controlled Trials

BACKGROUND

Vitamin D supplement is one of the current possible interventions to reduce fall and fracture. Despite having several studies on vitamin D supplement and fall and fracture reductions, the results are still inconclusive. We conducted a meta-analysis to examine the effect of vitamin D supplement in different forms and patient settings on fall and fracture.

METHODS

A systematic literature research was conducted in MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials to identify randomized controlled trials (RCTs) to compare the effects of vitamin D supplements on fall and fracture outcomes. Random-effect models were used to compute the weighted mean difference for continuous variables and the risk ratio for binary variables.

RESULTS

Forty-seven RCTs with 58,424 participants were identified reporting on fall outcome. Twenty-four of 47 studies with 40,102 subjects also reported fracture outcome. Major populations were elderly women with age less than 80 years. Overall, vitamin D supplement demonstrated a significant effect on fall reduction, RR = 0.948 (95% CI 0.914-0.984; P = .004, I = 41.52). By subgroup analyses, only vitamin D with calcium supplement significantly reduce fall incidence, RR = 0.881 (95% CI 0.821-0.945; P < .001, I = 49.19). Vitamin D3 supplement decreased incidence of fall but this occurred only when vitamin D3 was supplemented with calcium. Regarding fracture outcome, vitamin D supplement failed to show fracture lowering benefit, RR = 0.949 (95% CI 0.846-1.064; P = .37, I = 37.92). Vitamin D along with calcium supplement could significantly lower fracture rates, RR = 0.859 (95% CI 0.741-0.996; P = .045, I = 25.48).

CONCLUSIONS

The use of vitamin D supplement, especially vitamin D3 could reduce incidence of fall. Only vitamin D with calcium supplement showed benefit in fracture reduction.

Influence of vitamin D supplementation on lipid levels in polycystic ovary syndrome patients: a meta-analysis of randomized controlled trials

Objective

Observational studies have shown that circulating vitamin D (VitD) deficiency is associated with atherogenic lipid patterns among polycystic ovary syndrome (PCOS) patients. However, interventional studies have shown inconsistent results. The aim of this meta-analysis was to investigate how VitD supplementation influences lipid indices in PCOS patients.

Methods

The authors searched four electronic databases through August 2019 to identify randomized controlled trials (RCTs) that assessed the effect of VitD intervention on serum lipids among PCOS patients. Mean differences were generated for statistical evaluation.

Results

We included eight studies and performed nine comparisons across 467 participants. VitD supplementation reduced serum triglyceride levels (−11.88 mg/dL; 95% confidence interval [CI]: −17.03 to −6.73), total cholesterol (−9.09 mg/dL; 95% CI: −14.90 to −3.29), low-density lipoprotein cholesterol (−5.22 mg/dL; 95% CI: −10.32 to −0.13), and very-low-density lipoprotein cholesterol (−2.43 mg/dL; 95% CI: −3.69 to −1.17) compared with no VitD supplementation. However, high-density lipoprotein cholesterol levels showed no differences with or without VitD supplementation (−0.39 mg/dL; 95% CI: −1.39 to 0.61).

Conclusions

VitD supplementation improved serum lipid levels among PCOS patients, but serum high-density lipoprotein cholesterol levels were not changed. VitD intervention might benefit PCOS patients who are at high risk of an atherogenic lipid profile.

Exercise May Ameliorate the Detrimental Side Effects of High Vitamin D Supplementation on Muscle Function in Mice

Vitamin D is commonly prescribed to normalize deficiencies and to treat osteoporosis. However, the effect vitamin D supplements have on skeletal muscle health is equivocal. Although vitamin D is known to play a role in the various processes that maintain muscle integrity and function, recent studies utilizing high bolus dose vitamin D supplementation has demonstrated an increased risk of falls. Thus, the aim of this study was to investigate the effects of high vitamin D supplementation on skeletal muscle function with and without exercise enrichment. Four-week old C57BL/10 mice (n = 48) were separated into either normal vitamin D (1500 IU/kg diet; unsupplemented) or high vitamin D (20,000 IU/kg diet; supplemented) treatment groups. Each dietary group was further separated into interventional subgroups where mice either remained sedentary or received exercise-enrichment for 8 weeks in the form of voluntary running. Following the intervention period, whole body in vivo and ex vivo contractile analysis were performed. High vitamin D supplementation decreased force production in the slow-twitch soleus muscles of sedentary mice (p < .01); however, exercise normalized this effect. Eight weeks of exercise did not improve fatigue resistance of the extensor digitorum longus (EDL) or soleus muscles in unsupplemented mice, likely due to low levels of activation in these muscles. In contrast, fatigability was improved in the EDL (p < .01) and even more so in the soleus (p < .001) in the supplemented exercise-enriched group. Our data highlights that increasing vitamin D levels above normal reduces postural muscle force as seen in the soleus. Thus, unnecessary vitamin D supplementation may contribute to the increased risk of falls observed in some studies. Interestingly, when vitamin D supplementation was combined with exercise, force production was effectively restored, and fatigue resistance improved, even in muscles lowly activated. Regular exercise may modulate the effects of vitamin D on skeletal muscle, and be recommended for individuals receiving vitamin D supplements. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

The vitamin D and calcium controversy: an update

PURPOSE OF REVIEW

Calcium and vitamin D supplementation is widely recommended for prevention of falls and fracture, particularly in the elderly where calcium intakes and vitamin D levels are often inadequate. A number of meta-analyses have questioned the benefits of untargeted or 'holistic' supplementation for falls and fracture, and raised the possibility of adverse cardiovascular effects. This review provides an update on these controversies.

RECENT FINDINGS

Recent advances have largely centred around new trials of vitamin D and meta-analyses of published trials and observational studies. These articles have identified holistic vitamin D supplementation with or without calcium is unlikely to be an effective primary prevention strategy for falls or fracture. There has also been high-quality evidence that vitamin D, daily or as a bolus, does not reduce the risk of cardiovascular events.

SUMMARY

The benefits of vitamin D and calcium supplements for holistic fall and fracture prevention remain uncertain. Recent evidence supports the concept that high-dose vitamin D has adverse musculoskeletal effects. Future studies should focus on moderate daily doses. Finally, there remain inconsistent findings for adverse cardiovascular effects of calcium supplements with or without vitamin D. This uncertainty should be taken into account when evaluating the risk/benefits of supplementation.

Vitamin D Status in Paget Disease of Bone and Efficacy-Safety Profile of Cholecalciferol Treatment in Pagetic Patients with Hypovitaminosis D

Adequate vitamin D status is essential for skeletal health. Paget's disease of bone (PDB) is a common metabolic skeletal disorder, but data regarding the vitamin D status in PDB patients are lacking. We performed a case-control study to estimate vitamin D status in 708 PDB patients and in 1803 healthy controls from Italy and an observational prospective study to evaluate the efficacy-safety profile of oral cholecalciferol treatment [400.000 International Units (UI) of cholecalciferol administered in cycles of 8 weeks until 25OHD levels reaches 70 nmol/L as primary therapy and 50.000 UI of cholecalciferol administered every 2 weeks for 52 weeks for the maintenance therapy] in 82 PDB patients with hypovitaminosis D, i.e., 25OHD < 50 nmol/L. The main outcome measures for the prospective study were 25OHD levels, metabolic risk factors (RF) for nephrolithiasis, bone pain score (BPS), and pain medication score (PMS). Over half of PDB patients had hypovitaminosis D. Among PDB patients treated with cholecalciferol, 76 patients reached 25OHD levels ≥ 70 nmol/L after the first cycle of primary therapy and the remaining six patients after a second cycle. The maintenance therapy guaranteed 25OHD levels ≥ 70 nmol/L during the entire follow-up. The increase in 25OHD levels reduced PTH, BPS, and PMS levels, without changes in RF for nephrolithiasis. We can conclude that (i) hypovitaminosis D is frequent in PDB patients, (ii) cholecalciferol significantly increased 25OHD levels in PDB patients, and (iii) the correction of hypovitaminosis D improves the quality of life of PDB patients without inducing significant changes in RF for nephrolithiasis.

Effect of High-Dose Vitamin D Supplementation on Volumetric Bone Density and Bone Strength: A Randomized Clinical Trial

Importance

Few studies have assessed the effects of daily vitamin D doses at or above the tolerable upper intake level for 12 months or greater, yet 3% of US adults report vitamin D intakes of at least 4000 IU per day.

Objective

To assess the dose-dependent effect of vitamin D supplementation on volumetric bone mineral density (BMD) and strength.

Design, Setting, and Participants

Three-year, double-blind, randomized clinical trial conducted in a single center in Calgary, Canada, from August 2013 to December 2017, including 311 community-dwelling healthy adults without osteoporosis, aged 55 to 70 years, with baseline levels of 25-hydroxyvitamin D (25[OH]D) of 30 to 125 nmol/L.

Interventions

Daily doses of vitamin D3 for 3 years at 400 IU (n = 109), 4000 IU (n = 100), or 10 000 IU (n = 102). Calcium supplementation was provided to participants with dietary intake of less than 1200 mg per day.

Main Outcomes and Measures

Co-primary outcomes were total volumetric BMD at radius and tibia, assessed with high resolution peripheral quantitative computed tomography, and bone strength (failure load) at radius and tibia estimated by finite element analysis.

Results

Of 311 participants who were randomized (53% men; mean [SD] age, 62.2 [4.2] years), 287 (92%) completed the study. Baseline, 3-month, and 3-year levels of 25(OH)D were 76.3, 76.7, and 77.4 nmol/L for the 400-IU group; 81.3, 115.3, and 132.2 for the 4000-IU group; and 78.4, 188.0, and 144.4 for the 10 000-IU group. There were significant group × time interactions for volumetric BMD. At trial end, radial volumetric BMD was lower for the 4000 IU group (-3.9 mg HA/cm3 [95% CI, -6.5 to -1.3]) and 10 000 IU group (-7.5 mg HA/cm3 [95% CI, -10.1 to -5.0]) compared with the 400 IU group with mean percent change in volumetric BMD of -1.2% (400 IU group), -2.4% (4000 IU group), and -3.5% (10 000 IU group). Tibial volumetric BMD differences from the 400 IU group were -1.8 mg HA/cm3 (95% CI, -3.7 to 0.1) in the 4000 IU group and -4.1 mg HA/cm3 in the 10 000 IU group (95% CI, -6.0 to -2.2), with mean percent change values of -0.4% (400 IU), -1.0% (4000 IU), and -1.7% (10 000 IU). There were no significant differences for changes in failure load (radius, P = .06; tibia, P = .12).

Conclusions and Relevance

Among healthy adults, treatment with vitamin D for 3 years at a dose of 4000 IU per day or 10 000 IU per day, compared with 400 IU per day, resulted in statistically significant lower radial BMD; tibial BMD was significantly lower only with the 10 000 IU per day dose. There were no significant differences in bone strength at either the radius or tibia. These findings do not support a benefit of high-dose vitamin D supplementation for bone health; further research would be needed to determine whether it is harmful.

Trial Registration

ClinicalTrials.gov Identifier: NCT01900860.

Controversies Surrounding Vitamin D: Focus on Supplementation and Cancer

There has recently been a huge number of publications concerning various aspects of vitamin D, from the physiological to therapeutic fields. However, as a consequence of this very fast-growing scientific area, some issues still remain surrounded by uncertainties, without a final agreement having been reached. Examples include the definitions of vitamin D sufficiency and insufficiency, (i.e., 20 vs. 30 ng/mL), the relationship between 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone, (i.e., linear vs. no linear), the referent to consider, (i.e., total vs. free determination), the utility of screening versus universal supplementation, and so on. In this review, the issues related to vitamin D supplementation in subjects with documented hypovitaminosis, and the role of vitamin D in cancer will be concisely considered. Daily, weekly, or monthly administration of cholecalciferol generally leads to essentially similar results in terms of an increase in 25(OH)D serum levels. However, we should also consider possible differences related to a number of variables, (i.e., efficiency of intestinal absorption, binding to vitamin D binding protein, and so on). Thus, adherence to therapy may be more important than the dose regimen chosen in order to allow long-term compliance in a sometimes very old population already swamped by many drugs. It is difficult to draw firm conclusions at present regarding the relationship between cancer and vitamin D. In vitro and preclinical studies seem to have been more convincing than clinical investigations. Positive results in human studies have been mainly derived from post-hoc analyses, secondary end-points or meta-analyses, with the last showing not a decrease in cancer incidence but rather in mortality. We must therefore proceed with a word of caution. Until it has been clearly demonstrated that there is a causal relationship, these positive “non-primary, end-point results” should be considered as a background for generating new hypotheses for future investigations.

Vitamin D, Inflammation and Osteoporosis in Rheumatoid Arthritis

Patients with Rheumatoid Arthritis (RA) commonly develop osteoporosis and fragility fractures. This fact cannot be explained only with the use of glucocorticoids, known to be detrimental for bone health. RA is characterized by a chronic inflammation caused by the continuous activation of innate and adaptive immunity with proinflammatory cytokines overproduction. This process is detrimental for several organs and physiological processes, including the impairment of bone remodeling. We will briefly review the pathogenesis of inflammation-related bone loss in RA, describing well-known and new molecular pathways and focusing on vitamin D and Parathyroid Hormone role.

The Role of Vitamin D Oral Supplementation in Insulin Resistance in Women with Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

To evaluate the effect of vitamin D supplementation (alone or with co-supplementation) on insulin resistance in patients with polycystic ovary syndrome (PCOS).

METHODS

We performed a literature search of databases (Medline, Scopus, Web of Knowledge, Cochrane Library) and identified all reports of randomized controlled trials (RCTs) published prior to April 2018. We compared the effects of supplementation with vitamin D alone (dose from 1000 IU/d to 60,000 IU/week) or with co-supplements to the administration of placebos in women diagnosed with PCOS. The systematic review and meta-analysis protocol was registered in the International Prospective Register of Systematic Reviews (Prospero) as number CRD42018090572.

MAIN RESULTS

Eleven of 345 identified studies were included in the analysis; these involved 601women diagnosed with PCOS. Vitamin D as a co-supplement was found to significantly decrease fasting glucose concentrations and the HOMA-IR value. HOMA-IR also declined significantly when vitamin D was supplemented with a dose lower than 4000 IU/d.

CONCLUSIONS

Evidence from RCTs suggests that the supplementation of PCOS patients with continuous low doses of vitamin D (<4000 IU/d) or supplementation with vitamin D as a co-supplement may improve insulin sensitivity in terms of the fasting glucose concentration (supplementation with vitamin D in combination with other micronutrients) and HOMA-IR (supplementation with vitamin D in continuous low daily doses or as co-supplement).

The effect of vitamin D and selenomethionine on thyroid antibody titers, hypothalamic-pituitary-thyroid axis activity and thyroid function tests in men with Hashimoto's thyroiditis: A pilot study

BACKGROUND

Both selenium and vitamin D were found to reduce thyroid antibody titers in women with Hashimoto's thyroiditis.

METHODS

The study enrolled 37 young drug-naïve euthyroid men with autoimmune thyroiditis, who were treated for 6 months with either exogenous vitamin D (group A, n = 20) or selenomethionine (group B, n = 17). Serum titers of thyroid peroxidase and thyroglobulin antibodies, serum levels of thyrotropin and free thyroid hormones, serum levels of 25-hydroxyvitamin D, as well Jostel's thyrotropin, the SPINA-GT and the SPINA-GD indices were determined at the beginning and at the end of the study.

RESULTS

At baseline, there were no differences between the study groups. Both vitamin D and selenomethionine reduced antibody titers and increased the SPINA-GT index. Only selenomethionine affected the SPINA-GD index, while only vitamin D increased 25-hydroxyvitamin D levels. Neither selenomethionine nor vitamin D significantly affected thyrotropin and free thyroid hormone levels. The effect of vitamin D on antibody titers correlated with baseline and treatment-induced changes in serum levels of 25-hydroxivitamin D.

CONCLUSIONS

Both vitamin D and selenomethionine have a beneficial effect on thyroid autoimmunity in drug-naïve men with Hashimoto's thyroiditis.

Vitamin D and Ageing

One hundred years has passed since the discovery of vitamin D as the active component of cod-liver oil which cured the bone disease rickets. Since then our knowledge of vitamin D has expanded tremendously and has included recognition of the importance of UV radiation as a source of the vitamin as well as the discovery of the vitamin as a nutrient, a pro-hormone and a potent steroid hormone with a major role in calcium and bone metabolism. In the last 25 years or so, the discovery of the vitamin D receptor in over 30 different body tissues together with the existence of the alpha-1-hydroxylase enzyme in these tissues provided evidence of a pleiotropic role of vitamin D outside its classical role in the skeleton. These important discoveries have provided the basis for the increasing interest in vitamin D in the context of nutritional requirements for health including the prevention of chronic diseases of ageing. The recent publication of the Dietary Reference Intake report on vitamin D and calcium by the North American Institute of Medicine (IOM) is the most comprehensive report to date on the basis for setting nutritional requirements for vitamin D. This chapter will summarize the nutritional aspects of vitamin D and discuss the changes in vitamin D metabolism and requirements with ageing. It will summarize key evidence on the relationship between vitamin D status and some of the main ageing related health outcomes including bone, muscle and cognitive health as well as survival focusing on the published literature in very-old adults (those >= 85 years of age).

Vitamin D levels in schoolchildren: a cross-sectional study in Kuwait

Background

Ongoing studies in the Middle East, particularly in the Arabian Gulf countries, have reported extremely low levels of serum vitamin D across age and gender. In Kuwait, vitamin D deficiency is prevalent in adolescent girls and in adult women. A number of risk factors have been reported, among which gender, age, and obesity are a few. Because adequate vitamin D status is necessary to promote bone mineral accrual in childhood, and because low vitamin D levels have been associated with a wide range of health problems, there is concern that growing children with low vitamin D may be at higher risk for developing diseases. The aim of this study was to assess vitamin D levels in elementary schoolchildren.

Methods

Kuwaiti schoolchildren were recruited and assessed for their serum vitamin D, 25(OH)D, parathyroid hormone (PTH) and adjusted serum calcium (adj-Ca). Anthropometric measurements and data on lifestyle and health status were recorded during an interview.

Results

In a total of 199 schoolchildren, median (IQR) age was 8.5 (7.0–9.5 years), 25(OH)D was 30 (22–39 nmol/L), PTH was 4.7 (3.8–5.9 pmol/L), and adj-Ca was 2.39 (2.33–2.44 mmol/L). Boys had higher levels of 25(OH)D (18.3% vs 6.6% had levels ≥50 nmol/L) and lower levels of PTH (94.6% vs 80.2% had levels <7 pmol/L) than girls. Significant risk factors for 25(OH)D levels <25 nmol/L included being ≤8.5 years old (OR 4.95, 95% CI: 1.92–12.74), having PTH ≥7 pmol/L (OR 2.28, 95% CI: 1.17–4.46), being female (OR 2.44, 95% CI: 1.22–4.88), and being overweight or obese (OR 2.18, 95% CI: 1.11–4.26).

Conclusions

The results show relatively low levels of 25(OH)D in young schoolchildren in Kuwait, with lower levels in girls. Given the association of 25(OH)D with a wide range of ailments, it is necessary to further examine the causes and risk factors of low vitamin D in this age group to prevent associated health problems.

Vitamin D Effect on Bone Mineral Density and Fractures

One hundred years ago, vitamin D was identified as the cause and cure of osteomalacia. This role remains firmly established. Vitamin D influences skeletal mineralization principally through the regulation of intestinal calcium absorption. It has been proposed that vitamin D has direct beneficial effects on bone (besides the prevention of osteomalacia), but these have been difficult to establish in clinical trials. Meta-analyses of vitamin D trials show no effects on bone density or fracture risk when the baseline 25-hydroxyvitamin D is >40 nmol/L. A daily dose of 400 to 800 IU vitamin D₃ is usually adequate to correct such deficiency.

1β,25-Dihydroxyvitamin D3: A new vitamin D metabolite in human serum

BACKGROUND

The measurement of 1α,25(OH)₂D₃ in human serum poses a true challenge as concentrations are very low and structurally similar metabolites can interfere.

MATERIALS AND METHODS

During optimization of our in-house LC-MSMS method for serum 1α,25(OH)₂D₃ a previously co-eluting isobaric interference was separated. The isobar was identified as 1β,25(OH)₂D₃ by comparing retention time and fragmentation spectra to standards (other isobaric dihydroxylated vitamin D₃ analogs). 1β,25(OH)₂D₃ showed specific cluster formation (water), not present in 1α,25(OH)₂D₃. 1β,25(OH)₂D₃ was measured in serum of apparently healthy human volunteers (n=20), patients with high serum 25-hydroxyvitamin D [25(OH)D] concentrations (>50ng/mL) (n=33 among which 4 with very high levels (>150ng/mL)) and patients with kidney failure (n=68; 39 stage 1-3, 29 stage 4-5). Pearson's r was calculated for correlations and Mann-Whitney statistic to compare group medians.

RESULTS

Median serum 1β,25(OH)₂D₃ was 11pg/mL in apparently healthy volunteers and increased to 20pg/mL for serum 25(OH)D concentrations above 80ng/mL (n=22) (p<0.0001). 1β,25(OH)₂D₃ concentrations were significantly correlated to serum 25(OH)D concentrations (r=0.85) for the combined results from healthy volunteers and patient sera (n=53) (p<0.0001). For patients with kidney failure, median serum 1β,25(OH)₂D₃ was 7pg/mL and not different from the median level in healthy volunteers (p=0.06). The median concentration did not vary with different stages.

CONCLUSIONS

We present evidence for the widespread presence of 1β,25(OH)₂D₃, a new vitamin D metabolite, in human serum. The level increases with rising serum 25(OH)D concentrations and is particularly high in patients with very high 25(OH)D levels. We previously demonstrated that 1β,25(OH)₂D₃ is a poor genomic agonist but a potent non-genomic antagonist of 1α,25(OH)₂D_3. The clinical implications of the presence of this analog therefore require further exploration.

Impact of Calcium and Two Doses of Vitamin D on Bone Metabolism in the Elderly: A Randomized Controlled Trial

The optimal dose of vitamin D to optimize bone metabolism in the elderly is unclear. We tested the hypothesis that vitamin D, at a dose higher than recommended by the Institute of Medicine (IOM), has a beneficial effect on bone remodeling and mass. In this double-blind trial we randomized 257 overweight elderly subjects to receive 1000 mg of elemental calcium citrate/day, and the daily equivalent of 3750 IU/day or 600 IU/day of vitamin D3 for 1 year. The subjects' mean age was 71 ± 4 years, body mass index 30 ± 4 kg/m² , 55% were women, and 222 completed the 12-month follow-up. Mean serum 25 hydroxyvitamin D (25OHD) was 20 ng/mL, and rose to 26 ng/mL in the low-dose arm, and 36 ng/mL in the high-dose arm, at 1 year (p < 0.05). Plasma parathyroid hormone, osteocalcin, and C-terminal telopeptide (Cross Laps) levels decreased significantly by 20% to 22% in both arms, but there were no differences between the two groups for any variable, at 6 or 12 months, with the exception of serum calcitriol, which was higher in the high-dose group at 12 months. Bone mineral density (BMD) increased significantly at the total hip and lumbar spine, but not the femoral neck, in both study arms, whereas subtotal body BMD increased in the high-dose group only, at 1 year. However, there were no significant differences in percent change BMD between the two study arms at any skeletal site. Subjects with serum 25OHD <20 ng/mL and PTH level >76 pg/mL showed a trend for higher BMD increments at all skeletal sites, in the high-dose group, that reached significance at the hip. Adverse events were comparable in the two study arms. This controlled trial shows little additional benefit in vitamin D supplementation at a dose exceeding the IOM recommendation of 600 IU/day on BMD and bone markers, in overweight elderly individuals. © 2017 American Society for Bone and Mineral Research.

Vitamin D: Daily vs. Monthly Use in Children and Elderly-What Is Going On?

Vitamin D deficiency is highly prevalent among children and adults worldwide. Agreement exists that vitamin D deficiency should be corrected. However, the definitions of vitamin deficiency and effective vitamin D replacement therapy are inconsistent in the literature. Not only is the dosing regimen still under debate, but also the time and period of administration (i.e., daily vs. monthly dose). In pediatric as well as elderly subjects, dosing regimens with high vitamin D doses at less frequent intervals were proposed to help increase compliance to treatment: these became widespread in clinical practice, despite mounting evidence that such therapies are not only ineffective but potentially harmful, particularly in elderly subjects. Moreover, in the elderly, high doses of vitamin D seem to increase the risk of functional decline and are associated with a higher risk of falls and fractures. Achieving good adherence to recommended prophylactic regimens is definitely one of the obstacles currently being faced in view of the wide segment of the population liable to the treatment and the very long duration of prophylaxis. The daily intake for extended periods is in fact one of the frequent causes of therapeutic drop-outs, while monthly doses of vitamin D may effectively and safely improve patient compliance to the therapy. The aim of our paper is a quasi-literature review on dosing regimens among children and elderly. These two populations showed a particularly significant beneficial effect on bone metabolism, and there could be different outcomes with different dosing regimens.

Systematic Review of the Relationship between Vitamin D and Parkinson's Disease

BACKGROUND

Although vitamin D may have both protective and symptomatic effects in Parkinson's disease (PD), the evidence is scarce and not well understood. Also, 25-hydroxyvitamin D (vitamin D) is suggested to play a neuroprotective and neurotrophic role in the brain. Therefore, this review investigates the relationship between vitamin D and PD.

OBJECTIVE

Investigate the evidence for a relationship between vitamin D and PD by summarizing observational and interventional studies in humans, as well as relevant experimental studies.

METHODS

A systematic search was made in the Medline, Cochrane and Embase databases (from inception to March 2014). All identified titles were independently evaluated by two reviewers. Articles were selected based on the presence of PD-related outcome data. Included were observational studies (including genetic studies) and interventional studies in humans, as well as relevant animal studies.

RESULTS

A total of 20 studies (14 observational, 1 interventional and 5 rodent studies) were selected for analysis. Eight observational studies showed that serum 25(OH) D levels tend to be low in PD. One observational study indicated that low serum 25(OH) D may worsen automatic postural responses and one interventional study suggested that vitamin D supplementation can prevent worsening (based on the Hoehn and Yahr rating scale). Studies in rodent models of PD showed a protective effect of vitamin D treatment on dopaminergic neurons in the substantia nigra. Results of genetic studies on the association between vitamin D receptor polymorphisms and the risk of PD were contradictory.

CONCLUSION

The literature supports possible protective and symptomatic effects of vitamin D in PD. However, more observational and interventional studies in humans are needed to confirm and further elucidate the suggested beneficial effect of vitamin D on PD.

Effect of vitamin D on biochemical parameters in polycystic ovary syndrome women: a meta-analysis

AIM

To investigate the therapeutical effect of vitamin D supplementation on the metabolism and endocrine parameters of PCOS patients.

MATERIALS AND METHODS

Clinical studies investigating the therapeutic effect of vitamin D supplementation on PCOS patients were selected by searching PubMed, Embase, The Cochrane library and Web of Science until April 2016. The included articles were selected according to the inclusion criteria. Serum HOMA-IR, QUICKI, LDL, DHEAS, free testosterone (FT), total testosterone (TT), PTH, 25-hydroxy-vitamin D, and triglyceride of PCOS patients were enrolled for evaluating the therapeutic effects of vitamin D.

RESULTS

16 studies were included in this study. There was no significant difference between the placebo group and vitamin D group in the concentration of serum 25-hydroxy-vitamin D in patients with PCOS (P = 0.06). After treated with vitamin D, the serum 25-hydroxy-vitamin D in PCOS patients was increased (P < 0.00001), while the serum PTH (P = 0.003) and triglyceride (P = 0.006) were decreased. In addition, the serum HOMA-IR, QUICKI, LDL, DHEAS, FT, and TT in PCOS patients did not change. Subgroup analysis showed that the serum triglyceride of PCOS patients was decreased by low dose of vitamin D supplementation (<50,000 IU) (P = 0.03), but no significantly changed by high-dose vitamin D supplementation (≥50,000 IU) (P = 0.17).

CONCLUSION

Vitamin D supplementation significantly attenuates serum PTH and triglyceride in PCOS patients except for serum HOMA-IR, QUICKI, LDL, DHEAS, FT, and TT. Furthermore, less than 50,000 IU vitamin D supplementation is sufficient for decreasing serum triglyceride.

Vitamin D-Mediated Hypercalcemia: Mechanisms, Diagnosis, and Treatment

Hypercalcemia occurs in up to 4% of the population in association with malignancy, primary hyperparathyroidism, ingestion of excessive calcium and/or vitamin D, ectopic production of 1,25-dihydroxyvitamin D [1,25(OH)₂D], and impaired degradation of 1,25(OH)₂D. The ingestion of excessive amounts of vitamin D₃ (or vitamin D₂) results in hypercalcemia and hypercalciuria due to the formation of supraphysiological amounts of 25-hydroxyvitamin D [25(OH)D] that bind to the vitamin D receptor, albeit with lower affinity than the active form of the vitamin, 1,25(OH)₂D, and the formation of 5,6-trans 25(OH)D, which binds to the vitamin D receptor more tightly than 25(OH)D. In patients with granulomatous disease such as sarcoidosis or tuberculosis and tumors such as lymphomas, hypercalcemia occurs as a result of the activity of ectopic 25(OH)D-1-hydroxylase (CYP27B1) expressed in macrophages or tumor cells and the formation of excessive amounts of 1,25(OH)₂D. Recent work has identified a novel cause of non-PTH-mediated hypercalcemia that occurs when the degradation of 1,25(OH)₂D is impaired as a result of mutations of the 1,25(OH)₂D-24-hydroxylase cytochrome P450 (CYP24A1). Patients with biallelic and, in some instances, monoallelic mutations of the CYP24A1 gene have elevated serum calcium concentrations associated with elevated serum 1,25(OH)₂D, suppressed PTH concentrations, hypercalciuria, nephrocalcinosis, nephrolithiasis, and on occasion, reduced bone density. Of interest, first-time calcium renal stone formers have elevated 1,25(OH)₂D and evidence of impaired 24-hydroxylase-mediated 1,25(OH)₂D degradation. We will describe the biochemical processes associated with the synthesis and degradation of various vitamin D metabolites, the clinical features of the vitamin D-mediated hypercalcemia, their biochemical diagnosis, and treatment.

Hypercalcemia, hypercalciuria, and kidney stones in long-term studies of vitamin D supplementation: a systematic review and meta-analysis

BACKGROUND

Vitamin D supplementation is increasingly being used in higher doses in randomized controlled trials (RCTs). However, adverse events from very large annual doses of vitamin D have been shown in 2 RCTs, whereas in a third RCT, low-dose vitamin D, with calcium supplements, was shown to increase kidney stone risk.

OBJECTIVE

We analyzed the side effects related to calcium metabolism in RCTs, specifically hypercalcemia, hypercalciuria, and kidney stones, in participants who were given vitamin D supplements for ≥24 wk compared with in subjects in the placebo arm.

DESIGN

The following 3 main online databases were searched: Ovid Medline (PubMed), EMBASE, and the Cochrane Library. Software was used for the meta-analysis.

RESULTS

A total of 48 studies with 19,833 participants were identified, which reported ≥1 of the following side effects: hypercalcemia, hypercalciuria, or kidney stones. Of these studies, kidney stones were reported in only 9 trials with a tendency for fewer subjects reporting stones in the vitamin D arm than in the placebo arm (RR: 0.66, 95% CI: 0.41, 1.09; P = 0.10). In 37 studies, hypercalcemia was shown with increased risk shown for the vitamin D group (RR: 1.54; 95% CI: 1.09, 2.18; P = 0.01). Similar increased risk of hypercalciuria was shown in 14 studies for the vitamin D group (RR: 1.64; 95% CI: 1.06, 2.53; P = 0.03). In subgroup analyses, it was shown that the effect of vitamin D supplementation on risk of hypercalcemia, hypercalciuria, or kidney stones was not modified by baseline 25-hydroxyvitamin D, vitamin D dose and duration, or calcium co-supplementation.

CONCLUSIONS

Long-term vitamin D supplementation resulted in increased risks of hypercalcemia and hypercalciuria, which were not dose related. However, vitamin D supplementation did not increase risk of kidney stones. Additional large RCTs of long-term vitamin D supplementation are required to confirm these findings.

Vitamin D and spinal cord injury: should we care?

STUDY DESIGN

Narrative review.

OBJECTIVES

This review provides an overview of the etiological factors and consequences of vitamin D insufficiency in relation to spinal cord injury (SCI) as well as important considerations for vitamin D supplementation.

SETTING

Montreal, Canada.

METHODS

Literature search.

RESULTS

Vitamin D insufficiency is common in SCI individuals owing to the presence of many contributing factors including limited sun exposure and intake, use of medication and endocrine perturbations. Although there are several biological plausible mechanisms by which vitamin D may act upon musculoskeletal and cardiometabolic health, the impact of vitamin D insufficiency on such systems remains ill defined in SCI. In the absence of guidelines for the management of vitamin D insufficiency in this high-risk population and in an attempt to provide clinical guidance, considerations for vitamin D supplementation such as the type of vitamin D, dosing regimens and toxicity are discussed and tentative recommendations suggested with particular reference to issues faced by SCI patients.

CONCLUSION

Although high rates of vitamin D insufficiency are encountered in SCI individuals, its consequences and the amount of vitamin D required to prevent insufficiency are still unknown, indicating a need for more intervention studies with well-defined outcome measures. Routine screening and monitoring of vitamin D as well as treatment of suboptimal status should be instituted in both acute and chronic setting. The close interactions between vitamin D and related bone minerals should be kept in mind when supplementing SCI individuals, and practices should be individualized with clinical conditions.

Iranian consensus on use of vitamin D in patients with multiple sclerosis

Background

Accumulating evidences from experimental, epidemiologic and clinical studies support the potential linkage between poor vitamin D status and the risk of developing Multiple Sclerosis (MS), as well as, an adverse disease course. However, the results of the trials on the clinical outcomes of vitamin D supplementation in MS patients are less consistent which brought many discrepancies in routine practice. In this article we presented a summary of a symposium on vitamin D and MS. In this symposium we aim to review the current data about the relationship between vitamin D and MS, and suggest management guides for practicing neurologists.

Discussion

Generally, supplementation seems to be reasonable for all MS and clinically isolated syndrome (Rinaldi et al., Toxins 7:129–37, 2015) patients with serum 25(OH)D level below 40 ng/ml. In patients with vitamin D insufficiency or deficiency, a large replacing dose (e.g. 50,000 IU capsules of D per week for 8–12 week) is recommended. Panel also suggested: the checking of the serum vitamin D, and calcium level, as well as, patients’ compliance after the initial phase; a maintenance treatment of 1500–2000 IU daily or equivalent intermittent (weekly, biweekly or monthly) Dose, considering the patient’s compliance; routine check of serum vitamin D level at least two times a year especially at the beginning of spring and autumn; Serum vitamin D evaluation for first degree relatives of MS patients at high risk age and supplementation in case of insufficiency (25(OH)D less than 40 ng/ml); correction of vitamin D deficiency and insufficiency before pregnancy, as well as, a daily dose of 1500–2000 IU or equivalent biweekly intake in 2nd and 3rd trimesters; stopping supplementation if 25(OH)D serum level exceeds 100 ng/ml.

Summary

Although the results of high power studies are not available, correcting vitamin D status seems plausible in all MS and CIS patients. Maintaining the serum 25(OH)D level between 40 and 100 ng/ml is not known to exert adverse effect. More ever, it might be associated with lower disease activity.

Effect of vitamin D supplementation on measures of arterial stiffness: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Low vitamin D has been associated with poor arterial compliance in observational studies. Arterial stiffness has prognostic value for cardiovascular disease risk. The aim of this systematic review was to clarify the literature surrounding the use of vitamin D to ameliorate arterial stiffness.

METHODS

We conducted a systematic review of the MEDLINE, Scopus and EMBASE databases for randomized controlled clinical trials investigating the effect of vitamin D supplementation on pulse wave velocity (PWV) and/or augmentation index (AI) as indicators of arterial stiffness. We meta-analysed data and calculated standardized mean difference (SMD) and 95% confidence intervals (CI) using inverse-variance models on RevMan v5.3 software. Study quality was assessed using a modified Jadad scale.

RESULTS

A total of 607 unique records were identified, of which 18 satisfied our inclusion and exclusion criteria. Study quality was high, ranging from 9 to 12 (of 13). Study design in terms of vitamin D dosing protocol (range: 1000-5700 IU/day), follow-up times (range: 1-12 months), sample size (range: n = 29-183) and recruitment strategies varied markedly. Thirteen studies had data for meta-analysis. Vitamin D was associated with nonsignificant reductions in PWV [SMD = -0·10; 95% CI: -0·24, 0·04; P = 0·17; n = 806 from ten studies] and AI [-0·15; -0·32, 0·02; 0·08; n = 551 from eight studies].

DISCUSSION

There is inconsistent evidence to suggest that vitamin D supplementation improves indicators of arterial stiffness. This may be attributable to the heterogeneity in study design. Therefore, large and well-designed randomized studies are required to determine the casual relationships between vitamin D and arterial stiffness and cardiovascular risk.

A phase IV, two-armed, randomized, cross-over study comparing compliance with once-a-month administration of vitamin D3 to compliance with daily administration of a fixed-dose combination of vitamin D3 and calcium during two 6-month periods

In a randomized, cross-over study, once monthly administration of vitamin D3 was preferred over a once daily administration of a fixed-dose combination of vitamin D3 and calcium, with a better compliance but without any significant difference in the increase in vitamin D levels.

INTRODUCTION

The aim of the present study was to compare a once-monthly administration of vitamin D3 to a daily administration of a fixed-dose combination of vitamin D3 and calcium during two treatment periods of 6 months.

METHODS

One hundred volunteers aged 50 years old or older were randomized to receive either one drinkable ampoule containing 25,000 IU vitamin D3 (D-Cure®, SMB) once monthly (group VD) or one chewable tablet containing 1000 mg calcium carbonate + 800 IU vitamin D3 (Steovit Forte®, Takeda) once daily (group VDCa) during 6 months. After the first 6 months of treatment, the groups were reversed according to the randomized cross-over design. Treatment compliance (i.e. the primary outcome), preference, acceptability and vitamin D levels and adverse events were all collected.

RESULTS

For the two periods, the patients had a significantly higher compliance in the VD group than in the VDCa group (p < 0.0001). During the study, 50 (56.8 %) patients preferred the VD treatment, 16 (18.2 %) patients preferred the VDCa, and for 22 (25.0 %) patients, neither treatment was preferred. At the end of the first 6 months of treatment, the mean (SD) increase of 25(OH)D was 6.57 ng/mL (8.19) in the VD group and 3.88 ng/mL (10.0) in the VDCa group (p = 0.16 between groups).

CONCLUSION

In this study, a once-monthly administration of vitamin D3 was preferred over a once-daily administration of a fixed-dose combination of vitamin D3 and calcium, with a better compliance but without any significant difference in the increase in vitamin D levels.

Changing patterns of prescription in vitamin D supplementation in adults: analysis of a regional dataset

Scientific interest in vitamin D has greatly risen during the last 10 years. The analysis of the changes in vitamin D prescriptions and related costs in a regional prescription dataset has revealed a profound increase in the period 2006-2013. Further studies on cost-effectiveness of such increase in vitamin D supplementation are needed.

INTRODUCTION

The aim of this study was to analyze the changes in population-based prescription patterns of vitamin D supplements in the general population in an Italian regional setting during an 8-year period (2006-2013).

METHODS

Data have been retrieved from the database of reimbursed prescriptions of the Region of Tuscany containing all of the medical reimbursements for the whole regional population (total of 3,619,872 and 3,692,828 inhabitants in 2006 and 2013, respectively). Data referring to adult population (age 20-90+ years) have been considered for this analysis (3,033,530 in 2006 and 3,066,741 in 2013). Two different flows (pharmaceutical distribution dataset and general data flow) were taken into account, using the ATC5 coding system for vitamin D supplements alone or in combination with calcium or alendronate. The number of boxes dispensed was retrieved, the number of patients receiving a specific treatment was calculated, and a cost analysis was performed.

RESULTS

An upsurge in the prescriptions of vitamin D compounds was disclosed, mainly sustained by a 75.3-fold increase in cholecalciferol, in all age groups and both sexes. This occurred in parallel to a 4.3-fold rise in prescriptions of oral alendronate in combination with cholecalciferol, a slight decrease in dispensed alendronate alone, and a modest increase in the prescription of the combination of calcium salts and cholecalciferol, and calcium alone. The total cost for reimbursement by the Regional Health System for vitamin D-related compounds rose from €3,242,100 euros in 2006 to €8,155,778 in 2013.

CONCLUSION

The huge increase in vitamin D prescriptions and related costs in the last decade, as revealed by the analysis of a regional pharmaceutical dataset, reflects the increased awareness of the possible consequences of a poor vitamin D status. Further studies on cost-effectiveness of such increase in vitamin D supplementation are needed.

Vitamin D deficiency impairs glucose-stimulated insulin secretion and increases insulin resistance by reducing PPAR-γ expression in nonobese Type 2 diabetic rats

Human studies have provided relatively strong associations of poor vitamin D status with Type 2 diabetes but do not explain the nature of the association. Here, we explored the physiological pathways that may explain how vitamin D status modulates energy, lipid and glucose metabolisms in nonobese Type 2 diabetic rats. Goto-Kakizaki (GK) rats were fed high-fat diets containing 25 (VD-low), 1000 (VD-normal) or 10,000 (VD-high) cholecalciferol-IU/kg diet for 8 weeks. Energy expenditure, insulin resistance, insulin secretory capacity and lipid metabolism were measured. Serum 25-OH-D levels, an index of vitamin D status, increased dose dependently with dietary vitamin D. VD-low resulted in less fat oxidation without a significant difference in energy expenditure and less lean body mass in the abdomen and legs comparison to the VD-normal group. In comparison to VD-low, VD-normal had lower serum triglycerides and intracellular fat accumulation in the liver and skeletal muscles which was associated with down-regulation of the mRNA expressions of sterol regulatory element binding protein-1c and fatty acid synthase and up-regulation of gene expressions of peroxisome proliferator-activated receptors (PPAR)-α and carnitine palmitoyltransferase-1. In euglycemic hyperinsulinemic clamp, whole-body and hepatic insulin resistance was exacerbated in the VD-low group but not in the VD-normal group, possibly through decreasing hepatic insulin signaling and PPAR-γ expression in the adipocytes. In 3T3-L1 adipocytes 1,25-(OH)2-D (10 nM) increased triglyceride accumulation by elevating PPAR-γ expression and treatment with a PPAR-γ antagonist blocked the triglyceride deposition induced by 1,25-(OH)2-D treatment. VD-low impaired glucose-stimulated insulin secretion in hyperglycemic clamp and decreased β-cell mass by decreasing β-cell proliferation. In conclusion, vitamin D deficiency resulted in the dysregulation of glucose metabolism in GK rats by simultaneously increasing insulin resistance by decreasing adipose PPAR-γ expression and deteriorating β-cell function and mass.

Prevention of exacerbations in patients with COPD and vitamin D deficiency through vitamin D supplementation (PRECOVID): a study protocol

Background

Vitamin D is well known for its function in calcium homeostasis and bone mineralisation, but is increasingly studied for its potential immunomodulatory properties. Vitamin D deficiency is a common problem in patients with COPD. Previous studies have not demonstrated a beneficial effect of vitamin D on exacerbation rate in COPD patients. However, subgroup analyses suggested protective effects in vitamin D deficient patients. Our objective is to assess the effect of vitamin D supplementation on exacerbation rate specifically in vitamin D deficient COPD patients.

Methods/Design

We will perform a randomised, multi-center, double-blind, placebo-controlled intervention study. The study population consists of 240 COPD patients aged 40 years and older with vitamin D deficiency (25-hydroxyvitamin D concentration < 50 nmol/L). Participants will be recruited after an exacerbation and will be randomly allocated in a 1:1 ratio to receive vitamin D3 16800 IU or placebo orally once a week during 1 year. Participants will receive a diary card to register the incidence of exacerbations and changes in medication during the study period. Visits will be performed at baseline, at 6 months and at 12 months after randomisation. Participants will undergo spirometry, measurement of total lung capacity and assessment of maximal respiratory mouth pressure. Several physical performance and hand grip strength tests will be performed, questionnaires on quality of life and physical activity will be filled in, a nasal secretion sample and swab will be obtained and blood samples will be taken. The primary outcome will be exacerbation rate.

Discussion

This study will be the first RCT aimed at the effects of vitamin D supplementation on exacerbation rate in vitamin D deficient COPD patients. Also, in contrast to earlier studies that used infrequent dosing regimens, our trial will study effects of a weekly dose of vitamin D supplementation. Secondly, the immunomodulatory effects of vitamin D on host immune response of COPD patients and underlying mechanisms will be studied. Finally, the effects on physical functioning will be examined.

Trial registration

This trial is registered in ClinicalTrials.gov, ID number NCT02122627. Date of Registration April 2014.

Role of Vitamin D deficiency in extraskeletal complications: predictor of health outcome or marker of health status?

The relationship of vitamin D with extraskeletal complications, such as cardiovascular disease, cancer, and autoimmune disease, is of major interest considering its roles in key biological processes and the worldwide high prevalence of vitamin D deficiency. However, the causal relationships between vitamin D and most extraskeletal complications are weak. Currently, a heated debate over vitamin D is being conducted according to two hypotheses. In this review, we first present the different arguments that suggest a major role of vitamin D in a very broad type of extraskeletal complications (hypothesis #1). We then present results from recent meta-analyses of randomized controlled trials indicating a lack of association of vitamin D with major extraskeletal complications (hypothesis #2). We discuss different issues (e.g., causality, confounding, reverse causation, misclassification, and Mendelian randomization) that contribute to the favoring of one hypothesis over the other. While ultimately only one hypothesis is correct, we anticipate that the results from the ongoing randomized controlled trials will be unlikely to reconcile the divided experts.

Changing Incidence of Serum 25-Hydroxyvitamin D Values Above 50 ng/mL: A 10-Year Population-Based Study

OBJECTIVE

To determine the incidence trend of 25-hydroxyvitamin D (25(OH)D) values above 50 ng/mL and associated toxicity.

PATIENTS AND METHODS

We conducted a retrospective population-based study in Olmsted County, Minnesota, in the 10-year period from January 1, 2002, through December 31, 2011, by using the Rochester Epidemiology Project. Individuals were eligible if they resided in Olmsted County during the study period and had a measured 25(OH)D value above 50 ng/mL. The date of the first 25(OH)D value above 50 ng/mL was considered the index date for incidence determination. Hypercalcemia, the primary vitamin D toxicity, was considered potentially associated with the 25(OH)D concentration if it was measured within 3 months of the 25(OH)D measurement, and such cases had a medical record review.

RESULTS

Of 20,308 total 25(OH)D measurements, 1714 (8.4%), 123 (0.6%), and 37 (0.2%) unique persons had 25(OH)D values above 50, 80 and above, and 100 ng/mL and above, respectively. The age- and sex-adjusted incidence of 25(OH)D values above 50 ng/mL increased from 9 to 233 cases per 100,000 person-years from 2002 to 2011 (P<.001), respectively, and was greatest in persons aged 65 years and older (P<.001) and in women (P<.001). Serum 25(OH)D values were not significantly related to serum calcium values (P=.20) or with the risk of hypercalcemia (P=.24). A medical record review identified 4 cases (0.2%) in whom 25(OH)D values above 50 ng/mL were temporally associated with hypercalcemia, but only 1 case had clinical toxicity associated with the highest observed 25(OH)D value of 364 ng/mL.

CONCLUSION

The incidence of 25(OH)D values above 50 ng/mL increased significantly between 2002 and 2011 without a corresponding increase in acute clinical toxicity.

25-hydroxyvitamin D and increased all-cause mortality in very old women: the Newcastle 85+ study

OBJECTIVE

To investigate the associations between low and high concentrations of baseline serum 25-hydroxyvitamin D [25(OH)D] and all-cause mortality in very old (≥85 years) men and women over 6 years.

DESIGN, SETTING AND SUBJECTS

Prospective mortality data from 775 participants in the Newcastle 85+ Study were analysed for survival in relation to 25(OH)D (season-specific quartiles and predefined cut-off values) and sex using Cox proportional hazards models. The models were fitted to the entire and restricted (nonusers of vitamin D-containing supplements and medication) cohorts.

RESULTS

For the entire cohort, mortality was higher in both the lowest and highest 25(OH)D season-specific quartiles [SQ1: hazard ratio (HR) 1.31, 95% confidence interval (CI) 1.01-1.69, P = 0.04; SQ4: HR 1.44, 95% CI 1.12-1.85, P = 0.004] compared with the combined middle quartiles (SQ2 + SQ3), after adjustment for sociodemographic factors. The increased risk for the highest quartile remained significant after further adjustment for lifestyle variables (SQ4: HR 1.37, 95% CI 1.06-1.77, P = 0.02) and was seen only in women in sex-specific analyses. Similarly, in sensitivity analyses with predefined 25(OH)D cut-off values, the highest 25(OH)D concentration (≥75 nmol L(-1) ) was associated with a 2.4-fold increased risk of mortality in women (restricted cohort) after adjusting for all covariates.

CONCLUSION

Low and high season-specific 25(OH)D quartiles were associated with increased risks of mortality over 6 years in the very old; this effect was particularly noticeable in women, including those who reported taking vitamin D-containing supplements/medication.

Bimodal Influence of Vitamin D in Host Response to Systemic Candida Infection-Vitamin D Dose Matters

Vitamin D level is linked to susceptibility to infections, but its relevance in candidemia is unknown. We aimed to investigate the in vivo sequelae of vitamin D3 supplementation in systemic Candida infection. Implicating the role of vitamin D in Candida infections, we showed that candidemic patients had significantly lower 25-OHD concentrations. Candida-infected mice treated with low-dose 1,25(OH)2D3 had reduced fungal burden and better survival relative to untreated mice. Conversely, higher 1,25(OH)2D3 doses led to poor outcomes. Mechanistically, low-dose 1,25(OH)2D3 induced proinflammatory immune responses. This was mediated through suppression of SOCS3 and induction of vitamin D receptor binding with the vitamin D-response elements in the promoter of the gene encoding interferon γ. These beneficial effects were negated with higher vitamin D3 doses. While the antiinflammatory effects of vitamin D3 are well described, we found that, conversely, lower doses conferred proinflammatory benefits in Candida infection. Our study highlights caution against extreme deviations of vitamin D levels during infections.