Parameters of the thrombogram are associated with serum 25-hydroxyvitamin D levels at baseline, but not affected during supplementation with vitamin D

Is Circulating Vitamin D Status Associated with the Risk of Venous Thromboembolism? A Meta-Analysis of Observational Studies

BACKGROUND

Although vitamin D is antithrombotic, associations between serum vitamin D status and the risk of venous thromboembolism (VTE) remain inconsistent.

METHODS

We searched the EMBASE, MEDLINE, Cochrane Library, and Google Scholar databases from inception to June 2022 to identify observational studies examining associations between vitamin D status and VTE risk in adults. The primary outcome presented as odds ratio (OR) or hazard ratio (HR) was the association of vitamin D levels with the risk of VTE. Secondary outcomes included the impacts of vitamin D status (i.e., deficiency or insufficiency), study design, and the presence of neurological diseases on the associations.

RESULTS

Pooled evidence from a meta-analysis of sixteen observational studies, including 47648 individuals published from 2013 to 2021, revealed a negative relationship between vitamin D levels and the risk of VTE either based on OR (1.74, 95% confidence interval (CI): 1.37 to 2.20, p < 0.00001; I² = 31%, 14 studies, 16074 individuals) or HR (1.25, 95% CI: 1.07 to 1.46, p = 0.006; I² = 0%, 3 studies, 37,564 individuals). This association remained significant in subgroup analyses of the study design and in the presence of neurological diseases. Compared to individuals with normal vitamin D status, an increased risk of VTE was noted in those with vitamin D deficiency (OR = 2.03, 95% CI: 1.33 to 3.11) but not with vitamin D insufficiency.

CONCLUSIONS

This meta-analysis demonstrated a negative association between serum vitamin D status and the risk of VTE. Further studies are required to investigate the potential beneficial effect of vitamin D supplementation on the long-term risk of VTE.

Vitamin D Deficiency is Associated With Increased Plasminogen Activator Inhibitor 1/Plasminogen Activator Inhibitor 2 Ratio in Pregnancy

BACKGROUND

Vitamin D deficiency has recently been suggested as an independent risk factor for thrombosis. Notably, vitamin D deficiency is common in pregnant populations, whom already have an increased thrombotic risk. However, pregnant women are commonly excluded from studies investigating the hemostatic system, and knowledge on the impact of vitamin D on hemostasis in pregnancy is therefore limited.

METHODS

A cross-sectional study comparing the hemostatic profile of pregnant women (gestational week 12.9 ± 0.7) with vitamin D deficiency (≤50 nmol/L) (n = 70) and high adequate vitamin D status (≥100 nmol/L) (n = 59).

RESULTS

Vitamin D deficient women displayed increased plasminogen activator inhibitor 1 levels and an increased plasminogen activator inhibitor 1/plasminogen activator inhibitor 2 ratio, even after adjusting for factors with potential influence on hemostasis (body mass index, smoking and use of fish oil supplements).

CONCLUSIONS

Vitamin D deficiency is associated with increased plasminogen activator inhibitor 1/plasminogen activator inhibitor 2 ratio in pregnant women. As an increased plasminogen activator inhibitor 1/plasminogen activator inhibitor 2 ratio with high plasminogen activator inhibitor 1 levels may increase thrombotic risk and is associated with the development of pregnancy complications, further research is needed to determine the optimal vitamin D supplementation in pregnancy.

Is Vitamin D Deficiency Prothrombotic? A Systematic Review

Observational studies indicate a relationship between vitamin D deficiency and an increased risk of venous and arterial thrombotic events, but the underlying mechanisms behind this association are uncertain. This systematic review explores if there is an association between decreased vitamin D levels and a prothrombotic profile. The systematic literature search initially identified 3,214 studies (published until December 21, 2021) investigating the relationship between vitamin D and numerous hemostatic parameters. After the screening process, 18 observational and intervention studies fulfilled the inclusion criteria and were included in this systematic review. Parameters of primary hemostasis, secondary hemostasis, and fibrinolysis were investigated in six, thirteen, and fifteen of these studies, respectively. Most of the eligible studies did not identify significant associations between decreased vitamin D levels and hemostatic parameters. Some conflicting results were found between decreased vitamin D levels and thrombin generation parameters and the tissue factor pathway inhibitor. Conflicting results were also found between decreased vitamin D levels and fibrinolytic parameters, although the evidence may point toward weak associations with some regulators of fibrinolysis, mostly decreased tissue type plasminogen activator. Overall, our systematic review did not identify any definitive link between vitamin D deficiency and a prothrombotic profile, which might otherwise help explain the observed association between vitamin D deficiency and increased risk of thrombotic events. Moreover, there is no clinical evidence to confirm or refute a possible antithrombotic effect of vitamin D. Larger high-quality randomized controlled trials are needed to better elucidate the link between vitamin D deficiency and a prothrombotic risk profile.

Influence of Vitamin D Status on the Maintenance Dose of Warfarin in Patients Receiving Chronic Warfarin Therapy

INTRODUCTION

Considering the anticoagulant actions of vitamin D, we hypothesize that vitamin D status might affect the required dose of warfarin for maintaining the therapeutic international normalized ratio (INR).

METHODS

In a retrospective single-center cohort study, serum levels of 25-hydroxyvitamin D were assessed for 89 subjects receiving a stable dose of warfarin for 3 months or longer and had a stable INR between 2 and 3.5 for at least three consecutive visits. A warfarin sensitivity index (WSI), defined as the steady-state INR divided by the mean daily warfarin dose, was used for measuring the warfarin dose response. The relation between the serum level of 25-hydroxyvitamin D and WSI value and the difference in the mean WSI value between the subjects with different vitamin D status categories (sufficient, insufficient, and deficient) were assessed.

RESULTS

Twenty-one subjects had vitamin D deficiency, 43 had vitamin D insufficiency, and only 25 had normal levels of 25-hydroxyvitamin D. Based on the multiple linear regression analysis, there was a significant but weakly positive correlation between WSI and 25-hydroxyvitamin D serum levels, as the value of WSI increases by almost 0.0027434 for every unit increase in 25-hydroxyvitamin D serum level (p value = 0.041). Using one-way ANOVA analysis, there was a trend in a significant difference between the groups with different vitamin D status categories regarding the mean WSI value (F = 2.95, p value = 0.057), as subjects with sufficient vitamin D state compared to those with vitamin D deficiency had a higher WSI value.

CONCLUSIONS

Although the study's limitations limit our ability to draw definite conclusions, the present data suggest that in addition to other traditional factors, vitamin D status might also affect warfarin sensitivity and maintenance dose requirement. However, to more clearly explain this link, further studies with high involvement subjects are required.

Environmental Factors That Affect Parathyroid Hormone and Calcitonin Levels

Calciotropic hormones, parathyroid hormone (PTH) and calcitonin are involved in the regulation of bone mineral metabolism and maintenance of calcium and phosphate homeostasis in the body. Therefore, an understanding of environmental and genetic factors influencing PTH and calcitonin levels is crucial. Genetic factors are estimated to account for 60% of variations in PTH levels, while the genetic background of interindividual calcitonin variations has not yet been studied. In this review, we analyzed the literature discussing the influence of environmental factors (lifestyle factors and pollutants) on PTH and calcitonin levels. Among lifestyle factors, smoking, body mass index (BMI), diet, alcohol, and exercise were analyzed; among pollutants, heavy metals and chemicals were analyzed. Lifestyle factors that showed the clearest association with PTH levels were smoking, BMI, exercise, and micronutrients taken from the diet (vitamin D and calcium). Smoking, vitamin D, and calcium intake led to a decrease in PTH levels, while higher BMI and exercise led to an increase in PTH levels. In terms of pollutants, exposure to cadmium led to a decrease in PTH levels, while exposure to lead increased PTH levels. Several studies have investigated the effect of chemicals on PTH levels in humans. Compared to PTH studies, a smaller number of studies analyzed the influence of environmental factors on calcitonin levels, which gives great variability in results. Only a few studies have analyzed the influence of pollutants on calcitonin levels in humans. The lifestyle factor with the clearest relationship with calcitonin was smoking (smokers had increased calcitonin levels). Given the importance of PTH and calcitonin in maintaining calcium and phosphate homeostasis and bone mineral metabolism, additional studies on the influence of environmental factors that could affect PTH and calcitonin levels are crucial.

Pathophysiological Role and Therapeutic Implications of Vitamin D in Autoimmunity: Focus on Chronic Autoimmune Diseases

Vitamin D is a pleiotropic secosteroid yielding multiple actions in human physiology. Besides the canonical regulatory activity on bone metabolism, several non-classical actions have been described and the ability of vitamin D to partake in the regulation of the immune system is particularly interesting, though far stronger and convincing evidence has been collected in in vitro as compared to in vivo studies. Whether vitamin D is able to regulate at physiological concentrations the human immune system remains unproven to date. Consequently, it is not established if vitamin D status is a factor involved in the pathogenesis of immune-mediated diseases and if cholecalciferol supplementation acts as an adjuvant for autoimmune diseases. The development of autoimmunity is a heterogeneous process, which may involve different organs and systems with a wide range of clinical implications. In the present paper, we reviewed the current evidences regarding vitamin D role in the pathogenesis and management of different autoimmune diseases.

Thrombin generation and fibrin clot structure after vitamin D supplementation

OBJECTIVE

Vitamin D deficiency is associated with increased risks of arterial and venous cardiovascular events. Hypothetically, supplementation with vitamin D may lead to a less prothrombotic phenotype, as measured by global coagulation assays and fibrin clot structure.

METHODS

In this prospective cohort study, we enrolled adult outpatients attending the Primary Care Division of the Geneva University Hospitals with a severe vitamin D deficiency (25-hydroxyvitamin-D3 (25-OHD) <25 nmol/L), excluding obese patients or with a recent acute medical event. We evaluated changes in coagulation times, thrombin generation assay, clot formation and clot lysis time, 25-OHD and parathormone before and 1-3 months after cholecalciferol oral supplementation with one-time 300,000 IU then 800 IU daily. Paired t-tests with a two-sided alpha of 0.05 compared absolute mean differences.

RESULTS

The 48 participants had a mean age of 43.8 ± 13.8 years. After supplementation, 25-OHD levels increased from 17.9 ± 4.6 nmol/L to 62.5 ± 20.7 nmol/L 6.4 ± 3.0 weeks after inclusion. Endogenous thrombin potential and thrombin generation peak values both decreased significantly (-95.4 nM × min (95%CI -127.9 to -62.8), P < 0.001; -15.1 nM (-23.3 to -6.8), P < 0.001). The maximum absorbance by turbidimetry decreased significantly (P = 0.001) after supplementation. There was no change in clot lysis time, coagulation times or plasminogen activator inhibitor-1 and homocysteine levels.

CONCLUSIONS

In severe vitamin D deficiency, a high-dose cholecalciferol supplementation was associated with a reduction in thrombin generation and an average decreased number of fibrin protofibrils per fibers and fibrin fiber size measured by turbidimetry. This suggests that severe vitamin D deficiency may be associated with a potentially reversible prothrombotic profile.

The anti-thrombotic effects of vitamin D and their possible relationship with antiphospholipid syndrome

The importance of the immunomodulatory effects of vitamin D has recently been associated with autoimmune and chronic inflammatory diseases. Vitamin D deficiency has been linked to the development of autoimmune conditions. Antiphospholipid syndrome is an autoimmune disease characterized by thrombotic events and obstetric complications in patients with antiphospholipid antibodies. Current data show that patients with antiphospholipid syndrome have a high prevalence of vitamin D deficiency even without classic risk factors. Several studies have suggested vitamin D may have anti-thrombotic functions. In antiphospholipid syndrome, low vitamin D serum levels have been associated with thrombotic manifestations, suggesting a possible protective role of vitamin D in antiphospholipid syndrome. This literature review presents current evidence on the haemostatic functions of vitamin D and their possible relationship with the clinical manifestations of antiphospholipid syndrome.

Associations of Serum 25-Hydroxyvitamin D With Hemostatic and Inflammatory Biomarkers in the Multi-Ethnic Study of Atherosclerosis

CONTEXT

Mechanisms explaining documented associations of 25-hydroxyvitamin D [25(OH)D] deficiency with increased risks of cardiovascular disease (CVD) and venous thromboembolism may relate to adverse hemostatic and inflammatory responses.

OBJECTIVE

To evaluate whether 25(OH)D deficiency is associated with a prothrombotic and proinflammatory biological profile.

DESIGN

Cross-sectional analyses.

SETTING

The Multi-Ethnic Study of Atherosclerosis, a multicenter prospective cohort of American adults.

PARTICIPANTS

Up to 6554 adults free of CVD.

MAIN OUTCOME MEASURES

Ten hemostatic biomarkers (D-dimer, fibrinogen, factor VIII, plasmin-antiplasmin, and homocysteine [n = 6443]; von Willebrand factor, soluble tissue factor, plasminogen activator inhibitor-1 (PAI-1), total tissue factor pathway inhibitor (TFPI), and soluble thrombomodulin [n = 814]), and three inflammatory biomarkers (IL-6, C-reactive protein [n = 6443], and TNF-α soluble receptor [n = 3802]).

RESULTS

Among 6443 subjects (46.6% men; mean age, 62.1 years; mean body mass index, 28.3 kg/m(2)) of White (37.8%), Black (27.2%), Chinese (12.2%), and Hispanic (21.8%) race/ethnicity, mean 25(OH)D was 25.3 ng/mL. After multiple adjustment, 25(OH)D concentrations were associated with concentrations of IL-6 and homocysteine and also with concentrations of PAI-1 and TFPI: per 10 ng/mL decrement in 25(OH)D, 5.1% higher IL-6 (95% confidence interval [CI], 3.4-6.9; P < .001); 3.7% higher homocysteine (95% CI, 3.0-4.3; P < .001); 7.0% higher PAI-1 (95% CI, 0.9-13.6; P = .025); and 2.1% higher TFPI (95% CI, 0.0-4.2; P = .047), without racial/ethnic heterogeneity. No significant associations were observed for other hemostatic and inflammatory biomarkers.

CONCLUSIONS

Increased inflammation as reflected by higher circulating IL-6 and increased homocysteine concentrations may represent mechanisms linking 25(OH)D deficiency to greater risks of CVD and perhaps venous thromboembolism. Low concentrations of 25(OH)D were also associated with PAI-1 and TFPI concentrations, but not with other hemostatic biomarkers.

Determinants of parathyroid hormone response to vitamin D supplementation: a systematic review and meta-analysis of randomised controlled trials

This systematic review aimed to assess the determinants of the parathyroid hormone (PTH) level response to vitamin D supplementation. We searched Medline, Google Scholar and the reference lists of previous reviews. All randomised controlled trials (RCT) on vitamin D supplementation that involved apparently healthy human subjects with a report of PTH were selected. Potential studies were screened independently and in duplicate. Results are summarised as mean differences with 95% confidence intervals. Quality assessment, subgroup analysis, meta-analysis and meta-regression analysis were carried out. Thirty-three vitamin D supplementation RCT were included. Vitamin D supplementation significantly raised circulating 25-hydroxyvitamin D (25(OH)D) with significant heterogeneity among studies with a pooled mean difference (PMD) of 15.5 ng/ml (test for heterogeneity: P<0·001 and I 2=97·3%). Vitamin D supplementation significantly reduced PTH level with PMD of -8·0 pg/ml, with significant heterogeneity ((test for heterogeneity: P<0·001) and the I 2 value was 97·3%). In the subgroup analyses, the optimum treatment effect for PTH was observed with Ca doses of 600-1200 mg/d (-22·48 pg/ml), after the duration of a >12-month trial (-18·36 pg/ml), with low baseline 25(OH)D concentration of <20 ng/ml (-16·70 pg/ml) and in those who were overweight and obese (-18·11 pg/ml). Despite the present meta-analysis being hindered by some limitations, it provided some interesting evidence, suggesting that suppression of PTH level needs higher vitamin D intake (75 μg/d) than the current recommendations and longer durations (12 months), which should be taken into account for nutritional recommendations.

The effect of calcium plus vitamin D supplementation on the risk of venous thromboembolism. From the Women's Health Initiative Randomized Controlled Trial

Experimental and epidemiological studies suggest that vitamin D may be implicated in haemostatic regulations and influence the risk of venous thromboembolism (VTE). The aim of this study was to investigate whether oral supplementation of vitamin D3 combined with calcium reduces the risk of VTE. In the randomised, double-blind, placebo-controlled Women's Health Initiative Calcium Plus Vitamin D trial, 36,282 postmenopausal women aged 50-79 years were randomised to receive 1,000 mg of calcium carbonate and 400 IU of vitamin D3 per day (n=18,176) or a matching placebo (n=18,106) during an average of seven years. This secondary analysis of the trial compared the incidence of VTE by treatment group using an intention-to-treat Cox regression analysis. The incidence of VTE did not differ between women randomised to calcium plus vitamin D and women randomised to placebo (320 vs 348 VTE events, respectively; hazard ratio (HR) 0.92, 95 % confidence interval (CI) 0.79-1.07). Results were not modified in an analysis using inverse-probability weights to take non-adherence into account (HR 0.94, 95 %CI 0.73-1.22) or in multiple subgroups. Whereas the risk of a non-idiopathic VTE was similar between groups, the risk of idiopathic VTE was lower in women randomised to calcium plus vitamin D (40 vs 65 events; HR 0.62, 95 %CI 0.42-0.92). In conclusion, daily supplementation with 1,000 mg of calcium and 400 IU of vitamin D did not reduce the overall incidence of VTE in generally healthy postmenopausal women. However, the observed reduced risk of idiopathic VTE in women randomised to calcium and vitamin D warrants further investigations.

The Effect of Vitamin D Supplementation on Thrombin Generation Assessed by the Calibrated Automated Thrombogram

Observational and in vitro studies suggest that vitamin D may have antithrombotic activity. This study aimed to examine the relationship between vitamin D supplementation and thrombin generation. Serum 25-hydroxyvitamin D (25(OH)D) and thrombin generation parameters were measured in 73 healthy volunteers. Participants with serum 25(OH)D <50 nmol/L (n = 53) were treated with vitamin D3and tested for 25(OH)D and thrombin generation at the end of treatment. Lag time and time to peak decreased after treatment by a mean of -0.49 ± 0.51 minute (P< .001) and -0.76 ± 0.70 minute (P< .001), respectively, whereas endogenous thrombin potential and peak height increased after treatment by a mean of 170.1 ± 339.8 nmol/L minute (P= .001) and 34.2 ± 47.8 nmol/L (P< .001), respectively. Treatment with vitamin D supplementation seems to have prothrombotic effect in patients with vitamin D insufficiency. These findings should be interpreted with caution and need to be replicated in future studies.

Vitamin D supplementation for prevention of mortality in adults

BACKGROUND

Available evidence on the effects of vitamin D on mortality has been inconclusive. In a recent systematic review, we found evidence that vitamin D3 may decrease mortality in mostly elderly women. The present systematic review updates and reassesses the benefits and harms of vitamin D supplementation used in primary and secondary prophylaxis of mortality.

OBJECTIVES

To assess the beneficial and harmful effects of vitamin D supplementation for prevention of mortality in healthy adults and adults in a stable phase of disease.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index-Expanded and Conference Proceedings Citation Index-Science (all up to February 2012). We checked references of included trials and pharmaceutical companies for unidentified relevant trials.

SELECTION CRITERIA

Randomised trials that compared any type of vitamin D in any dose with any duration and route of administration versus placebo or no intervention in adult participants. Participants could have been recruited from the general population or from patients diagnosed with a disease in a stable phase. Vitamin D could have been administered as supplemental vitamin D (vitamin D3 (cholecalciferol) or vitamin D2 (ergocalciferol)) or as an active form of vitamin D (1α-hydroxyvitamin D (alfacalcidol) or 1,25-dihydroxyvitamin D (calcitriol)).

DATA COLLECTION AND ANALYSIS

Six review authors extracted data independently. Random-effects and fixed-effect meta-analyses were conducted. For dichotomous outcomes, we calculated the risk ratios (RRs). To account for trials with zero events, we performed meta-analyses of dichotomous data using risk differences (RDs) and empirical continuity corrections. We used published data and data obtained by contacting trial authors.To minimise the risk of systematic error, we assessed the risk of bias of the included trials. Trial sequential analyses controlled the risk of random errors possibly caused by cumulative meta-analyses.

MAIN RESULTS

We identified 159 randomised clinical trials. Ninety-four trials reported no mortality, and nine trials reported mortality but did not report in which intervention group the mortality occurred. Accordingly, 56 randomised trials with 95,286 participants provided usable data on mortality. The age of participants ranged from 18 to 107 years. Most trials included women older than 70 years. The mean proportion of women was 77%. Forty-eight of the trials randomly assigned 94,491 healthy participants. Of these, four trials included healthy volunteers, nine trials included postmenopausal women and 35 trials included older people living on their own or in institutional care. The remaining eight trials randomly assigned 795 participants with neurological, cardiovascular, respiratory or rheumatoid diseases. Vitamin D was administered for a weighted mean of 4.4 years. More than half of the trials had a low risk of bias. All trials were conducted in high-income countries. Forty-five trials (80%) reported the baseline vitamin D status of participants based on serum 25-hydroxyvitamin D levels. Participants in 19 trials had vitamin D adequacy (at or above 20 ng/mL). Participants in the remaining 26 trials had vitamin D insufficiency (less than 20 ng/mL).Vitamin D decreased mortality in all 56 trials analysed together (5,920/47,472 (12.5%) vs 6,077/47,814 (12.7%); RR 0.97 (95% confidence interval (CI) 0.94 to 0.99); P = 0.02; I(2) = 0%). More than 8% of participants dropped out. 'Worst-best case' and 'best-worst case' scenario analyses demonstrated that vitamin D could be associated with a dramatic increase or decrease in mortality. When different forms of vitamin D were assessed in separate analyses, only vitamin D3 decreased mortality (4,153/37,817 (11.0%) vs 4,340/38,110 (11.4%); RR 0.94 (95% CI 0.91 to 0.98); P = 0.002; I(2) = 0%; 75,927 participants; 38 trials). Vitamin D2, alfacalcidol and calcitriol did not significantly affect mortality. A subgroup analysis of trials at high risk of bias suggested that vitamin D2 may even increase mortality, but this finding could be due to random errors. Trial sequential analysis supported our finding regarding vitamin D3, with the cumulative Z-score breaking the trial sequential monitoring boundary for benefit, corresponding to 150 people treated over five years to prevent one additional death. We did not observe any statistically significant differences in the effect of vitamin D on mortality in subgroup analyses of trials at low risk of bias compared with trials at high risk of bias; of trials using placebo compared with trials using no intervention in the control group; of trials with no risk of industry bias compared with trials with risk of industry bias; of trials assessing primary prevention compared with trials assessing secondary prevention; of trials including participants with vitamin D level below 20 ng/mL at entry compared with trials including participants with vitamin D levels equal to or greater than 20 ng/mL at entry; of trials including ambulatory participants compared with trials including institutionalised participants; of trials using concomitant calcium supplementation compared with trials without calcium; of trials using a dose below 800 IU per day compared with trials using doses above 800 IU per day; and of trials including only women compared with trials including both sexes or only men. Vitamin D3 statistically significantly decreased cancer mortality (RR 0.88 (95% CI 0.78 to 0.98); P = 0.02; I(2) = 0%; 44,492 participants; 4 trials). Vitamin D3 combined with calcium increased the risk of nephrolithiasis (RR 1.17 (95% CI 1.02 to 1.34); P = 0.02; I(2) = 0%; 42,876 participants; 4 trials). Alfacalcidol and calcitriol increased the risk of hypercalcaemia (RR 3.18 (95% CI 1.17 to 8.68); P = 0.02; I(2) = 17%; 710 participants; 3 trials).

AUTHORS' CONCLUSIONS

Vitamin D3 seemed to decrease mortality in elderly people living independently or in institutional care. Vitamin D2, alfacalcidol and calcitriol had no statistically significant beneficial effects on mortality. Vitamin D3 combined with calcium increased nephrolithiasis. Both alfacalcidol and calcitriol increased hypercalcaemia. Because of risks of attrition bias originating from substantial dropout of participants and of outcome reporting bias due to a number of trials not reporting on mortality, as well as a number of other weaknesses in our evidence, further placebo-controlled randomised trials seem warranted.

Suboptimal effect of different vitamin D3 supplementations and doses adapted to baseline serum 25(OH)D on achieved 25(OH)D levels in patients with a recent fracture: a prospective observational study

OBJECTIVE

Guidelines on the need for dose adaptation of vitamin D3 supplementation according to baseline serum 25(OH)D are inconclusive. The effects of increasing doses of vitamin D3 at lower baseline serum 25(OH)D values on the serum 25(OH)D after 4.2 and 11 months were determined in an observational study.

DESIGN

A prospective observational study.

METHODS

Out of 1481 consecutive women and men with a recent clinical fracture, 707 had a baseline 25(OH)D level <50 nmol/l and were supplemented with increasing doses of vitamin D3 (400, 800, 1700, and ≥3500 IU/day) according to the lower baseline 25(OH)D. Final analysis was restricted to the 221 participants who had full follow-up data available for 11 months.

RESULTS

Serum 25(OH)D ≥50 nmol/l was achieved in 57-76% of patients after 4.2 months and in 73-79% after 11 months. These percentages were similar for all doses (P=0.06 and P=0.91 respectively). The mean achieved 25(OH)D was similar for all dose groups (56.1-64.0 nmol/l after 4.2 months and 60.2-76.3 nmol/l after 11 months). With multivariate analysis, the increase in 25(OH)D (17±32.0 after 4.2 months and 24.3±34.0 nmol/l after 11 months) was dependent on the baseline 25(OH)D (P<0.001), not on supplementation dose, season, age, BMI, or gender.

CONCLUSIONS

The increase in serum 25(OH)D was significantly larger with higher vitamin D3 supplementation doses. However, this dose-effect response was mainly explained by the baseline 25(OH)D, not the supplementation dose, with a greater magnitude of response at lower baseline 25(OH)D concentrations. In 21-27% of patients, serum 25(OH)D3 levels did not reach 50 nmol/l after 11 months, at any dose. Further studies are needed to identify possible causes of suboptimal response such as non-compliance, undiagnosed malabsorption syndromes, or variability in cholecalciferol content of the vitamin D supplements.

Evaluation of serum 25-hydroxyvitamin d as a predictor of carotid intima-media thickness and carotid total plaque area in nonsmokers: the tromsø study

Objective. Altered calcium homeostasis has been linked to increased intima-media thickness (IMT) and plaques. We aimed to investigate whether serum 25-hydroxyvitamin D (25(OH)D) and serum calcium are associated with IMT and plaques in nonsmoking population. Methods. Ultrasound of the right carotid artery with the measurements of IMT and plaques was performed in 4194 nonsmoking subjects with available measurements of serum 25(OH)D and total calcium. Linear regression was applied to study the linear relationships between variables. Multinomial logistic regression was used to evaluate predictors of increased IMT and total plaque area (TPA), adjusted for age, body mass index, systolic blood pressure, and total cholesterol. Results. There was no significant linear relationship between mean IMT, TPA, and either serum 25(OH)D or total serum calcium. One SD increase in serum 25(OH)D was independently associated with increased odds of being in the highest quartile of IMT in men (OR 1.30, 95% CI 1.12, 1.51). In women, 1 SD increase in serum 25(OH)D was independently associated with increased risk of being in the upper tertile of TPA (OR 1.15, 95% CI 1.01, 1.33). Conclusions. Impaired calcium homeostasis has no consistent association with mean IMT and TPA; however, increased serum 25(OH)D may predict subclinical atherosclerosis in nonsmokers.

Effect of a single, oral, high-dose vitamin D supplementation on endothelial function in patients with peripheral arterial disease: a randomised controlled pilot study

OBJECTIVE

Apart from its role in bone metabolism, vitamin D may also influence cardiovascular disease. The objective of this study was: (1) to determine the effect of a single, oral, high-dose vitamin D supplementation on endothelial function and arterial stiffness in patients with peripheral arterial disease (PAD) and (2) to investigate the impact of this supplementation on coagulation and inflammation parameters.

METHODS

In this double-blind, placebo-controlled, interventional pilot study, we screened 76 Caucasian patients with PAD for vitamin D deficiency. Sixty-two were randomised to receive a single, oral supplementation of 100,000 IU vitamin D3 or placebo. At baseline and after 1 month, we measured serum vitamin D and parathormone levels, and surrogate parameters for cardiovascular disease.

RESULTS

Sixty-five of 76 patients (86%) had low 25-hydroxyvitamin D levels (<30 ng ml(-1)); of those, 62 agreed to participate in the study. At baseline, only parathormone was related to vitamin D. In supplemented patients, vitamin D levels increased from 16.3 ± 6.7 to 24.3 ± 6.2 ng ml(-1) (P < 0.001), with wide variations between single patients; in the placebo group vitamin levels did not change. Seasonal factors accounted for a decrease of vitamin D levels by 8 ng ml(-1) between summer and winter. After 1 month, none of the measured parameters was influenced by vitamin substitution.

CONCLUSION

In this pilot study, most patients with PAD were vitamin D deficient. Vitamin D supplementation increased serum 25-hydroxyvitamin D without influencing endothelial function, arterial stiffness, coagulation and inflammation parameters, although the study was underpowered for definite conclusions.

Vitamin D and antiphospholipid syndrome

Vitamin D (vitD) has been shown to have multiple immunomodulatory properties. Hypovitaminosis D has been described in many systemic autoimmune diseases. Antiphospholipid syndrome (APS), an autoimmune disease characterized by immune-mediated thrombosis and pregnancy loss, is a peculiar model for studying vitD, since these patients do not usually have a full-blown autoimmune disease, nor do they have particular restrictions regarding sun exposure. We assessed 25-OH vitD levels in 115 APS and 128 normal healthy donors (NHD) with the LIAISON® chemiluminescent immunoassay by DiaSorin (Italy). Median values were lower in APS patients than in NHD, with the greatest difference occurring during summertime ( p < 0.01), suggesting that APS patients may be somehow prevented from vitD generation upon sun exposure. In our cohort, APS patients may have been instructed to use sunscreens in the presence of positive antinuclear antibodies (ANA). Comparing patients with positive and negative ANA, we found comparable vitD levels during the summer. By subdividing APS patients according to clinical features, thrombotic APS patients showed significantly lower levels than did pure obstetric APS patients ( p < 0.01). In conclusion, our study confirms previous reports of hypovitaminosis D in APS patients, making them more similar to patients with other systemic autoimmune diseases than NHD. Hypovitaminosis D may be part of the mosaic of factors that determine autoimmunity, rather than a consequence of chronic disease and its treatment. The observation that patients with thrombotic APS, an aggressive phenotype, may be more deficient than those with exclusive obstetric manifestations fits well with the beneficial effects of vitD on thrombosis described both in vitro and in vivo. Therefore, there may be a rationale to assess the efficacy of vitD supplementation in APS patients.

Vitamin D, cardiovascular disease and mortality

A poor vitamin D status, i.e. low serum levels of 25-hydroxyvitamin D [25(OH)D], is common in the general population. This finding is of concern not only because of the classic vitamin D effects on musculoskeletal outcomes, but also because expression of the vitamin D receptor (VDR) and vitamin D metabolizing enzymes in the heart and blood vessels suggests a role of vitamin D in the cardiovascular system. VDR-knockout mice suffer from cardiovascular disease (CVD), and various experimental studies suggest cardiovascular protection by vitamin D, including antiatherosclerotic, anti-inflammatory and direct cardio-protective actions, beneficial effects on classic cardiovascular risk factors as well as suppression of parathyroid hormone (PTH) levels. In epidemiological studies, low levels of 25(OH)D are associated with increased risk of CVD and mortality. Data from randomized controlled trials (RCTs) are sparse and have partially, but not consistently, shown some beneficial effects of vitamin D supplementation on cardiovascular risk factors (e.g. arterial hypertension). We have insufficient data on vitamin D effects on cardiovascular events, but meta-analyses of RCTs indicate that vitamin D may modestly reduce all-cause mortality. Despite accumulating data suggesting that a sufficient vitamin D status may protect against CVD, we still must wait for results of large-scale RCTs before raising general recommendations for vitamin D in the prevention and treatment of CVD. In current clinical practice, the overall risks and costs of vitamin D supplementation should be weighed against the potential adverse consequences of untreated vitamin D deficiency.

Does vitamin D deficiency contribute to increased rates of cardiovascular disease and type 2 diabetes in African Americans?

African Americans have higher rates of type 2 diabetes (T2D) and some forms of cardiovascular disease (CVD) than do European Americans. African Americans also have much higher rates of vitamin D deficiency. There is emerging evidence that vitamin D deficiency may be a risk factor for hypertension, T2D, and CVD, but the extent to which racial disparities in disease rates are explained by racial differences in vitamin D status is uncertain. Despite a large number of observational studies and a limited number of clinical trials that examined 25-hydroxyvitamin D [25(OH)D] concentrations as a potential determinant of CVD and T2D or its precursors, it remains uncertain whether improving vitamin D status would reduce risk of these conditions in the general US population or in African Americans specifically. However, if the associations reported from the observational studies are of the estimated magnitudes and causal, vitamin D supplementation could potentially have a strong preventive effect on some of these conditions and could reduce race-related disparities in their prevalence. Because of the low 25(OH)D concentrations of many, if not most, African Americans, and the low risk associated with vitamin D supplementation, it is important to obtain more definitive answers to these questions.

Vitamin D and cardiometabolic health: a review of the evidence

The cardiometabolic syndrome (MetS) is a clustering of related metabolic abnormalities including abdominal adiposity, insulin resistance, hypertension, dyslipidaemia and increased inflammatory and thrombotic markers, which is linked to increased risk of type 2 diabetes, CVD and overall mortality. Several cross-sectional and prospective studies have shown an association between low vitamin D status, as indicated by concentrations of serum 25-hydroxyvitamin D (s25(OH)D), and increased prevalence of the MetS and individual CVD risk factors. These epidemiological observations are supported by mechanistic studies but experimental data are limited. The available data from intervention studies are largely confounded as most vitamin D supplementation trials were mainly carried out to explore the role of Ca in CVD and include Ca in the treatment arms. Inadequate consideration of seasonal effects on s25(OH)D concentrations is also a common design flaw in most studies. Further complications arise from shared risk factors such as adiposity and ageing, which predispose individuals to exhibit both a more pronounced risk profile and relatively lower s25(OH)D concentrations. In conclusion, while epidemiological associations are promising and a rationale for low vitamin D status as a potentially modifiable risk factor for CVD is supported by mechanistic data, suitable experimental data from appropriately designed trials are just beginning to emerge. As yet, this body of literature is too immature to draw firm conclusions on the role of vitamin D in CVD prevention. Carefully controlled vitamin D trials in well-described population groups using intervention doses that are titrated against target s25(OH)D concentrations could yield potentially valuable outcomes that may have a positive impact on CVD risk modification.