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

Biochemical characteristics and calcium and PTH levels of patients with high normal and elevated serum 25(OH)D levels in Turkey: DeVIT-TOX survey

Vitamin D intake over the recommended dose is usually associated with high serum 25(OH)D levels and generally not associated with symptoms of hypercalcemia. High doses of cholecalciferol need to be avoided to protect against vitamin D toxicity and related complications. Strict adherence to the clinical guidelines for treating vitamin D deficiency can ensure safe and effective treatment.

PURPOSE

We observed a tendency to use high doses of cholecalciferol for vitamin D deficiency treatment or vitamin D supplementation. We aimed to determine the biochemical characteristics of patients with high normal and elevated serum 25(OH)D levels.

METHODS

An online invitation was sent to all tertiary endocrinology clinics in Turkey to complete an online retrospective survey (DeVIT-TOX Survey) for patients diagnosed with high serum 25(OH)D levels (> 88 ng/mL) between January 2019 and December 2019. The patients were evaluated according to the presence of signs and symptoms of hypercalcemia and doses of vitamin D intake, evaluated into the following three groups according to their 25(OH)D levels: group 1, > 150 ng/mL; group 2, 149-100 ng/mL; and group 3, 99-88 ng/mL.

RESULTS

A total of 253 patients were included in the final analysis (female/male: 215/38; mean age, 51.5 ± 15.6 years). The average serum 25(OH)D level was 119.9 ± 33 (range, 88-455) ng/mL, and the average serum calcium level was 9.8 ± 0.7 (range, 8.1-13.1) mg/dL. Most (n = 201; 75.4%) patients were asymptomatic despite having high serum 25(OH)D and calcium levels. The serum 25(OH)D level was significantly higher in the symptomatic groups than in the asymptomatic groups (138.6 ± 64 ng/mL vs. 117.7 ± 31 ng/mL, p < 0.05). The most common cause (73.5%) associated with high serum 25(OH)D levels was the inappropriate prescription of a high dose of oral vitamin D (600.000-1.500.000 IU) for treating vitamin D deficiency/insufficiency in a short time (1-3 months). The cut-off value of 25 (OH) D level in patients with hypercalcemia was found to be 89 ng/mL [median 116.5 (89-216)].

CONCLUSIONS

High dose of vitamin D intake is associated with a high serum 25 OH D level, without symptoms of hypercalcemia. Inappropriate prescription of vitamin D is the primary cause for elevated 25(OH) D levels and related hypercalcemia. Hypercalcemia may not be observed in every patient at very high 25(OH) D levels. Adherence to the recommendation of guidelines is essential to ensure safe and effective treatment of vitamin D deficiency.

Conundrum of vitamin D on glucose and fuel homeostasis

As an endocrine hormone, vitamin D plays an important role in bone health and calcium homeostasis. Over the past two decades, the non-calcemic effects of vitamin D were extensively examined. Although the effect of vitamin D on beta cell function were known for some time, the effect of vitamin D on glucose and fuel homeostasis has attracted new interest among researchers. Yet, to date, studies remain inconclusive and controversial, in part, due to a lack of understanding of the threshold effects of vitamin D. In this review, a critical examination of interventional trials of vitamin D in prevention of diabetes is provided. Like use of vitamin D for bone loss, the benefits of vitamin D supplementation in diabetes prevention were observed in vitamin D-deficient subjects with serum 25-hydroxyvitamin D < 50 nmol/L (20 ng/mL). The beneficial effect from vitamin D supplementation was not apparent in subjects with serum 25-hydroxyvitamin D > 75 nmol/L (30 ng/mL). Furthermore, no benefit was noted in subjects that achieved serum 25-hydroxyvitamin D > 100 nmol/L (40 ng/mL). Further studies are required to confirm these observations.

Screening for Vitamin D Deficiency in Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

Low serum vitamin D levels have been associated with adverse clinical outcomes; identifying and treating deficiency may improve outcomes.

OBJECTIVE

To review the evidence about screening for vitamin D deficiency in adults.

DATA SOURCES

PubMed, EMBASE, the Cochrane Library, and trial registries through March 12, 2020; bibliographies from retrieved articles, outside experts, and surveillance of the literature through November 30, 2020.

STUDY SELECTION

Fair- or good-quality, English-language randomized clinical trials (RCTs) of screening with serum 25-hydroxyvitamin D (25[OH]D) compared with no screening, or treatment with vitamin D (with or without calcium) compared with placebo or no treatment conducted in nonpregnant adults; nonrandomized controlled intervention studies for harms only. Treatment was limited to studies enrolling or analyzing participants with low serum vitamin D levels.

DATA EXTRACTION AND SYNTHESIS

Two reviewers assessed titles/abstracts and full-text articles, extracted data, and assessed study quality; when at least 3 similar studies were available, meta-analyses were conducted.

MAIN OUTCOMES AND MEASURES

Mortality, incident fractures, falls, diabetes, cardiovascular events, cancer, depression, physical functioning, and infection.

RESULTS

Forty-six studies (N = 16 205) (77 publications) were included. No studies directly evaluated the health benefits or harms of screening. Among community-dwelling populations, treatment was not significantly associated with mortality (pooled absolute risk difference [ARD], 0.3% [95% CI, -0.6% to 1.1%]; 8 RCTs, n = 2006), any fractures (pooled ARD, -0.3% [95% CI, -2.1% to 1.6%]; 6 RCTs, n = 2186), incidence of diabetes (pooled ARD, 0.1% [95% CI, -1.3% to 1.6%]; 5 RCTs, n = 3356), incidence of cardiovascular disease (2 RCTs; hazard ratio, 1.00 [95% CI, 0.74 to 1.35] and 1.09 [95% CI, 0.68 to 1.76]), incidence of cancer (2 RCTs; hazard ratio, 0.97 [95% CI, 0.68 to 1.39] and 1.01 [95% CI, 0.65 to 1.58], or depression (3 RCTs, various measures reported). The pooled ARD for incidence of participants with 1 or more falls was -4.3% (95% CI, -11.6% to 2.9%; 6 RCTs). The evidence was mixed for the effect of treatment on physical functioning (2 RCTs) and limited for the effect on infection (1 RCT). The incidence of adverse events and kidney stones was similar between treatment and control groups.

CONCLUSIONS AND RELEVANCE

No studies evaluated the direct benefits or harms of screening for vitamin D deficiency. Among asymptomatic, community-dwelling populations with low vitamin D levels, the evidence suggests that treatment with vitamin D has no effect on mortality or the incidence of fractures, falls, depression, diabetes, cardiovascular disease, cancer, or adverse events. The evidence is inconclusive about the effect of treatment on physical functioning and infection.

Screening for Vitamin D Deficiency in Adults: US Preventive Services Task Force Recommendation Statement

IMPORTANCE

Vitamin D is a fat-soluble vitamin that performs an important role in calcium homeostasis and bone metabolism and also affects many other cellular regulatory functions outside the skeletal system. Vitamin D requirements may vary by individual; thus, no one serum vitamin D level cutpoint defines deficiency, and no consensus exists regarding the precise serum levels of vitamin D that represent optimal health or sufficiency.

OBJECTIVE

To update its 2014 recommendation, the US Preventive Services Task Force (USPSTF) commissioned a systematic review on screening for vitamin D deficiency, including the benefits and harms of screening and early treatment.

POPULATION

Community-dwelling, nonpregnant adults who have no signs or symptoms of vitamin D deficiency or conditions for which vitamin D treatment is recommended.

EVIDENCE ASSESSMENT

The USPSTF concludes that the overall evidence on the benefits of screening for vitamin D deficiency is lacking. Therefore, the balance of benefits and harms of screening for vitamin D deficiency in asymptomatic adults cannot be determined.

RECOMMENDATION

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for vitamin D deficiency in asymptomatic adults. (I statement).

Vitamin D regulation of energy metabolism in cancer

Vitamin D exerts anti-cancer effects in recent clinical trials and preclinical models. The actions of vitamin D are primarily mediated through its hormonal form, 1,25-dihydroxyvitamin D (1,25(OH)₂ D). Previous literature describing in vitro studies has predominantly focused on the anti-tumourigenic effects of the hormone, such as proliferation and apoptosis. However, recent evidence has identified 1,25(OH)₂ D as a regulator of energy metabolism in cancer cells, where requirements for specific energy sources at different stages of progression are dramatically altered. The literature suggests that 1,25(OH)₂ D regulates energy metabolism, including glucose, glutamine and lipid metabolism during cancer progression, as well as oxidative stress protection, as it is closely associated with energy metabolism. Mechanisms involved in energy metabolism regulation are an emerging area in which vitamin D may inhibit multiple stages of cancer progression.

Vitamin D supplements: The pharmacists' perspective

OBJECTIVE

The purpose of this narrative review was to provide guidance for pharmacists concerning vitamin D supplementation.

METHODS

Relevant studies were identified in a search of MEDLINE/PubMed, EBSCOhost, and Google Scholar from January 1966 to September 2020 using the search terms vitamin D, vitamin D₂, vitamin D₃, calcitriol, and vitamin D deficiency. Abstracts were reviewed for relevance and, if relevant, full-text articles were retrieved and reviewed. References were checked, and citation searches using identified studies were conducted. The literature search included English-language studies involving administration of vitamin D monotherapy compared with placebo.

RESULTS

Serum 25-hydroxyvitamin D levels of less than 12 ng/mL indicate a vitamin D deficiency. The Institute of Medicine recommends a daily intake of 600 IU of vitamin D in individuals aged up to 70 years and 800 IU in those aged above 70 years. Vitamin D is labeled for rickets, osetomalacia, hypophosphatemia (familial or secondary), renal osteodystrophy, and corticosteroid-induced osteoporosis. When used for these indications, vitamin D should be prescribed with appropriate monitoring by a qualified health care practitioner. There is evidence for vitamin D supplementation in individuals aged 75 years or older and in those with problems associated with mobility, gait, or balance. There is insufficient evidence to support vitamin D supplementation in the prevention of cardiovascular disease, cancer, asthma, chronic obstructive pulmonary disease exacerbations, new-onset type 2 diabetes, infectious lung diseases, cognitive dysfunction, Alzheimer disease, and depression, or in prenatal use.

CONCLUSION

Pharmacists can provide evidence-based recommendations concerning the indications, dosing, monitoring, and adverse effects of vitamin D supplements.

Does the High Prevalence of Vitamin D Deficiency in African Americans Contribute to Health Disparities?

African Americans have higher incidence of, and mortality from, many health-related problems than European Americans. They also have a 15 to 20-fold higher prevalence of severe vitamin D deficiency. Here we summarize evidence that: (i) this health disparity is partly due to insufficient vitamin D production, caused by melanin in the skin blocking the UVB solar radiation necessary for its synthesis; (ii) the vitamin D insufficiency is exacerbated at high latitudes because of the combination of dark skin color with lower UVB radiation levels; and (iii) the health of individuals with dark skin can be markedly improved by correcting deficiency and achieving an optimal vitamin D status, as could be obtained by supplementation and/or fortification. Moderate-to-strong evidence exists that high 25-hydroxyvitamin D levels and/or vitamin D supplementation reduces risk for many adverse health outcomes including all-cause mortality rate, adverse pregnancy and birth outcomes, cancer, diabetes mellitus, Alzheimer's disease and dementia, multiple sclerosis, acute respiratory tract infections, COVID-19, asthma exacerbations, rickets, and osteomalacia. We suggest that people with low vitamin D status, which would include most people with dark skin living at high latitudes, along with their health care provider, consider taking vitamin D3 supplements to raise serum 25-hydroxyvitamin D levels to 30 ng/mL (75 nmol/L) or possibly higher.

The role of vitamin D in prevention of type 2 diabetes. A meta-analysis

BACKGROUND AND AIMS

Recently, there are evidences that have shown vitamin D homeostasis has an impact in the development of type 2 diabetes. However, still it is unclear if vitamin D supplementation reduces the risk of overt diabetes. This meta-analysis of cross-sectional studies and RCTs was conducted to evaluate the role of vitamin D in prevention of type 2 diabetes and to elucidate this controversial topic.

METHODS

A systematic search for English-language literature was done via PUBMED/Medline and Google Scholar up to March 2020. Based on a fixed and random effects model, the OR, HR and 95% CI were used to evaluate the combined risk. This study followed Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) Guidelines.

RESULTS

After eligibility assessment 10 studies with a total of 34,882 participants were included in meta-analysis. Meta-analysis of cross-sectional studies suggested that there was a statistically significant association between the vitamin D and type 2 Diabetes; the pooled OR (95%CI) was 1.77 [1.51, 2.07] (P < 0.001). Meta-analysis of RCTs have shown that there was no statistically significant association between vitamin D supplementation and prevention of type 2 Diabetes, the pooled HR (95%CI) was 0.89 [0.77, 1.02] (P = 0.08).

CONCLUSION

In conclusion, this meta-analysis suggests that there is association between the vitamin D and type 2 diabetes. However, the result of RCTs suggests emphasis of future studies for genetic factors such as polymorphic variants of the VDR gene as one factor in this complex process.

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.

Effect of Vitamin D Supplementation on the Incidence of Diabetes Mellitus

CONTEXT

The effect of vitamin D supplementation on the risk of type 2 diabetes mellitus (T2DM) remains controversial because most randomized controlled trials (RCTs) have been small or have reported low doses of vitamin D.

OBJECTIVE

To conduct a meta-analysis of RCTs testing vitamin D supplementation in the prevention of T2DM.

DATA SOURCES

Database search of PubMed/MEDLINE, EMBASE, and the Cochrane Library was performed by 2 reviewers from inception through September 15, 2019.

STUDY SELECTION

We included RCTs that reported the effect of vitamin D supplementation for at least 1 year on T2DM prevention.

DATA EXTRACTION

Two independent reviewers extracted the data. The risk ratios (RRs) and 95% confidence intervals (CIs) were reported. Primary outcome of the meta-analysis was the incidence of T2DM.

DATA SYNTHESIS

Nine RCTs were included (43 559 participants). The mean age (standard deviation) was 63.5 (6.7) years. The RR for vitamin D compared with placebo was 0.96 (95% CI, 0.90-1.03); P = 0.30. In trials testing moderate to high doses of supplementation (≥1000 IU/day), all conducted among participants with prediabetes, the RR for vitamin D compared with placebo was 0.88 (95% CI, 0.79-0.99). In contrast, the trials testing lower doses, which were conducted in general population samples, showed no risk reduction (RR, 1.02; 95% CI, 0.94-1.10; P, interaction by dose = 0.04).

CONCLUSION

In patients with prediabetes, vitamin D supplementation at moderate to high doses (≥1000 IU/day), significantly reduced the incidence risk of T2DM, compared with placebo.

Effects of Vitamin D Supplementation on Prevention of Type 2 Diabetes in Patients With Prediabetes: A Systematic Review and Meta-analysis

BACKGROUND

While observational studies have shown an association between vitamin D insufficiency and diabetes, it is unclear whether intervention with vitamin D supplements can lower the risk of type 2 diabetes mellitus (T2DM).

PURPOSE

To assess whether vitamin D supplementation reduces the risk of T2DM in people with prediabetes.

DATA SOURCES

We searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) from inception to 5 July 2019.

STUDY SELECTION

We included randomized controlled trials assessing vitamin D supplementation versus placebo in relation to new-onset T2DM in people with prediabetes.

DATA EXTRACTION

We screened studies and extracted data from published trials independently.

DATA SYNTHESIS

We identified eight eligible trials with a total of 4,896 subjects. Vitamin D supplementation significantly reduced the risk of T2DM (risk ratio [RR] 0.89 [95% CI 0.80-0.99]; I ² = 0%). Benefit was found in nonobese subjects (RR 0.73 [95% CI 0.57-0.92]) but not in obese subjects (RR 0.95 [95% CI 0.84-1.08]) (P _interaction = 0.048). The reversion of prediabetes to normoglycemia occurred in 116 of 548 (21.2%) participants in the vitamin D group and 75 of 532 (14.1%) in the control group. Vitamin D supplementation increased reversion rate of prediabetes to normoglycemia (RR 1.48 [95% CI 1.14-1.92]; I ² = 0%.) LIMITATIONS: Definitions of prediabetes and new-onset diabetes in eligible studies were different, and long-term data on outcomes of T2DM prevention were lacking.

CONCLUSIONS

In persons with prediabetes, vitamin D supplementation reduces the risk of T2DM and increases the reversion rate of prediabetes to normoglycemia. The benefit of the prevention of T2DM could be limited to nonobese subjects. Individual participant data meta-analyses are needed to confirm these findings.

Vitamin D supplementation, cardiac events and stroke: A systematic review and meta-regression analysis

INTRODUCTION

Observational data has suggested a link between vitamin D deficiency and coronary heart disease (CHD). However, randomized controlled trials (RCTs) have failed to show benefit. The objective of this study is to analyze the RCTs investigating vitamin D supplementation and the risk of CHD and stroke.

METHODS

All RCTs that compared vitamin D supplementation to placebo and evaluated nonfatal myocardial infarction (MI), cardiac mortality, stroke and CHD events (a composite of cardiac mortality, MI, unstable angina and revascularization) were included. Rate ratios (RR) were calculated for each endpoint and to test for heterogeneity of treatment effect (HTE) the Chi2 and I2 tests were used for younger vs. older participants, shorter vs. longer trial duration, vitamin D supplements with vs. without calcium, and daily vs. monthly dosages of vitamin D. A meta-regression was performed with baseline vitamin D concentration as the covariate.

RESULTS

22 RCTs were identified (n = 83,200). Vitamin D supplementation had no effect on nonfatal MI (RR 0.98, 95% confidence interval (CI) 0.89-1.08), cardiac death (RR 0.94, CI 0.84-1.06), CHD events (RR 1.00, CI 0.91-1.10), or stroke (RR, 0.97, CI 0.9-1.03). When performing the meta-regression with baseline circulating 25-hydroxyvitamin D (25(OH)D) concentrations as the covariate, vitamin D supplementation's treatment effect on CVD outcomes was not associated with baseline 25(OH)D.

CONCLUSION

Vitamin D did not reduce CHD and stroke. A linear relationship does not exist between baseline 25(OH)D and vitamin D supplementation's effect on CVD. Vitamin D levels should be checked and repleted in those with an absolute indication.

Serum PTH is not a good marker for defining a threshold for vitamin D deficiency

OBJECTIVE

In addition to its skeletal effects, vitamin D may also be important for health in general. It is uncertain what level of serum 25-hydroxyvitamin D (25(OH)D), marker of vitamin D status, is sufficient for these effects. With decreasing serum 25(OH)D levels there is an increase in serum PTH. The point at which this occurs has been considered as a threshold for vitamin D sufficiency. The thresholds found have varied widely and have mainly been based on observational studies. However, to truly establish a threshold for vitamin D effects, this has to be based on randomized controlled trials (RCTs).

METHODS

The study included 2803 subjects from a general health survey, the Tromsø study, and pooled individual person data from five vitamin D intervention studies (n = 1544). Serum parathyroid hormone (PTH) and change in PTH after vitamin D supplementation were related to serum 25(OH)D levels in steps of 25 nmol/L (<24, 25-49, 50-74, 75-99, and >99 nmol/L).

RESULTS

In the Tromsø study, in the females there was a gradual decrease in serum PTH with increasing serum 25(OH)D with no apparent plateau, whereas in the males the decrease in PTH in subjects with serum 25(OH)D >74 nmol/l was marginal. In pooled RCTs, there was a significant reduction in serum PTH by vitamin D supplementation regardless of baseline serum 25(OH)D level.

CONCLUSIONS

The use of the serum PTH-25(OH)D relation from observational studies to determine a threshold for vitamin D sufficiency is highly questionable.

High-Dose Vitamin D-Mediated Hypercalcemia as a Potential Risk Factor in Central Nervous System Demyelinating Disease

The exact cause of multiple sclerosis (MS) is unknown; however, it is considered to be an inflammatory disease of the central nervous system (CNS) triggered by a combination of both environmental and genetic factors. Vitamin D deficiency is also discussed as a possible disease-promoting factor in MS, as low vitamin D status is associated with increased formation of CNS lesions, elevated number of relapses and accelerated disease progression. However, it remains unclear whether this association is causal and related and most importantly, whether vitamin D supplementation in MS is of direct therapeutic benefit. Recently, we could show that in a murine model of MS, administration of a moderate vitamin D dose was of clinical benefit, while excessive vitamin D supplementation had a negative effect on disease severity. Of note, disease exacerbation was associated with high-dose vitamin D caused secondary hypercalcemia. Mechanistically dissecting this outcome, we found that hypercalcemia independent of vitamin D similarly triggered activation of disease-perpetuating T cells. These findings caution that vitamin D should be supplemented in a controlled and moderate manner in patients with MS and concomitantly highlight calcium as a novel potential MS risk factor by itself. In this review, we will summarize the current evidence from animal and clinical studies aiming to assess whether vitamin D may be of benefit in patients with MS. Furthermore, we will discuss any possible secondary effects of vitamin D with a particular focus on the role of calcium on immune cells and in the pathogenesis of CNS demyelinating disease.

Serum Vitamin D Concentration ≥75 nmol/L Is Related to Decreased Cardiometabolic and Inflammatory Biomarkers, Metabolic Syndrome, and Diabetes; and Increased Cardiorespiratory Fitness in US Adults

A serum vitamin D [25-hydroxyvitamin D, 25(OH)D] concentration of ≥75 nmol/L is recommended for optimal health. We investigated the relationship between serum 25(OH)D and metabolic syndrome (MetS), diabetes, cardiometabolic biomarkers, and cardiorespiratory fitness (CRF) in US adults using clinical cut points recommended by health organizations. Data from USA's National Health and Nutrition Examination Surveys were used. Prevalences and likelihood of having MetS and diabetes according to clinical cut points for serum 25(OH)D (<30 nmol/L, 30-<50 nmol/L, 50-<75 nmo/L, and ≥75 nmol/L) were determined with multivariate logistic regression. Relations between serum 25(OH)D and various cardiometabolic biomarkers, CRF, MetS, and diabetes were tested using multivariable adjusted regression. Prevalence of MetS and diabetes were significantly lower in individuals with serum 25(OH)D ≥75 nmol/L (MetS, 21.6%; diabetes, 4.1%) compared to those with 25(OH)D <30 nmol/L (MetS, 45.5%; diabetes, 11.6%) (p < 0.0001). Individuals with serum 25(OH)D ≥75 nmol/L had significantly lower waist circumference (p < 0.0001), C-reactive protein (p = 0.003), glycated hemoglobin (p < 0.0002), fasting triglycerides (p < 0.0001), total homocysteine (p < 0.0001), and insulin resistance (p = 0.0001) and had significantly higher HDL-cholesterol (p < 0.0001) and maximal oxygen uptake (marker for CRF) (p< 0.0009) compared to those with 25(OH)D <30 nmol/L. In conclusion, serum 25(OH)D ≥75 nmol/L is associated with positive indicators related to cardiometabolic diseases in US adults.

Effects of vitamin D supplementation on the glycemic control of pre-diabetic individuals: a systematic review

Introduction

Introduction: research shows the potential effect of vitamin D supplementation with an improvement in the glycemic profile of pre-diabetic patients. Objective: this study evaluates the effects of vitamin D supplementation on glycemic control markers in pre-diabetic individuals. Methods: we analyzed studies published over the last ten years, and indexed in the Science Direct, PubMed, and LILACS databases. We searched studies using health descriptors related to vitamin D, pre-diabetes, and glycemic control markers. We considered randomized controlled trials eligible for inclusion. All phases of selection, data extraction, and risk of bias assessment were carried out by two independent evaluators. Results: we identified 309 articles, of which 4 met the inclusion criteria. Of these, 3 studies have shown that vitamin D supplementation does not alter glycemic control markers in pre-diabetic individuals. Only one study showed a positive effect after supplementation with 60,000 IU/month of vitamin D3 for 12 months, with a significant reduction in the concentrations of glycated hemoglobin, fasting glucose, and two-hour postprandial glucose. Conclusion: there is insufficient scientific evidence to confirm the beneficial effects of vitamin D supplementation on glycemic control markers in pre-diabetic individuals.

Impact of the Glycemic Control and Duration of Type 2 Diabetes on Vitamin D Level and Cardiovascular Disease Risk

BACKGROUND AND AIMS

To investigate the impact of glycemic control and T2D duration on vitamin D status and cardiovascular disease (CVD) risk among Saudi patients.

METHODS

This case-control study was conducted in King Faisal Specialist Hospital, Saudi Arabia. A total of 25 nondiabetic controls and 92 patients with confirmed T2D, aged 20-60 years, were included. Patients with T2D were divided into the following groups based on disease duration (newly diagnosed: ≈6 months and long duration: ≥5 years) and glycemic control based on their glycated hemoglobin (HbA_1C) level with a threshold of ≤0.053 mol/mol: newly diagnosed controlled (NC, n = 25), newly diagnosed uncontrolled (NU, n = 25), newly diagnosed uncontrolled (NU, n = 25), newly diagnosed uncontrolled (NU, n = 25), newly diagnosed uncontrolled (NU.

RESULTS

Our study showed that T2D duration was an independent predictor of vitamin D deficiency. The longer disease duration, the lower odds of being vitamin D deficient (odds ratio (OR) = 0.05, 95% CI: 0.01-0.29, p < 0.05). No significant association was observed between vitamin D and HbA_1C levels. In the NU group, CVD risk scores were directly correlated with serum 25(OH)D (r = 0.53, p < 0.05). No significant association was observed between vitamin D and HbA_1C levels. In the NU group, CVD risk scores were directly correlated with serum 25(OH)D (r = 0.53, p < 0.05). No significant association was observed between vitamin D and HbA_1C levels. In the NU group, CVD risk scores were directly correlated with serum 25(OH)D (.

CONCLUSION

Duration of diabetes rather than glycemic control is associated with vitamin D deficiency. Glycemic uncontrol may augment vitamin D deficiency-associated CVD risk in both newly diagnosed and old patients with type 2 diabetes.

The effect of omega-3 and vitamin D co-supplementation on glycemic control and lipid profiles in reproductive-aged women with pre-diabetes and hypovitaminosis D: a randomized controlled trial

BACKGROUND

Prediabetes can predispose the individual to type 2 diabetes in the long-term. The present study was conducted to determine the effectiveness of vitamin D and omega-3 co-supplementation on glycemic control and serum lipid profiles in women of reproductive age with prediabetes and hypovitaminosis D.

METHODS

The present factorial, triple-blind, clinical trial was conducted on 168 women of reproductive age with prediabetes and hypovitaminosis D. The participants were assigned to four groups based on block randomization method: the placebo group received omega-3 and vitamin D placebos; the omega-3 group took omega-3 supplements and vitamin D placebos; the vitamin D group received omega-3 placebos and vitamin D supplements and the co-supplementation group. The groups received every 2 weeks 50,000 IU pearls of vitamin D and twice-daily doses of 1000-mg omega-3 tablets or placebos for 8 weeks. Dietary intake, physical activity, anthropometric indices and blood biochemical tests were measured at the beginning and end of the study. Analysis was performed using two-way mixed ANOVA.

RESULTS

A significant reduction was observed in fasting glucose, insulin, homeostasis model assessment-beta cell function, weight and waist circumference in the co-supplementation group compared to the other three groups (P < 0.05). Moreover, high-density lipoprotein-cholesterol levels increased significantly in the co-supplementation group compared to the other three groups (P < 0.05). Despite the fact that homeostasis model assessment-insulin resistance, total cholesterol, triglyceride and low-density lipoprotein-cholesterol levels decreased after intervention in the co-supplementation group, there was no significant difference between the groups in these outcomes.

CONCLUSION

Vitamin D and omega-3 co-supplementation improved fasting serum glucose, insulin, high-density lipoprotein-cholesterol level, homeostasis model assessment-beta cell function, weight and waist circumference in women of reproductive age with prediabetes and hypovitaminosis D. This co-supplementation can therefore be recommended for glycemic control in these women.Trial registration Iranian Registry of Clinical Trials Code: IRCT20100130003226N17. Registered on 9 Feb. 2019.

The role of vitamin D supplementation for primary prevention of cancer: meta-analysis of randomized controlled trials

Background: In the USA cancer is the second leading cause of mortality, as such, primary prevention of cancer is a major public health concern. Vitamin D supplementation has been studied as a primary prevention method for multiple diseases including cardiovascular disease, osteoporosis, diabetes mellitus and cancer. The role of Vitamin D as primary prevention of cancer is still controversial. With fast emergence of large randomized controlled trials (RCTs) in that regards, we aimed to evaluate the efficacy of Vitamin D supplementation as primary prophylaxis for cancer.

Methods: A comprehensive electronic database search was conducted for all RCTs where comparison of Vitamin D supplementation versus placebo for the prevention of any type of disease with at least 3 years of Vitamin D supplementation was used and where cancer incidence or mortality was reported. The primary outcome was cancer-related mortality and cancer incidence. We calculated risk ratios (RRs) and 95% confidence intervals (CIs) using a random-effects model at the longest follow-up.

Results: We included 10 RCTs with 79,055 total patients, mean age of 68.07 years, a female percentage of 78.02% and a minimum follow-up of 4 years and more. Vitamin D was associated with significant reduction of cancer-related mortality compared with placebo (RR 0.87; 95% CI: 0.79–0.96; P = 0.05: I² = 0%). Compared with placebo, Vitamin D was not associated with significant reduction of cancer incidence (RR: 0.96; 95% CI: 0.86–1.07; P = 0.46; I² = 31%).

Conclusion: With inclusion of studies, which did not primarily examine vitamin D for the purpose of preventing cancer or reducing cancer mortality our meta-analysis highlights that the use of vitamin D supplementation for primary prevention of cancer is encouraged as it does possibly decrease cancer-related mortality once cancer is diagnosed; however, it has no role or effect on cancer incidence.

Effect of vitamin D3 supplementation on insulin resistance and β-cell function in prediabetes: a double-blind, randomized, placebo-controlled trial

BACKGROUND

Observational studies have suggested an inverse association between low serum 25-hydroxyvitamin D [25(OH)D] concentrations and development of type 2 diabetes. High-quality trials are required to test the hypothesis that vitamin D is a direct contributor to type 2 diabetes pathogenesis.

OBJECTIVE

The purpose of this double-blind randomized placebo-controlled trial was to investigate the effect of vitamin D3 supplementation on insulin resistance (IR) and β-cell function in people with prediabetes and suboptimal vitamin D status (<50 nmol/L).

METHODS

Sixty-six individuals were randomly assigned to receive 3000 IU (75 µg) vitamin D3 or placebo daily for 26 wk. Compliance was monitored by pill count and change in serum 25(OH)D concentration using LC-MS. The primary endpoint was between-group difference in change in IR assessed using a 2-step euglycemic-hyperinsulinemic clamp combined with infusion of tritiated glucose. An oral-glucose-tolerance test was performed pre- and postintervention to calculate indices of β-cell function. Between-group comparisons were made using ANCOVA.

RESULTS

In total, 64 participants completed the study. Baseline serum 25(OH)D concentrations in the vitamin D3 and placebo group were 30.7 and 30.0 nmol/L, with status increasing by 70.5 nmol/L and 5.3 nmol/L, respectively (between-group difference in vitamin D: 65.8 nmol/L; 95% CI: 54.2, 77.3 nmol/L; P < 0.01), after supplementation. There was no difference between groups in measures of whole-body, peripheral, or hepatic IR or in any measure of glycemic control or β-cell function.

CONCLUSION

This study employed a robust assessment of IR and β-cell function and targeted a high-risk population with low 25(OH)D status at baseline and found that vitamin D3 supplementation had no effect on insulin action in people with prediabetes.This trial was registered on clinicaltrials.gov as NCT01889810.

Association between vitamin D supplementation and mortality: systematic review and meta-analysis

OBJECTIVE

To investigate whether vitamin D supplementation is associated with lower mortality in adults.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

DATA SOURCES

Medline, Embase, and the Cochrane Central Register from their inception to 26 December 2018.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised controlled trials comparing vitamin D supplementation with a placebo or no treatment for mortality were included. Independent data extraction was conducted and study quality assessed. A meta-analysis was carried out by using fixed effects and random effects models to calculate risk ratio of death in the group receiving vitamin D supplementation and the control group.

MAIN OUTCOME MEASURES

All cause mortality.

RESULTS

52 trials with a total of 75 454 participants were identified. Vitamin D supplementation was not associated with all cause mortality (risk ratio 0.98, 95% confidence interval 0.95 to 1.02, I²=0%), cardiovascular mortality (0.98, 0.88 to 1.08, 0%), or non-cancer, non-cardiovascular mortality (1.05, 0.93 to 1.18, 0%). Vitamin D supplementation statistically significantly reduced the risk of cancer death (0.84, 0.74 to 0.95, 0%). In subgroup analyses, all cause mortality was significantly lower in trials with vitamin D₃ supplementation than in trials with vitamin D₂ supplementation (P for interaction=0.04); neither vitamin D₃ nor vitamin D₂ was associated with a statistically significant reduction in all cause mortality.

CONCLUSIONS

Vitamin D supplementation alone was not associated with all cause mortality in adults compared with placebo or no treatment. Vitamin D supplementation reduced the risk of cancer death by 16%. Additional large clinical studies are needed to determine whether vitamin D₃ supplementation is associated with lower all cause mortality.

STUDY REGISTRATION

PROSPERO registration number CRD42018117823.

Vitamin D Supplementation and Prevention of Type 2 Diabetes

BACKGROUND

Observational studies support an association between a low blood 25-hydroxyvitamin D level and the risk of type 2 diabetes. However, whether vitamin D supplementation lowers the risk of diabetes is unknown.

METHODS

We randomly assigned adults who met at least two of three glycemic criteria for prediabetes (fasting plasma glucose level, 100 to 125 mg per deciliter; plasma glucose level 2 hours after a 75-g oral glucose load, 140 to 199 mg per deciliter; and glycated hemoglobin level, 5.7 to 6.4%) and no diagnostic criteria for diabetes to receive 4000 IU per day of vitamin D₃ or placebo, regardless of the baseline serum 25-hydroxyvitamin D level. The primary outcome in this time-to-event analysis was new-onset diabetes, and the trial design was event-driven, with a target number of diabetes events of 508.

RESULTS

A total of 2423 participants underwent randomization (1211 to the vitamin D group and 1212 to the placebo group). By month 24, the mean serum 25-hydroxyvitamin D level in the vitamin D group was 54.3 ng per milliliter (from 27.7 ng per milliliter at baseline), as compared with 28.8 ng per milliliter in the placebo group (from 28.2 ng per milliliter at baseline). After a median follow-up of 2.5 years, the primary outcome of diabetes occurred in 293 participants in the vitamin D group and 323 in the placebo group (9.39 and 10.66 events per 100 person-years, respectively). The hazard ratio for vitamin D as compared with placebo was 0.88 (95% confidence interval, 0.75 to 1.04; P = 0.12). The incidence of adverse events did not differ significantly between the two groups.

CONCLUSIONS

Among persons at high risk for type 2 diabetes not selected for vitamin D insufficiency, vitamin D₃ supplementation at a dose of 4000 IU per day did not result in a significantly lower risk of diabetes than placebo. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others; D2d ClinicalTrials.gov number, NCT01942694.).

Skeletal and Extraskeletal Actions of Vitamin D: Current Evidence and Outstanding Questions

The etiology of endemic rickets was discovered a century ago. Vitamin D is the precursor of 25-hydroxyvitamin D and other metabolites, including 1,25(OH)2D, the ligand for the vitamin D receptor (VDR). The effects of the vitamin D endocrine system on bone and its growth plate are primarily indirect and mediated by its effect on intestinal calcium transport and serum calcium and phosphate homeostasis. Rickets and osteomalacia can be prevented by daily supplements of 400 IU of vitamin D. Vitamin D deficiency (serum 25-hydroxyvitamin D <50 nmol/L) accelerates bone turnover, bone loss, and osteoporotic fractures. These risks can be reduced by 800 IU of vitamin D together with an appropriate calcium intake, given to institutionalized or vitamin D-deficient elderly subjects. VDR and vitamin D metabolic enzymes are widely expressed. Numerous genetic, molecular, cellular, and animal studies strongly suggest that vitamin D signaling has many extraskeletal effects. These include regulation of cell proliferation, immune and muscle function, skin differentiation, and reproduction, as well as vascular and metabolic properties. From observational studies in human subjects, poor vitamin D status is associated with nearly all diseases predicted by these extraskeletal actions. Results of randomized controlled trials and Mendelian randomization studies are supportive of vitamin D supplementation in reducing the incidence of some diseases, but, globally, conclusions are mixed. These findings point to a need for continued ongoing and future basic and clinical studies to better define whether vitamin D status can be optimized to improve many aspects of human health. Vitamin D deficiency enhances the risk of osteoporotic fractures and is associated with many diseases. We review what is established and what is plausible regarding the health effects of vitamin D.

Extra-Skeletal Effects of Vitamin D

The vitamin D receptor is expressed in multiple cells of the body (other than osteoblasts), including beta cells and cells involved in immune modulation (such as mononuclear cells, and activated T and B lymphocytes), and most organs in the body including the brain, heart, skin, gonads, prostate, breast, and gut. Consequently, the extra-skeletal impact of vitamin D deficiency has been an active area of research. While epidemiological and case-control studies have often suggested a link between vitamin D deficiency and conditions such as type 1 and type 2 diabetes, connective tissue disorders, inflammatory bowel disorders, chronic hepatitis, food allergies, asthma and respiratory infections, and cancer, interventional studies for the most part have failed to confirm a causative link. This review examines available evidence to date for the extra-skeletal effects of vitamin D deficiency, with a focus on randomized controlled trials and meta-analyses.

25-Hydroxyvitamin D and the risk of incident diabetes in Hong Kong Chinese

OBJECTIVE

To investigate the relationship between serum 25-hydroxyvitamin D (25(OH)D) and risk of incident diabetes in Hong Kong Chinese, after accounting for the effect of multiple bone- and mineral-related markers.

DESIGN

We conducted a retrospective study on the Hong Kong Osteoporosis Study cohort. Incident diabetes was ascertained using electronic medical records. Serum 25(OH)D was measured at baseline and its association with incident diabetes was evaluated using multivariable Cox proportional-hazard regression.

PARTICIPANTS

Individuals (n 4342) aged 20 years or above (1395 men, 2947 women; mean age 54·3 (sd 16·5) years) from the Hong Kong Osteoporosis Study, who were free of diabetes at baseline, were included.

RESULTS

During 40 124·7 person-years of follow-up (a median of 9·2 years), 443 participants developed diabetes. Mean 25(OH)D was 63·34 (sd 13·07) nmol/l. Age-, sex- and BMI-adjusted Cox proportional-hazard regression showed no significant difference in the risk of incident diabetes between the lowest and the highest quintiles of 25(OH)D. In the analysis of the interaction effect between 25(OH)D and serum Ca, the interaction term did not affect the risk of incident diabetes significantly (P = 0·694). Similarly, there was no significant interaction of different subgroups (age, sex, BMI, femoral-neck T-score, serum Ca levels) with serum 25(OH)D.

CONCLUSIONS

The present study finds that serum vitamin D level is not associated with the risk of incident diabetes in Hong Kong Chinese and this relationship is not modified by serum Ca level.

Vitamin D supplementation after the second year of life: joint position of the Committee on Nutrition, German Society for Pediatric and Adolescent Medicine (DGKJ e.V.), and the German Society for Pediatric Endocrinology and Diabetology (DGKED e.V.)

Background

Low vitamin D serum concentrations have been associated with rickets and other disorders in observational studies. Since vitamin D serum concentrations in children and adolescents are frequently below reference values, it is debated whether vitamin D should be supplemented after infancy.

Methods

The effects of vitamin D supplementation in children > 2 years of age are analyzed based on a literature review of randomized controlled trials (RCTs).

Results

Vitamin D supplementation can potentially reduce the risk for influenza infections and improve asthma bronchiale exacerbation; however, it has no impact on asthma bronchiale severity. Vitamin D supplementation has no relevant effect on attention-deficit/hyperactivity disorders, cardiac failure, hypertension, or incidence of type II diabetes mellitus. Vitamin D supplementation has no effect on the rate of multiple sclerosis relapses, but on the number of new lesions detected by MRI. For other endpoints, RCTs are lacking.

Conclusion

Based on currently available studies, routine vitamin D supplementation is not be recommended for children aged > 2 years, even when they have serum concentrations below reference values. Routine vitamin D supplementation is not recommended in children who do not have risk factors and chronic diseases which are associated with calcium or vitamin D resorption disorders.

Vitamin D supplementation and total cancer incidence and mortality: a meta-analysis of randomized controlled trials

BACKGROUND

Previous meta-analyses of randomized controlled trials (RCTs) of vitamin D supplementation and total cancer incidence and mortality found inconsistent results, and most included trials administered generally low doses of vitamin D (≤1100 IU/day). We updated the meta-analysis by incorporating recent RCTs that have tested higher doses of vitamin D supplements.

MATERIALS AND METHODS

PubMed and Embase were searched from the inception to November 2018. Summary relative risks (RRs) and 95% confidence intervals (CIs) were estimated using a random-effects model.

RESULTS

For total cancer incidence, 10 trials were included [6537 cases; 3-10 years of follow-up; 54-135 nmol/l of attained levels of circulating 25(OH) vitamin D [25(OH)D] in the intervention group]. The summary RR was 0.98 (95% CI, 0.93-1.03; P = 0.42; I2 = 0%). The results remained null across subgroups tested, including even when attained 25(OH)D levels exceeded 100 nmol/l (RR, 0.95; 95% CI, 0.83-1.09; P = 0.48; I2 = 26%). For total cancer mortality, five trials were included [1591 deaths; 3-10 years of follow-up; 54-135 nmol/l of attained levels of circulating 25(OH)D in the intervention group]. The summary RR was 0.87 (95% CI, 0.79-0.96; P = 0.005; I2 = 0%), which was largely attributable to interventions with daily dosing (as opposed to infrequent bolus dosing). No statistically significant heterogeneity was observed by attained levels of circulating 25(OH)D (Pheterogeneity = 0.83), with RR being 0.88 (95% CI, 0.78-0.98; P = 0.02; I2 = 0%) for ≤100 nmol/l and 0.85 (95% CI, 0.70-1.03; P = 0.11; I2 = 0%) for >100 nmol/l.

CONCLUSIONS

In an updated meta-analysis of RCTs, vitamin D supplementation significantly reduced total cancer mortality but did not reduce total cancer incidence.

Clinical Advances in Immunonutrition and Atherosclerosis: A Review

Atherosclerosis is a chronic low-grade inflammatory disease that affects large and medium-sized arteries and is considered to be a major underlying cause of cardiovascular disease (CVD). The high risk of mortality by atherosclerosis has led to the development of new strategies for disease prevention and management, including immunonutrition. Plant-based dietary patterns, functional foods, dietary supplements, and bioactive compounds such as the Mediterranean Diet, berries, polyunsaturated fatty acids, ω-3 and ω-6, vitamins E, A, C, and D, coenzyme Q10, as well as phytochemicals including isoflavones, stilbenes, and sterols have been associated with improvement in atheroma plaque at an inflammatory level. However, many of these correlations have been obtained in vitro and in experimental animals' models. On one hand, the present review focuses on the evidence obtained from epidemiological, dietary intervention and supplementation studies in humans supporting the role of immunonutrient supplementation and its effect on anti-inflammatory response in atherosclerotic disease. On the other hand, this review also analyzes the possible molecular mechanisms underlying the protective action of these supplements, which may lead a novel therapeutic approach to prevent or attenuate diet-related disease, such as atherosclerosis.

Adverse events from large dose vitamin D supplementation taken for one year or longer

In recent years, clinical trials increasingly have given large doses of vitamin D supplements to investigate possible health benefits beyond bone at high 25-hydroxyvitamin D levels. However, there are few publications on the safety of high-dose vitamin D given long term. The study objective was to investigate the cumulative relative risk (RR) of total adverse events, kidney stones, hypercalcemia and hypercalciuria from ≥2800 IU/d vitamin D₂ or D₃ supplementation, followed for one year or more in randomized controlled trials (RCTs). A systematic review was conducted in Medline Ovid, EMBASE and Cochrane in March 2018 to update results of studies published since a previous review in October 2015. RCTs were included if they gave vitamin D₂ or D₃ at ≥2800 IU/d for at least one year and reported on total adverse events or at least one calcium-related adverse event. There were a total of 32 studies that met the inclusion criteria. Of these, only 15 studies (3150 participants) reported one or more event of the outcomes of interest. Long-term high-dose vitamin D supplementation did not increase total adverse events compared to placebo in 1731 participants from 10 studies (RR = 1.05; 95% CI = 0.88, 1.24; p = 0.61), nor kidney stones in 1336 participants from 5 studies (RR = 1.26; 95% CI = 0.35, 4.58; p = 0.72). However, there was a trend for vitamin D to increase risk of hypercalcemia in 2598 participants from 10 studies (RR = 1.93; 95% CI = 1.00, 3.73; p = 0.05); while its effect on hypercalciuria in only 276 participants from 3 studies was inconclusive (RR = 1.93; 95% CI = 0.83, 4.46; p = 0.12). In conclusion, one year or longer supplementation with a large daily, weekly or monthly dose of vitamin D₂ /D₃ did not significantly increase a risk of total adverse events or kidney stones, although there was a trend towards increased hypercalcemia, and possibly for hypercalciuria.

The role of vitamin D in the pathogenesis and treatment of diabetes mellitus: a narrative review

Diabetes mellitus, a metabolic disorder associated with chronic complications, is traditionally classified into two main subtypes. Type 1 diabetes mellitus (T1DM) results from gradual pancreatic islet β cell autoimmune destruction, extending over months or years. Type 2 diabetes mellitus (T2DM) is a heterogeneous disorder, with both insulin resistance and impairment in insulin secretion contributing to its pathogenesis. Vitamin D is a fat-soluble vitamin with an established role in calcium metabolism. Recently, several studies have provided evidence suggesting a role for it in various non-skeletal metabolic conditions, including both types of diabetes mellitus. Preclinical studies of vitamin D action on insulin secretion, insulin action, inflammatory processes, and immune regulation, along with evidence of an increase of hypovitaminosis D worldwide, have prompted several epidemiological, observational, and supplementation clinical studies investigating a potential biological interaction between hypovitaminosis D and diabetes. This narrative review aims to summarize current knowledge on the effect of vitamin D on T1DM and T2DM pathogenesis, prevention, and treatment, as well as on micro- and macrovascular complications of the disease. Furthermore, on the basis of current existing evidence, we aim to highlight areas for potential future research.

Laboratory trend in vitamin D status in Ireland: Dual concerns about low and high 25OHD

Serum 25-hydroxyvitamin D (25OHD) is the pre-eminent estimate of vitamin D status that we have been measuring in a hospital laboratory setting since the 1970s. We previously evaluated the trend in 25OHD results in our laboratory from 1993 to 2013. Using a time series analysis of monthly average 25OHD results the trend was modelled, and this was used to forecast monthly average 25OHD from 2014 to 2016. In this study, all 25OHD results from 2014 to 2016 were retrieved (n = 67,922) and trimmed to 40,307 results after duplicates were excluded. The average monthly actual 25OHD was almost identical to the average monthly forecast 25OHD (p = 0.028) with a strong correlation between the actual 25OHD and forecast 25OHD (r = 0.69, p < 0.001). This upward trend is attributed to higher oral intake of vitamin D. We have a dual concern: policies to prevent hypovitaminosis D must be offset by strategies to avert hypervitaminosis D.

Controversies in Vitamin D: Summary Statement From an International Conference

CONTEXT

Vitamin D is classically recognized as a regulator of calcium and phosphorus metabolism. Recent advances in the measurement of vitamin D metabolites, diagnosis of vitamin D deficiency, and clinical observations have led to an appreciation that along with its role in skeletal metabolism, vitamin D may well have an important role in nonclassical settings. Measurement of the circulating form of vitamin D that best describes total body stores, namely 25-hydroxyvitamin D, can be unreliable despite many sophisticated methodologies that have been proposed and implemented. Likewise, evidence from clinical studies showing a beneficial role of vitamin D in different disease states has been controversial and at times speculative. Moreover, the target concentrations of 25-hydroxyvitamin D to address a number of putative links between vitamin D inadequacy and nonskeletal diseases are further areas of uncertainty.

SETTING

To address these issues, an international conference on "Controversies in Vitamin D" was held in Pisa, Italy, in June 2017. Three main topics were addressed: (i) vitamin D assays and the definition of hypovitaminosis D; (ii) skeletal and extraskeletal effects of vitamin D; (iii) therapeutics of vitamin D.

RESULTS

This report provides a summary of the deliberations of the expert panels of the conference.

CONCLUSIONS

Despite great advances in our appreciation of vitamin D metabolism, measurements, biological actions on classical and nonclassical tissues, and therapeutics, all of which this report summarizes, much more work remains to be done so that our knowledge base can become even more secure.

The Role of Vitamin D Binding Protein, Total and Free 25-Hydroxyvitamin D in Diabetes

Vitamin D is important for bone health, but may also have extra-skeletal effects. Vitamin D and its binding protein DBP have immunological effects and may therefore be important in the development of type 1 diabetes (T1DM), and low serum levels of 25-hydroxyvitamin D (25(OH)D) are associated with later development of type 2 diabetes (T2DM). However, it has so far been difficult to convincingly show an effect of vitamin D supplementation on prevention or treatment of diabetes. The serum level of 25(OH)D has traditionally been used as a marker of a subject's vitamin D status. This measurement includes both 25(OH)D bound to DBP and albumin as well as the free from of 25(OH)D. However, according to the free hormone hypothesis, the free form is the biologically active. Previously the free form of 25(OH)D had to be calculated based on measurements of 25(OH)D, DBP, and albumin, but recently a method for direct measurement of free 25(OH)D has become commercially available. This is important in clinical conditions where the amount of DBP is affected, and has caused a renewed interest in which vitamin D metabolite to measure in clinical situations. In the present review the relations between DBP, total and free 25(OH)D in T1DM and T2DM are described.

Effects of Lifestyle Modification and Anti-diabetic Medicine on Prediabetes Progress: A Systematic Review and Meta-Analysis

Background: Pre-diabetes is a risk factor for full-blown diabetes; it presents opportunities to prevent the actual diseases. It is therefore essential to identify effective preventive strategies, and to clarify the direction of future research. Methods: PubMed, Embase and Cochrane Central Register of Controlled Trials were searched using key terms (Supplementary Table 1). We applied network meta-analysis to multiple comparisons among various diabetic preventive strategies, including lifestyle and pharmacological interventions; traditional meta-analysis for the synthesis of basal metabolic changes after interventions; and trial sequential analysis for determinations as to whether analysis conclusions meet expectations. Results: We included 32 randomized controlled trials comprising 43,669 patients and 14 interventions in the meta-analysis. Both lifestyle modifications and anti-diabetic medications improved physical conditions, including weight loss, blood glucose, and blood pressure. Network meta-analysis suggested that the progression of diabetes could be delayed to varying degrees by lifestyle and pharmacological interventions, except for angiotensin-converting enzyme inhibitors, statins, sulfonylureas and vitamin D. The risk ratios (RR) [95% credible interval (CrI)] compared with control were: GLP-1RAs 0.28 (0.15, 0.50), Orlistat 0.33 (0.18, 0.55), TZM 0.33 (0.16, 0.63), TZD 0.39 (0.27, 0.53), LST 0.54 (0.32, 0.88), lifestyle 0.58 (0.49, 0.67), LSM 0.62 (0.45, 0.80), GI 0.66 (0.46, 0.88), SU 0.67 (0.40, 1.00), Vitamin D 0.91 (0.59, 1.40), ACEI 0.93 (0.62, 1.40), statins 1.20 (0.84, 1.60). Conclusions: In adults with pre-diabetes, firm evidence supports the notion that lifestyle modifications and metformin reduces the incidence of diabetes with an average of 20% relative risk reduction, while statins increase the relative risk 20%. We found that lifestyle modifications, promising long-term strategies involving three factors (nutrition, exercise, and weight loss) contribute to health by reducing BMI, body weight, waist and hip circumference, systolic and diastolic pressure, fasting, and 2-h postprandial blood glucose, total cholesterol and by increasing HDL. We made this determination using TSA, avoiding further waste of experimental resources.

MANAGEMENT OF ENDOCRINE DISEASE: Therapeutics of Vitamin D

OBJECTIVE

The central role of vitamin D in bone health is well recognized. However, controversies regarding its clinical application remain. We therefore aimed to review the definition of hypovitaminosis D, the skeletal and extra-skeletal effects of vitamin D and the available therapeutic modalities.

DESIGN

Narrative and systematic literature review.

METHODS

An international working group that reviewed the current evidence linking bone and extra-skeletal health and vitamin D therapy to identify knowledge gaps for future research.

RESULTS

Findings from observational studies and randomized controlled trials (RCTs) in vitamin D deficiency are discordant, with findings of RCTs being largely negative. This may be due to reverse causality with the illness itself contributing to low vitamin D levels. The results of many RCTs have also been inconsistent. However, overall evidence from RCTs shows vitamin D reduces fractures (when administered with calcium) in the institutionalized elderly. Although controversial, vitamin D reduces acute respiratory tract infections (if not given as bolus monthly or annual doses) and may reduce falls in those with the lowest serum 25-hydroxyvitamin D (25OHD) levels. However, despite large ongoing RCTs with 21 000–26 000 participants not recruiting based on baseline 25OHD levels, they will contain a large subset of participants with vitamin D deficiency and are adequately powered to meet their primary end-points.

CONCLUSIONS

The effects of long-term vitamin D supplementation on non-skeletal outcomes, such as type 2 diabetes mellitus (T2DM), cancer and cardiovascular disease (CVD) and the optimal dose and serum 25OHD level that balances extra-skeletal benefits (T2DM) vs risks (e.g. CVD), may soon be determined by data from large RCTs.

Monthly high-dose vitamin D3 supplementation and self-reported adverse events in a 4-year randomized controlled trial

BACKGROUND

The use of high-dose vitamin D supplementation has increased in recent years. However, relatively little is known about the safety of long-term high doses.

AIMS

To investigate the safety of a monthly high-dose of vitamin D₃ supplementation taken for up to 4 years.

METHODS

Data were collected in a randomized, double blind, placebo-controlled trial of 5108 adults aged 50-84 years old from Auckland, New Zealand. Participants were given monthly doses of 100,000 IU vitamin D₃ or placebo, for a median of 3.3 years (range 2.5-4.2 years). They answered an open-ended question in a monthly questionnaire about any adverse events they attributed to the study capsules, which were coded blindly. Incidence rates per person months were calculated for categories of adverse events. Cox regression model used to calculate hazard ratio of time to first adverse-event.

RESULTS

In total, 419 (16.5%) participants taking vitamin D and 399 (15.8%) taking placebo reported ≥1 adverse event. Compared to placebo, the hazard ratio (HR) of reporting first adverse event in the vitamin D group was 1.03 (95% CI: 0.90, 1.18; p = 0.63). Despite a slightly higher incidence of recurrent adverse events in vitamin D arm, the incidence rate ratio (1.17) was not significantly higher in vitamin D (95% CI: 0.97, 1.41; p = 0.10). All regression results were adjusted for age, sex, and ethnicity. There was no difference between study arms in terms of participants' allocation perception (p = 0.52).

CONCLUSION

Monthly supplementation of 100,000 IU vitamin D3 for a median of 3.3 years did not affect participant-reported adverse events.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: ACTRN12611000402943; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=ACTRN12611000402943.

Long-term treatment with metformin in type 2 diabetes and vitamin D levels: A post-hoc analysis of a randomized placebo-controlled trial

AIMS

To study the effects of metformin, as compared to placebo, on serum levels of vitamin D (25-hydroxyvitamin D [25(OH)D]) in patients with advanced type 2 diabetes.

MATERIALS AND METHODS

In the HOME trial, a randomized placebo-controlled trial, 390 insulin-treated patients with type 2 diabetes were treated with 850 mg metformin or placebo thrice daily for 52 months. In a post-hoc analysis, we examined changes in the combined levels of 25(OH)D₂ and 25(OH)D₃ at 4 and 16 months during the study.

RESULTS

Mean combined 25(OH)D at baseline was 68.2 nmoL/L (95% confidence interval [CI]: 65.5-71.1). In mixed model analysis, metformin, as compared to placebo, had no effect on 25(OH)D levels during 16 months (coefficient: 1.002 per month, multiplicative model; 95% CI: 0.998-1.006, P = .30). Metformin was associated with a small increase of 25(OH)D₂ (coefficient: 1.012 per month; 95% CI: 1.003-1.021, P = .008). However, 25(OH)D₂ is only a very small fraction (3%) of 25(OH)D. Seasonal variation had the biggest impact on 25(OH)D levels. Vitamin B12 levels were not associated with the levels of 25(OH)D.

CONCLUSION

Metformin had no effect on serum 25(OH)D during 16 months in the setting of a clinical randomized controlled trial in patients with type 2 diabetes. Our results show that metformin doesn't lead to vitamin D deficiency.

Baseline Characteristics of the Vitamin D and Type 2 Diabetes (D2d) Study: A Contemporary Prediabetes Cohort That Will Inform Diabetes Prevention Efforts

OBJECTIVE

To describe baseline characteristics of the Vitamin D and Type 2 Diabetes (D2d) study, the first large U.S. diabetes prevention clinical trial to apply current American Diabetes Association (ADA) criteria for prediabetes.

RESEARCH DESIGN AND METHODS

This is a multicenter (n = 22 sites), randomized, double-blind, placebo-controlled, primary prevention clinical trial testing effects of oral daily 4,000 IU cholecalciferol (D3) compared with placebo on incident diabetes in U.S. adults at risk for diabetes. Eligible participants were at risk for diabetes, defined as not meeting criteria for diabetes but meeting at least two 2010 ADA glycemic criteria for prediabetes: fasting plasma glucose (FPG) 100-125 mg/dL, 2-h postload glucose (2hPG) after a 75-g oral glucose load 140-199 mg/dL, and/or a hemoglobin A1c (HbA1c) 5.7-6.4% (39-46 mmol/mol).

RESULTS

A total of 2,423 participants (45% of whom were women and 33% nonwhite) were randomized to cholecalciferol or placebo. Mean (SD) age was 59 (9.9) years and BMI 32 (4.5) kg/m2. Thirty-five percent met all three prediabetes criteria, 49% met the FPG/HbA1c criteria only, 9.5% met the 2hPG/FPG criteria only, and 6.3% met the 2hPG/HbA1c criteria only. Black participants had the highest mean HbA1c and lowest FPG concentration compared with white, Asian, and other races (P < 0.01); 2hPG concentration did not differ among racial groups. When compared with previous prediabetes cohorts, the D2d cohort had lower mean 2hPG concentration but similar HbA1c and FPG concentrations.

CONCLUSIONS

D2d will establish whether vitamin D supplementation lowers risk of diabetes and will inform about the natural history of prediabetes per contemporary ADA criteria.

Vitamin D Supplementation, Serum 25(OH)D Concentrations and Cardiovascular Disease Risk Factors: A Systematic Review and Meta-Analysis

Background: Cardiovascular disease (CVD) risk factors are associated with low serum 25 hydroxyvitamin D (25(OH)D) concentrations in observational studies; however, clinical trial findings are inconsistent.

Objective: We assessed the effect of vitamin D supplementation and increased serum 25(OH)D concentrations on CVD risk factors in a systemic review and meta-analysis of randomized controlled trials (RCTs).

Design: MEDLINE, CINAHL, EMBASE, and Google Scholar were searched for RCTs that evaluated vitamin D supplementation and cardiovascular outcomes [blood pressure, parathyroid hormone (PTH), serum high-sensitivity C-reactive protein (hs-CRP), total cholesterol, high and low density lipoprotein (HDL and LDL, respectively), triglycerides, peak wave velocity (PWV) and Augmentation Index (AI)] from 1992 through 2017. Meta-analysis was based on a random-effects model and inverse variance method to calculate standardized mean difference (SMD) as effect sizes, followed by a leave-one-out method for sensitivity analysis. Risk of publication bias was assessed using Cochrane checklist and Begg funnel plots. The systematic review is registered as CRD42015025346.

Results: We identified 2341 studies from which 81 met inclusion criteria. The meta-analysis indicated a significant reduction in systolic blood pressure (SMD = −0.102 ± 0.04 mmHg, 95% confidence interval (CI), −0.20 to −0.03), diastolic blood pressure (SMD = −0.07 ± 0.03 mmHg, 95% CI, −0.14 to −0.006), serum PTH (SMD = −0.66 ± 0.08 ng/L, 95% CI, −0.82 to −0.49), hs-CRP (SMD = −0.20 ± 0.07 mg/L, 95% CI, −0.34 to −0.06), total cholesterol (SMD = −0.15 ± 0.06 mmol/L, 95% CI, −0.25 to −0.04), LDL (SMD = −0.10 ± 0.05 mmol/L, 95% CI, −0.20 to −0.003), triglycerides (SMD = −0.12 ± 0.06 mmol/L, 95% CI, −0.23 to −0.003) and a significant increase in HDL (SMD = 0.09 ± 0.04 mmol/L, 95% CI, 0.00 to 0.17) with vitamin D supplementation. These findings remained significant in sensitivity analyses for blood pressure, lipid profile, serum PTH, and serum hs-CRP. There was no significant effect of vitamin D supplementation on PWV (SMD = −0.20 ± 0.13 m/s, 95% CI, −0.46 to 0.06, p = 0.14) and AI (SMD = −0.09 ± 0.14%, 95% CI, −0.37 to 0.19, p = 0.52) for vitamin D supplemented groups.

Conclusion: These findings suggest that vitamin D supplementation may act to protect against CVD through improving risk factors, including high blood pressure, elevated PTH, dyslipidemia, and inflammation.

Vitamin D Supplementation, Glycemic Control, and Insulin Resistance in Prediabetics: A Meta-Analysis

Diabetes prevention is a public health priority. Vitamin D supplementation may help prevent the development of diabetes in persons at increased risk. We performed a meta-analysis of controlled clinical trials that assessed glycemic outcome measures among adults at risk for type 2 diabetes, including prediabetes, overweight, or obesity. We searched PUBMED/ MEDLINE, CINAHL, and Google Scholar databases for trials published prior to April 2017. Placebo-controlled clinical trials with random allocation to vitamin D with or without calcium supplementation were selected. Data collection included country, study design, inclusion criteria, sample size, form, and dose of vitamin D, supplementation interval, control group, duration, participant characteristics, comorbidities, baseline and follow-up serum 25-hydroxyvitamin D [25(OH)D] concentration, and available outcome measures [glycosylated hemoglobin (HbA1c), fasting plasma glucose, plasma glucose after 2-hour oral glucose tolerance test, and homeostatic model assessment of insulin resistance (HOMA-IR)]. Data synthesis was conducted using random-effect models (PROSPERO registration no. CRD42017055326). Twenty-eight trials, representing 3848 participants, met the eligibility criteria. Compared with the control group, vitamin D supplementation significantly reduced HbA1c level by -0.48% (95% CI, -0.79 to -0.18), fasting plasma glucose level by -0.46 mmol/L (95% CI, -0.74 to -0.19), and HOMA-IR level by -0.39 (95% CI, -0.68 to -0.11). Subgroup analysis revealed that the effects of vitamin D supplementation on different glycemic measures were influenced by age, calcium coadministration, vitamin D deficiency, serum 25(OH)D level after supplementation, and duration of supplementation. Vitamin D supplementation and improved vitamin D status improved glycemic measures and insulin sensitivity and may be useful as part of a preventive strategy for type 2 diabetes.

Higher Levels of Serum 25-Hydroxyvitamin D Are Related to Improved Glucose Homeostasis in Women with Postmenopausal Osteoporosis

BACKGROUND

Postmenopausal osteoporosis (PMO) is associated with other comorbidities such as impaired glucose homeostasis and cardiovascular disease. Vitamin D insufficiency is highly prevalent and may be a common link between these disorders. However, the relationship between circulating 25-hydroxyvitamin D [25(OH)D] and insulin resistance in women with PMO has not been well evaluated. The aim of this study was to assess the relationship between circulating levels of 25(OH)D and parameters of glucose homeostasis in a cohort of women with PMO to establish a serum concentration threshold of 25(OH)D for improved glycemic parameters.

MATERIALS AND METHODS

This cross-sectional study included 40 women with PMO. We measured 25(OH)D serum levels and glucose homeostasis parameters (glucose and insulin levels, insulin sensitivity, and β-secretion index HOMA2-%S and HOMA2-%B, respectively). Anthropometric, biochemical, and clinical parameters and bone markers were also evaluated.

RESULTS

Circulating levels of 25(OH)D were related to glucose parameters (negatively with HOMA2-%B and insulin levels and positively with HOMA2-%S) in women with PMO, resulting in an indicator of insulin sensitivity independent of age, body mass index, percent body fat, and undercarboxylated osteocalcin. Patients with serum 25(OH)D ≥45 ng/mL showed lower HOMA2-%B values and insulinemia and greater HOMA2-%S.

CONCLUSIONS

Our results support the hypothesis that circulating 25(OH)D levels are related to improved glucose homeostasis in women with PMO. However, this relationship was apparent only in the presence of high circulating levels of 25(OH)D.

Vitamin D supplementation does not improve CVD risk factors in vitamin D-insufficient subjects

OBJECTIVE

Low serum 25(OH)D levels are associated with cardiovascular disease (CVD) and some of its risk factors. However, in interventional studies, the effects of vitamin D supplementation have been uncertain, possibly due to inclusion of vitamin D-sufficient subjects. Our aim was therefore to examine effects of vitamin D supplementation on CVD risk factors in vitamin D-insufficient subjects.

DESIGN

Double-blinded randomized controlled trial.

METHODS

A 4-month interventional study with high-dose vitamin D (100,000 IU loading dose, followed by 20,000 IU/week) or placebo with measurements of blood pressure, lipids (total-, LDL- and HDL-cholesterol, triglycerides, apolipoproteins A1 and B), and glucose metabolism parameters (blood glucose, HbA_1c, serum human receptors for advanced glycation end products (sRAGE), insulin, C-peptide and HOMA-IR).

RESULTS

A total of 422 subjects with mean serum 25(OH)D level 34 nmol/L were included, with 411 subjects completing the study. Serum 25(OH)D levels increased with 56 nmol/L and decreased with 4 nmol/L in the vitamin D and placebo group, respectively. We found no statistically significant differences between the two groups in any of the measured CVD risk factors, except for a minor increase in sRAGE in the vitamin D group. Stratified analyses of subjects with low baseline serum 25(OH)D levels alone, or combined with blood pressure, lipid and HOMA-IR values above the median for the cohort, did not skew the results in favour of vitamin D supplementation.

CONCLUSION

Supplementation with vitamin D in subjects with baseline vitamin D insufficiency does not improve CVD risk factor profile.

Effect of vitamin D supplementation on fasting plasma glucose, insulin resistance and prevention of type 2 diabetes mellitus in non-diabetics: A systematic review and meta-analysis

Increasing epidemiological studies suggest that there is an association between vitamin D deficiency and risk of type 2 diabetes mellitus (T2DM). Therefore, randomized clinical trials (RCTs) have been performed to observe the effect of vitamin D supplementation on preventing T2DM, decreasing fasting plasma glucose (FPG) and improving insulin resistance to confirm the association between vitamin D and T2DM. However, the results of RCTs on controlling FPG level, improving insulin resistance and preventing T2DM in non-diabetics are inconsistent. In the present study, a systematic meta-analysis considering individual variation and intervention strategy was conducted to establish an objective and definitive conclusion. The results suggested that vitamin D supplementation had no significant effect on controlling FPG level, improving insulin resistance or preventing T2DM in non-diabetics in a pooled meta-analysis of 23 articles (containing 28 RCTs). However, stratified analysis indicated that supplementation of vitamin D had differential effects on FPG control, insulin sensitivity improvement and T2DM prevention in individuals with different baseline states: FPG was decreased for those with BMI <25 (P=0.048) or 20≤ 25(OH)D <30 ng/ml (P=0.002); insulin resistance was improved for those with 25(OH)D ≥30 ng/ml (P=0.021); and risk of T2DM was lower for pre-diabetic individuals (P=0.047) or for those with 25≤ BMI <30 (P=0.032). Additionally, the effect on T2DM prevention was improved when the supplement dose was >2,000 IU/day (P=0.047) and with intervention without calcium (P=0.047). Thus, further trials should focus on individual baselines and the supplementation strategy of vitamin D in the prevention of T2DM.