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

Classification and identification of risk factors for type 2 diabetes

The risk factors for type 2 diabetes mellitus (T2DM) have been increasingly researched, but the lack of systematic identification and categorization makes it difficult for clinicians to quickly and accurately access and understand all the risk factors, which are categorized in this paper into five categories: Social determinants, lifestyle, checkable/testable risk factors, history of illness and medication, and other factors, which are discussed in a narrative review. Meanwhile, this paper points out the problems of the current research, helps to improve the systematic categorisation and practicality of T2DM risk factors, and provides a professional research basis for clinical practice and industry decision-making.

3. Prevention or Delay of Diabetes and Associated Comorbidities: Standards of Care in Diabetes-2025

The American Diabetes Association (ADA) "Standards of Care in Diabetes" includes the ADA's current clinical practice recommendations and is intended to provide the components of diabetes care, general treatment goals and guidelines, and tools to evaluate quality of care. Members of the ADA Professional Practice Committee, an interprofessional expert committee, are responsible for updating the Standards of Care annually, or more frequently as warranted. For a detailed description of ADA standards, statements, and reports, as well as the evidence-grading system for ADA's clinical practice recommendations and a full list of Professional Practice Committee members, please refer to Introduction and Methodology. Readers who wish to comment on the Standards of Care are invited to do so at professional.diabetes.org/SOC.

Vitamin D and major chronic diseases

Numerous observational studies have demonstrated a significant inverse association between vitamin D status and the risk of major chronic disease, including type 2 diabetes (T2D), cardiovascular disease (CVD), and cancer. However, findings from Mendelian randomization (MR) studies and randomized controlled trials (RCTs) suggest minimal or no benefit of increased vitamin D levels. We provide an overview of recent literature linking vitamin D to major chronic diseases. Because emerging evidence indicates a potential threshold effect of vitamin D, future well-designed studies focused on diverse populations with vitamin D deficiency or insufficiency are warranted for a more comprehensive understanding of the effect of maintaining sufficient vitamin D status on the prevention of major chronic diseases.

Role of vitamin D in prevention of type 2 diabetes mellitus: A systematic review and meta‑analysis

The escalating prevalence of diabetes mellitus, projected to affect over 700 million by 2045, underscores the urgent need for effective management and prevention strategies, with type 2 diabetes mellitus (T2DM) constituting over 90% of these cases globally. The present meta-analysis aims to rigorously evaluate the potential of vitamin D supplementation in mitigating the onset of T2DM, amidst the backdrop of its biological plausibility yet inconclusive evidence regarding its efficacy in reducing new incidences of the disease. A comprehensive literature search up to December 2023 in MEDLINE, EMBASE and the Cochrane Library, employing a strategy focused on diabetes and vitamin D, identified randomized controlled trials (RCTs) that explore the impact of vitamin D supplementation on T2DM onset in adults with impaired glucose regulation, incorporating quality assessment via the Cochrane ROB2 tool and utilizing meta-analysis with RevMan Web to evaluate effect magnitude and heterogeneity. In a meta-analysis of 11 RCTs with 5,221 prediabetic patients, vitamin D supplementation was associated with a 10% reduction in the progression to T2DM [RR, 0.90; 95% CI, (0.81-0.99)] and a significant increase in regression to normoglycemia [RR, 1.24; 95% CI, (1.08-1.43)], with no significant heterogeneity or publication bias observed. This meta-analysis of 11 RCTs shows that vitamin D supplementation in prediabetic patients lowers the risk of T2DM and promotes regression to normoglycemia, with no significant differences in subgroup analyses or interaction with baseline vitamin D levels, ethnicity, or body mass index (BMI). Despite indications from some trials that baseline vitamin D status may influence outcomes, the present comprehensive analysis found benefits of vitamin D across diverse populations, including non-obese individuals, without conclusive evidence linking supplementation to changes in BMI or age-specific advantages.

Evaluating the Effect of Vitamin D Supplementation on Type 2 Diabetes Risk: A Systematic Review

Although observational studies have linked vitamin D deficiency to diabetes, it is unknown if taking vitamin D supplements can reduce the chance of developing type 2 diabetes mellitus (T2DM). The purpose of this systematic review is to determine whether vitamin D supplementation lowers the risk of type 2 diabetes. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used to search for studies based on pre-established inclusion and exclusion criteria. Five different databases (Scopus, Web of Science, PubMed, Google Scholar, and Cochrane Library) were used to search for relevant studies. These databases contained 1,916 relevant research papers that were examined for duplication using the EndNote software. After a careful text analysis, only 13 of these articles were found to be pertinent. The Newcastle-Ottawa Scale (NOS) was used to assess the risk of bias in each included study. Ten of the 13 trials examined how vitamin D supplementation affected the homeostasis model assessment of insulin resistance (HOMA-IR) of the patients. Patients using vitamin D supplements saw a drop in their HOMA-IR in six of these RCTs but an increase in four of them. The vitamin D group had a lower HOMA-IR than the placebo cohort in seven of the 10 trials that examined HOMA-IR. Despite the impact on insulin resistance, there is not enough data to conclude that vitamin D supplement significantly lowers the incidence of T2DM. To impact clinical guidelines about supplementation with vitamin D among people at risk of type 2 diabetes, more studies in this area might be beneficial.

Vitamin D levels do not correlate with severity of idiopathic peripheral neuropathy

BACKGROUND AND AIMS

Peripheral neuropathy (PN) is a common neurological condition in elderly adults. Vitamin D deficiency has been associated with diabetic and chemotherapy-induced neuropathy, but its role in idiopathic PN, in which no underlying cause of neuropathy can be identified, has not been investigated.

METHODS

Two hundred thirty patients with idiopathic PN enrolled in the Peripheral Neuropathy Research Registry (PNRR) at Johns Hopkins University School of Medicine had vitamin D testing information on record. Linear and logistic regressions were used to investigate the relationship between absolute vitamin D level or vitamin D insufficiency (<20 ng/mL) and both the severity of neuropathy as measured by the reduced total neuropathy score (TNSr) and severity of neuropathic pain.

RESULTS

Sixteen (7%) patients were vitamin D insufficient (<20 ng/mL). Controlling for factors known to correlate with severity of neuropathy, there was no correlation between absolute vitamin D levels and TNSr (correlation coefficient 0.01, 95% CI -0.03 to 0.07, p = .59) and no association between vitamin D insufficiency and TNSr (correlation coefficient 0.3, 95% CI -2.8 to 3.4, p = .86). Vitamin D insufficiency was not associated with the presence of neuropathic pain (OR 4.1, 95% CI 0.6-26.0, p = .13), and there was no correlation between vitamin D levels and pain score (correlation coefficient 0.01, 95% CI -0.02 to 0.03, p = .59).

INTERPRETATION

In a single-center cohort of patients with idiopathic PN, there was no correlation between vitamin D levels and the severity of neuropathy or neuropathic pain.

Vitamin D Supplementation: Shedding Light on the Role of the Sunshine Vitamin in the Prevention and Management of Type 2 Diabetes and Its Complications

As the incidence of type 2 diabetes mellitus (T2DM) continues to increase globally, researchers are keen to investigate various interventions to mitigate its impact. Among these, vitamin D supplementation has attracted significant attention due to its influence on insulin secretion from the pancreas and insulin receptors in body cells. A substantial body of evidence indicates that vitamin D supplementation can reduce low-grade inflammation, a critical factor in developing insulin resistance. In addition, vitamin D aids in sustaining low resting concentrations of reactive oxygen species and free radicals, normalizes Ca2+ signaling, diminishes the expression of cytokines that are pro-inflammatory, and enhances the production of cytokines that are anti-inflammatory. This review discusses the effects of vitamin D on the glycemic control of individuals with T2DM and evaluates the impact of vitamin D supplementation on glycemic markers in this population. The investigation employs a comprehensive analysis of the existing literature with a special focus on recent studies published in the past decade. Based on the findings in the literature, it can be concluded that vitamin D supplementation alongside anti-diabetic medications may enhance glycemic control and potentially reduce the risk of diabetic complications. The evidence supports the notion that vitamin D supplementation can be a valuable addition to pharmacological agents for the management of T2DM, potentially enhancing glycemic control and overall health outcomes in affected individuals.

Multifaceted Roles of Vitamin D for Diabetes: From Immunomodulatory Functions to Metabolic Regulations

Numerous studies have established associations between vitamin D and diabetes. The vitamin D receptor is widely distributed throughout the human body, including in pancreatic beta cells (β-cells), hepatocytes, and immune cells. Therefore, vitamin D's effect on the risk, progression, or complications of diabetes may be mediated through various mechanisms. These include the regulation of insulin secretion or sensitivity and modulation of β-cell function and its immunomodulatory and anti-inflammatory effects. This review extensively explores the relationship between vitamin D status and diabetes, as well as the preventive or therapeutic effects of vitamin D supplementation on diabetes from human studies. Additionally, it examines in detail the impact of vitamin D on immune and inflammatory responses in the diabetic milieux and β-cell function to better understand the underlying mechanisms through which vitamin D influences diabetes.

Vitamin D and risk of developing type 2 diabetes in the SUN project: a prospective cohort study

PURPOSE

Vitamin D deficiency has been associated with multiple chronic diseases, including metabolic disorders such as insulin resistance and type 2 diabetes (T2D). The aim of the study was to analyze the association between validated predicted serum vitamin D status and the risk of developing T2D in a large prospective cohort based on a Mediterranean population.

METHODS

The SUN project is a prospective and dynamic Spanish cohort that gathers university graduates who have answered lifestyle questionnaires, including a validated Food Frequency Questionnaire. The association between predicted serum vitamin D and the risk of T2D was assessed through Cox regression models according to quartiles (Q) of predicted vitamin D at baseline. The models were adjusted for potential confounders and sensitivity analyses were performed to ensure the robustness of our findings.

RESULTS

Our study included a total of 18,594 participants and after a total follow-up of 238,078 person-years (median follow-up of 13.5 years), 209 individuals were diagnosed with incident T2D. We found a significant inverse association between predicted levels of serum vitamin D and the risk of developing T2D, after adjusting for potential confounders and performing different sensitivity analyses (hazard ratio Q4 vs. Q1: 0.48, 95% CI 0.26-0.88; p for trend = 0.032).

CONCLUSION

The outcomes suggest that higher levels of vitamin D at baseline may be associated with a reduced risk of developing T2D.

The interplay between vitamin D status, subclinical inflammation, and prediabetes

Vitamin D's role extends beyond classical calcium and phosphate homeostasis to encompass a pivotal influence on immune modulation and metabolic health. The mechanisms by which vitamin D exerts these effects involve its conversion to hormonally active calcitriol, which binds intracellular vitamin D receptors, initiating various downstream cascades. In this review, we tease out the evidence showing the relationship between vitamin D deficiency and prediabetes within the context of subclinical inflammation, with a special focus on the novel monocyte-to-HDL ratio (MHR), a novel inflammatory marker reflecting subclinical inflammation. This was based on a thorough literature review using reputable databases covering the period from 1980 to 2024. In light of this, we discuss calcitriol's anti-inflammatory effects and consequently link vitamin D deficiency to both overt and subclinical inflammation. Additionally, the utility of several biomarkers, notably MHR, in investigating this association is also discussed. We further reviewed the role of vitamin D deficiency in precipitating prediabetes and type 2 diabetes mellitus (T2DM) via insulin resistance, decreased insulin synthesis and secretion, and subclinical inflammation. Taken together, this mini review highlights that vitamin D deficiency is significantly associated with subclinical inflammation, playing a critical role in the development of prediabetes and the progression to T2DM. Addressing vitamin D deficiency through appropriate interventions may serve as a preventative measure against the development of prediabetes and T2DM.

Receptors and Signaling Pathways Controlling Beta-Cell Function and Survival as Targets for Anti-Diabetic Therapeutic Strategies

Preserving the function and survival of pancreatic beta-cells, in order to achieve long-term glycemic control and prevent complications, is an essential feature for an innovative drug to have clinical value in the treatment of diabetes. Innovative research is developing therapeutic strategies to prevent pathogenic mechanisms and protect beta-cells from the deleterious effects of inflammation and/or chronic hyperglycemia over time. A better understanding of receptors and signaling pathways, and of how they interact with each other in beta-cells, remains crucial and is a prerequisite for any strategy to develop therapeutic tools aimed at modulating beta-cell function and/or mass. Here, we present a comprehensive review of our knowledge on membrane and intracellular receptors and signaling pathways as targets of interest to protect beta-cells from dysfunction and apoptotic death, which opens or could open the way to the development of innovative therapies for diabetes.

Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline

BACKGROUND

Numerous studies demonstrate associations between serum concentrations of 25-hydroxyvitamin D (25[OH]D) and a variety of common disorders, including musculoskeletal, metabolic, cardiovascular, malignant, autoimmune, and infectious diseases. Although a causal link between serum 25(OH)D concentrations and many disorders has not been clearly established, these associations have led to widespread supplementation with vitamin D and increased laboratory testing for 25(OH)D in the general population. The benefit-risk ratio of this increase in vitamin D use is not clear, and the optimal vitamin D intake and the role of testing for 25(OH)D for disease prevention remain uncertain.

OBJECTIVE

To develop clinical guidelines for the use of vitamin D (cholecalciferol [vitamin D3] or ergocalciferol [vitamin D2]) to lower the risk of disease in individuals without established indications for vitamin D treatment or 25(OH)D testing.

METHODS

A multidisciplinary panel of clinical experts, along with experts in guideline methodology and systematic literature review, identified and prioritized 14 clinically relevant questions related to the use of vitamin D and 25(OH)D testing to lower the risk of disease. The panel prioritized randomized placebo-controlled trials in general populations (without an established indication for vitamin D treatment or 25[OH]D testing), evaluating the effects of empiric vitamin D administration throughout the lifespan, as well as in select conditions (pregnancy and prediabetes). The panel defined "empiric supplementation" as vitamin D intake that (a) exceeds the Dietary Reference Intakes (DRI) and (b) is implemented without testing for 25(OH)D. Systematic reviews queried electronic databases for publications related to these 14 clinical questions. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology was used to assess the certainty of evidence and guide recommendations. The approach incorporated perspectives from a patient representative and considered patient values, costs and resources required, acceptability and feasibility, and impact on health equity of the proposed recommendations. The process to develop this clinical guideline did not use a risk assessment framework and was not designed to replace current DRI for vitamin D.

RESULTS

The panel suggests empiric vitamin D supplementation for children and adolescents aged 1 to 18 years to prevent nutritional rickets and because of its potential to lower the risk of respiratory tract infections; for those aged 75 years and older because of its potential to lower the risk of mortality; for those who are pregnant because of its potential to lower the risk of preeclampsia, intra-uterine mortality, preterm birth, small-for-gestational-age birth, and neonatal mortality; and for those with high-risk prediabetes because of its potential to reduce progression to diabetes. Because the vitamin D doses in the included clinical trials varied considerably and many trial participants were allowed to continue their own vitamin D-containing supplements, the optimal doses for empiric vitamin D supplementation remain unclear for the populations considered. For nonpregnant people older than 50 years for whom vitamin D is indicated, the panel suggests supplementation via daily administration of vitamin D, rather than intermittent use of high doses. The panel suggests against empiric vitamin D supplementation above the current DRI to lower the risk of disease in healthy adults younger than 75 years. No clinical trial evidence was found to support routine screening for 25(OH)D in the general population, nor in those with obesity or dark complexion, and there was no clear evidence defining the optimal target level of 25(OH)D required for disease prevention in the populations considered; thus, the panel suggests against routine 25(OH)D testing in all populations considered. The panel judged that, in most situations, empiric vitamin D supplementation is inexpensive, feasible, acceptable to both healthy individuals and health care professionals, and has no negative effect on health equity.

CONCLUSION

The panel suggests empiric vitamin D for those aged 1 to 18 years and adults over 75 years of age, those who are pregnant, and those with high-risk prediabetes. Due to the scarcity of natural food sources rich in vitamin D, empiric supplementation can be achieved through a combination of fortified foods and supplements that contain vitamin D. Based on the absence of supportive clinical trial evidence, the panel suggests against routine 25(OH)D testing in the absence of established indications. These recommendations are not meant to replace the current DRIs for vitamin D, nor do they apply to people with established indications for vitamin D treatment or 25(OH)D testing. Further research is needed to determine optimal 25(OH)D levels for specific health benefits.

A Systematic Review Supporting the Endocrine Society Clinical Practice Guidelines on Vitamin D

CONTEXT

Low vitamin D status is common and is associated with various common medical conditions.

OBJECTIVE

To support the development of the Endocrine Society's Clinical Practice Guideline on Vitamin D for the Prevention of Disease.

METHODS

We searched multiple databases for studies that addressed 14 clinical questions prioritized by the guideline panel. Of the 14 questions, 10 clinical questions assessed the effect of vitamin D vs no vitamin D in the general population throughout the lifespan, during pregnancy, and in adults with prediabetes; 1 question assessed dosing; and 3 questions addressed screening with serum 25-hydroxyvitamin D (25[OH]D). The Grading of Recommendations Assessment, Development and Evaluation approach was used to assess certainty of evidence.

RESULTS

Electronic searches yielded 37 007 citations, from which we included 151 studies. In children and adolescents, low-certainty evidence suggested reduction in respiratory tract infections with empiric vitamin D. There was no significant effect on select outcomes in healthy adults aged 19 to 74 years with variable certainty of evidence. There was a very small reduction in mortality among adults older than 75 years with high certainty of evidence. In pregnant women, low-certainty evidence suggested possible benefit on various maternal, fetal, and neonatal outcomes. In adults with prediabetes, moderate certainty of evidence suggested reduction in the rate of progression to diabetes. Administration of high-dose intermittent vitamin D may increase falls, compared to lower-dose daily dosing. We did not identify trials on the benefits and harms of screening with serum 25(OH)D.

CONCLUSION

The evidence summarized in this systematic review addresses the benefits and harms of vitamin D for the prevention of disease. The guideline panel considered additional information about individuals' and providers' values and preferences and other important decisional and contextual factors to develop clinical recommendations.

Vitamin D efficacy in type 1 and type 2 diabetes

It is well known that vitamin D has a profound effect on calcium and bone metabolism, but its influence on other organs (extraskeletal effect) has been proposed. Consistently, vitamin D deficiency is associated with an increased incidence of various diseases, including type 1 and type 2 diabetes, as reported by many observational studies. However, there has been no consensus on whether vitamin D deficiency is a causative factor in the incidence of diabetes mellitus. There have been no randomized controlled trials (RCTs) aimed at preventing the onset of type 1 diabetes with vitamin D intake. In addition, the results of RCTs evaluating the preventive effect of vitamin D supplementation on type 2 diabetes development have been inconsistent. The recent observational studies, randomized controlled trials, and meta-analyses are confirming that vitamin D or active vitamin D administration is effective in preventing the incident of type 1 and type 2 diabetes.

Vitamin D and human health: evidence from Mendelian randomization studies

We summarized the current evidence on vitamin D and major health outcomes from Mendelian randomization (MR) studies. PubMed and Embase were searched for original MR studies on vitamin D in relation to any health outcome from inception to September 1, 2022. Nonlinear MR findings were excluded due to concerns about the validity of the statistical methods used. A meta-analysis was preformed to synthesize study-specific estimates after excluding overlapping samples, where applicable. The methodological quality of the included studies was evaluated according to the STROBE-MR checklist. A total of 133 MR publications were eligible for inclusion in the analyses. The causal association between vitamin D status and 275 individual outcomes was examined. Linear MR analyses showed genetically high 25-hydroxyvitamin D (25(OH)D) concentrations were associated with reduced risk of multiple sclerosis incidence and relapse, non-infectious uveitis and scleritis, psoriasis, femur fracture, leg fracture, amyotrophic lateral sclerosis, anorexia nervosa, delirium, heart failure, ovarian cancer, non-alcoholic fatty liver disease, dyslipidemia, and bacterial pneumonia, but increased risk of Behçet's disease, Graves' disease, kidney stone disease, fracture of radium/ulna, basal cell carcinoma, and overall cataracts. Stratified analyses showed that the inverse association between genetically predisposed 25(OH)D concentrations and multiple sclerosis risk was significant and consistent regardless of the genetic instruments GIs selected. However, the associations with most of the other outcomes were only pronounced when using genetic variants not limited to those in the vitamin D pathway as GIs. The methodological quality of the included MR studies was substantially heterogeneous. Current evidence from linear MR studies strongly supports a causal role of vitamin D in the development of multiple sclerosis. Suggestive support for a number of other health conditions could help prioritize conditions where vitamin D may be beneficial or harmful.

Vitamin D and Dyslipidemia: Is There Really a Link? A Narrative Review

Nowadays, the interest in the extraskeletal effects of vitamin D is growing. In the literature, its several possible actions have been confirmed. Vitamin D seems to have a regulatory role in many different fields-inflammation, immunity, and the endocrine system-and many studies would demonstrate a possible correlation between vitamin D and cardiovascular disease. In this paper, we deepened the relationship between vitamin D and dyslipidemia by reviewing the available literature. The results are not entirely clear-cut: on the one hand, numerous observational studies suggest a link between higher serum vitamin D levels and a beneficial lipid profile, while on the other hand, interventional studies do not demonstrate a significant effect. Understanding the possible relationship between vitamin D and dyslipidemia may represent a turning point: another link between vitamin D and the cardiovascular system.

Vitamin D status, vitamin D receptor polymorphisms, and risk of type 2 diabetes: A prospective cohort study

CONTEXT

Vitamin D status has been associated with risk of type 2 diabetes (T2D), but evidence is scarce regarding whether such relation differs by glycemic status.

OBJECTIVE

To prospectively investigate the association between serum 25-hydroxyvitamin D [25(OH)D] and risk of incident T2D across the glycemic spectrum and the modification effect of genetic variants in vitamin D receptor (VDR).

METHODS

This prospective study included 379,699 participants without T2D at baseline from the UK Biobank. Analyses were performed according to glycemic status and HbA1c levels. Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% CIs.

RESULTS

During a median of 14.1 years of follow-up, 6,315 participants with normoglycemia and 9,085 prediabetes patients developed T2D. Compared to individuals with 25(OH)D <25 nmol/L, the multivariable-adjusted hazard ratios (95% CIs) of incident T2D for those with 25(OH)D ≥75 nmol/L was 0.62 (0.56, 0.70) among the normoglycemia and 0.64 (0.58, 0.70) among the prediabetes. A significant interaction was observed between 25(OH)D and VDR polymorphisms among participants with prediabetes (Pinteraction=0.017), whereby the reduced HR of T2D associated with higher 25(OH)D was more prominent in those carrying T allele of rs1544410. Triglycerides levels mediated 26% and 34% of the association between serum 25(OH)D and incident T2D among participants with normoglycemia and prediabetes.

CONCLUSIONS

Higher serum 25(OH)D concentrations were associated with lower T2D risk across the glycemic spectrum below the threshold for diabetes, and the relations in prediabetes were modified by VDR polymorphisms. Improving lipid profile, mainly triglycerides, accounted for part of the favorable associations.

Preservation of β-Cells as a Therapeutic Strategy for Diabetes

The preservation of pancreatic islet β-cells is crucial in diabetes mellitus, encompassing both type 1 and type 2 diabetes. β-cell dysfunction, reduced mass, and apoptosis are central to insufficient insulin secretion in both types. Research is focused on understanding β-cell characteristics and the factors regulating their function to develop novel therapeutic approaches. In type 1 diabetes (T1D), β-cell destruction by the immune system calls for exploring immunosuppressive therapies, non-steroidal anti-inflammatory drugs, and leukotriene antagonists. Islet transplantation, stem cell therapy, and xenogeneic transplantation offer promising strategies for type 1 diabetes treatment. For type 2 diabetes (T2D), lifestyle changes like weight loss and exercise enhance insulin sensitivity and maintain β-cell function. Additionally, various pharmacological approaches, such as cytokine inhibitors and protein kinase inhibitors, are being investigated to protect β-cells from inflammation and glucotoxicity. Bariatric surgery emerges as an effective treatment for obesity and T2D by promoting β-cell survival and function. It improves insulin sensitivity, modulates gut hormones, and expands β-cell mass, leading to diabetes remission and better glycemic control. In conclusion, preserving β-cells offers a promising approach to managing both types of diabetes. By combining lifestyle modifications, targeted pharmacological interventions, and advanced therapies like stem cell transplantation and bariatric surgery, we have a significant chance to preserve β-cell function and enhance glucose regulation in diabetic patients.

Vitamin D and cardiovascular diseases

Vitamin D has an established role in calcium homeostasis but its deficiency is emerging also as a new risk factor for cardiovascular disease (CVD). In particular, several epidemiological and clinical studies have reported a close association between low vitamin D levels and several cardiovascular risk factors and major CVDs, such as coronary artery disease, heart failure, and cardiac arrhythmias. In all these clinical settings, vitamin D deficiency seems to predispose to increased morbidity, mortality, and recurrent cardiovascular events. Despite this growing evidence, interventional trials with supplementation of vitamin D in patients at risk of or with established CVD are still controversial. In this chapter, we summarize the currently available evidence on the links between vitamin D deficiency and major cardiovascular risk factors and CVD, in terms of both clinical relevance and potential therapeutic implications.

Vitamin D supplementation modulates glycated hemoglobin (HBA1c) in diabetes mellitus

Diabetes is a metabolic illness that increases protein glycosylation in hyperglycemic conditions, which can have an impact on almost every organ system in the body. The role of vitamin D in the etiology of diabetes under RAGE (receptor for advanced glycation end products) stress has recently received some attention on a global scale. Vitamin D's other skeletal benefits have generated a great deal of research. Vitamin D's function in the development of type 1 and type 2 diabetes is supported by the discovery of 1,25 (OH)2D3 and 1-Alpha-Hydroylase expression in immune cells, pancreatic beta cells, and several other organs besides the bone system. A lower HBA1c level, metabolic syndrome, and diabetes mellitus all seems to be associated with vitamin D insufficiency. Most of the cross-sectional and prospective observational studies that were used to gather human evidence revealed an inverse relationship between vitamin D level and the prevalence or incidence of elevated HBA1c in type 2 diabetes. Several trials have reported on the impact of vitamin D supplementation for glycemia or incidence of type 2 diabetes, with varying degrees of success. The current paper examines the available data for a relationship between vitamin D supplementation and HBA1c level in diabetes and discusses the biological plausibility of such a relationship.

Cardiovascular and Cerebrovascular Outcomes With Vitamin D Supplementation: A Systematic Review and Meta-Analysis

Vitamin D supplementation has seen a sharp increase in the primary healthcare setting but its efficacy in decreasing the risk of cardiovascular and cerebrovascular events is yet to be reliably established. We aim to determine whether vitamin D supplementation can significantly impact the risk of cardiovascular and cerebrovascular events. An extensive literature search of PubMed, Embase, and Cochrane CENTRAL was conducted from inception till August 2023 to include all the articles comparing vitamin D and placebo. Cardiovascular and cerebrovascular outcomes were presented as risk ratios (RR) with 95% confidence intervals (CIs) and pooled using a random effects model. Thirty-six trials consisting of 493,389 participants were included in our analysis. Our pooled analysis demonstrated no significant difference between vitamin D supplementation and placebo for the risk of cardiovascular mortality (RR 1.01, 95% CI 0.94-1.08; P = 0.80), stroke or cerebrovascular events (RR 1.03, 95% CI 0.95-1.11; P = 0.48), myocardial infarction (MI) (RR 0.98, 95% CI 0.91-1.06; P = 0.65), cerebrovascular mortality (RR 1.00, 95% CI 0.68-1.46; P = 0.99), arrhythmias (RR 0.98, 95% CI 0.66-1.44; P = 0.90) and hemorrhagic or ischemic stroke. There was no significant heterogeneity between the studies in any analysis. There was no significant difference in the risk of cardiovascular and cerebrovascular outcomes with vitamin D supplementation or placebo. Additional large high-powered studies focused on high-risk and vitamin D-deficient populations are required to resolve the current discrepancy in the literature and provide a definitive conclusion to this end.

Vitamin D Supplementation and Cardiovascular Disease Risks in More Than 134000 Individuals in 29 Randomized Clinical Trials and 157000 Individuals in 30 Prospective Cohort Studies: An Updated Systematic Review and Meta-analysis

BACKGROUND

According to the findings from observational studies and clinical trials assessing the effect of vitamin D supplements on cardiovascular diseases (CVDs), there are still contradictory results. This systematic review aimed to assess the effect of vitamin D supplements on CVDs considering cohort studies and clinical trials. Study Design: A systematic review.

METHODS

MEDLINE/PubMed, Science Direct, Embase, and Cochrane Library databases were reviewed by two reviewers independently until 2022. The study effect is risk ratio (RR) and 95% confidence interval (CI) according to Mantel Haenszel's random-effects model. Then, Stata version 14 was used for statistical analysis.

RESULTS

In clinical trial studies, the incidence of CVDs among the vitamin D-consuming group was not significantly different from that in the placebo group (RR: 0.99, 95% CI: 0.95-1.03; P=0.77; I 2=0%). CVD mortality was also not significantly different between the two groups (RR: 0.97, 95% CI: 0.90-1.05; P=0.72; I2=0%). In cohort studies, circulating 25 (OH) D increased the risk of CVD incidence by 31% (RR: 1.31, 95% CI: 1.19-1.45) and CVD mortality by 37% (RR: 1.37, 95% CI: 1.17-1.61).

CONCLUSION

According to current evidence from clinical trials, vitamin D supplementation should not be recommended for CVD prevention. However, there is a direct association between vitamin D deficiency and the incidence of CVDs as well as its mortality. According to the results of clinical trial studies carrying higher levels of scientific evidence, it can be concluded that vitamin D supplementation does not exert a significant effect on the incidence, mortality, and reduction of CVDs.

Cross-sectional study of the associations between circulating vitamin D concentrations and insulin resistance in children aged 9-10 years of South Asian, black African Caribbean and white European origins

BACKGROUND

Lower circulating vitamin D 25-hydroxyvitamin D (25(OH)D) concentrations are associated with higher type 2 diabetes risk in adults, although causality remains uncertain. However, associations between 25(OH)D and type 2 diabetes risk markers in children have been little studied, particularly in ethnic minority populations. We examined whether 25(OH)D concentrations were associated with insulin resistance in children and whether lower 25(OH)D concentrations in South Asians and black African Caribbeans could contribute to their higher insulin resistance.

METHODS

Cross-sectional study of 4650 UK primary school children aged 9-10 years of predominantly South Asian, black African Caribbean and white European ethnicity. Children had fasting blood measurements of circulating 25(OH)D metabolite concentrations, insulin and glucose.

RESULTS

Lower 25(OH)D concentrations were observed in girls, South Asians and black African Caribbeans. In analyses adjusted for age, sex, month, ethnic group and school, circulating 25(OH)D was inversely associated with fasting insulin (-0.38%, 95% CI -0.49% to -0.27%), homoeostasis model assessment (HOMA) insulin resistance (-0.39%, 95% CI -0.50% to -0.28%) and fasting glucose (-0.03%, 95% CI -0.05% to -0.02%) per nmol/L increase in 25(OH)D; associations did not differ between ethnic groups. Ethnic differences in fasting insulin and HOMA insulin resistance (higher among South Asian and black African Caribbeans) were reduced by >40% after adjustment for circulating 25(OH)D concentrations.

CONCLUSION

Circulating vitamin D was inversely associated with insulin resistance in all ethnic groups; higher insulin resistance in South Asian and black African children were partly explained by their lower vitamin D levels. Whether vitamin D supplementation can reduce emerging type 2 diabetes risk needs further evaluation.

Vitamin D and Metabolic Syndrome in Working Age Subjects from an Obesity Clinic

Serum vitamin D (VitD) levels have been inversely related with metabolic syndrome (MetS), although the direct impact of VitD is still debated. This study examined 879 subjects of working age from an obesity and occupational clinic in Milan, Italy. Among these participants, 316 had MetS, while 563 did not. A multiple logistic regression analysis was conducted to determine the odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) for MetS in relation to serum VitD levels. After controlling for age, sex, leisure time physical activity, and body mass index (BMI), individuals with VitD levels between 20 and 29.9 ng/dL, or at least 30 ng/dL, had approximately half the risk of developing MetS (OR: 0.52, 95% CI: 0.32-0.86 and OR: 0.50, 95% CI: 0.25-0.99, respectively) compared to those with VitD levels below 10 ng/dL. This study presents further evidence of the beneficial effect of adequate VitD levels on the risk of MetS in a population of overweight/obese workers, even after adjusting for BMI. This study supports the importance of testing for and-if required-supplementing VitD in individuals with metabolic risk factors.

Serum 25(OH)D Concentration, Vitamin D Supplementation, and Risk of Cardiovascular Disease and Mortality in Patients with Type 2 Diabetes or Prediabetes: a Systematic Review and Dose-Response Meta-Analysis

BACKGROUND

Evidence is uncertain about the association between serum 25-hydroxyvitamin D (25(OH)D) concentration and health outcomes in people with type 2 diabetes.

OBJECTIVES

We aimed to assess the association between vitamin D status and all-cause mortality and cardiovascular disease in people with type 2 diabetes.

METHODS

We did a systematic search in PubMed, Scopus, CENTRAL, and Web of Science until May 2022. We selected 1) cohort studies investigating the association between serum 25(OH)D concentration and mortality or cardiovascular disease in people with type 2 diabetes or prediabetes and 2) randomized trials of vitamin D supplementation in these patients. We used random-effects pairwise meta-analyses to calculate summary relative risks (RRs) and 95% confidence intervals (CI).

RESULTS

21 cohort studies and 6 randomized trials were included. Compared with sufficient vitamin D status (≥50 nmol/L), the RR of all-cause mortality was 1.36 (95% CI: 1.23, 1.49; n = 11 studies, GRADE = moderate) for vitamin D insufficiency (25 to <50 nmol/L), and 1.58 (1.33, 1.83; n = 16, GRADE = moderate) for deficiency (<25 nmol/L). Similar findings were observed for cardiovascular mortality and morbidity but not for cancer mortality. The certainty of evidence ranged from very low to moderate. Dose-response meta-analyses indicated nonlinear associations, with the lowest risk at 25(OH)D ∼60 nmol/L for all-cause and cardiovascular mortality. Supplementation with vitamin D did not reduce the risk of all-cause mortality (RR: 0.96, 95% CI: 0.79, 1.16; risk difference per 1000 patients: 3 fewer, 95% CI: 16 fewer, 12 more; n = 6 trials with 7316 participants; GRADE = low) or the risk of cardiovascular mortality and morbidity (very low- to low-certainty evidence).

CONCLUSIONS

Vitamin D deficiency and insufficiency are associated with a higher risk of all-cause and cardiovascular mortality in patients with type 2 diabetes or prediabetes. Vitamin D deficiency should be corrected in patients with type 2 diabetes to reach normal serum 25(OH)D concentrations, preferably 60 nmol/L.

SYSTEMATIC REVIEW REGISTRATION

This systemic review was registered at PROSPERO as CRD42022326429 (=https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=326429).

Effect of vitamin D on regression to normal glucose regulation and individual glycemic measures: A secondary analysis among participants adherent to the trial protocol in the randomized clinical trial vitamin D and type 2 diabetes (D2d) study

AIMS

To examine the effect of vitamin D on regression to normal glucose regulation (NGR) and individual glycemic measures in the D2d study.

METHODS

In per-protocol analyses, we examined time to new-onset diabetes; time to new-onset NGR defined as first occurrence of: 2-or-3 glycemic criteria in the normal range (NGR-1) or fasting plasma glucose (FPG) and 2-hour post-load-glucose (2hPG) in the normal range (NGR-2); proportion meeting NGR at the last study visit; and change in FPG, 2hPG, and HbA1c.

RESULTS

Among 2423 participants, hazard ratio [HR] for diabetes was 0.84 [95%CI, 0.71, 0.99]). HR (95%CI) was 1.16 (0.99, 1.36) for new-onset NGR-1 and 1.06 (0.87, 1.30) for NGR-2. At the last visit, NGR-1 occurred in 12.4% vs. 9.5% participants in the vitamin D vs. placebo group (rate ratio for vitamin D 1.31 [1.02, 1.70]); whereas, NGR-2 occurred in 8.7% vs. 6.0% (rate ratio for vitamin D 1.45 [1.05, 2.00]). During follow-up, FPG, HbA1c, and 2hPG increased in both groups. Mean difference in FPG favored vitamin D (-0.80 mg/dL; 95%CI, -1.26, -0.33).

CONCLUSIONS

In secondary analyses among participants adherent to the trial protocol, vitamin D lowered risk of developing diabetes and increased likelihood of NGR at the end of the study.

Serum and supplemental vitamin D levels and insulin resistance in T2DM populations: a meta-analysis and systematic review

Observational studies have shown a negative correlation between Vitamin D level and the likelihood of developing insulin resistance (IR) and/or diabetes over time, yet evidence remains inconsistent. In this meta-analysis and systematic review, we strive to define the potential association between serum or supplemental Vitamin D Levels and insulin resistance respectively, as well as the contribution of Vitamin D to type 2 diabetes, and to summarize the biologic plausibility of Vitamin D. Four databases (PubMed, Embase, Cochrane Library, and Web of Science) were searched for this Systematic Literature Review (SLR) to find appropriate observational studies and clinical trials published in English through to July 2022. EndNote (version X9) is used to manage the literature search results. We calculated Standard Mean Differences (SMDs) and Risk Ratios (RRs) with their 95% Confidence Intervals (CIs), separately, for continuous and dichotomous outcomes. The correlation coefficients were normalized to z values through Fisher's z-transformation to calculate the relevant statistics. Meta-analyses were carried out for all comparisons, based on a random-effects pooling model. Data analysis was performed using RevMan (version 5.3) and STATA (version 15.1). All statistical tests were two-sided, with P < 0.05 were regarded as significant. In our current meta-analysis, there are 18 RCTs and 20 observational studies including 1243 and 11,063 participants respectively. In the overall analysis, the diabetic with Vitamin D supplement treatment group showed significantly improve serum insulin (SMD =  - 0.265, 95% CI - 0.394 to - 0.136, P < 0.05), glucose (SMD =  - 0.17, 95% CI - 0.301to - 0.039, P < 0.05) and HOMA-IR (SMD =  - 0.441, 95% CI - 0.582 to - 0.3, P < 0.05) compared with the routine treatment group. Correlation analysis results showed that all three outcomes were significantly correlated in a negative manner with raised Vitamin D (insulin: r =  - 0.08 95% =  - 0.12 to - 0.04; glucose: r =  - 0.06 95% =  - 0.11 to - 0.01; HOMA-IR: r =  - 0.08 95% =  - 0.09 to - 0.06). Results of overall analysis proved that vitamin D has shown significant effect on regulates insulin resistance, and there is a significant inverse association between serum Vitamin D level and IR. Vitamin D supplementation is expected to be integrated into conventional medical approaches to prevent type 2 diabetes and to mitigate the burden of diabetes for individuals and society.PROSPERO registration number: CRD42022348295.

The effects of vitamin D on all-cause mortality in different diseases: an evidence-map and umbrella review of 116 randomized controlled trials

Purpose

To conduct a solid evidence by synthesizing meta-analyses and updated RCTs about the effects of vitamin D on all-cause mortality in different health conditions.

Methods

Data sources: Pubmed, Embase, Web of Science, the Cochrane Library, Google Scholar from inception until 25th April, 2022. Study selection: English-language, meta-analyses and updated RCTs assessing the relationships between vitamin D and all-cause mortality. Data synthesis: Information of study characteristics, mortality, supplementation were extracted, estimating with fixed-effects model. A Measurement Tool to Assess Systematic Reviews, Grading of Recommendations Assessment, Development and Evaluation, and funnel plot was used to assess risk of bias. Main outcomes: All-cause mortality, cancer mortality, cardiovascular disease mortality.

Results

In total of 27 meta-analyses and 19 updated RCTs were selected, with a total of 116 RCTs and 149, 865 participants. Evidence confirms that vitamin D reduces respiratory cancer mortality (RR, 0.56 [95%CI, 0.33 to 0.96]). All-cause mortality is decreased in patients with COVID-19 (RR, 0.54[95%CI, 0.33 to 0.88]) and liver diseases (RR, 0.64 [95%CI, 0.50 to 0.81]), especially in liver cirrhosis (RR, 0.63 [95%CI, 0.50 to 0.81]). As for other health conditions, such as the general health, chronic kidney disease, critical illness, cardiovascular diseases, musculoskeletal diseases, sepsis, type 2 diabetes, no significant association was found between vitamin D and all-cause mortality.

Conclusions

Vitamin D may reduce respiratory cancer mortality in respiratory cancer patients and all-cause mortality in COVID-19 and liver disorders' patients. No benefits showed in all-cause mortality after vitamin D intervention among other health conditions. The hypothesis of reduced mortality with vitamin D still requires exploration.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=252921, identifier: CRD42021252921.

Vitamin D Supplementation and Its Impact on Mortality and Cardiovascular Outcomes: Systematic Review and Meta-Analysis of 80 Randomized Clinical Trials

BACKGROUND

The impact of vitamin D supplementation on cardiovascular outcomes and mortality risk reduction remains unclear due to conflicting study findings.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs), published between 1983 and 2022, that reported the effect of vitamin D supplementation in adults versus placebo or no treatment on all-cause mortality (ACM), cardiovascular mortality (CVM), non-cardiovascular mortality (non-CVM), and cardiovascular morbidities. Only studies with a follow-up period longer than one year were included. The primary outcomes were ACM and CVM. Secondary outcomes were non-CVM, myocardial infarction, stroke, heart failure, and major or extended adverse cardiovascular events. Subgroup analyses were performed according to low-, fair- and good-quality RCTs.

RESULTS

Eighty RCTs were assessed, including 82,210 participants receiving vitamin D supplementation and 80,921 receiving placebo or no treatment. The participants' mean (SD) age was 66.1 (11.2) years, and 68.6% were female. Vitamin D supplementation was associated with a lower risk of ACM (OR: 0.95 [95%CI 0.91-0.99] p = 0.013), was close to statistical significance for a lower risk of non-CVM (OR: 0.94 [95%CI 0.87-1.00] p = 0.055), and was not statistically associated with a lower risk of any cardiovascular morbi-mortality outcome. Meta-analysis of low-quality RCTs showed no association with cardiovascular or non-cardiovascular morbi-mortality outcomes.

CONCLUSIONS

The emerging results of our meta-analysis present evidence that vitamin D supplementation appears to decrease the risk of ACM (especially convincing in the fair- and good-quality RCTs), while not showing a decrease in the specific cardiovascular morbidity and mortality risk. Thus, we conclude that further research is warranted in this area, with well-planned and executed studies as the basis for more robust recommendations.

Vitamin D: 100 years of discoveries, yet controversy continues

Over the past 100 years, many major breakthroughs and discoveries have occurred in relation to vitamin D research. These developments include the cure of rickets in 1919, the discovery of vitamin D compounds, advances in vitamin D molecular biology, and improvements in our understanding of endocrine control of vitamin D metabolism. Furthermore, recommended daily allowances for vitamin D have been established and large clinical trials of vitamin D, aimed at clarifying the effect of Vitamin D in the prevention of multiple diseases, have been completed. However, disappointingly, these clinical trials have not fulfilled the expectations many had 10 years ago. In almost every trial, various doses and routes of administration did not show efficacy of vitamin D in preventing fractures, falls, cancer, cardiovascular diseases, type 2 diabetes, asthma, and respiratory infections. Although concerns about side-effects of long-term high-dose treatments, such as hypercalcaemia and nephrocalcinosis, have been around for four decades, some trials from the past 5 years have had new and unexpected adverse events. These adverse events include increased fractures, falls, and hospitalisations in older people (aged >65 years). Several of these clinical trials were powered appropriately for a primary outcome but did not include dose response studies and were underpowered for secondary analyses. Furthermore, more attention should be paid to the safety of high doses of vitamin D supplementation, particularly in older people. In addition, despite universal recommendations by osteoporosis societies for combining calcium supplements with vitamin D there remains insufficient data about their efficacy and effect on fracture risk in the highest risk groups. More trials are needed for people with severe vitamin D deficiency (ie, serum 25-hydroxyvitamin D <25nmol/L [10ng/mL]). In this Personal View, we summarise and discuss some of the major discoveries and controversies in the field of vitamin D.

The Effect of Vitamin D Supplementation on Incidence of Type 2 Diabetes: A Systematic Review

With the clinical increase in Type 2 Diabetes worldwide, several interventions to decrease its incidence have been investigated. One such intervention is Vitamin D supplementation, as it affects Insulin secretion from the pancreas and Insulin receptors in the cells of the body. This systematic review addresses whether or not Vitamin D supplementation has a role in reducing the risk of developing Type 2 Diabetes. Systematic searches were conducted on PubMed, and Cochrane Library mainly but also checked Google Scholar. Randomized controlled trials, systematic trials and cohort studies were retrieved that included keywords pertaining to Vitamin D supplementation and the incidence of Type 2 Diabetes. Exclusion criteria included studies that looked at different forms of Diabetes, studies including patients aged less than 18 or more than 85 years of age and studies that were not English language. For all the trials identified, the incidence of Type 2 Diabetes among the cohort receiving vitamin D supplementation was compared to the cohort receiving placebo medication. Additionally, the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) was analyzed to observe if there was a difference between Insulin resistance among these two cohorts between the start of the trials and the end. Thirteen randomized controlled trials were identified. Seven of these identified incidences of Type 2 Diabetes as a research outcome, out of which six showed no statistically significant impact of vitamin D on the incidence of Type 2 Diabetes. Out of the 13 trials, 10 analyzed the impact of vitamin D supplementation on patients' HOMA-IR. In six of these trials, patients receiving vitamin D supplementation had a decrease in their HOMA-IR, while it increased in 4 trials. In seven of the ten trials that analyzed for HOMA-IR, the HOMA-IR was less in the vitamin D cohort than the placebo cohort. There is insufficient evidence to suggest that vitamin D supplementation significantly reduces the incidence of Type 2 Diabetes despite its effects on insulin resistance. Further research in this area would be helpful in order to influence clinical guidelines on vitamin D supplementation among patients at risk of Type 2 Diabetes.

Pharmacological inhibitors of β-cell dysfunction and death as therapeutics for diabetes

More than 500 million adults suffer from diabetes worldwide, and this number is constantly increasing. Diabetes causes 5 million deaths per year and huge healthcare costs per year. β-cell death is the major cause of type 1 diabetes. β-cell secretory dysfunction plays a key role in the development of type 2 diabetes. A loss of β-cell mass due to apoptotic death has also been proposed as critical for the pathogenesis of type 2 diabetes. Death of β-cells is caused by multiple factors including pro-inflammatory cytokines, chronic hyperglycemia (glucotoxicity), certain fatty acids at high concentrations (lipotoxicity), reactive oxygen species, endoplasmic reticulum stress, and islet amyloid deposits. Unfortunately, none of the currently available antidiabetic drugs favor the maintenance of endogenous β-cell functional mass, indicating an unmet medical need. Here, we comprehensively review over the last ten years the investigation and identification of molecules of pharmacological interest for protecting β-cells against dysfunction and apoptotic death which could pave the way for the development of innovative therapies for diabetes.

Effects of vitamin D supplementation on the regulation of blood lipid levels in prediabetic subjects: A meta-analysis

This meta-analysis aimed to systematically investigate whether vitamin D supplementation reduces blood lipid—total cholesterol (TC), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), and triglyceride (TG)—levels in prediabetic individuals. Pubmed, Web of Science, Cochrane Library, Embase, CNKI, and WANFANG databases were searched for studies published before 13 February 2022 (including 13 February 2022). Five articles were included. The results showed that vitamin D intervention led to a significant reduction in TG compared with control or placebo treatment (−0.42 [−0.59, −0.25], P &lt; 0.001). Subgroup analyses showed that this effect was particularly significant among the studies that included obese subjects (−0.46 [−0.65, −0.28], P &lt; 0.001), the studies that also included men (not only women) (−0.56 [−0.78, −0.34], P &lt; 0.001), and the studies with intervention durations longer than 1 year (−0.46 [−0.65, −0.28], P &lt; 0.001). Both relatively low doses of 2,857 IU/day (−0.65 [−0.92, −0.38], P &lt; 0.001) and relatively high doses of 8,571 IU/day (−0.28 [−0.54, −0.02] P = 0.04) of vitamin D supplementation reduced TG levels, and the effect was observed both in Northern Europe (−0.65 [−0.92, −0.38], P &lt; 0.001) and Asian (−0.25 [−0.48, −0.03], P = 0.03) country subgroups. No significant effects on TC, HDL-C, and LDL-C were shown. In conclusion, vitamin D supplementation might beneficially affect TG levels in individuals with prediabetes. Particularly longer durations of treatment, more than 1 year, with doses that correct vitamin deficiency/insufficiency, can have a beneficial effect. This meta-analysis was registered at www.crd.york.ac.uk/prospero (CRD42020160780).

Vitamin D and Risk for Type 2 Diabetes in People With Prediabetes : A Systematic Review and Meta-analysis of Individual Participant Data From 3 Randomized Clinical Trials

BACKGROUND

The role of vitamin D in people who are at risk for type 2 diabetes remains unclear.

PURPOSE

To evaluate whether administration of vitamin D decreases risk for diabetes among people with prediabetes.

DATA SOURCES

PubMed, Embase, and ClinicalTrials.gov from database inception through 9 December 2022.

STUDY SELECTION

Eligible trials that were specifically designed and conducted to test the effects of oral vitamin D versus placebo on new-onset diabetes in adults with prediabetes.

DATA EXTRACTION

The primary outcome was time to event for new-onset diabetes. Secondary outcomes were regression to normal glucose regulation and adverse events. Prespecified analyses (both unadjusted and adjusted for key baseline variables) were conducted according to the intention-to-treat principle.

DATA SYNTHESIS

Three randomized trials were included, which tested cholecalciferol, 20 000 IU (500 mcg) weekly; cholecalciferol, 4000 IU (100 mcg) daily; or eldecalcitol, 0.75 mcg daily, versus matching placebos. Trials were at low risk of bias. Vitamin D reduced risk for diabetes by 15% (hazard ratio, 0.85 [95% CI, 0.75 to 0.96]) in adjusted analyses, with a 3-year absolute risk reduction of 3.3% (CI, 0.6% to 6.0%). The effect of vitamin D did not differ in prespecified subgroups. Among participants assigned to the vitamin D group who maintained an intratrial mean serum 25-hydroxyvitamin D level of at least 125 nmol/L (≥50 ng/mL) compared with 50 to 74 nmol/L (20 to 29 ng/mL) during follow-up, cholecalciferol reduced risk for diabetes by 76% (hazard ratio, 0.24 [CI, 0.16 to 0.36]), with a 3-year absolute risk reduction of 18.1% (CI, 11.7% to 24.6%). Vitamin D increased the likelihood of regression to normal glucose regulation by 30% (rate ratio, 1.30 [CI, 1.16 to 1.46]). There was no evidence of difference in the rate ratios for adverse events (kidney stones: 1.17 [CI, 0.69 to 1.99]; hypercalcemia: 2.34 [CI, 0.83 to 6.66]; hypercalciuria: 1.65 [CI, 0.83 to 3.28]; death: 0.85 [CI, 0.31 to 2.36]).

LIMITATIONS

Studies of people with prediabetes do not apply to the general population. Trials may not have been powered for safety outcomes.

CONCLUSION

In adults with prediabetes, vitamin D was effective in decreasing risk for diabetes.

PRIMARY FUNDING SOURCE

None. (PROSPERO: CRD42020163522).

Controversial Impact of Vitamin D Supplementation on Reducing Insulin Resistance and Prevention of Type 2 Diabetes in Patients with Prediabetes: A Systematic Review

BACKGROUND

Prediabetes has become a worldwide health problem. Multiple clinical trials have been conducted to determine the potential benefits of vitamin D supplementation in preventing the conversion to diabetes, but the results are inconsistent. The aims of this study were to evaluate the current knowledge and to suggest recommendations for researchers on designing future trials regarding that matter.

METHODS

Four databases were searched for randomized control trials from the last 10 years about vitamin D and insulin resistance. The systematic electronic literature search identified 2645 studies, of which thirty-eight qualified for full-text reading and discussion. Finally, eight trials were included.

RESULTS

Final results of seven trials reported that supplementation of vitamin D does not reduce insulin resistance nor reduces the risk of diabetes mellitus type 2 development in prediabetes. Only one trial showed improvements in fasting glucose and HOMA-IR.

CONCLUSIONS

Due to the great variation and biases in study designs, an unambiguous interpretation of the results is not possible. To eliminate those vulnerabilities in the future, we made certain suggestions for study design. Long-term and well-designed studies are still required.

Vitamin D, Gut Microbiota, and Cardiometabolic Diseases-A Possible Three-Way Axis

Metabolic syndrome (MetSyn) is a precursor for several cardiometabolic diseases such as obesity, type-2 diabetes mellitus (T2DM), and cardiovascular diseases. Emerging evidence suggests that vitamin D deficiency links to cardiometabolic diseases through microbiota. A combination of poor vitamin D status and dysbiosis may contribute to the progression of cardiometabolic diseases. Therefore, in this review, we present the relationship among vitamin D, microbiota, and cardiometabolic diseases with a focus on MetSyn. We searched major databases for reports on vitamin D, microbiota, and MetSyn until June 2022. We reviewed 13 reports on the relation between vitamin D and MetSyn (6 randomized controlled and 7 cross-sectional studies) and 6 reports on the effect of vitamin D on the gut microbiome. Adequate vitamin D status has a beneficial effect on gut microbiota, therefore preventing the progression of MetSyn. Further, well-controlled studies are needed for a better understanding of the mechanisms of action involving vitamin D and microbiota in the pathogenesis of cardiometabolic diseases.

Vitamin D in the older population: a consensus statement

BACKGROUND

This paper reports results from the 5th International Conference "Controversies in Vitamin D" that was held in Stresa, Italy, 15-18 September 2021. The conference is part of this series that started in 2017 and has been conducted annually since. The objective of these conferences is to identify timely and controversial topics related to Vitamin D. Dissemination of the results of the conference through publications in peer-reviewed journals is an important means by which the most up to date information can be shared with physicians, investigators, and other health care professionals. Vitamin D and aging, the subject of this paper was featured at the conference.

METHODS

Participants were selected to review available literature on assigned topics related to vitamin D and aging and to present their findings with illustrative material, the intent of which was to stimulate discussion and to arrive at a consensus. The presentations were directed towards the following areas: impact of aging on vitamin D production and levels; skeletal effects of vitamin D deficiency in the older population; falls and vitamin D in the aging; potential extra skeletal effects of vitamin D; and strategies to prevent vitamin D deficiency. A final topic was related to how vitamin D might influence the efficacy of vaccines for Covid-19.

RESULTS

Hypovitaminosis D can lead to several skeletal and extra-skeletal outcomes. Older adults are at risk for vitamin D deficiency as both production and metabolism of vitamin D change with aging due to factors, such as reduced sun exposure and reduced production capacity of the skin. Skeletal consequences of these age-related changes can include reduced bone mineral density, osteomalacia and fractures. Potential extra-skeletal effects can include added risks for falls, reduced muscle strength, diabetes, cancer, and cardiovascular disease. Strategies to avoid these vitamin D deficiency-related negative outcomes include sun exposure, food fortification, and supplementation. While aging does not diminish sufficient reserve capacity for cutaneous vitamin D production, concerns about skin cancers and practical matters for the institutionalized elderly limit this option. Supplementation with vitamin D is the best option either pharmacologically or through food fortification. Regardless of treatment strategies, interventions to restore sufficient vitamin D status will show positive results only in those who are truly deficient. Thus, treatment goals should focus on avoiding 25(OH)D serum levels <30 nmol/l, with a goal to reach levels >50 nmol/l.

CONCLUSIONS

The results of this conference has led to consensus on several issues. Vitamin D supplementation should be combined with calcium to reduce fractures in the older population. The goal for adequate Vitamin D status should be to reach a serum level of 25(OH)D >50 nmol/l. It appears that daily low-dose vitamin D regimens reduce the risk of falling, especially in the elderly, compared with infrequent, large bolus doses that may increase it. The role of Vitamin D supplementation on muscle strength remains to be clarified. On the other hand, supplementation decreases the risk of progression to T2D from prediabetes among those who are Vitamin Ddeficient. Of three possible strategies to establish vitamin D sufficiency - sunshine exposure, food fortification, and supplementation - the latter seems to be the most effective and practical in the aging population.

Vitamin D supplementation for the prevention of total cancer incidence and mortality: An updated systematic review and meta-analysis

Introduction

Previous randomized controlled trials (RCTs) and meta-analyses of RCTs evaluating vitamin D supplementation for the prevention of cancer incidence and mortality have found inconsistent results and no meta-analysis has assessed the quality of the evidence available. We, therefore, aimed to perform an updated meta-analysis by including recent large-scale RCTs and assessing the quality of the pooled evidence.

Methods

We searched several databases and trial registers from inception to April 2022. We used a random-effects model to estimate pooled risk ratios (RRs) and 95% confidence intervals (CIs). We used the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) considerations to evaluate the certainty of evidence.

Results

We included 13 RCTs in our study. Vitamin D supplementation had no effect on the risk of total cancer incidence (RR 0.99, 95% CI: 0.94-1.04; I 2 = 0%), total cancer mortality (RR 0.93, 95% CI: 0.84-1.03; I 2 = 24%) and total mortality (RR 0.92, 95% CI: 0.82-1.04; I 2 = 36%). The overall quality of evidence was high for all outcomes.

Discussion

Vitamin D supplementation is ineffective in reducing total cancer incidence and mortality in largely vitamin D-replete older adult populations. Future research should be based on populations with a higher prevalence of vitamin D deficiency and should involve more extended follow-up periods.

Study protocol

PROSPERO database, CRD42021285401.

The association of serum vitamin D with incident diabetes in an African American population

BACKGROUND

Incident diabetes risk is inversely proportional to 25-hydroxyvitamin D [25(OH)D] levels among non-Hispanic white but is unclear among African American (AA) populations. Serum 25(OH)D2 may be an important component of total 25(OH)D among AA populations due to higher levels of melanin.

OBJECTIVE

To assess the association of serum 25(OH)D with incident diabetes among AAs and stratify by detectable 25(OH)D2.

DESIGN

Serum 25(OH)D2 and 25(OH)D3 were collected from 2000 to 2004 among AA participants in the Jackson Heart Study. A cosinor model was used to adjust for the seasonality of 25(OH)D3; 25(OH)D3 and 25(OH)D2 were combined to ascertain total 25(OH)D. Incident diabetes (fasting glucose ≥126 mg/dl, use of diabetes drugs, or HbA1c ≥6.5%) was assessed over 12 years among adults without diabetes at baseline. Participants with missing baseline covariates or diabetes follow-up were excluded. Hazard ratios (HR) were estimated using Cox modeling, adjusting for age, sex, education, occupation, smoking, physical activity, alcohol use, aldosterone, and body-mass index.

RESULTS

Among 3311 adults (mean age 53.3 years, 63% female) 584 participants developed diabetes over a median of 7.7 years. After adjustment, 25(OH)D ≥20 compared to <12 ng/ml was associated with a HR 0.78 (95% CI: 0.61, 1.00). Among participants with detectable 25(OH)D2 and 25(OH)D3 (n = 1671), 25(OH)D ≥ 20 ng/ml compared to <12 ng/ml was associated with a 35% (HR 0.65, 95% CI: 0.46, 0.91) lower risk of diabetes.

CONCLUSIONS

Higher levels of 25(OH)D may be protective against the development of diabetes among AA individuals, particularly among those with detectable 25(OH)D2 and 25(OH)D3.

The Progression of Prediabetes to Type 2 Diabetes in Children and Adolescents in the United States: Current Challenges and Solutions

Prediabetes, the precursor of type 2 diabetes (T2D), is on the rise among children and adolescents in the United States. The natural history of prediabetes is poorly characterized in children compared to adults. The available data indicate a phenotype of an accelerated β-cell failure in youth with prediabetes. Data from randomized controlled trials showed no benefit on β-cell preservation or A1c in youth with prediabetes from therapeutic agents such as metformin and insulin. As a result, the American Diabetes Association recommends only lifestyle intervention, but not therapeutic agents, for the management of prediabetes in children and adolescents. These recommendations for lifestyle modification in youth, largely derived from data in adults, lack the precision necessary for efficacy in youth. However, a recent 4-year real-world study on youth reported that adherence to nutrition visits was associated with a 4-fold reduction in the likelihood of progressing from prediabetes to T2D. The finding that this reversal is associated with reduced insulin resistance (IR) and not with decreased body weight is novel and provides the foundation for trialing investigational products that may protect β-cells and reduce IR and/or body weight. This study provides the much-needed foundation for further exploration of the impact of lifestyle modification in conjunction with other approaches for the reversal of prediabetes in youth. The systematization of the protocol for medical nutrition therapy for the reversal of prediabetes in youth will ensure optimal and consistent results from adherent patients. This communication provides updates on the pathobiology of prediabetes in youth and a clear direction for efficacious studies in the field.

Vitamin D, parathyroid hormone, glucose metabolism and incident diabetes in the multiethnic study of atherosclerosis

INTRODUCTION

Higher concentrations of serum 25-hydroxyvitamin D (25(OH)D) and lower concentrations of parathyroid hormone (PTH) are associated with lower insulin resistance and incident diabetes in non-Hispanic White and Hispanic Americans. Results are mixed in other populations, with no observational studies in a large multiethnic cohort. The association of serum 25(OH)D with diabetes may vary by adiposity level.

RESEARCH DESIGN AND METHODS

Among 5611 participants in the Multi-Ethnic Study of Atherosclerosis without diabetes at baseline, cross-sectional associations of serum 25(OH)D with homeostasis model assessment of insulin resistance (HOMA-IR) and HOMA-β were examined using linear regressions. The association of 25(OH)D with incident diabetes over 9 years was examined using Cox proportional hazard regression.

RESULTS

Black Americans had the highest proportion of individuals with 25(OH)D<20 ng/mL (61%) and White Americans had the least (17%). Serum 25(OH)D was inversely associated with HOMA-IR in fully adjusted models (-0.34% difference in HOMA-IR per ng/mL higher 25(OH)D, p<0.0001). Longitudinally, a 1 ng/mL higher serum 25(OH)D was associated with 2% lower risk of incident diabetes (HR 0.982, CI 0.974 to 0.991), and a 1 pg/mL higher serum PTH was associated with 1% higher risk of incident diabetes (HR 1.007, CI 1.004 to 1.010), both prior to adjustment for waist circumference. After adjusting for waist circumference, a 1 ng/mL higher 25(OH)D was associated with 1% lower risk of incident diabetes (HR 0.991, CI 0.983 to 1.000). The magnitude of association of serum 25(OH)D with incident diabetes was largest at lower waist circumference (p for interaction=0.025). There was no heterogeneity by race/ethnicity (p=0.317).

CONCLUSIONS

Serum 25(OH)D is inversely associated with insulin resistance and incident diabetes in a diverse cohort, including non-Hispanic White, Black, Hispanic and Chinese Americans. Future research should explore mechanisms for the interaction between serum 25(OH)D and adiposity in this relationship.

Vitamin D supplementation and risk of stroke: A meta-analysis of randomized controlled trials

Background

Previous observational studies have supported the hypothesis that vitamin D supplementation protects against stroke. However, several current intervention studies contradict this observation. Therefore, we conducted a meta-analysis to investigate further the association between vitamin D supplementation and the risk of stroke.

Methods

This meta-analysis was conducted in accordance with the PRISMA statement and included all the randomized controlled trials (RCTs) that analyzed the relationship between vitamin D supplementation and the risk of stroke. A literature search strategy was established, and the following Medical Search Terms (MeSH) were used: “vitamin D,” “Calcitriol,” “Calcifediol,” “Cholecalciferol,” “25-Hydroxyvitamin D 2,” “ergocalciferols,” “stroke,” and stroke-derived terms. We searched for articles published before January 2022 in several databases, namely, PubMed, Web of Science, EMBASE, and The Cochrane Library. We also reviewed references included in relevant published meta-analyses and searched the http://www.ClinicalTrials.gov website for additional RCTs. The Q test and I2 were utilized to assess the degree of heterogeneity among the studies. Review Manager 5.3 and STATA16.0 software programs were used to assess the literature quality and perform statistical analyses.

Results

In total, twenty-four RCTs (86,202 participants) were included. There was no statistical heterogeneity among the RCTs (I2 = 0.0%, P = 0.94) included in this meta-analysis. We determined that vitamin D supplementation was not associated with a reduced risk of stroke compared with the placebo (RR = 1.02, 95% CI: 0.93–1.13, P = 0.65). In total, 10 studies only included women, and 14 studies included women and men among the 24 RCTs. Therefore, we performed a subgroup analysis based on sex. After the subgroup analysis, the effect remained statistically insignificant (mixed-sex group: RR = 1.06, 95% CI: 0.93–1.22, P = 0.37, women group: RR = 0.98, 95% CI: 0.86–1.13, P = 0.80). The results were generally comparable, based on age, body mass index (BMI), follow-up period, baseline 25-hydroxyvitamin D (25(OH)D) levels, the designated endpoint, latitude, vitamin D dosage, type of vitamin D administered, and an absence or presence of concurrent calcium supplementation (P &gt; 0.05).

Conclusion

Our study revealed that additional vitamin D supplementation did not reduce the risk of stroke. Therefore, additional RCTs of similar design should not be encouraged to assess any association between vitamin D supplementation and reduced stroke risk.

The Weak Relationship between Vitamin D Compounds and Glucose Homeostasis Measures in Pregnant Women with Obesity: An Exploratory Sub-Analysis of the DALI Study

Studies on the relationship between vitamin D (VitD) and glucose homeostasis usually consider either total VitD or 25OHD3 but not 25OHD2 and epimers. We aimed to evaluate the cross-sectional association of VitD compounds with glucose homeostasis measurements in pregnant women with overweight/obesity participating in the Vitamin D And Lifestyle Intervention for Gestational Diabetes Mellitus Prevention study. Methods: The analysis included 912 women. Inclusion criteria: <20 weeks gestation, body mass index ≥29 kg/m2 and information on exposure and outcome variables at baseline. Measurements: A 75 g OGTT at <20, 24−28 and 35−37 weeks gestation (except if previous diabetes diagnosis). Exposure variables: 25OHD2, 25OHD3 and C3-epimer. Outcome variables: fasting and post-challenge insulin sensitivity and secretion indices, corresponding disposition indices (DI), plasma glucose at fasting and 1 and 2 h, hyperglycemia in pregnancy (HiP). Statistics: Multivariate regression analyses with adjustment. Results: Baseline VitD sufficiency was 66.3%. Overall, VitD compounds did not show strong associations with any glucose homeostasis measures. 25OHD3 showed direct significant associations with: FPG at <20 and 24−28 weeks (standardized β coefficient (β) 0.124, p = 0.030 and 0.111, p = 0.026 respectively), 2 h plasma glucose at 24−28 weeks (β 0.120, p = 0.018), and insulin sensitivity (1/HOMA-IR, β 0.127, p = 0.027) at 35−37 weeks; it showed an inverse association with fasting DI (QUCKI*HOMA-β) at <20 and 24−28 weeks (β −0.124, p = 0.045 and β −0.148, p = 0.004 respectively). 25OHD2 showed direct associations with post-challenge insulin sensitivity (Matsuda, β 0.149, p = 0.048) at 24−28 weeks) and post-challenge DI (Matsuda*Stumvoll phase 1) at 24−28 and 35−37 weeks (β 0.168, p = 0.030, β 0.239, p = 0.006). No significant association with C3-epimer was observed at any time period. Conclusions: In these women with average baseline VitD in sufficiency range, VitD compounds did not show clear beneficial associations with glucose homeostasis measures.

Association between Vitamin D Supplementation and Cancer Mortality: A Systematic Review and Meta-Analysis

Simple Summary

It has been questioned whether vitamin D supplements can reduce the mortality and incidence of tumors. In this systematic review and meta-analysis of 12 randomized controlled trials with a total of 72,669 participants, vitamin D supplementation could not reduce the cancer mortality or cancer incidence. Our results suggest a reconsideration of the previous view that vitamin D supplementation could reduce overall cancer mortality is needed.

Abstract

Background: Vitamin D deficiency is related to increased cancer risk and deaths. However, whether vitamin D supplementation reduces cancer mortality remains unclear, and several randomized controlled trials yield inconsistent results. Methods: Medline, Embase, and the Cochrane Central Register of Controlled Trials were searched from their inception until 28 June 2022, for randomized controlled trials investigating vitamin D supplementation. Pooled relative risks (RRs) and their 95% confidence intervals (CIs) were estimated. Trials with vitamin D supplementation combined with calcium supplementation versus placebo alone and recruiting participants with cancer at baseline were excluded in the present study. Results: This study included 12 trials with a total of 72,669 participants. Vitamin D supplementation did not reduce overall cancer mortality (RR 0.96, 95% CI 0.80–1.16). However, vitamin D supplementation was associated with a reduction in lung cancer mortality (RR 0.63, 95% CI 0.45–0.90). Conclusions: Vitamin D supplementation could not reduce cancer mortality in this highly purified meta-analysis. Further RCTs that evaluate the association between vitamin D supplementation and total cancer mortality are still needed.

Association of Vitamin D Supplementation with Cardiovascular Events: A Systematic Review and Meta-Analysis

BACKGROUND

low vitamin D status has been associated with an increased incidence of cardiovascular events. However, whether vitamin D supplementation would reduce the incidence of cardiovascular events remains unclear.

PURPOSE

To perform a systematic review and meta-analysis of the effect of vitamin D supplementation on the mortality and incidence of cardiovascular events.

DATA SOURCES

We searched Medline, Embase, and the Cochrane Central Register of Controlled Trials from their inception until 3 May 2022.

STUDY SELECTION

Two authors searched for randomized clinical trials that reported vitamin D supplementation's effect on cardiovascular events outcomes.

DATA EXTRACTION

Two authors conducted independent data extraction.

DATA SYNTHESIS

We identified 41,809 reports; after exclusions, 18 trials with a total of 70,278 participants were eligible for analysis. Vitamin D supplementation was not associated with the mortality of cardiovascular events (RR 0.96, 95% CI 0.88-1.06, I2 = 0%), the incidence of stroke (RR 1.05, 95% CI 0.92-1.20, I2 = 0%), myocardial infarction (RR 0.97, 95% CI 0.87-1.09, I2 = 0%), total cardiovascular events (RR 0.97, 95% CI 0.91-1.04, I2 = 27%), or cerebrovascular events (RR 1.01, 95% CI 0.87-1.18, I2 = 0%).

LIMITATION

Cardiovascular events were the secondary outcome in most trials and thus, might be selectively reported.

CONCLUSION

In this meta-analysis of randomized clinical trials, vitamin D supplementation was not associated with a lower risk of cardiovascular events than no supplementation. These findings do not support the routine use of vitamin D supplementation in general.

Rapidly Increasing Serum 25(OH)D Boosts the Immune System, against Infections-Sepsis and COVID-19

Vitamin D deficiency is a global public health problem, a pandemic that commonly affects the elderly and those with comorbidities such as obesity, diabetes, hypertension, respiratory disorders, recurrent infections, immune deficiency, and malignancies, as well as ethnic minorities living in temperate countries. The same groups were worst affected by COVID-19. Since vitamin D deficiency weakens the immune system, it increases the risk of infections, complications, and deaths, such as from sepsis and COVID-19. Deficiency can be remedied cost-effectively through targeted food fortification, supplementation, and/or daily safe sun exposure. Its endocrine functions are limited to mineral metabolism, musculoskeletal systems, specific cell membrane interactions, and parathyroid gland functions. Except for the rapid, endocrine, and cell membrane-based non-genomic functions, all other biological and physiological activities of vitamin D depend on the adequate intracellular synthesis of 1,25(OH)2D (calcitriol) in peripheral target cells via the genome. Calcitriol mediates autocrine (intracrine) and paracrine signalling in immune cells, which provides broader, protective immune functions crucial to overcoming infections. The synthesis of 1,25(OH)2D (calcitriol) in peripheral target cells is dependent on diffusion and endocytosis of D3 and 25(OH)D from the circulation into them, which requires maintenance of serum 25(OH)D concentration above 50 ng/mL. Therefore, in acute infections such as sepsis and respiratory infections like COVID-19, it is necessary to rapidly provide its precursors, D3 and 25(OH)D, through the circulation to generate adequate intracellular calcitriol. Immune defence is one of the crucial non-hormonal functions of vitamin D. A single oral (bolus) dose or divided upfront loading doses between 100,000 and 500,000 IU, using 50,000 IU vitamin D3 increase the serum 25(OH)D concentrations to a therapeutic level of above 50 ng/mL that lasts between two to three months. This takes three to five days to raise serum 25(OH)D. In contrast, a single oral dose of calcifediol (0.014 mg/kg body weight) can generate the needed 25(OH)D concentration within four hours. Considering both D3 and 25(OH)D enter immune cells for generating calcitriol, using the combination of D3 (medium-term) and calcifediol (immediate) is cost-effective and leads to the best clinical outcome. To maximise protection against infections, particularly to reduce COVID-19-associated complications and deaths, healthcare workers should advise patients on safe sun exposure, adequate vitamin D supplementation and balanced diets containing zinc, magnesium, and other micronutrients to support the immune system. Meanwhile, governments, the World Health Organisation, the Centers for Disease Control, and governments should consider similar recommendations to physicians and the public, change the outdated vitamin D and other micronutrient recommendations directed to their population, and organise targetted food fortification programs for the vulnerable groups. This article discusses a rational approach to maintaining a sustained serum 25(OH)D concentration above 50 ng/mL, necessary to attain a robust immune system for overcoming infections. Such would cost-effectively improve the population’s health and reduce healthcare costs. It also describes three cost-effective, straightforward protocols for achieving and sustaining therapeutic serum 25(OH)D concentrations above 50 ng/mL (>125 nmol/L) to keep the population healthy, reduce absenteeism, improve productivity, and lower healthcare costs.

Vitamin D supplementation and total cancer incidence and mortality by daily vs. infrequent large-bolus dosing strategies: a meta-analysis of randomised controlled trials

BACKGROUND

Efficacy of vitamin D supplementation may vary by dosing strategies and adiposity. To address such heterogeneity, we performed a meta-analysis of randomised controlled trials of vitamin D supplementation and total cancer outcomes.

METHODS

PubMed and Embase were searched through January 2022. Summary relative risk (SRR) and 95% confidence interval (CI) were estimated using the DerSimonian-Laird random-effects model.

RESULTS

For total cancer incidence (12 trials), the SRR for vitamin D supplementation vs. control group was 0.99 (95% CI, 0.94-1.03; P = 0.54; I² = 0%). No significant association was observed regardless of whether the supplement was given daily or infrequently in a large-bolus. Yet, among trials testing daily supplementation, a significant inverse association was observed among normal-weight individuals (SRR, 0.76; 95% CI, 0.64-0.90; P = 0.001, I² = 0%), but not among overweight or obese individuals (P_{heterogeneity} = 0.02). For total cancer mortality (six trials), the SRR was 0.92 (95% CI, 0.82-1.03; P = 0.17; I² = 33%). A significant inverse association emerged (SRR, 0.87; 95% CI, 0.78-0.96; P = 0.007; I² = 0%) among studies testing daily supplementations but not among studies that testing infrequent large-bolus supplementations (P_{heterogeneity} = 0.09).

CONCLUSIONS

For vitamin D supplementation, daily dosing, but not infrequent large-bolus dosing, reduced total cancer mortality. For total cancer incidence, bolus dosing did not reduce the risk and the benefits of daily dosing were limited to normal-weight individuals.

Effect of active vitamin D treatment on development of type 2 diabetes: DPVD randomised controlled trial in Japanese population

OBJECTIVE

To assess whether eldecalcitol, an active vitamin D analogue², can reduce the development of type 2 diabetes among adults with impaired glucose tolerance.

DESIGN

Double blinded, multicentre, randomised, placebo controlled trial.

SETTING

Three hospitals in Japan, between June 2013 and August 2019.

PARTICIPANTS

People aged 30 years and older who had impaired glucose tolerance defined by using a 75 g oral glucose tolerance test and glycated haemoglobin level.

INTERVENTIONS

Participants were randomised to receive active vitamin D (eldecalcitol 0.75 μg per day; n=630) or matching placebo (n=626) for three years.

MAIN OUTCOMES

The primary endpoint was incidence of diabetes. Prespecified secondary endpoints were regression to normoglycaemia and incidence of type 2 diabetes after adjustment for confounding factors at baseline. In addition, bone densities and bone and glucose metabolism markers were assessed.

RESULTS

Of the 1256 participants, 571 (45.5%) were women and 742 (59.1%) had a family history of type 2 diabetes. The mean age of participants was 61.3 years. The mean serum 25-hydroxyvitamin D concentration at baseline was 20.9 ng/mL (52.2 nmol/L); 548 (43.6%) participants had concentrations below 20 ng/mL (50 nmol/L). During a median follow-up of 2.9 years, 79 (12.5%) of 630 participants in the eldecalcitol group and 89 (14.2%) of 626 in the placebo group developed type 2 diabetes (hazard ratio 0.87, 95% confidence interval 0.67 to 1.17; P=0.39). Regression to normoglycaemia was achieved in 145 (23.0%) of 630 participants in the eldecalcitol group and 126 (20.1%) of 626 in the placebo group (hazard ratio 1.15, 0.93 to 1.41; P=0.21). After adjustment for confounding factors by multivariable fractional polynomial Cox regression analysis, eldecalcitol significantly lowered the development of diabetes (hazard ratio 0.69, 0.51 to 0.95; P=0.020). In addition, eldecalcitol showed its beneficial effect among the participants with the lower level of basal insulin secretion (hazard ratio 0.41, 0.23 to 0.71; P=0.001). During follow-up, bone mineral densities of the lumbar spine and femoral neck and serum osteocalcin concentrations significantly increased with eldecalcitol compared with placebo (all P<0.001). No significant difference in serious adverse events was observed.

CONCLUSIONS

Although treatment with eldecalcitol did not significantly reduce the incidence of diabetes among people with pre-diabetes, the results suggested the potential for a beneficial effect of eldecalcitol on people with insufficient insulin secretion.

TRIAL REGISTRATION

UMIN Clinical Trials Registry UMIN000010758.