Vitamin D status and its relationship to body fat, final height, and peak bone mass in young women

Combined Oral Contraceptives: Association with Serum 25-Hydroxyvitamin D and Calcium and Bone Homeostasis

Background: Use of combined oral contraceptives (COCs) has been found to increase serum 25-hydroxyvitamin D [25(OH)D] but effects on calcium and bone homeostasis are unclear. Materials and Methods: Serum 25(OH)D, parathyroid hormone (PTH), alkaline phosphatase (ALK) and estradiol, dietary intake of bone-related nutrients and foods, bone mineral density (BMD), and body fat were compared in adult women (20-35 years; body mass index 21.5 ± 2.3 kg/m2) users (+COC, n = 32) and nonusers (-COC, n = 20) of COC. Biochemical markers were measured by automated assays. BMD at total body (TB), lumbar spine (LS), femoral neck (FN) and trochanter (TR), and body fat, were measured by dual-energy X-ray absorptiometry. Dietary intake was assessed by a food frequency questionnaire. Results: Intake of calcium, dairy foods, and fruits and vegetables, were adequate and did not differ by COC. Mean 25(OH)D was 35% higher in +COC (110.4 ± 27.3 nmol/L, 44.2 ± 1.8 ng/mL) compared with -COC (81.7 ± 22.8 nmol/L, 32.7 ± 2.3 ng/mL; p < 0.001). Mean PTH, ALK, and estradiol were 28%, 12%, and 62% lower, respectively, in +COC compared with -COC (p ≤ 0.05). Mean BMD z-scores (all sites) were adequate and did not differ by COC. There were no correlations between 25(OH)D and dietary, biochemical, and body composition variables. PTH was inversely correlated with TR-BMD z-score in -COC (r = -0.47; p = 0.04), and ALK was inversely correlated with TB-, TR-, and LS-BMD z-scores in -COC (r ≤ -0.43; p ≤ 0.04), but not in +COC. Conclusions: Increased serum 25(OH)D with COC use was paralleled by expected physiologic adjustments in calcium and bone homeostasis, and adequate bone mass status, in nonobese young adult women consuming bone-healthy diets.

High dose dietary vitamin D allocates surplus calories to muscle and growth instead of fat via modulation of myostatin and leptin signaling

Obesity occurs because the body stores surplus calories as fat rather than as muscle. Fat secretes a hormone, leptin, that modulates energy balance at the brain. Changes in fat mass are mirrored by changes in serum leptin. Elevated leptin prompts the brain to decrease appetite and increase energy expenditure. In obesity, however, impaired leptin sensitivity mutes these leptin-mediated changes. We have limited understanding of what controls leptin production by fat or leptin sensitivity in the brain. Muscle produces a hormone, myostatin, that plays a role in muscle analogous to the one that leptin plays in fat. Absent myostatin leads to increased muscle mass and strength. As with leptin, we also do not know what controls myostatin production or sensitivity. Although fat mass and muscle mass are closely linked, the interplay between leptin and myostatin remains obscure. Here we describe an interplay linked thru vitamin D. Conventionally, it is thought that vitamin D improves strength via trophic effects at the muscle. However, we find here that high dose dietary vitamin D allocates excess calories to muscle and linear growth instead of storage as fat. Vitamin D mediates this allocation by decreasing myostatin production and increasing leptin production and sensitivity. That is, high dose vitamin D improves integration of organismal energy balance. Obesity, aging and other chronic inflammatory diseases are associated with increased fat mass and decreased muscle mass and function (e.g. sarcopenia). Our work provides a physiologic framework for how high-dose vitamin D would increase allocation of calories to muscle instead of fat in these pathologies. Additionally, our work reveals a novel link between the myostatin and leptin signaling whereby myostatin conveys energy needs to modulate leptin effects on calorie allocation. This result provides evidence to update the conventional model of energy stores sensing to a new model of energy balance sensing. In our proposed model, integration of leptin and myostatin signaling allows control of body composition independent of weight. Furthermore, our work reveals how physiologic seasonal variation in vitamin D may be important in controlling season-specific metabolism and calorie allocation to fat in winter and muscle and growth in summer.

Fat as a Friend or Foe of the Bone

PURPOSE OF REVIEW

The objective of this review is to summarize the literature on the prevalence and diagnosis of obesity and its metabolic profile, including bone metabolism, focusing on the main inflammatory and turnover bone mediators that better characterize metabolically healthy obesity phenotype, and to summarize the therapeutic interventions for obesity with their effects on bone health.

RECENT FINDINGS

Osteoporosis and fracture risk not only increase with age and menopause but also with metabolic diseases, such as diabetes mellitus. Thus, patients with high BMI may have a higher bone fragility and fracture risk. However, some obese individuals with healthy metabolic profiles seem to be less at risk of bone fracture. Obesity has become an alarming disease with growing prevalence and multiple metabolic comorbidities, resulting in a significant burden on healthcare and increased mortality. The imbalance between increased food ingestion and decreased energy expenditure leads to pathological adipose tissue distribution and function, with increased secretion of proinflammatory markers and harmful consequences for body tissues, including bone tissue. However, some obese individuals seem to have a healthy metabolic profile and may not develop cardiometabolic disease during their lives. This healthy metabolic profile also benefits bone turnover and is associated with lower fracture risk.

Nutrient Deficiency After Bariatric Surgery in Adolescents: A Systematic Review and Meta-Analysis

OBJECTIVE

This systematic review and meta-analysis study aimed to estimate changes in blood nutrient concentrations and nutrient deficiencies in adolescents following bariatric surgery.

METHODS

We searched PubMed, Scopus, and the Web of Science to find studies published between January 2000 and August 2023. Observational studies reporting the mean blood concentration of nutrients before and after bariatric surgery or the proportion of nutrient deficiencies after the surgery in healthy adolescents were selected.

RESULTS

Fifteen studies were included. Gastric bypass and sleeve gastrostomy were the most common types of surgery. Vitamin D, iron, or ferritin, vitamin B12, calcium, and folic acid were the most studied nutrients, respectively. Other nutrients examined in the studies included zinc, phosphorus, and albumin. The serum ferritin increased by 21 mcg/L (95% CI = 10.0, 32.0 mcg/L) after the surgery, but there were no significant alterations in other nutrients. The postoperative prevalence of low albumin, ferritin, vitamin D, and vitamin B12 levels was 10%, 49%, 41%, and 20%, respectively. Also, 23% had an iron deficiency, and 10% had a calcium deficiency after bariatric surgery.

CONCLUSIONS

The serum ferritin level increased following bariatric surgery in adolescents. Vitamin D and ferritin deficiencies were estimated to be present in more than one-third of adolescents after the surgery.

Vitamin D Metabolites Are Associated With Musculoskeletal Injury in Young Adults: A Prospective Cohort Study

The relationship between vitamin D metabolites and lower body (pelvis and lower limb) overuse injury is unclear. In a prospective cohort study, we investigated the association between vitamin D metabolites and incidence of lower body overuse musculoskeletal and bone stress injury in young adults undergoing initial military training during all seasons. In 1637 men and 530 women (aged 22.6 ± 7.5 years; body mass index [BMI], 24.0 ± 2.6 kg/m- 2 ; 94.3% white ethnicity), we measured serum 25-hydroxyvitamin D (25(OH)D) and 24,25-dihydroxyvitamin D (24,25(OH)2 D) by high-performance liquid chromatography tandem mass spectrometry, and 1,25-dihydroxyvitamin D (1,25(OH)2 D) by immunoassay during week 1 of training. We examined whether the relationship between 25(OH)D and 1,25(OH)2 D:24,25(OH)2 D ratio was associated with overuse injury. During 12 weeks of training, 21.0% sustained ≥1 overuse musculoskeletal injury, and 5.6% sustained ≥1 bone stress injury. After controlling for sex, BMI, 2.4 km run time, smoking, bone injury history, and Army training course (Officer, standard, or Infantry), lower body overuse musculoskeletal injury incidence was higher for participants within the second lowest versus highest quartile of 24,25(OH)2 D (odds ratio [OR] = 1.62; 95% confidence interval [CI] 1.13-2.32; p = 0.009) and lowest versus highest cluster of 25(OH)D and 1,25(OH)2 D:24,25(OH)2 D (OR = 6.30; 95% CI 1.89-21.2; p = 0.003). Lower body bone stress injury incidence was higher for participants within the lowest versus highest quartile of 24,25(OH)2 D (OR = 4.02; 95% CI 1.82-8.87; p < 0.001) and lowest versus highest cluster of 25(OH)D and 1,25(OH)2 D:24,25(OH)2 D (OR = 22.08; 95% CI 3.26-149.4; p = 0.001), after controlling for the same covariates. Greater conversion of 25(OH)D to 24,25(OH)2 D, relative to 1,25(OH)2 D (ie, low 1,25(OH)2 D:24,25(OH)2 D), and higher serum 24,25(OH)2 D were associated with a lower incidence of lower body overuse musculoskeletal and bone stress injury. Serum 24,25(OH)2 D may have a role in preventing overuse injury in young adults undertaking arduous physical training. © 2023 Crown copyright and The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR). This article is published with the permission of the Controller of HMSO and the King's Printer for Scotland.

Assessing vitamin D metabolism - four decades of experience

One hundred years ago, the role of vitamin D for bone mineralization and the prevention of rickets was discovered. Vitamin D comprises a group of over 50 metabolites with multiple functions that go far beyond calcium homeostasis and bone mineralization. Approximately 50 years ago, first methods for the measurement of 25-hydroxyvitamin D (25(OH)D) in human blood were developed. Over the years, different analytical principals were employed including competitive protein binding assays, high-performance liquid chromatography, various immunoassay and mass spectrometric formats. Until the recent standardization of serum 25(OH)D measurement, agreement between methods was unsatisfactory. Since then, comparability has improved, but substantial variability between methods remains. With the advent of liquid chromatography tandem mass spectrometry (LC-MS/MS), the accurate determination of 25(OH)D and other metabolites, such as 24,25(OH)2D, becomes increasingly accessible for clinical laboratories. Easy access to 25(OH)D testing has triggered extensive clinical research showing that large parts of the population are vitamin D deficient. The variable response of vitamin D deficient individuals to supplementation indicates that assessing patients' vitamin D stores by measuring 25(OH)D provides limited insight into the metabolic situation. Meanwhile, first evidence has emerged suggesting that the simultaneous measurement of 25(OH)D, 24,25(OH)2D and other metabolites allows a dynamic evaluation of patients' vitamin D status on metabolic principals. This may help to identify patients with functional vitamin D deficiency from those without. It can be expected that research into the assessment vitamin D status will continue for another 50 years and that this will help rationalizing our approach in clinical practice.

Association between serum vitamin D levels and visceral adipose tissue among adolescents: a cross-sectional observational study in NHANES 2011–2015

Background

In recent years, obesity and vitamin D deficiency are more prevalent among adolescents. Improving our knowledge of the link between vitamin D and visceral adipose tissue (VAT) is essential for the health of adolescents. This study aimed to examine the connection between serum vitamin D levels and VAT mass among adolescents participating in the United States.

Methods

This is a cross-sectional study that used data from the 2011 to 2015 National Health and Nutrition Examination Survey (NHANES). The connection between serum vitamin D levels and VAT was investigated using weighted multiple linear regression models. Potential nonlinear relationships were explored using smooth curve fitting.

Results

The analysis included 3171 adolescents aged 12–19 years. Vitamin D levels were shown to be inversely linked with VAT in the full-adjusted model (β = − 0.34, 95% CI: − 0.49 to − 0.19). When stratified analyses by gender, this negative relationship persisted in the girls’ group (β = − 0.39, 95% CI: − 0.60 to − 0.19), but not in the boys’ group (β = − 0.06, 95% CI: − 0.25 to 0.13). When stratified analysis by race, this negative relationship persisted in the Mexican American group (β = − 0.61, 95% CI: − 1.03 to − 0.19), and the non-Hispanic White group (β = − 0.27, 95% CI: − 0.54 to − 0.01), but not in the other groups.

Conclusions

Our findings confirmed that serum vitamin D levels negatively correlated with VAT among adolescents in the United State, especially in girls, the Mexican American and non-Hispanic White. Further research is needed to determine whether increasing serum vitamin D levels decrease VAT among adolescents.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03688-2.

The interactive effect of vitamin D3 supplementation and vitamin D receptor polymorphisms on weight and body composition in overweight women with hypovitaminosis D: a randomized, double-blind, placebo-controlled clinical trial

Different responses to vitamin D supplementation may be due to genes involved in vitamin D metabolism, including the vitamin D receptor (VDR) gene. The present study aimed to determine the interactive effect of vitamin D supplementation and VDR polymorphisms, including FokI (rs2228570) and BsmI (1544410) on weight and body composition in overweight women with hypovitaminosis D. This study comprised two phases: a double-blind, randomized and a before-after clinical trial. In the first phase, 50 healthy overweight women aged 20-45 years with hypovitaminosis D were randomly categorized into intervention and control groups and were given 50 000 IU/w vitamin D3 or placebo for 12 weeks. In the second phase, 75 women received 50 000 IU/w of vitamin D3 for 12 weeks. All variables were measured at baseline and after 12 weeks. Circulating 25(OH)D was measured using an ELISA kit. Anthropometric indices were calculated according to standard protocol (WHO-TRH-854). Body composition was determined using the body impedance analysis method. The VDR polymorphisms were detected using the PCR sequence. Supplementation resulted in a significant increase in the level of 25(OH)D in the intervention group but did not affect the anthropometric profile of the subjects. When considering FokI genotypes, carriers of the FF genotype had higher fat mass reduction than carriers of Ff + ff genotypes.

Comparative Study of the Effects of Two Dietary Sources of Vitamin D on the Bone Metabolism, Welfare and Birth Progress of Sows Fed Protein- and Phosphorus-Reduced Diets

To investigate the influence of two dietary sources of vitamin D on the vitamin D status, bone metabolism, welfare and birth progress of gestating and lactating sows, forty-nine multiparous sows were randomly assigned to one of two diets: “CON” (n = 25; 50 μg vitamin D3/kg feed) and “HYD” (n = 24; 50 μg 25-hydroxycholecalciferol/kg feed). The basal diets were protein- and phosphorus-reduced. The trial started on day 3 ante insemination of the sows and ended with weaning of the piglets on day 28 postpartum. Dietary supplementation of 25-hydroxycholecalciferol resulted in improved maternal vitamin D status (p < 0.001), fewer gait changes (p < 0.01) and longer standing time after feeding (day 5 ante partum; p < 0.05) compared to vitamin D3. However, the bone markers CrossLaps and osteocalcin were not affected. Overall, the present results suggest that sows fed 25-hydroxycholecalciferol instead of vitamin D3 showed improved locomotion and stance strength. However, this outcome is probably not related to altered bone metabolism. The underlying mechanisms must be investigated in further studies.

Vitamin D deficiency is associated with higher risks for SARS-CoV-2 infection and COVID-19 severity: a retrospective case-control study

Robust evidence of whether vitamin D deficiency is associated with COVID-19 infection and its severity is still lacking. The aim of the study was to evaluate the association between vitamin D levels and the risks of SARS-CoV-2 infection and severe disease in those infected. A retrospective study was carried out among members of Clalit Health Services (CHS), the largest healthcare organization in Israel, between March 1 and October 31, 2020. We created two matched case-control groups of individuals for which vitamin D levels and body mass index (BMI) were available before the pandemic: group (A), in which 41,757 individuals with positive SARS-CoV-2 PCR tests were matched with 417,570 control individuals without evidence of infection, and group (B), in which 2533 patients hospitalized in severe condition for COVID-19 were matched with 2533 patients who were tested positive for SARS-CoV-2, but were not hospitalized. Conditional logistic models were fitted in each of the groups to assess the association between vitamin D levels and outcome. An inverse correlation was demonstrated between the level of vitamin D and the risks of SARS-CoV-2 infection and of severe disease in those infected. Patients with very low vitamin D levels (< 30 nmol/L) had the highest risks for SARS-CoV-2 infection and also for severe COVID-19 when infected-OR 1.246 [95% CI 1.210-1.304] and 1.513 [95% CI 1.230-1.861], respectively. In this large observational population study, we show a significant association between vitamin D deficiency and the risks of SARS-CoV-2 infection and of severe disease in those infected.

Low serum 25-hydroxyvitamin D level is associated with obesity and atherogenesis in adolescent boys

PURPOSE

We investigated the relationship of 25-hydroxyvitamin D (25[OH]D) level with obesity and atherosclerosis in Japanese adolescents.

METHODS

We examined 492 children (247 boys and 245 girls) aged 12-13 years. The serum 25(OH)D level was compared among underweight, healthy weight, and overweight children. Spearman correlation coefficient analysis was performed to examine the relationships between the 25(OH)D level and body mass index (BMI), plasma lipids, and blood pressure and to compare the latter between the normal (≥20 ng/mL) and low (<20 ng/mL) 25(OH)D groups. Further, we performed a multiple regression analysis to assess the effect on the 25(OH)D level.

RESULTS

The serum 25(OH)D level was significantly lower in overweight (20.5±2.7 ng/mL) than in healthy-weight boys (22.4±3.3 ng/mL) (P=0.004). Spearman correlation coefficients comparing the relationship of the 25(OH)D level with BMI, high-density lipoprotein cholesterol (HDL-C), and atherogenic index indicated significance in boys (ρ=-0.238 [P<0.0001], ρ=0.197 [P=0.002], and ρ=-0.146 [P=0.022], respectively). In boys, the multiple regression analysis results showed that BMI had negative and HDL-C had positive effects on the 25(OH)D level. The first was higher and the latter was lower in boys with low 25(OH)D level than in those with normal levels, respectively (P<0.05). No significant correlations were detected in girls.

CONCLUSION

Low serum 25(OH)D level was associated with obesity and increased atherogenic risk in adolescent boys only. This sex difference was probably mediated by body composition, sun exposure, estrogen, and adiponectin, which are characteristics of puberty.

Serum Vitamin D Levels in Relation to Abdominal Obesity in Children and Adolescents: A Systematic Review and Dose-Response Meta-Analysis

Background

Findings of epidemiological studies that investigated the relationship between serum vitamin D levels and abdominal obesity were inconsistent. To evaluate the relationship between blood vitamin D levels and abdominal obesity in children and adolescents, we did a comprehensive review and dose-response meta-analysis.

Methods

A comprehensive search in electronic databases including Scopus, Web of Science (ISI), MEDLINE (Pubmed), EMBASE, and Google Scholar was conducted, up to May 2021, for epidemiological studies that investigated the linkage between serum vitamin D levels (as the exposure) and abdominal obesity (as the outcome) in children and adolescents.

Results

Combining 19 effect sizes from 14 cross-sectional studies that included 29,353 apparently healthy children illustrated that the highest vs. lowest level of serum vitamin D was related to a 35% reduced odds of abdominal obesity [odds ratio (OR): 0.65; 95% CI: 0.50, 0.84]. Linear dose-response analysis revealed that each 10 ng/ml increase in serum vitamin D levels was related to a 7% decrease in odds of abdominal obesity (OR: 0.93; 95% CI: 0.90, 0.95), only among investigations that used percentiles of waist circumference (>75th or 90th) to define the disorder (including 6,868 total subjects and 1,075 cases with abdominal obesity). Increasing serum vitamin D levels from 20 to 40 ng/ml was related to reduce odds of abdominal obesity in children.

Conclusion

A negative relationship between blood vitamin D levels and abdominal obesity in children and adolescents was discovered in this meta-analysis of epidemiologic studies. Among investigations that used waist circumference percentiles to define the disorder, the relationship was in a dose-response manner. To affirm this relationship, more research studies are needed, particularly using a prospective design.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021261319, PROSPERO 2021, identifier: CRD42021261319.

Associations between serum 25-hydroxyvitamin D, body mass index and body fat composition among Emirati population: Results from the UAE healthy future study

INTRODUCTION

Vitamin D deficiency and insufficiency are highly prevalent among several populations across the globe. Numerous studies have shown a significant correlation between body-mass-index (BMI) and Vitamin D status, however, some results differed according to ethnicity. Despite the abundance of sunshine throughout the year, vitamin D deficiency is prominent in the United Arab Emirates (UAE). In this study, we analyzed the UAE Healthy Future Study (UAEHFS) pilot data to investigate the association between serum 25-hydroxyvitamin D (25(OH)D) and % body fat (BF) composition as well as BMI.

MATERIAL AND METHODS

Data from a total of 399 Emirati men and women aged ≥ 18 years were analyzed. Serum 25(OH)D and standard measures of weight and height were included in the analyses. Vitamin D deficiency was defined as serum 25(OH)D concentration<20 ng/ml. Multivariate quantile regression models were performed to explore the relationship between serum 25(OH)D levels and % BF composition and BMI correspondingly.

RESULTS

There were 281 (70.4%) males and 118 (29.6%) females included in this study. More than half of the study participants had vitamin D insufficiency (52.4%), and nearly a third had vitamin D deficiency (30.3%); while only 17.3% had optimal levels. A statistically significant negative association between serum 25(OH) D levels and % BF composition was observed at intermediate percentiles while a statistically significant negative association between serum 25(OH)D and BMI was only observed at the median (50th percentile).

CONCLUSION

The study findings support the association between low serum 25(OH) D levels (low vitamin D status) and high % BF composition and high BMI among adult Emiratis. Further longitudinal data from the prospective UAEHFS could better elucidate the relationship between serum 25(OH) D levels, % BF composition, and BMI in the context of various health outcomes among this population.

The association between serum 25-hydroxyvitamin D concentrations and serum lipids in the Southern Thai population

INTRODUCTION

Dyslipidaemia is a major risk factor for cardiovascular diseases (CVD). Vitamin D deficiency has been found to be associated with CVD. However, the relationships between vitamin D and lipids are inconsistent. The aim of this study was to investigate the relationship between vitamin D status and serum lipids in Southern Thai subjects.

MATERIAL AND METHODS

A total of 726 healthy subjects in Southern Thailand were enrolled in the study. Serum 25-hydroxyvitamin D (25(OH)D), lipid profiles, fasting plasma glucose, anthropometric data, blood pressure, and body composition were measured. The relationship between serum 25(OH)D levels and biochemical data was evaluated by partial correlation and multiple linear regression analyses. The association of serum 25(OH)D levels with dyslipidaemia was analysed using multivariate regression analysis.

RESULTS

Serum 25(OH)D levels were negatively correlated with body mass index (BMI), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and body composition parameters after adjusting for age in women. Multiple linear regression analysis showed that TC and BMI were independent predictors for 25(OH)D concentrations in women. Multivariate logistic regression analysis showed that the odds ratio of hypertriglyceridaemia (OR = 0.51; 95% CI: 0.32-0.80, p = 0.004) and reduced high-density lipoprotein cholesterol (HDL-C) (OR = 0.43; 95% CI: 0.26-0.71, p = 0.001) were significantly lower in vitamin D sufficiency when compared with hypovitaminosis D in women.

CONCLUSIONS

Vitamin D sufficiency could reduce risk of hypertriglyceridaemia and reduced HDL-C, particularly in women, suggesting that vitamin D sufficiency may have beneficial effects on lipids and a decreased risk for CVD in Thai women.

The Vitamin D Metabolite Ratio Is Associated With Changes in Bone Density and Fracture Risk in Older Adults

Recent studies have suggested that 25-hydroxyvitamin D (25(OH)D) may be a poor biomarker of bone health, in part because measured levels incorporate both protein-bound and free vitamin D. The ratio of its catabolic product (24,25-dihydroxyvitamin D [24,25(OH)₂ D]) to 25(OH)D (the vitamin D metabolite ratio [VMR]) may provide more information on sufficient vitamin D stores and is not influenced by vitamin D-binding protein concentrations. We evaluated whether the VMR or 25(OH)D are more strongly associated with bone loss and fracture risk in older adults. We performed a retrospective cohort study of 786 community-dwelling adults aged 70 to 79 years who participated in the Health Aging and Body Composition study. Our primary outcomes were annual changes in bone density and incident fracture. The mean age of these participants was 75 ± 3 years, 49% were female, 42% were Black, and 23% had an estimated glomerular filtration rate (eGFR) <60 mL/mL/1.73m² . In fully adjusted models, a 50% lower VMR was associated with 0.3% (0.2%, 0.6%) more rapid decline in total hip bone mineral density (BMD). We found similar relationships with thoracic and lumbar spine BMD. In contrast, 25(OH)D₃ concentrations were not associated with longitudinal change in BMD. There were 178 fractures during a mean follow-up of 10 years. Each 50% lower VMR was associated with a 49% (95% confidence interval [CI] 1.06, 2.08) greater fracture risk, whereas lower 25(OH)D₃ concentrations were not significantly associated with fracture risk (hazard ratio [HR] per 50% lower 1.07 [0.80, 1.43]). In conclusion, among a diverse cohort of community-dwelling older adults, a lower VMR was more strongly associated with both loss of BMD and fracture risk compared with 25(OH)D₃ . Trials are needed to evaluate the VMR as a therapeutic target in persons at risk for worsening BMD and fracture. © 2021 American Society for Bone and Mineral Research (ASBMR).

Association of serum 25-hydroxyvitamin D concentration with anthropometric measures in children and adolescents: the CASPIAN-V study

BACKGROUND

Serum 25-hydroxyvitamin D (25(OH)D) concentrations reflect vitamin D status, with deficiency implicated as an underlying factor for many adverse health effects. This study aims to analyze the association between vitamin D status and different anthropometric measures in a large pediatric population.

METHODS

This nationwide cross-sectional study was conducted in 2019 in blood samples obtained from school students of 30 provinces in Iran. Participants were 2596 children and adolescents aged 7-18 years. Weight, height, waist circumference (WC), hip circumference (HC), neck circumference (NC), and wrist circumference (WrC) were measured. Body mass index (BMI) and waist-to-height ratio (W/HtR) were calculated. Serum 25(OH)D concentrations were measured using chemiluminescent immunoassay.

RESULTS

Participants consisted of 55% boys, 71.3% urban inhabitants, with a mean (SD) age of 12.1 (3.0) years. Overall, vitamin D deficiency was documented in 10.6% of participants, insufficiency in 60.4%, and sufficiency in 29% of the population studied. The mean of BMI and WC was higher in the vitamin D deficient than in the vitamin D sufficient group (19.31 kg/m² and 69.24 cm vs. 18.34 kg/m² and 65.73 cm, respectively, P < 0.01). Multivariate linear regression models revealed a significant association of vitamin D insufficiency with WC and W/HtR (P < 0.05). Likewise, in the multivariate regression models, vitamin D deficiency was associated with BMI, WC, and W/HtR (P < 0.05).

CONCLUSION

Our findings on the inverse association between vitamin D status and some anthropometric measures underscore the importance of providing vitamin D by fortification and supplementation programs of vitamin D for the pediatric population.

LEVEL OF EVIDENCE

V.

Serum 25-hydroxyvitamin D concentrations are inversely associated with body adiposity measurements but the association with bone mass is non-linear in postmenopausal women

Vitamin D deficiency has been linked to increased adiposity and decreased bone density. It is not known if vitamin D is linked to adiposity measures and bone mass in postmenopausal Qatar women. We investigated an association between serum vitamin D [25-hydroxyvitmain D (25(OH)D)] and adiposity measurements in postmenopausal women using Qatar Biobank data (n = 935). The post-menopausal status was self-reported by participants. Multivariate adjusted regression was applied to determine the association between serum 25(OH)D and body adiposity markers and bone mass. Serum 25(OH)D was significantly, inversely associated with body mass index (p < 0.0005), waist circumference (0.044), fat mass (p < 0.003), gynoid fat (p < 0.001), and android fat (p < 0.009). Serum 25(OH)D appeared to have an inverse 'U' association with several adiposity measures. Overall, body adiposity markers were the lowest in the 4^th quartile serum 25(OH)D and significantly lower compared to the 1^st quartile serum 25(OH)D. In multivariable adjusted analysis, no association was found between serum 25(OH)D concentration and bone mass when serum 25(OH)D was categorized. In a continuous variable analysis, the association between 25(OH)D and bone mass was significant, non-linear, inverse 'U'. In conclusion, serum 25-hydroxyvitamin D was inversely associated with adiposity measures and non-linearly associated to bone mass in postmenopausal Qatari women.

Prenatal nutrition supplementation and growth biomarkers in preadolescent Bangladeshi children: A birth cohort study

Little is known about the usefulness of biomarkers to study the influence of prenatal nutrition supplementation in improving child growth. Anthropometry is not always straightforward to understand how nutrition might impact growth, especially in settings with high rates of malnutrition and infections. We examined the effects of prenatal supplementation on growth and growth biomarkers and the relationship between anthropometric measures and growth biomarkers of children at 4.5 and 9 years of age. Children were enrolled from a longitudinal cohort, where mothers were randomized into daily supplementation with either early‐food (≤9 gestation week [GW]) or usual‐food (~20 GW) (608 kcal 6 days/week); they were further randomized to receive 30‐mg or 60‐mg iron with 400‐μg folic acid, or multiple micronutrients (MM) in rural Bangladesh. Anthropometric data were collected from mothers at GW8 and children at 4.5 (n = 640) and 9 years (n = 536). Fasting blood was collected from children at each age. Early‐food supplementation showed reduced stunting and underweight at 4.5 and 9 years age respectively compared to usual‐food. Prenatal supplementations did not have any effect on growth biomarkers except for STAT5b expression which was lower in the early‐food compared to the usual‐food group (β = −0.21; 95 CI% = −0.36, −0.07). Plasma concentrations of 25‐hydroxy vitamin D and calcium were both inversely associated with weight‐for‐age and body mass index‐for‐age Z‐scores at 9 years, particularly in early‐food and MM groups. Although there was minimal effect on child growth by prenatal supplementations, the associations of biomarkers with anthropometric indices were predominantly driven by timing of food or MM supplementations.

Vitamin D as a Potential Preventive Agent For Young Women's Breast Cancer

Clinical studies backed by research in animal models suggest that vitamin D may protect against the development of breast cancer, implicating vitamin D as a promising candidate for breast cancer prevention. However, despite clear preclinical evidence showing protective roles for vitamin D, broadly targeted clinical trials of vitamin D supplementation have yielded conflicting findings, highlighting the complexity of translating preclinical data to efficacy in humans. While vitamin D supplementation targeted to high-risk populations is a strategy anticipated to increase prevention efficacy, a complimentary approach is to target transient, developmental windows of elevated breast cancer risk. Postpartum mammary gland involution represents a developmental window of increased breast cancer promotion that may be poised for vitamin D supplementation. Targeting the window of involution with short-term vitamin D intervention may offer a simple, cost-effective approach for the prevention of breast cancers that develop postpartum. In this review, we highlight epidemiologic and preclinical studies linking vitamin D deficiency with breast cancer development. We discuss the underlying mechanisms through which vitamin D deficiency contributes to cancer development, with an emphasis on the anti-inflammatory activity of vitamin D. We also discuss current evidence for vitamin D as an immunotherapeutic agent and the potential for vitamin D as a preventative strategy for young woman's breast cancer.

Vitamin D and the athlete-patient: state of the art

Vitamin D deficiency is common in athletes. The conventional measurement of vitamin D levels provides a general indicator of body stores. However, there are nuances in its interpretation as values of 25(OH)D do not correlate absolutely with the amount of 'bioavailable' vitamin to the cells. Vitamin D should be regarded as a hormone and influences between 5% and 10% of our total genome. Determining the precise effect of the vitamin, isolated from the actions of other cofactors, is not straightforward and restricts our complete understanding of all of its actions. Deficiency has harmful effects on not only bone and muscle but also wider areas, including immunity and respiratory and neurological activities. More caution should be applied regarding the ability of supranormal vitamin D levels to elevate athletic performance. Hopefully, future research will shed more light on optimal levels of vitamin D and supplementation regimes, and improved understanding of its intracellular control of our genetic mechanisms and how extrinsic influences modify its activity.

The Relation between Changes in Vitamin D and Vitamin B12 Levels, Body Mass Index and Outcome in Methadone Maintenance Treatment Patients

Patients' Body Mass Index (BMI) increase during methadone maintenance treatment (MMT), and both Vitamins D and B12 deficiencies may be associated with BMI. We studied the relations between BMI, these vitamins and treatment outcome in patients with opioid use disorder receiving MMT. Vitamin B12 levels were available for 272 patients and Vitamin D levels were available for 260 patients. Of those 112 and 80 respectively had two measures (at admission or thereafter, and while stabilized or after one year in treatment). Patients' BMI levels and long-term retention were analyzed. Vitamin B12 was lower in patients abusing cocaine/amphetamine on admission. Vitamin D did not change over time, but a significant weight gain could be observed in 38 patients whose vitamin D was elevated compared to 42 whose levels were not, (25.4 ± 4.8 to 28.8 ± 5.2 vs. 24.3 ± 3.7 to 25.5 ± 4.0, p(Time) < 0.0005, p(Group) = 0.03, p(interaction) = 0.02). BMI changes correlated with vitamin D levels change (r = 0.26, p = .04). Longer cumulative retention was observed among the elevated vitamin D group (8.1 years, 95% CI 6.3-9.8) in comparison with the non-elevated group (4.8y 95% CI 3.6-6.1, Kaplan Meier, p = .02). Stimulants misuse was associated with low B12 levels. Vitamin D elevation is associated with weight gain and longer retention in treatment.

Vitamin D deficiency serves as a precursor to stunted growth and central adiposity in zebrafish

Emerging evidence demonstrates the importance of sufficient vitamin D (1α, 25-dihydroxyvitamin D3) levels during early life stage development with deficiencies associated with long-term effects into adulthood. While vitamin D has traditionally been associated with mineral ion homeostasis, accumulating evidence suggests non-calcemic roles for vitamin D including metabolic homeostasis. In this study, we examined the hypothesis that vitamin D deficiency (VDD) during early life stage development precedes metabolic disruption. Three dietary cohorts of zebrafish were placed on engineered diets including a standard laboratory control diet, a vitamin D null diet, and a vitamin D enriched diet. Zebrafish grown on a vitamin D null diet between 2-12 months post fertilization (mpf) exhibited diminished somatic growth and enhanced central adiposity associated with accumulation and enlargement of visceral and subcutaneous adipose depots indicative of both adipocyte hypertrophy and hyperplasia. VDD zebrafish exhibited elevated hepatic triglycerides, attenuated plasma free fatty acids and attenuated lipoprotein lipase activity consistent with hallmarks of dyslipidemia. VDD induced dysregulation of gene networks associated with growth hormone and insulin signaling, including induction of suppressor of cytokine signaling. These findings indicate that early developmental VDD impacts metabolic health by disrupting the balance between somatic growth and adipose accumulation.

A comprehensive genetic and epidemiological association analysis of vitamin D with common diseases/traits in the UK Biobank

Vitamin D has been intensively studied for its association with human health, but the scope of such association and the causal role of vitamin D remain controversial. We aim to comprehensively investigate the links between vitamin D and human health through both epidemiological and Mendelian randomization (MR) analyses. We examined the epidemiological associations between serum 25-hydroxyvitamin D (25(OH)D) concentration and 90 diseases/traits in 326,409 UK Biobank (UKBB) Europeans. The causal relations between 25(OH)D and 106 diseases/traits were investigated by performing MR analysis using genome-wide significant 25(OH)D-associated variants (N = 143) from the largest UKBB GWAS to date. In epidemiological analysis, we found 25(OH)D was associated with 45 diseases/traits across cardiovascular/metabolic diseases, psychiatric/neurological diseases, autoimmune/inflammatory diseases, cancer, musculoskeletal diseases, and quantitative traits. In MR-analysis, we presented evidence suggesting potential causal role of 25(OH)D in increasing height (β = .064, 95% confidence interval [CI] = 0.019-0.11) and preventing the risk of ovarian cancer (odds ratio [OR] = 0.96, 95% CI = 0.93-0.99), multiple sclerosis (OR = 0.96, 95% CI = 0.94-0.98), leg fracture (OR = 0.60, 95% CI = 0.45-0.80) and femur fracture (OR = 0.53, 95% CI = 0.32-0.84). These findings confirmed associations of vitamin D with a broad spectrum of diseases/traits and supported the potential causal role of vitamin D in promoting health.

25-Hydroxyvitamin D, Vitamin D Binding Protein, Bioavailable 25-Hydroxyvitamin D, and Body Composition in a Diverse Sample of Women Collegiate Indoor Athletes

Women athletes are at higher risk for bone diseases; yet, information on vitamin D status ((25(OH)D), vitamin D binding protein (VDBP), and bioavailable 25(OH)D is limited. Collegiate athletes (n = 36) from volleyball (WVB), basketball (WBB), and track and field (WTF) were measured for (25(OH)D), VDBP, and bioavailable 25(OH)D; body composition and bone mineral density (BMD); and skin pigmentation. Participants self-reported daily vitamin D intake and sun exposure. One-way analysis of variance analyzed mean differences in measures across sports. Linear regression examined relationships between 25(OH)D; VDBP; bioavailable 25(OH)D; and whole body, hip, and spine BMD. Participants' (mean ± SD, 19.4 ± 1.4 years, 172.75 ± 8.21 cm, 70.9 ± 13.2 kg, and 22.9 ± 4.1% body fat) overall mean 25(OH)D was 70.5 ± 32.25 nmol/L, and 28% of participants were deemed inadequate and 61% below thresholds identified as sufficient for athletes. Although WBB athletes consumed higher (p = 0.007) dietary vitamin D (760.9 ± 484.2 IU/d) than WVB (342.6 ± 257.8) and WTF (402.3 ± 376.4) athletes did, there were no differences across sport in serum 25(OH)D. WVB and WTF had higher bioavailable 25(OH)D than WBB. No relationships existed between vitamin D status and body composition. Vitamin D inadequacy was identified among 1/3 of women indoor sport athletes. Consistent monitoring of vitamin D status and diet are recommended to sustain athlete health and sport performance.

The effects of vitamin D and curcuminoids supplementation on anthropometric measurements and blood pressure in type 2 diabetic patients with coexisting hypovitaminosis D: A double-blind, placebo-controlled randomized clinical trial

BACKGROUND AND AIMS

Curcuminoids and vitamin D have been shown to improve blood pressure and body weight in diabetic animals; however, consistent findings in type 2 diabetes mellitus (T2DM) patients are limited. This study was performed to evaluate the effects of curcuminoids and vitamin D, simultaneously or singly on anthropometric measurements and blood pressure in T2DM patients with insufficient vitamin D level.

METHODS

In this randomized, placebo-controlled clinical trial, eighty T2DM patients were randomly assigned into 4 groups receiving (1) 500 mg/day curcuminoids; (2) 50,000 IU/week vitamin D₃; (3) 50,000 IU/week vitamin D₃ plus 500 mg/d curcuminoids; or (4) placebos for 12 weeks. Blood pressure and anthropometric measurements were evaluated before and after intervention.

RESULTS

Intergroup comparisons showed that Vitamin D (main effect) significantly reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP) (P = 0/000). Curcuminoids (main effect) significantly reduced DBP (P = 0/001). Interaction effects showed that curcuminoids significantly prevented the effect of vitamin D on the reduction of SBP (P = 0.006). Whereas, vitamin D and curcuminoids had a synergistic effect on DBP reduction (P = 0.006). The comparison of changes in anthropometric measurements between the four groups showed no significant differences in the raw and adjusted models. In-group comparisons showed that SBP, DBP, waist to hip circumference (WHR), body fat mass (BFM), percent body fat (PBF) and visceral fat area (VFA) values were significantly reduced in all groups except the placebo group compared to baseline values. Only in the CR-D group, there was a significant reduction in body weight (P = 0/047).

CONCLUSIONS

Curcuminoids and vitamin D may have beneficial effects on blood pressure and anthropometric measurements in T2DM patients. CLINICAL REGISTRATION: http://www.IRCT.ir:IRCT2017041213678N22.

Obesity and Vitamin D Insufficiency among Adolescent Girls and Young Adult Women from Korea

Although there is evidence of the biological mechanisms by which obesity may induce vitamin D insufficiency or deficiency, limited epidemiological studies have been conducted, especially among Asian adolescent girls and young adult women who are at a high risk of vitamin D deficiency. This study aimed to examine the cross-sectional association between obesity and vitamin D insufficiency among adolescent girls and young adult women in Korea. We used data from the Korea National Health and Nutrition Examination Survey (KNHANES) 2008–2014, and 3623 girls and young adult women aged 12–29 years were included. Demographic and lifestyle data were collected using a self-administered questionnaire from the health interview survey. Serum 25-hydroxyvitamin D (25(OH)D) level, body mass index (BMI), and body fat percentage (BF%) were measured during health examinations. Multivariable logistic regression was used considering the complex, multistage probability sample design of KNHANES. In the multivariable-adjusted analyses, obese girls and women, defined by BMI, were more likely to have a higher prevalence of vitamin D insufficiency (odds ratio [OR]: 1.49, 95% confidence interval [CI]: 1.03–2.17). This association was also evident for BF%. Participants with ≥30% BF% had a significantly higher prevalence of vitamin D insufficiency (OR: 1.52, 95% CI: 1.07–2.16). Obesity may worsen vitamin D insufficiency among adolescents and young women because of the fat-soluble characteristics of vitamin D and related health behaviors, such as a lack of outdoor activity. Further large-scale prospective cohort studies or randomized controlled trials are warranted to confirm this causality.

The optimal vitamin D cut-off value associated with hyperglycemia in an Iranian population

Background

Vitamin D deficiency may accelerate the risk of type 2 diabetes mellitus. The association of vitamin D with hyperglycemia may be influenced by lifestyle.

Objective

To evaluate the relationship between vitamin D status and hyperglycemia among the workers' population.

Methods

This was a medical records review of 7054 Iranian factory workers participating in an annual health check-up for employees. Of those, potential participants were included in this analysis if data for serum 25-hydroxyvitamin D [25(OH) D] levels were also available.

Results

Data of 429 male participants were used for this analysis. Of those, 61.07% had serum 25(OH)D concentrations lower than the sufficient level [≥20 ng/ml]. Hyperglycemic participants had significantly lower 25(OH)D than those with normal fasting blood glucose (FBG). Regression analyses highlighted serum 25(OH)D as a significant determinant of hyperglycemia [OR: 0.943(0.901, 988); p = 0.01]. The association between 25(OH)D and FBG remained significant after adjustment for potential confounders (p = 0.008). Using the ROC analysis, the serum 25(OH)D value of 14.7 ng/ml was the optimal cut-off point to predict hyperglycemia in this population (sensitivity: 63.6%, specificity: 62.3%, p = 0.01).

Conclusion

Our results revealed a considerable proportion of participants with serum 25(OH)D below the optimal level as well as a significant inverse association between vitamin D status and hyperglycemia among the factory workers. These findings highlight the importance of including the evaluation of vitamin D status as a part of annual health examinations for employees, and may help health policy- makers prevent or delay type 2 diabetes mellitus among the workers' population.

Vitamin D Status Differs by Sex, Sport-Season, and Skin Pigmentation among Elite Collegiate Basketball Players

Vitamin D plays a key role in bone health, musculoskeletal function, and sport performance. Collegiate athletes competing in indoor sports may be at greater risk of vitamin D deficiency due to limited outdoor time. Therefore, the purpose was to assess 25-hydroxyvitamin D (25(OH)D) concentrations among collegiate men and women basketball (MBB, WBB) athletes. National Collegiate Athletic Association Division I men (MBB, n = 11) and women (WBB, n = 9) were tested during the off-season (T1; July) and pre-season (T2; October). Measurements included serum 25(OH)D; skin pigmentation, bone mineral density, and daily sun exposure (self-reported). Paired t-tests determined changes in 25(OH)D by sport-season and sex. Pearson correlations examined relationships between outcome variables. MBB athletes (mean ± SD; 19.6 ± 1.3 years) showed a reduction in 25(OH)D (T1: 64.53 nmol·L⁻¹ ± 11.96) (T2: 56.11 nmol·L⁻¹ ± 7.90) (p = 0.001). WBB (20.1 ± 1.1 years) had no change in 25(OH)D (T1: 99.07 nmol·L⁻¹ ± 49.94. T2: 97.56 nmol·L⁻¹ ± 36.47, p = 0.848). A positive association between 25(OH)D and skin pigmentation was observed (r = 0.47, p = 0.038). 25(OH)D was inversely correlated with lean body mass (LBM), body mass (BM), and bone mineral density (BMD), while a positive association was seen between 25(OH)D and skin pigmentation. In summary, 25(OH)D insufficiency was prevalent amongst male collegiate basketball athletes, with 25(OH)D levels being lower in the pre-season (October) than the off-season (July). Furthermore, darker skin pigmentation significantly correlated with 25(OH)D, indicating that individuals with darker skin tones may be at a greater risk of insufficiency/deficiency. More research is needed to examine the relationships between 25(OH)D and bone health in athletes.

Seasonal variation of serum 25-hydroxyvitamin D and parameters of bone and mineral disorder in dialysis patients

BACKGROUND

Vitamin D deficiency is common among dialysis patients and may impact blood concentrations of calcium, phosphorus, intact parathyroid hormone (iPTH), and alkaline phosphatase (ALP). Seasonal variation of serum 25-hydroxyvitamin D [25(OH)D] concentrations has been well established for the general population; however, less is known about circannual variation in 25(OH)D as well as other parameters of mineral and bone disorder among dialysis patients.

METHOD

Based on 57,500 serum 25(OH)D measurements collected over two years from January 2009 to December 2010 among 25,025 dialysis patients, we evaluated the circannual variations in serum concentrations of 25(OH)D, calcium, phosphorus, iPTH, and ALP by a linear regression model with a cosinor function for the time period (month). We adjusted for potential confounders including case-mix variables, and ultraviolet index.

RESULTS

Serum 25(OH)D concentrations showed significant circannual variation and mean serum 25(OH)D was 3.2 ng/mL higher in summer than in winter. Furthermore, 25(OH)D concentration increased steadily by 1.3 ng/mL per year. While serum calcium concentrations showed statistically significant but clinically negligible seasonal variation (0.02 mg/dL in peak-trough difference), serum phosphorus did not follow such a pattern. Serum iPTH concentrations also showed a modest seasonal variation with 9% higher values in winter than in summer. Concordantly, ALP concentrations in the winter were 2% higher than in the summer time. Seasonal variation of 25(OH)D was greater in male (vs. female), African-American (vs. non-African-American), and younger (vs. older) dialysis patients.

CONCLUSION

Serum 25(OH)D and iPTH concentrations show seasonal variation among dialysis patients while the variation in other parameters of mineral and bone disorder was clinically irrelevant, if any. Serum 25(OH)D also showed a gradual increase over time. Clinicians and researchers should be aware of these changes when interpreting laboratory results in dialysis patients.

High prevalence of vitamin D insufficiency in professional handball athletes

OBJECTIVES

Vitamin D affects multiple body functions through the regulation of gene expression. In sports medicine, its influence on musculoskeletal health and performance is of particular interest. Vitamin D insufficiency might decrease athletic performance and increase the risk of musculoskeletal injuries. Several studies have demonstrated vitamin D deficiency in professional athletes; however, the prevalence of vitamin D insufficiency in professional handball players is yet unknown.

METHODS

The study was planned as a prospective, non-interventional study. We examined 70 male elite handball athletes (first league) in a pre-competition medical assessment in July. Age, height, weight, body mass index, 25-OH vitamin D, calcium, and parathyroid hormone were evaluated, and a sun exposure score was calculated. Players were then divided into two groups of vitamin D levels: insufficient (<30 ng/mL) and sufficient (≥30 ng/mL).

RESULTS

The mean 25-OH vitamin D level of the 70 players was 33.5 ± 10.9 ng/mL (median 32.2, IQR 26.5-38.9 ng/mL). Thirty-nine (55.7%) had sufficient and 31 (44.3%) insufficient levels. Athletes with sufficient vitamin D levels had significantly lower parathyroid hormone levels than athletes with insufficiency (24.9 ± 12.1 vs. 33.5 ± 15.1 ng/mL, p = 0.02). All other parameters evaluated demonstrated no significant difference between the two groups.

CONCLUSION

Vitamin D insufficiency is a common finding in professional handball athletes even in summer, which might negatively affect physical performance. Furthermore, it might lead to an increased risk of musculoskeletal injuries and infections. This should be evaluated in further studies.

Relationship Between Vitamin D Status From Childhood to Early Adulthood With Body Composition in Young Australian Adults

Context

Vitamin D plays a role in the differentiation and metabolism of skeletal muscle and, possibly, adipose tissue; however, the relationship between vitamin D status during growth and body composition in early adulthood is unclear.

Objective

We examined associations between vitamin D status in childhood, adolescence, and early adulthood with body composition at age 20 years.

Design, Setting, Participants

We studied 821 offspring (385 females) of the Western Australian Pregnancy Cohort Study who had ≥3 serum 25-hydroxyvitamin D [25(OH)D] at age 6, 14, 17, and 20 years and body composition assessed at age 20 using dual-energy x-ray absorptiometry. The participants were grouped into four vitamin D status trajectories: consistently lower, decreasing, increasing, and consistently higher.

Results

The mean serum 25(OH)D at the study visits was 72.7 to 86.8 nmol/L. In males, serum 25(OH)D at 17 and 20 years was positively associated with lean body mass (LBM), and 25(OH)D at age 20 correlated negatively with fat body mass (FBM). Males with a consistently higher 25(OH)D trajectory had a 2.3- to 3.7-kg greater LBM and 4.1- to 6.0-kg lower FBM at 20 years compared with those with consistently lower or decreasing trajectories (P < 0.05 for all). In females, 25(OH)D at 14, 17, and 20 years was negatively associated with FBM. Females with increasing or consistently higher 25(OH)D trajectories had a 5.2- to 6.8-kg lower FBM at age 20 compared with those with a consistently lower trajectory (P < 0.05 for all).

Conclusions

In the present predominantly white, relatively vitamin D-replete cohort, a higher vitamin D status trajectory from childhood to early adulthood was associated with a greater LBM in males and lower FBM in both sexes at age 20.

Serum 25-hydroxyvitamin D fluctuations in military personnel during 6-month summer operational deployments in Afghanistan

Soldier operational performance is determined by their fitness, nutritional status, quality of rest/recovery, and remaining injury/illness free. Understanding large fluctuations in nutritional status during operations is critical to safeguarding health and well-being. There are limited data world-wide describing the effect of extreme climate change on nutrient profiles. This study investigated the effect of hot-dry deployments on vitamin D status (assessed from 25-hydroxyvitamin D (25(OH)D) concentration) of young, male, military volunteers. Two data sets are presented (pilot study, n 37; main study, n 98), examining serum 25(OH)D concentrations before and during 6-month summer operational deployments to Afghanistan (March to October/November). Body mass, percentage of body fat, dietary intake and serum 25(OH)D concentrations were measured. In addition, parathyroid hormone (PTH), adjusted Ca and albumin concentrations were measured in the main study to better understand 25(OH)D fluctuations. Body mass and fat mass (FM) losses were greater for early (pre- to mid-) deployment compared with late (mid- to post-) deployment (P<0·05). Dietary intake was well-maintained despite high rates of energy expenditure. A pronounced increase in 25(OH)D was observed between pre- (March) and mid-deployment (June) (pilot study: 51 (sd 20) v. 212 (sd 85) nmol/l, P<0·05; main study: 55 (sd 22) v. 167 (sd 71) nmol/l, P<0·05) and remained elevated post-deployment (October/November). In contrast, PTH was highest pre-deployment, decreasing thereafter (main study: 4·45 (sd 2·20) v. 3·79 (sd 1·50) pmol/l, P<0·05). The typical seasonal cycling of vitamin D appeared exaggerated in this active male population undertaking an arduous summer deployment. Further research is warranted, where such large seasonal vitamin D fluctuations may be detrimental to bone health in the longer-term.

Relation of Serum 25(OH)-Vitamin D to Fat Mass and Lean Mass, Bone Mineral Content and Body Composition in Adults – a DXA-Based Study

Obesity has been linked with vitamin D deficiency in a number of cross-sectional studies, reviews and meta-analyses. The aim of the present study was to assess the correlations of plasma 25(OH) vitamin D levels with indices of body composition examined by DXA with an emphasis on lean and bone mass as well as on indices such as android/gynoid fat, appendicular lean mass, fat-mass indexes (FMI) and fat-free mass indexes (FFMI). 62 adult subjects consented to participate – 27 men (43.5%) and 35 women (56.5%). Their mean age was 45.3 ± 9.5 years. Fan-beam dual-energy X-ray (DXA) body composition analysis was performed on a Lunar Prodigy Pro bone densitometer with software version 12.30. Vitamin D was measured by electro-hemi-luminescent detection as 25(OH) D Total (ECLIA, Elecsys 2010 analyzer, Roche Diagnostics). Statistical analyses were done using the SPSS 23.0 statistical package. The serum 25(OH)D level was correlated significantly only to the whole body bone mineral content, the appendicular lean mass index (ALMI) and the ALM-to-BMI index, underlining a predominant role for lean and fat-free mass. Vitamin D showed a very weak correlation to % Body Fat and the Fat Mass Index (FMI) in men only. Moreover, the multiple regression equation including the associated parameters could explain only 7% of the variation in the serum 25(OH) D levels. Our conclusion was, that there are differences in the associations of the vitamin D levels with the different body composition indices, but these associations are generally very weak and therefore – negligible.

Associations of different body fat deposits with serum 25-hydroxyvitamin D concentrations

BACKGROUND & AIMS

Obesity is a well-established risk factor of vitamin D deficiency. However, it is unclear which fat deposit is most strongly related to serum 25-hydroxyvitamin D (25(OH)D) concentrations. Our aim was to distinguish the specific contributions of total body fat (TBF), abdominal subcutaneous adipose tissue (aSAT), visceral adipose tissue (VAT) and hepatic fat on 25(OH)D concentrations.

METHODS

We performed a cross-sectional analysis of the Netherlands Epidemiology of Obesity study, a population-based cohort study. We used linear regression analyses to examine associations of TBF, aSAT, VAT (n = 2441) and hepatic fat (n = 1980) with 25(OH)D concentrations. Standardized values were used to compare the different fat deposits.

RESULTS

Mean (SD) age and 25(OH)D concentrations of the study population was 56 (6) years and 70.8 (24.2) nmol/L, respectively. TBF was inversely associated with 25(OH)D concentrations in women, but not in men. One percent higher TBF was associated with 0.40 nmol/L (95%CI: -0.67 to -0.13) lower 25(OH)D. aSAT was not associated with 25(OH)D concentrations. One cm² higher VAT was associated with 0.05 nmol/L (-0.09 to -0.02) lower 25(OH)D in men, and 0.06 nmol/L (-0.10 to -0.01) lower 25(OH)D in women. Hepatic fat was only associated with 25(OH)D in men. A tenfold increase in hepatic fat was associated with 6.21 nmol/L (-10.70 to -1.73) lower 25(OH)D. Regressions with standardized values showed VAT was most strongly related to 25(OH)D.

CONCLUSIONS

In women, TBF and VAT were inversely related to 25(OH)D concentrations. In men, VAT and hepatic fat were inversely related to 25(OH)D concentrations. In both groups, VAT was most strongly associated with 25(OH)D concentrations.

Vitamin D and the Athlete: Current Perspectives and New Challenges

The last decade has seen a dramatic increase in general interest in and research into vitamin D, with many athletes now taking vitamin D supplements as part of their everyday dietary regimen. The most recognized role of vitamin D is its regulation of calcium homeostasis; there is a strong relationship between vitamin D and bone health in non-athletic individuals. In contrast, data have consistently failed to demonstrate any relationship between serum 25[OH]D and bone health, which may in part be due to the osteogenic stimulus of exercise. Vitamin D may interact with extra-skeletal tissues such as muscle and the immune system to modulate recovery from damaging exercise and infection risk. Given that many athletes now engage in supplementation, often consuming extreme doses of vitamin D, it is important to assess whether excessive vitamin D can be detrimental to health. It has been argued that toxic effects only occur when serum 25[OH]D concentrations are greater than 180 nmol·l^-1, but data from our laboratory have suggested high-dose supplementation could be problematic. Finally, there is a paradoxical relationship between serum 25[OH]D concentration, ethnicity, and markers of bone health: Black athletes often present with low serum 25[OH]D without physiological consequences. One explanation for this could be genetic differences in vitamin D binding protein due to ethnicity, resulting in greater concentrations of bioavailable (or free) vitamin D in some ethnic groups. In the absence of any pathology, screening may be unnecessary and could result in incorrect supplementation. Data must now be re-examined, taking into consideration bioavailable or "free" vitamin D in ethnically diverse groups to enable new thresholds and target concentrations to be established; perhaps, for now, it is time to "set vitamin D free".

Vitamin D Levels: Do We Need to Assess Only in Disease?

BACKGROUND

Vitamin D is conventionally known as sunshine vitamin and is synthesized endogenously in sunlight. Vitamin D is known to be a key regulator of bone metabolism, the function of genes, and essential for the development of the whole body. Deficiency of Vitamin D is now become a major worldwide epidemic health problem.

AIM

The present study was conducted with the objective of determining the prevalence of Vitamin D deficiency (VDD) in urban population of a district in south Punjab, across various characteristics of population such as gender, age, and socioeconomic status.

MATERIALS AND METHODS

A cross-sectional population survey was conducted in the urban population of the district. A total of 120 healthy volunteers of either sex participated and their 25-hydroxy Vitamin D concentrations in serum samples were estimated using ELISA. The participants were divided into three categories as follows: Vitamin D deficient, insufficient, or sufficient, on the basis of normal standardized serum levels of Vitamin D <20, 20-30, and >30 ng/ml, respectively.

RESULTS

Of 120 healthy individuals, 95% of the study participants had VDD or insufficiency and only 5% had adequate Vitamin D levels. In each age group, females showed lower Vitamin D levels as compared to males. Furthermore, high body mass index value was associated with low Vitamin D. Upper-class individuals also showed low levels of Vitamin D as compared to other socioeconomic classes' individuals.

CONCLUSIONS

Overall, high prevalence of VDD among the apparently healthy urban population of the district was observed and gives an alarming sign about continuously increasing prevalence of hypovitaminosis D among healthy population.

Serum 25-Hydroxyvitamin D Concentrations Are Inversely Correlated with Hepatic Lipid Content in Male Collegiate Football Athletes

Lower serum 25-hydroxyvitamin D (25(OH)D) concentrations are associated with more weight and fat mass gain in adults in the general population, but it is unknown whether this is the case in collegiate football athletes with greater body weight. This study aimed to investigate associations of serum 25(OH)D concentrations with body fat and ectopic fat accumulation, and to determine which fat indicators are closely related to serum 25(OH)D in male collegiate football athletes. Thirty-four collegiate athletes aged 21 years were recruited. Serum 25(OH)D concentrations and the levels of visceral fat area (VFA), vastus lateralis intramyocellular lipid (IMCL), extramyocellular lipid (EMCL), and intrahepatic lipid (IHCL) were measured. Serum 25(OH)D concentrations were negatively associated with the IHCL values (r = −0.372, p = 0.030), and the relationship remained after adjustment for several factors (r = −0.378, p = 0.047). Additionally, multiple stepwise regression analysis of IHCL content as the dependent variable indicated that 25(OH)D concentrations were a stronger predictor of IHCL content (β = −0.363, p = 0.030) than % body fat and VO₂peak_FFM. Higher serum 25(OH)D concentrations are more closely related to lower IHCL content rather than any other fat indicators, suggesting that increasing serum 25(OH)D concentrations may have some effect that inhibits lipid accumulation in hepatic tissue, especially in heavy athletes.

Effect of vitamin D supplementation on anthropometric indices among overweight and obese women: A double blind randomized controlled clinical trial

AIMS

The aim of this study was to investigate effect of vitamin D supplementation on anthropometric indices among women with overweight and obesity.

METHODS

This double blind randomize clinical trial was conducted on 66 overweight and obese women. Those in intervention group received oral supplement of vitamin D 50,000 IU (1250 mcg) per 25 day and in control group participants received placebo for 3 months. Anthropometric indices were measured before and after 3 months intervention. Before the intervention a 24-h dietary recall (3 days) were used to assess dietary intake of individuals. Independent t test and multivariate repeated measure were used to data analysis.

RESULTS

The mean difference of anthropometric indices, serum calcium, 25 (OH) D₃ and serum PTH between the intervention and control groups were significant (P < 0/05). However, no significant differences in serum phosphorus between the intervention and control groups were seen.

CONCLUSION

Supplementation with vitamin D 50 μg for each day for 3 months resulted in a significant reduction in anthropometric indices in women with obesity and overweight with normal primary 25(OH) D₃ serum levels.

Positive Correlations Between Free Vitamin D and Bone Variables in a Group of Young Lebanese Women

Optimizing bone mass in adulthood is of great importance to prevent the occurrence of osteoporosis in later age. Vitamin D is an essential component of bone health. Low-serum vitamin D is associated with low bone mineral density (BMD), which is an important predictor of fracture risk. However, most cells, apart from renal tubular cells, are exposed to free rather than to total 25-hydroxyvitamin D. Whether free vitamin D would be a better marker than total vitamin D is still under debate. The aim of the present study was to explore the relationships between serum total vitamin D, vitamin D-binding protein (BP), free vitamin D, and bone parameters in a group of young Lebanese women. This study included 88 young female adults aged between 18 and 35 yr. Body composition and BMD were assessed by dual-energy X-ray absorptiometry, and the lumbar spine trabecular bone score was derived. Bone mineral content (BMC) and BMD were measured at the whole body (WB), the lumbar spine (L1-L4), the total hip (TH), and the femoral neck (FN). To evaluate hip bone geometry, dual-energy X-ray absorptiometry scans were analyzed at the FN, the intertrochanteric region, and the femoral shaft by the Hip Structure Analysis program. The cross-sectional area, the index of axial compression strength, and the section modulus (Z), as well as index of bending strength, were measured from bone mass profiles. Composite indices of FN strength (compressive strength index [CSI], bending strength index, and impact strength index [ISI]) were calculated as previously described. Direct measurement of free 25-hydroxyvitamin D concentrations was performed by immunoassay, which detects free vitamin D by ELISA on a microtiter plate. Serum vitamin D BP was measured using a Quantikine ELISA kit, which employed the quantitative sandwich enzyme immunoassay technique. Serum free vitamin D was positively correlated with WB BMC (r = 0.26, p < 0.05), WB BMD (r = 0.29, p < 0.05), L1-L4 BMD (r = 0.28, p < 0.05), TH BMD (r = 0.34, p < 0.01), FN BMD (r = 0.29, p < 0.05), CSI (r = 0.24, p < 0.05), and ISI (r = 0.28, p < 0.05). No positive correlations were detected between the total vitamin D level, the vitamin D BPs, and BMD. The positive associations between free vitamin D and several bone variables (WB BMC, WB BMD, L1-L4 BMD, TH BMD, FN BMD, CSI, bending strength index, and ISI) remained significant after adjustment for weight. In conclusion, the current study suggests that the free vitamin D serum level is a stronger positive determinant of bone parameters and hip bone strength indices in young female adults than total serum vitamin D.

Fat Mass Is Associated with Serum 25-Hydroxyvitamin D Concentration Regardless of Body Size in Men

There are no large community-based studies examining the association of body size vs. body fat with vitamin D status. Association of serum 25-hydroxyvitamin D (25OHD) with body weight and subcategories of body weight defined by fat mass were evaluated in a large, free living population. Out of a total of 29,235 subjects from the 2008–2010 Korean National Health and Nutrition Examination Survey, the relevant data included 6458 subjects over 50 years of age who were analyzed cross-sectionally. Serum 25OHD concentrations were compared in men (n = 3164) and in women (n = 3294) by tertiles of body weight and body fat mass, as measured by Dual-energy X-ray Absorptiometry (DXA) within sex-specific tertiles of body weight. Serum 25OHD was weakly inversely correlated with body weight in the men and the women after adjustment for age (r = −0.075 and −0.073, respectively, p < 0.001 for both). Within each tertile of body weight, serum 25OHD decreased progressively as fat mass increased in men. This pattern was similar in the women but not consistently significant. Whereas body weight predicted a small decrease in serum 25OHD in the men and the women, greater adiposity, for any given weight, predicted larger decreases in the men, but not consistently in women.

The effect of vitamin D supplementation on insulin resistance, visceral fat and adiponectin in vitamin D deficient women with polycystic ovary syndrome: a randomized placebo-controlled trial

INTRODUCTION

Low plasma 25-hydroxy-vitamin D (25OHD) is associated with polycystic ovary syndrome (PCOS). Vitamin D deficiency may contribute to the development of insulin resistance, visceral fat and low level of adiponectin which are common feature in PCOS women. This study aimed to evaluate the effect of vitamin D supplementation on insulin resistance, visceral fat, and adiponectin in hypovitaminosis D women with polycystic ovary syndrome.

METHODS

In this randomized, placebo-controlled clinical trial, 44 PCOS women aged 20-38 years with plasma 25OHD <20 ng/mL were randomized in the intervention or placebo groups and followed for 8 weeks. Participants received 50,000 IU of oral vitamin D3 once weekly in the intervention group or placebo. The visceral adipose tissue, Insulin resistance (HOMA-IR), HOMA-B, QUICKI, and circulating adiponectin were compared before and after the intervention within groups using paired tests and the mean changes were analyzed between two groups by independent t-test.

RESULTS

Of 44 eligible participates, 36 patients (81.8%) completed the study. After 8 week intervention, vitamin D supplementation compared to the placebo group significantly decreased fasting plasma glucose (FPG) (7.67 ± 7.66 versus 1.71 ± 7.50 mg/dL, p = .001) and significantly increased homeostasis model of assessment-estimated B cell function (HOMA-B) (129.76 ± 121.02 versus 48.32 ± 128.35, p = .014), Adiponectin (5.17 ± 8.09 versus -5.29 ± 8.64 mg/dL, p = .001), and serum vitamin D level (28.24 ± 6.47 versus 3.55 ± 4.25 ng/mL, p = .001).

CONCLUSION

Vitamin D supplementation in vitamin D deficient women with PCOS, improved the FPG, HOMA-B, Adiponectin, and serum vitamin D level.

Vitamin D in pediatric age: consensus of the Italian Pediatric Society and the Italian Society of Preventive and Social Pediatrics, jointly with the Italian Federation of Pediatricians

Vitamin D plays a pivotal role in the regulation of calcium-phosphorus metabolism, particularly during pediatric age when nutritional rickets and impaired bone mass acquisition may occur.Besides its historical skeletal functions, in the last years it has been demonstrated that vitamin D directly or indirectly regulates up to 1250 genes, playing so-called extraskeletal actions. Indeed, recent data suggest a possible role of vitamin D in the pathogenesis of several pathological conditions, including infectious, allergic and autoimmune diseases. Thus, vitamin D deficiency may affect not only musculoskeletal health but also a potentially wide range of acute and chronic conditions. At present, the prevalence of vitamin D deficiency is high in Italian children and adolescents, and national recommendations on vitamin D supplementation during pediatric age are lacking. An expert panel of the Italian Society of Preventive and Social Pediatrics reviewed available literature focusing on randomized controlled trials of vitamin D supplementation to provide a practical approach to vitamin D supplementation for infants, children and adolescents.

Vitamin D supplementation and body fat mass: a systematic review and meta-analysis

Studies have indicated that 25-hydroxyvitamin D (25(OH)D) level in obese is lower than normal weight subjects; however, results of studies that investigated relationship between 25(OH)D and fat mass are inconsistent. In addition, several randomized clinical trials (RCTs) have studied the influence of cholecalciferol supplement on percentage fat mass (PFM) but their results are conflicting. The objectives were to investigate the association between vitamin D3 and PFM pooling together observational studies and RCTs. PubMed/MEDLINE, Cochrane, and Scopus were comprehensively searched from inception to September 2016. The Fisher's Z (SE) of correlation coefficient and mean (SD) of changes in PFM from baseline were used to perform meta-analysis in observational studies and RCTs, respectively. To determine potential source of heterogeneity, subgroup and meta-regression analyses were conducted. Pooling correlation coefficients showed an inverse association between PFM (Fisher's Z: - 0.24, 95% CI: - 0.30 to -0 .18) and FM (Fisher's Z: - 0.32, 95% CI: - 0.43 to - 0.22) and 25(OH)D. Subgroup analysis revealed continent but not gender influence on the effect size. Meta-regression analysis indicated that age, latitude, and longitude are not sources of heterogeneity. Combining trials showed vitamin D3 supplementation had a mild but insignificant effect on PFM (- 0.31%, 95% CI: - 1.07 to 0.44). Subgroup analyses indicated that type of cholecalciferol and treatment regimens explain source of heterogeneity. Age, baseline body mass index, dose of cholecalciferol, length of study, female (%), and baseline 25(OH)D are not source of heterogeneity. In conclusion, our results state that 25(OH)D level is inversely correlated with PFM but cholecalciferol supplementation had no effect on PFM.

Vitamin D prevents lipid accumulation in murine muscle through regulation of PPARγ and perilipin-2 expression

Vitamin D plays an important role in regulation of skeletal muscle tone and contraction. Serum vitamin D status is linked to muscle power and force in adolescent girls, and vitamin D deficiency is associated with myopathies in children and poorer physical performance in the elderly. We previously reported that vitamin D deficiency is linked to a significant increase in muscle fatty infiltration in healthy young women, and studies in patients with neuromuscular disorders also associate muscle weakening and lipid content. In order to better understand the link between vitamin D status and skeletal muscle lipid metabolism, we compared the effect of a low (25IU/kg) or normal (1000IU/kg) vitamin D₃ diet on muscle fat in female FVB mice maintained in a room without UVB lighting to minimize endogenous vitamin D production. Animals on low vitamin D diet displayed lower circulating 25(OH)D levels and a dramatic increase (287±52% compared to normal diet, p<0.0001) in lipid deposition in skeletal muscle accompanied by muscle fiber disorganization. Lipid droplet staining increased by 242±23% (p<0.0001) in low vitamin D diet, and lipid droplet coat protein perilipin-2 and nuclear receptor transcription factor PPARγ expression levels were increased compared to mice fed the normal vitamin D diet: average staining for PLIN2: 0.22±0.08 (25IU/kg diet) vs 0.10±0.02 (1000IU/kg). Average staining for PPARγ: 0.24±0.06 (25IU/kg diet) vs 0.07±0.04 (1000IU/kg) p<0.0001. Tissue mass spectrometry imaging revealed major differences in muscle phospholipids profile depending on diet. In vitro, 1,25(OH)₂D₃ treatment of 3T3-L1 pre-adipocytes inhibited appearance of lipid droplets by 79±9.3%, and caused a 80±10% and 25±8% (p=0.001) reduction in PPARγ and perilipin-2 mRNA levels (by qPCR) compared to control cells. In summary, we report here the first in vivo model illustrating the important structural muscle fiber disorganization and fat accumulation inside and outside muscle fibers that accompany vitamin D deficiency. Furthermore, we show that the underlying mechanisms involve PPARγ and perilipin-2.

Winter vitamin D3 supplementation does not increase muscle strength, but modulates the IGF-axis in young children

PURPOSE

To explore whether muscle strength, the insulin-like growth factor axis (IGF-axis), height, and body composition were associated with serum 25-hydroxyvitamin D [25(OH)D] and affected by winter vitamin D supplementation in healthy children, and furthermore to explore potential sex differences.

METHODS

We performed a double-blind, placebo-controlled, dose-response winter trial at 55ºN. A total of 117 children aged 4-8 years were randomly assigned to either placebo, 10, or 20 µg/day of vitamin D₃ for 20 weeks. At baseline and endpoint, we measured muscle strength with handgrip dynamometer, fat mass index (FMI), fat free mass index (FFMI), height, plasma IGF-1, IGF-binding protein 3 (IGFBP-3), and serum 25(OH)D.

RESULTS

At baseline, serum 25(OH)D was positively associated with muscle strength, FFMI, and IGFBP-3 in girls only (all p < 0.01). At endpoint, baseline-adjusted muscle strength, FMI and FFMI did not differ between intervention groups. However, baseline-adjusted IGF-1 and IGFBP-3 were higher after 20 µg/day compared to placebo (p = 0.043 and p = 0.006, respectively) and IGFBP-3 was also higher after 20 µg/day compared to 10 µg/day (p = 0.011). Children tended to be taller after 20 µg/day compared to placebo (p = 0.064). No sex interactions were seen at endpoint.

CONCLUSIONS

Avoiding the winter-related decline in serum 25(OH)D may influence IGF-1 and IGFBP-3 in children. Larger trials are required to confirm these effects, and the long-term implication for linear growth.

The 24,25 to 25-hydroxyvitamin D ratio and fracture risk in older adults: The cardiovascular health study

25-hydroxyvitamin D [25(OH)D] may not optimally indicate vitamin D receptor activity. Higher concentrations of its catabolic product 24,25-dihydroxyvitmin D [24,25(OH)₂D] and a higher ratio of 24,25(OH)₂D to 25(OH)D (the vitamin D metabolite ratio [VMR]) may provide additional information on receptor activity. We compared the strength of associations of these markers with serum PTH concentrations, hip bone mineral density (BMD), and risk of incident hip fracture in community-living older participants in the Cardiovascular Health Study. Among 890 participants, the mean age was 78years, 60% were women, and the mean 25(OH)D was 28±11ng/ml. In cross-sectional analysis, the strength of association of each vitamin D measure with PTH was similar; a 1% higher 25(OH)D, 24,25(OH)₂D, and VMR were associated with 0.32%, 0.25%, and 0.26% lower PTH, respectively (p<0.05 for all). Among 358 participants with available BMD data, we found no associations of 25(OH)D or VMR with BMD, whereas higher 24,25(OH)₂D was modestly associated with greater hip BMD (1% higher 24,25(OH)₂D associated with 0.04% [95% CI 0.01-0.08%] higher BMD). Risk of incident hip fracture risk was evaluated using a case-cohort design. There were 289 hip fractures during a mean follow up time of 8.4years. Both higher 24,25(OH)₂D and VMR were associated with lower risk of hip fracture (HR per SD higher, 0.73 [0.61, 0.87] and 0.74 [0.61, 0.88], respectively) whereas 25(OH)D was not associated with hip fracture (HR 0.93 [0.79, 1.10]). We conclude that evaluating vitamin D status by incorporating assessment of 24,25(OH)D and the VMR provides information on bone health above and beyond 25(OH)D alone.

Associations of vitamin D with insulin resistance, obesity, type 2 diabetes, and metabolic syndrome

The aim of this study is to determine the relationships of vitamin D with diabetes, insulin resistance obesity, and metabolic syndrome. Intra cellular vitamin D receptors and the 1-α hydroxylase enzyme are distributed ubiquitously in all tissues suggesting a multitude of functions of vitamin D. It plays an indirect but an important role in carbohydrate and lipid metabolism as reflected by its association with type 2 diabetes (T2D), metabolic syndrome, insulin secretion, insulin resistance, polycystic ovarian syndrome, and obesity. Peer-reviewed papers, related to the topic were extracted using key words, from PubMed, Medline, and other research databases. Correlations of vitamin D with diabetes, insulin resistance and metabolic syndrome were examined for this evidence-based review. In addition to the well-studied musculoskeletal effects, vitamin D decreases the insulin resistance, severity of T2D, prediabetes, metabolic syndrome, inflammation, and autoimmunity. Vitamin D exerts autocrine and paracrine effects such as direct intra-cellular effects via its receptors and the local production of 1,25(OH)₂D₃, especially in muscle and pancreatic β-cells. It also regulates calcium homeostasis and calcium flux through cell membranes, and activation of a cascade of key enzymes and cofactors associated with metabolic pathways. Cross-sectional, observational, and ecological studies reported inverse correlations between vitamin D status with hyperglycemia and glycemic control in patients with T2D, decrease the rate of conversion of prediabetes to diabetes, and obesity. However, no firm conclusions can be drawn from current studies, because (A) studies were underpowered; (B) few were designed for glycemic outcomes, (C) the minimum (or median) serum 25(OH) D levels achieved are not measured or reported; (D) most did not report the use of diabetes medications; (E) some trials used too little (F) others used too large, unphysiological and infrequent doses of vitamin D; and (G) relative paucity of rigorous clinical data on the effects of vitamin D sufficiency on non-calcium endpoints. Although a large number of observational studies support improving T2D, insulin resistance, obesity, and metabolic syndrome with vitamin D adequacy, there is a lack of conclusive evidence from randomized control clinical trials that, these disorders are prevented following optimization of serum levels of 25(OH)D. However, none of the currently conducted clinical studies would resolve these issues. Thus, specifically designed, new clinical studies are needed to be conducted in well-defined populations, following normalizing the serum vitamin D levels in vitamin D deficient prediabetes subjects, to test the hypothesis that hypovitaminosis D worsens these disorders and correction would alleviate it.