Optimal vitamin D status: a critical analysis on the basis of evidence-based medicine

Prevalence and Treatment of Vitamin D Deficiency in Young Male Russian Soccer Players in Winter

Vitamin D (25(OH)D) insufficiency and deficiency are highly prevalent in adult soccer players and can exceed 80% even in regions with high insolation; however, the treatment of this condition is often complicated. The aim of the present study was to examine the prevalence of vitamin D insufficiency and deficiency in youth Russian soccer players and the efficacy of its treatment. Participants were 131 young male football players (age 15.6 ± 2.4 years). Low vitamin D levels (below 30 ng/mL) were observed in 42.8% of the analyzed participants. These athletes were split in two groups composed of persons with vitamin D deficiency (serum vitamin D below 21 ng/mL) and insufficiency (serum vitamin D in range of 21–29 ng/mL). A dietary supplement of 5000 IU cholecalciferol per day was administered for two months. After the treatment, an average 92% increase in vitamin D concentration was observed (before treatment—19.7 ± 5.4 ng/mL, after treatment—34.7 ± 8.6 ng/mL, p < 0.001) and 74% of the post-treatment values were within the reference range (30–60 ng/mL). Serum concentration of vitamin D increased by 200% ± 98% (p < 0.001) during the first month of treatment with vitamin D deficiency and insufficiency being successfully treated in 83% of the football players. In summary, the prevalence of vitamin D insufficiency and deficiency was high in young Russian soccer players. Furthermore, it was indicated that the daily usage of cholecalciferol in a dose 5000 IU was an effective and well-tolerated treatment for vitamin D insufficiency. No linear dependency between the duration of treatment and increase in vitamin 25(OH)D concentration was observed.

Vitamin D in physiological and pathological aging: Lesson from centenarians

Vitamin D is a secosteroid hormone that exerts a pleiotropic action on a wide spectrum of tissues, apparatuses and systems. Thus, vitamin D has assumed an increasingly dominant role as a key determinant of biological mechanisms and specific clinical conditions. Older people frequently present vitamin D deficiency, a status potentially influencing several mechanisms responsible for different age-related diseases. Centenarians symbolize the ideal model for investigating the peculiar traits of longevity, as they have reached an age close to the estimated limit of the human lifespan. Interestingly, despite the profound heterogeneity of centenarians in terms of health status, all these people share the same condition of severe vitamin D deficiency, suggesting that they may have implemented a number of adaptive strategies to cope with the age-related physiological derangement of vitamin D metabolism. The lesson deriving from centenarians' experience suggests that: i) severe vitamin D deficiency does not preclude the possibility of reaching extreme longevity, ii) strategies to prevent hypovitaminosis D may be useful to slow down the processes of "fragilization" occurring in aged people, iii) beneficial effects of vitamin D supplementation need to be confirmed regarding longevity.

New developments in our understanding of vitamin metabolism, action and treatment

Although vitamin D has been reported to have pleiotropic effects including effects on the immune system and on cancer progression, the principal action of vitamin D is the maintenance of calcium and phosphate homeostasis. The importance of vitamin D in this process is emphasized by the consequences of vitamin D deficiency which includes rickets in children and osteomalacia in adults. Vitamin D deficiency has also been reported to increase the risk of falls and osteoporotic fractures. Although vitamin D fortification of foods (including dairy products) has contributed to a marked decrease in rickets in the Western world, vitamin D deficiency in children and adults is still prevalent world-wide. This review summarizes new developments in our understanding of vitamin D endocrine system and addresses clinical syndromes related to abnormalities in vitamin D metabolism and action. In addition, the current understanding of the evaluation of vitamin D deficiency and sufficiency and recommendations for achieving vitamin D sufficiency are discussed.

The Dependence of Running Speed and Muscle Strength on the Serum Concentration of Vitamin D in Young Male Professional Football Players Residing in the Russian Federation

Background: Vitamin D insufficiency is prevalent among athletes, and it can negatively affect physical performance. At the same time, most of the available data were obtained from untrained individuals of various ages, and published studies performed in athletes led to contradictory conclusions. Methods: This cohort prospective study examined the serum concentration of 25-hydroxycalciferol (25(OH)D) and its association with running speed and muscle power in 131 young football players (mean age 15.6 ± 2.4 years). Results: 25(OH)D levels were below reference in 42.8% (serum 25(OH)D <30 ng/mL) and above reference in 30.5% of the participants (serum 25(OH)D 61–130 ng/mL). A comparison of the results of 5, 15, and 30 m sprint tests and the standing long jump test found no statistically significant differences between the two groups. Athletes from the 25(OH)D-insufficient group were treated with 5000 IU cholecalciferol supplement daily for 60 days. After the treatment, the 25(OH)D concentration increased by 79.2% and was within reference in 84% of the treated athletes (serum 25(OH)D 30–60 ng/mL). Testing was repeated after the end of treatment, and a statistically significant increase in the results of the 5, 15, and 30 m sprint tests was observed (Cohen’s d was 0.46, 0.33, and 0.34, respectively), while the results of the standing long jump test remained unchanged. Body height, body weight, and lean body mass of the football players also increased. Conclusions: These findings indicate that there is likely no correlation between serum levels of 25(OH)D, muscle power, and running speed in young professional football players, and the changes observed post-treatment might have been caused by changes in the anthropometric parameters. During the study, all the anthropometric parameters changed, but the amount of lean body mass only correlated with the results of the 5 m sprint.

Effectiveness and safety of steady versus intermittent high dose vitamin D supplementation for the prevention of falls and fractures among adults: a protocol for systematic review and network meta-analysis

INTRODUCTION

Clinical trials and systematic reviews of trials involving vitamin D supplementation have mainly focused on defining the optimal amount of vitamin D dosage. However, the comparative effectiveness of different dosing schedules (ie, daily vs bolus dosing schedule) has been largely unexplored; and currently, there is no consensus regarding the optimal vitamin D dosing schedule. Our objective is to conduct a systematic review and network meta-analysis (NMA) to evaluate the comparative effectiveness and safety of steady (eg, daily, weekly) and intermittent high-dose (eg, monthly, yearly) vitamin D dosing schedules; and to determine the effectiveness of the various dosing schedules and combinations of treatments.

METHODS AND ANALYSIS

We will conduct a systematic search and review of literature from major medical databases (MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov) involving studies that compare vitamin D supplementation alone or in combination with calcium. Only randomised controlled trials (RCTs) will be considered. We will, however, consider various settings (eg, community, institutional care) and study designs (eg, cluster RCTs, cross-over trials). Our primary outcomes include falls and fractures including hip-fracture and non-vertebral fractures. Secondary outcomes will include muscle strength, physical performance, gait and mobility limitation. A Bayesian NMA will be conducted, and the results will be presented in the form of treatment effect estimates and ranking probabilities, with corresponding CIs. Pairwise meta-analysis will also be conducted for studies reporting head-to-head comparisons. Subgroup analysis will be performed with respect to pre-determined subgroups; including vitamin D status as measured by serum 25-hydroxyvitamin D levels, age and follow-up time. Sensitivity analysis will also be performed with respect to risk of bias.

ETHICS AND DISSEMINATION

This study is a systematic review and meta-analysis of published RCTs; therefore, no ethical approval is required. Results will be disseminated through open access peer-reviewed publications.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018112662.

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

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

The Effect of Vitamin D Deficiency Correction on the Outcomes in Women After Carpal Tunnel Release

PURPOSE

Studies suggest that vitamin D supplementation improves myelination and recovery after nerve injuries. The purpose of this study was to evaluate whether correction of vitamin D level leads to better surgical outcomes in women with both carpal tunnel syndrome (CTS) and vitamin D deficiency.

METHODS

We retrospectively reviewed 84 vitamin D-deficient women with CTS who underwent carpal tunnel release and then received daily vitamin D supplementation of 1,000 IU vitamin D for 6 months. We also reviewed 35 control patients who were vitamin D-nondeficient at baseline and thus did not receive the supplementation. At baseline and 6 months after surgery, we measured serum vitamin D levels, the Disabilities of the Arm, Shoulder, and Hand (DASH) score, motor conduction velocity, and grip and pinch strengths. We compared the outcomes of CTS related to vitamin D levels. We also correlated baseline and follow-up vitamin D levels with the assessed parameters.

RESULTS

At 6 months, 59 patients became vitamin D-nondeficient (≥ 20 ng/mL) and 25 were still vitamin D-deficient (< 20 ng/mL). Patients who became vitamin D-nondeficient had subtle but better DASH scores than patients who were still vitamin D-deficient or the control patients. Vitamin D levels at 6 months were found to have significant correlation with the DASH score at 6 months. Vitamin D levels at 6 months did not have significant correlation with motor conduction velocity or grip and pinch strengths.

CONCLUSIONS

Women with CTS and vitamin D deficiency showed subtle but better DASH scores after surgery when vitamin D deficiency was corrected by supplementation.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Carboxy terminal collagen crosslinks as a prognostic risk factor for fall-related fractures in individuals with established spinal cord injury

Study design

Prospective cohort study.

Objective

To study associations between specific bone turnover markers and fall-related fractures in individuals with spinal cord injury (SCI).

Setting

Rehabilitation Hospital.

Methods

Carboxy terminal collagen crosslinks (CTX), type-1 procollagen N-terminal (P1NP), albumin-corrected calcium (Ca²⁺), parathyroid hormone (PTH) and vitamin D were examined in a cohort of 106 participants with SCI at least 1 year post injury. The participants were followed for 1 year monitoring fall-related fractures.

Results

In total, 29 out of 106 reported having experienced a fall-related fracture post-injury at baseline, and 5 out of 100 had experienced a fall-related bone fracture during the 1 year follow-up. Our main findings were that high levels of serum CTX increased the odds of being in the fracture group, and that 25-hydroxy vitamin D (25 OHD) levels, Ca²⁺, PTH or P1NP were not associated with being in the fracture group.

Conclusions

We here present an association between high-CTX plasma levels at baseline and fall-related fractures reported during a 1-year follow-up among individuals with established SCI. We recommend studies with larger SCI populations before further clinical implications can be drawn.

Association between 25-Hydroxyvitamin D, Parathyroid Hormone, Vitamin D and Calcium Intake, and Bone Density in Healthy Adult Women: A Cross-Sectional Analysis from the D-SOL Study

There is still limited data on the association between 25-hydroxyvitamin D (25(OH)D), parathyroid hormone (PTH), and bone health in healthy younger adults, particularly in Latin America. This cross-sectional analysis aimed to investigate the associations of 25(OH)D and plasma PTH concentrations with bone parameters, and potential confounders, in women living in a high (England) or low (Brazil) latitude country. Bone was assessed by either peripheral quantitative computed tomography (pQCT) (England) or dual-energy x-ray absorptiometry (DXA) scan (Brazil), serum 25(OH)D concentrations by high performance liquid chromatography tandem mass spectrometry (HPLC-MS) and PTH by the chemiluminescent method. In participants living in England, total volumetric bone mineral density (vBMD) was significantly higher in women <29 years compared to ≥30 years, and total and cortical vBMD values at the 66% site were negatively correlated with weight and body mass index (BMI). In participants living in Brazil, age was positively correlated with bone mineral density (BMD) at the femur and bone mineral content (BMC), and weight, BMI, and body fat were correlated with BMD (lumbar spine and femur) and BMC. PTH concentrations were negatively correlated with 25(OH)D concentrations, and the prevalence of secondary hyperparathyroidism was 28.6% (n = 14) in participants with concentrations <25 nmol/L and 12.2% (n = 41) with concentrations between 25 and 49.9 nmol/L, compared to 6.3% (n = 79) in those with concentrations ≥50 nmol/L. In conclusion, weight and BMI were significantly correlated with bone parameters in both groups and age was significantly correlated with BMD at the femoral neck for women living in Brazil only. Although 25(OH)D concentrations were not correlated to bone parameters at any sites, in either country, PTH concentrations showed a significant correlation with total vBMD at the 66% site for women living in England. Secondary hyperparathyroidism was more common amongst those with deficient and insufficient vitamin D status.

Hypovitaminosis D: Is It Time to Consider the Use of Calcifediol?

Hypovitaminosis D is becoming a notable health problem worldwide. A consensus exists among several different medical societies as to the need for adequate levels of vitamin D for bone and general health. The correct method by which to restore normal vitamin D levels is still a matter of debate. Although cholecalciferol remains the most commonly distributed form of vitamin D supplementation worldwide, several drugs with vitamin D activity are available for clinical use, and making the correct selection for the individual patient may be challenging. In this narrative review, we aim to contribute to the current knowledge base on the possible and appropriate use of calcifediol-the 25-alpha-hydroxylated metabolite-in relation to its chemical characteristics, its biological properties, and its pathophysiological aspects. Furthermore, we examine the trials that have aimed to evaluate the effect of calcifediol on the restoration of normal vitamin D levels. Calcifediol is more soluble than cholecalciferol in organic solvents, due to its high polarity. Good intestinal absorption and high affinity for the vitamin-D-binding protein positively affect the bioavailability of calcifediol compared with cholecalciferol. In particular, orally administered calcifediol shows a much shorter half-life than oral cholecalciferol. Most findings suggest that oral calcifediol is about three- to five-fold more powerful than oral cholecalciferol, and that it has a higher rate of intestinal absorption. Accordingly, calcifediol can be particularly useful in treating diseases associated with decreased intestinal absorption, as well as obesity (given its lower trapping in the adipose tissue) and potentially neurological diseases treated with drugs that interfere with the hepatic cytochrome P-450 enzyme system, resulting in decreased synthesis of calcifediol. Up to now, there has not been enough clinical evidence for its use in the context of osteoporosis treatment.

Current vitamin D status in European and Middle East countries and strategies to prevent vitamin D deficiency: a position statement of the European Calcified Tissue Society

Vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) <50 nmol/L or 20 ng/mL) is common in Europe and the Middle East. It occurs in <20% of the population in Northern Europe, in 30-60% in Western, Southern and Eastern Europe and up to 80% in Middle East countries. Severe deficiency (serum 25(OH)D <30 nmol/L or 12 ng/mL) is found in >10% of Europeans. The European Calcified Tissue Society (ECTS) advises that the measurement of serum 25(OH)D be standardized, for example, by the Vitamin D Standardization Program. Risk groups include young children, adolescents, pregnant women, older people (especially the institutionalized) and non-Western immigrants. Consequences of vitamin D deficiency include mineralization defects and lower bone mineral density causing fractures. Extra-skeletal consequences may be muscle weakness, falls and acute respiratory infection, and are the subject of large ongoing clinical trials. The ECTS advises to improve vitamin D status by food fortification and the use of vitamin D supplements in risk groups. Fortification of foods by adding vitamin D to dairy products, bread and cereals can improve the vitamin D status of the whole population, but quality assurance monitoring is needed to prevent intoxication. Specific risk groups such as infants and children up to 3 years, pregnant women, older persons and non-Western immigrants should routinely receive vitamin D supplements. Future research should include genetic studies to better define individual vulnerability for vitamin D deficiency, and Mendelian randomization studies to address the effect of vitamin D deficiency on long-term non-skeletal outcomes such as cancer.

A systematic review and meta-analysis of the response of serum 25-hydroxyvitamin D concentration to vitamin D supplementation from RCTs from around the globe

BACKGROUND/OBJECTIVES

Optimal doses of vitamin D (VitD) supplement in different populations are unclear. We aim to evaluate the relationship between VitD supplementation and post-intervention serum 25-hydroxyvitamin D [25(OH)D] concentration, to provide a recommended dosage of VitD for achieving an optimal 25(OH)D concentration for different populations.

SUBJECTS/METHODS

Literature search was conducted in Embase, etc. Randomized controlled trials about VitD supplemental intakes and their effect on 25(OH)D concentration were enrolled. The effect on 25(OH)D concentration between different supplementation doses in each population group was compared by meta-analysis. Multivariate meta-regression model is utilized to establish reference intake dosage of VitD.

RESULTS

A total of 136 articles were included about children (3-17 years), adults (18-64 years), postmenopausal women, the elderly ( >64 years), pregnant, or lactating women. Overall, intervention groups obtained higher 25(OH)D concentration than controls and there was obvious dose-response effect between intake dose and 25(OH)D concentration. Baseline 25(OH)D concentration and age were significant indicators for 25(OH)D concentration. To reach sufficient 25(OH)D concentration (75 nmol/L), the recommended VitD supplemental intakes was 1340 and 2250 IU/day for children and pregnant women, 2519 and 797 IU/day for European adults aged 18-64 and 65-85 years, 729, 2026, and 1229 IU/day for adults in North America, Asia and Middle East and Africa, respectively.

CONCLUSIONS

Regional- and age-specific recommended dosages of VitD supplements for population to achieve optimal 25(OH)D concentrations have been suggested.

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

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

The Relationship Between Vitamin D Deficiency and Insulin Resistance in Pregnant Women with Gestational Diabetes

BACKGROUND

Diabetes Mellitus is one of the most common medical disorders in pregnancy. The possibility of vitamin D deficiency as a pathogenesis for impaired glucose tolerance tests show a probable role of vitamin D in insulin secretion and reduction of insulin resistance. This study was assigned to evaluate relation between serum vitamin D level and insulin resistance in Gestational Diabetes Mellitus (GDM).

METHODS

This cross sectional study was done throughout one year between 2015-2016 in GDM patients (age, 20-40 years). After history taking and physical examination, the laboratory tests including : Fasting Blood Sugar (FBS), Glucose Tolerance Test (GTT), calcium, phosphorous, parathormone, 25(OH) vitamin D, insulin, HbA1C, TG, LDL, HDL were performed for all patients. Insulin resistance was calculated according to HOMA-IR formula. Vitamin D level was compared between patients with and without insulin resistance.

RESULTS

This research was performed in 93 GDM patients with average age (30.3 ± 5.6). Thirty eight patients with insulin resistance and 55 patients without insulin resistance were detected. The prevalence of vitamin D deficiency was 91.4% in all patients. There was no significant difference in vitamin D levels between insulin resistant and non insulin resistant group (P-value=0.51). In all variable parameters, only FBS and triglyceride level in insulin resistant group were more than non insulin resistant group (P-value<0.05).

CONCLUSION

Obtained results showed not significant relationship between vitamin D deficiency and insulin resistance in GDM patients.

Vitamin D, Inflammation and Osteoporosis in Rheumatoid Arthritis

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

Limitations of platform assays to measure serum 25OHD level impact on guidelines and practice decision making

CONTEXT

Liquid Chromatography Mass Spectroscopy (LC-MS/MS) is the preferred method to measure 25 hydroxyvitamin D (25OHD) levels, but laboratories are increasingly adopting automated platform assays.

OBJECTIVE

We assessed the performance of commonly used automated immunoassays, with that of LC-MS/MS, and the National Institute of Standards and Technology (NIST) reference values, to measure 25OHD levels.

METHODS/SETTING

We compared serum 25OHD levels obtained from 219 elderly subjects, enrolled in a vitamin D trial, using the Diasorin Liaison platform assay, and the tandem LC-MS/MS method. We also assessed the performance of the Diasorin and Roche automated assays, expressed as mean % bias from the NIST standards, based on the vitamin D External Quality Assessment Scheme (DEQAS) reports, from 2013 to 2017.

RESULTS

Serum 25OHD levels were significantly lower in the Diasorin compared to LC-MS/MS assay at baseline, 18.5 ± 7.8 vs 20.5 ± 7.6 ng/ml (p < 0.001), and all other time points. Diasorin (25OHD) = 0.76 × LC-MS/MS (25OHD) + 4.3, R² = 0.596. The absolute bias was independent of 25OHD values, and the pattern unfit for any cross-calibration. The proportion of subjects considered for vitamin D treatment based on pre-set cut-offs differed significantly between the 2 assays. There also was wide variability in the performance of both automated assays, compared to NIST reference values.

CONCLUSION

The performance of most widely used automated assays is sub-optimal. Our findings underscore the pressing need to re-consider current practices with regard to 25OHD measurements, interpretation of results from research studies, meta-analyses, the development of vitamin D guidelines, and their relevance to optimizing health.

Vitamin D assays and the definition of hypovitaminosis D: results from the First International Conference on Controversies in Vitamin D

The First International Conference on Controversies in Vitamin D was held in Pisa, Italy, 14-16 June 2017. The meeting's purpose was to address controversies in vitamin D research, review the data available, to help resolve them, and suggest a research agenda to clarify areas of uncertainty. The serum 25-hydroxyvitamin D [25(OH)D] concentration [i.e. the sum of 25(OH)D3 and 25(OH)D2 ] remains the critical measurement for defining vitamin D status. Assay variation for 25(OH)D has contributed to the current chaos surrounding efforts to define hypovitaminosis D. An essential requirement to develop a consensus on vitamin D status is that measurement of 25(OH)D and, in the future, other potential vitamin D biomarkers [e.g. 1α,25(OH)2 D3 , 3-epi-25(OH)D, 24,25(OH)2 D3, vitamin D-binding protein, free/bioavailable 25(OH)D and parathyroid hormone] be standardized/harmonized, to allow pooling of research data. Vitamin D Standardization Program tools are described and recommended for standardizing 25(OH)D measurement in research. In the future, similar methodology, based on National Institute for Standards and Technology standard reference materials, must be developed for other candidate markers of vitamin D status. Failure to standardize/harmonize vitamin D metabolite measurements is destined to promulgate continued chaos. At this time, 25(OH)D values below 12 ng ml-1 (30 nmol l-1 ) should be considered to be associated with an increased risk of rickets/osteomalacia, whereas 25(OH)D concentrations between 20 ng ml-1 and 50 ng ml-1 (50-125 nmol l-1 ) appear to be safe and sufficient in the general population for skeletal health. In an effort to bridge knowledge gaps in defining hypovitaminosis D, an international study on rickets as a multifactorial disease is proposed.

Vitamin D insufficiency: Definition, diagnosis and management

Severe vitamin D deficiency can be defined as the dose of vitamin D or serum 25OHD concentrations needed to prevent nutritional rickets or osteomalacia. There is large international consensus that these diseases can be prevented by 400 IU of vitamin D/d and 25OHD above 30 nmol/l (12 ng/ml). Vitamin D deficiency can also accelerate the risk of fractures and probably also of falls in elderly subjects but there is no consensus on the required daily doses or minimal 25OHD threshold for these endpoints. The majority of experts consider 800 IU/d and serum 25OHD above 50 nmol/l (20 ng/ml) as sufficient, with a minority opinion aiming for 75 nmol/l or even higher. For other extra-skeletal endpoints, no hard evidence is available to define whether or not this is causally related to vitamin D status. Therefore, for these endpoints no minimal dosage or 25OHD threshold can be defined.

Effect of Vitamin D supplementation on body composition and cardiorespiratory fitness in overweight men-a randomized controlled trial

PURPOSE

Several observational studies have shown an association between vitamin D deficiency and non-skeletal major health issues including impaired cardiorespiratory fitness and adiposity. Only a few studies have examined the impact of vitamin D supplementation on these conditions and the results are ambiguous. The aim of this study was to examine the effect of vitamin D supplementation on body composition and cardiorespiratory fitness in overweight/obese men with vitamin D deficiency.

METHODS

This study was a prospective, placebo controlled, double blinded, randomized trial with a study period of 6 months. Forty overweight/obese men (BMI > 25 kg/m²) with vitamin D deficiency (25(OH)D ≤ 55 nmol/L) were randomized to receive either 2000 IU Cholecalciferol drops or the equivalent amount of drops of placebo. At baseline and follow up body composition and cardiorespiratory fitness were measured and blood samples were obtained. Body composition was measured using bioelectrical impedance analysis (BIA) and cardiorespiratory fitness using cardiopulmonary exercise test (CPET). The primary outcomes were changes in percentage body fat and in maximum oxygen uptake (VO_2max).

RESULTS

No statistically significant difference between the placebo and the intervention group regarding changes in percentage body fat (p = 0.54) and VO_2max (p = 0.90) was observed. Moreover, there was no statistically significant difference between the groups concerning changes in BMI (p = 0.26), maximum load (p = 0.89) and oxygen uptake at anaerobic threshold (AT) (p = 0.14).

CONCLUSIONS

We conclude that treatment with 2000 IU/d vitamin D for 6 months does not impact body composition or maximum oxygen uptake in overweight/obese men with vitamin D deficiency.

Hypovitaminosis D: comparison between patients with hip fracture and patients with vertebral fractures

This study analyses the difference in 25OH-vitamin D values between two groups of patients both affected by severe osteoporosis with fragility fractures, but one group has vertebral fractures and the other one has hip fractures. Patients with hip fractures have vitamin D values lower than patients with vertebral fractures.

INTRODUCTION

The purpose of this study was to evaluate 25OHD levels in patients with fragility vertebral fractures (VF) and hip fractures (HF) and make a comparison between the groups.

METHODS

In the first group were enrolled ambulatory patients with 3 or more moderate to severe VF; in the second group were enrolled patients hospitalized in the Department of Orthogeriatrics undergoing surgery for HF. For all patients, we collected values of 25OHD and PTH. The group of patients with VF was further subdivided into pre-existing VF or recent VF treated within 30 days with vertebroplasty.

RESULTS

The sample consists of 180 subjects divided into two groups: 90 with VF and 90 with HF. The average value of 25OHD in the total sample was 13.2 ± 9.6 ng/ml, Vitamin D was significantly lower in the HF group than the VF group (p < 0.001)(VF 18.6 ± 9.7 ng/ml, HF 7.9 ± 5.7 ng/ml). The mean PTH value in the total sample was 67.5 ± 54.9 pg/ml and PTH was significantly higher in the HF group compared to the group with VF (p < 0.001) (VF 55.6 ± 27.2 pg/ml, HF 78.7 ± 70.2 pg/ml). The mean 25OHD value in the recent VF group is 16.0 ± 6.6 ng/ml while in the pre-existing VF group is 19.5 ± 10.4 ng/ml with a statistically significant difference (p < 0.001).

CONCLUSIONS

Patients of the same age with severe osteoporosis have a lower 25OHD value when the fracture occur at the hip and is recent, probably this is due to the inflammation caused by fracture and/or surgical intervention.

Serum 25-Hydroxy Vitamin D Levels in Turkish Adolescent Girls with Polycystic Ovary Syndrome and the Correlation with Clinical/Biochemical Parameters

STUDY OBJECTIVE

Polycystic ovary syndrome (PCOS) is a common endocrinopathy among female adolescents and young women. The aim of this study was to investigate the relationship between serum 25-hydroxy vitamin D (25[OH] D) levels and metabolic parameters and other characteristics of PCOS and non-PCOS adolescents.

DESIGN

Case-control study.

SETTING AND PARTICIPANTS

We analyzed 31 girls with PCOS as defined using the Rotterdam criteria and 35 girls were non-PCOS control participants.

INTERVENTIONS AND MAIN OUTCOME MEASURES

The serum 25(OH) D level was measured. Anthropometric, clinical, endocrine, and metabolic components were determined in both groups.

RESULTS

The group with PCOS showed no difference in the level of serum 25(OH) D (14.58 ± 6.15 vs 16.02 ± 7.87; P = .414). In addition to this, no significant correlations were found between serum 25(OH) D levels and endocrine or metabolic parameters in either PCOS patients or control participants.

CONCLUSION

There was no difference in the level of serum 25(OH) D between PCOS patients and matched control participants. Vitamin D deficiency was common among the patients as well as in the control participants. Also, we did not find any relationship between serum 25(OH) D levels and clinical or metabolic profiles in the 2 groups.

Combined treatment with benzo[a]pyrene and 1α,25-dihydroxyvitamin D3 induces expression of plasminogen activator inhibitor 1 in monocyte/macrophage-derived cells

Benzo[a]pyrene (BaP) is an environmental pollutant found in cigarette smoke and is implicated as a causative agent of tobacco-related diseases, such as arteriosclerosis. In contrast, vitamin D signaling, which is principally mediated by conversion of vitamin D to the active form, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], decreases cardiovascular disease risk. However, combined treatment with BaP and 1,25(OH)₂D₃ enhances BaP toxicity, including BaP-DNA adduct formation. We further investigated the cross-talk between BaP and 1,25(OH)₂D₃ signaling pathways, and found that combined treatment with these compounds induces mRNA and protein expression of plasminogen activator inhibitor 1 (PAI-1) in monocyte/macrophage-derived THP-1 and U937 cells. Protein synthesis inhibitor treatment did not inhibit induction of the PAI-1 gene (SERPINE1) in these cells. BaP plus 1,25(OH)₂D₃ induced differentiation markers, inhibited cellular proliferation, and induced apoptosis and oxidative stress in these cells. Reactive oxygen species scavenger treatment suppressed apoptosis but not SERPINE1 induction in cells treated with BaP plus 1,25(OH)₂D₃. Thus, combined treatment with BaP and 1,25(OH)₂D₃ induced SERPINE1 mRNA expression in these cells through a mechanism that does not require de novo protein synthesis or reactive oxygen species production. These findings suggest that induction of the proinflammatory factor PAI-1 plays a role in BaP toxicity. Interestingly, PAI-1 knockdown decreased expression of the cell surface antigen CD14, a monocytic differentiation marker, in THP-1 cells treated with BaP plus 1,25(OH)₂D₃. PAI-1 induction may also be related to a function of monocytes/macrophages in response to xenobiotic and vitamin D signaling.

The When, What & How of Measuring Vitamin D Metabolism in Clinical Medicine

We now have the ability to measure a number of different vitamin D metabolites with very accurate methods. The most abundant vitamin D metabolite, 25-hydroxyvitamin D, is currently the best marker for overall vitamin D status and is therefore most commonly measured in clinical medicine. The added value of measuring metabolites beyond 25-hydroxyvitamin D, like 1,25-, and 24,25-dihydroxyvitamin D is not broadly appreciated. Yet, in some more complicated cases, these metabolites may provide just the information needed for a legitimate diagnosis. The problem at present, is knowing when to measure, what to measure and how to measure. For 25-hydroxyvitamin D, the most frequently used automated immunoassays do not meet the requirements of today’s standards for certain patient groups and liquid chromatography-tandem mass spectrometry is the desired method of choice in these individuals. The less frequently measured 1,25-dihydroxyvitamin D metabolite enables us to identify a number of conditions, including 1α-hydroxylase deficiency, hereditary vitamin D-resistant rickets and a number of granulomatous diseases or lymphoproliferative diseases accompanied by hypercalcaemia. Furthermore, it discriminates between the FGF23-mediated and non-FGF23-mediated hypophosphatemic syndromes. The 24,25-dihydroxyvitamin D metabolite has proven its value in the diagnosis of idiopathic infantile hypercalcaemia and has the potential of having value in identifying other diseases. For both metabolites, the understanding of the origin of differences between assays is limited and requires further attention. Nonetheless, in every way, appropriate measurement of vitamin D metabolism in the clinical laboratory hinges eminently on the comprehension of the value of the different metabolites, and the importance of the choice of method.

Alterations in the vitamin D endocrine system during pregnancy: A longitudinal study of 855 healthy Norwegian women

To ensure optimal calcium accrual in the fetal skeleton, a substantial rise occurs in 1,25-dihydroxyvitamin D (1,25(OH)2D), but is dependent on sufficient 25-hydroxyvitamin (25(OH)D). Large longitudinal studies addressing free 25(OH)D and 1,25(OH)2D during pregnancy are scarce. We aimed to assess levels of and relationship between 25(OH)D, 1,25(OH)2D, vitamin D-binding protein (DBP), parathyroid hormone (PTH), and free 25(OH)D during pregnancy; determinants of vitamin D status; and association between vitamin D indices or PTH and pregnancy outcomes (gestational diabetes mellitus and birthweight). Altogether 855 pregnant Norwegian Caucasian women from Trondheim and Stavanger (latitude 63°N and 58°N) were recruited; 94 were lost to follow-up. The study was originally a randomized controlled trial (2007-2009) with gestational diabetes as primary outcome. Data were collected in second and third trimester. In third trimester, 246 (34%) had vitamin D insufficiency and 52 (7%) deficiency (25(OH)D <50 and <30nmol/L, respectively). During wintertime in third trimester, 61 (47%) from Trondheim and 23 (51%) from Stavanger exhibited vitamin D insufficiency. PTH was elevated in 27 (3.7%). Estimate of change between trimesters was (95% CI): 25(OH)D -1.8 (-2.8 to -0.7) nmol/L, DBP 0.62 (0.57 to 0.66) μmol/L, calculated free 25(OH)D -1.7 (-2.0 to -1.4) pmol/L, PTH 0.81 (0.72 to 0.90) pmol/L, 1,25(OH)2D (sub-analysis) 31.4 (CI 24.7 to 38.2) pmol/L. A decrease in 1,25(OH)2D occurred in 45% of those with vitamin D deficiency, and they also exhibited lower levels than women with adequate vitamin D status. No association of vitamin D indices and PTH with pregnancy outcomes was observed. Women in Trondheim displayed lower 25(OH)D levels, despite minor latitudinal differences. Less than one-fifth adhered to the authorities' vitamin D recommendations. These findings demonstrate that hypovitaminosis D is prevalent among pregnant women living in northern latitudes, especially during the dark season, and there is an unmet need to ensure adequate vitamin D intake.

RCTS are the only appropriate way to demonstrate the role of vitamin D in health

Despite thousands of vitamin D studies published, including hundreds of reviews and meta-analyses, it is still uncertain if supplementation with vitamin D will have positive health effects, except for the skeleton. This cannot be answered by doing more observational studies as it is impossible to control for confounding factors and reverse causality. The only way to firmly prove positive vitamin D effects is by doing the properly designed randomized controlled trials (RCTs). However, it has been difficult to show the expected positive effects by vitamin D supplementation in RCTs, which may indicate that the effects, if present must be small. On the other hand, results from Mendelian randomization studies have shown promising results at least for mortality and multiple sclerosis. In the near future, results from several large RCTs with hard endpoints will be available. If these show positive results, the main question on vitamin D and health is answered. If they turn out negative, they will be criticized for having included subjects without vitamin D deficiency, and some studies might not have used an optimal dosing regimen. New and better-designed RCTs will then be needed, but will be very hard to perform.

Limitations of vitamin D supplementation trials: Why observational studies will continue to help determine the role of vitamin D in health

Observational studies have shown that low vitamin D status is associated with an increased risk of a wide range of diseases. The body of observational evidence now is so large, that there have been many calls for randomized controlled trials (RCT) of vitamin D supplementation to confirm once and for all whether increasing body vitamin D levels prevents these diseases. These calls have arisen because of concern that confounding and reverse causation may explain many of the results from observational studies. However, RCTs also are prone to limitations that compromise their validity. These include low response rates that affect their external validity; and biases that affect their internal validity, such as recruitment of vitamin D sufficient people which decreases the power to detect beneficial effects, studies of long-term outcomes requiring participation for many years which decreases compliance and retention, and easy access for participants to vitamin D supplements and blood testing which increase contamination and unblinding. Because of these potential limitations, it is possible that RCTs of vitamin D supplementation may not to give a clear answer by themselves. Future decisions about the role of vitamin D in health are likely to be based on the evidence from a range of study designs including RCTs, mendelian randomization studies and other observational designs.

Low free 25-hydroxyvitamin D and high vitamin D binding protein and parathyroid hormone in obese Caucasians. A complex association with bone?

Background

Studies have shown altered vitamin D metabolism in obesity. We assessed differences between obese and normal-weight subjects in total, free, and bioavailable 25-hydroxyvitamin D (25(OH)D, 25(OH)D_Free, and 25(OH)D_Bio, respectively), vitamin D binding protein (DBP), parathyroid hormone (PTH) and bone traits.

Methods

595 37-47-year-old healthy Finnish men and women stratified by BMI were examined in this cross-sectional study. Background characteristic and intakes of vitamin D and calcium were collected. The concentrations of 25(OH)D, PTH, DBP, albumin and bone turnover markers were determined from blood. 25(OH)D_Free and 25(OH)D_Bio were calculated. pQCT was performed at radius and tibia.

Results

Mean±SE (ANCOVA) 25(OH)D_Free (10.8±0.6 vs 12.9±0.4 nmol/L; P = 0.008) and 25(OH)D_Bio (4.1±0.3 vs 5.1±0.1 nmol/L; P = 0.003) were lower in obese than in normal-weight women. In men, 25(OH)D (48.0±2.4 vs 56.4±2.0 nmol/L, P = 0.003), 25(OH)D_Free (10.3±0.7 vs 12.5±0.6 pmol/L; P = 0.044) and 25(OH)D_Bio (4.2±0.3 vs 5.1±0.2 nmol/L; P = 0.032) were lower in obese. Similarly in all subjects, 25(OH)D, 25(OH)D_Free and 25(OH)D_Bio were lower in obese (P<0.001). DBP (399±12 vs 356±7mg/L, P = 0.008) and PTH (62.2±3.0 vs 53.3±1.9 ng/L; P = 0.045) were higher in obese than in normal-weight women. In all subjects, PTH and DBP were higher in obese (P = 0.047and P = 0.004, respectively). In obese women, 25(OH)D was negatively associated with distal radius trabecular density (R² = 0.089, P = 0.009) and tibial shaft cortical strength index (CSI) (R² = 0.146, P = 0.004). 25(OH)D_Free was negatively associated with distal radius CSI (R² = 0.070, P = 0.049), radial shaft cortical density (CorD) (R² = 0.050, P = 0.045), and tibial shaft CSI (R² = 0.113, P = 0.012). 25(OH)D_Bio was negatively associated with distal radius CSI (R² = 0.072, P = 0.045), radial shaft CorD (R² = 0.059, P = 0.032), and tibial shaft CSI (R² = 0.093, P = 0.024).

Conclusions

The associations between BMI and 25(OH)D, 25(OH)D_Free, and 25(OH)D_Bio, DBP, and PTH suggest that obese subjects may differ from normal-weight subjects in vitamin D metabolism. BMI associated positively with trabecular bone traits and CSI in our study, and slightly negatively with cortical bone traits. Surprisingly, there was a negative association of free and bioavailable 25(OH)D and some of the bone traits in obese women.

The concept of the personal vitamin D response index

Humans are able to synthesize vitamin D₃ in their skin when exposed to UV-B, but seasonal variations, textile coverage and predominant indoor activities often make supplementation with the compound necessary. There is some dispute on the desired vitamin D status, measured via the serum concentration of the most stable vitamin D₃ metabolite, 25-hydroxyvitamin D₃, and the respective recommended daily supplementation. A possible answer may be provided by the concept of the personal vitamin D response index describing the efficiency of the molecular response to supplementation with vitamin D. The concept is based on the fact that vitamin D₃ activates via its metabolite 1α,25-dihydroxyvitamin D₃ the transcription factor vitamin D receptor and thus has a direct effect on the epigenome and transcriptome of many human tissues and cell types. Individuals can be distinguished into high, mid and low responders to vitamin D via measuring vitamin D sensitive molecular parameters, such as changes in the epigenetic status and the respective transcription of genes of mobile immune cells from blood or the level of proteins or metabolites in serum. Thus, we suggest that the need for vitamin D supplementation depends on the vitamin D status in relation to the personal vitamin D response index of an individual rather than on the vitamin D status alone.

Evolution of Serum 25OHD in Response to Vitamin D3-Fortified Yogurts Consumed by Healthy Menopausal Women: A 6-Month Randomized Controlled Trial Assessing the Interactions between Doses, Baseline Vitamin D Status, and Seasonality

BACKGROUND

Adequate vitamin D status contributes to bone fragility risk reduction and possibly other pathological conditions that occur with aging. In response to pharmaceutical vitamin D3 supplements, several studies have documented the influence of doses, baseline status, and seasonality on serum 25-hydroyvitamin D (s25OHD).

OBJECTIVE

Using fortified yogurt, we investigated in one randomized controlled trial how both baseline status, as assessed by measuring s25OHD prior the onset of the trial, and the season of enrollment quantitatively influenced the response to the supplemented (Suppl.) of vitamin D3 (VitD3) in healthy community-dwelling women.

METHODS

A 24-week controlled trial was conducted in menopausal women (mean age: 61.5). Participants were randomized into 3 groups (Gr): Gr.Suppl.0, time controls maintaining dietary habits; Gr.Suppl.5 and Gr.Suppl.10 consuming one and two 125-g servings of VitD3-fortified yogurts with 5- and 10-µg daily doses, respectively. The 16 intervention weeks lasted from early January to mid-August, the 8 follow-up weeks, without product, from late August to mid-October. Before enrollment, subjects were randomized into 2 s25OHD strata: low stratum (LoStr): 25-50 nmol/L; high stratum (HiStr): >50-75 nmol/L.

RESULTS

All enrolled participants adhered to the protocol throughout the 24-week study: Gr.Suppl.0 (n = 45), Gr.Suppl.5 (n = 44), and Gr.Suppl.10 (n = 44). Over the 16 intervention and 8 follow-up weeks, s25OHD increased in both supplemented groups, more in Gr.Suppl.10 than in Gr.Suppl.5. At the end of the intervention, the subject proportion with s25OHD ≥ 50 nmol/L was 37.8, 54.5, and 63.6% in Gr.Suppl.0, Gr.Suppl.5, and Gr.Suppl.10, respectively. The constant rate of s25OHD per supplemental VitD3 microgram was greater in LoStr than HiStr. The s25OHD increase was greater with late (mid-March) than early (mid-January) inclusion.

CONCLUSION

This randomized trial demonstrates (1) a dose-dependent s25OHD improvement related to fortified yogurt consumption; (2) an inversely baseline-dependent increase in s25OHD; and (3) a seasonal effect that highlights the importance of VitD3-fortified foods during winter, even at 5 µg/d, in healthy menopausal women.

Vitamin D in adolescence: evidence-based dietary requirements and implications for public health policy

Vitamin D is a unique nutrient. First, it acts as a pro-hormone and secondly, the requirement for vitamin D can be met by both endogenous synthesis from sunlight and by dietary sources. This complicates the determination of dietary requirements for vitamin D, which along with the definition of optimal vitamin D status, have been highly controversial and much debated over recent years. Adolescents are a population group at high risk of low vitamin D status, which is concerning given the important role of vitamin D, and calcium, in promoting normal bone mineralisation and attainment of peak bone mass during this rapid growth phase. Dietary vitamin D recommendations are important from a public health perspective in helping to avoid deficiency and optimise vitamin D status for health. However limited experimental data from winter-based dose-response randomised trials in adolescents has hindered the development of evidence-based dietary requirements for vitamin D in this population group. This review will highlight how specifically designed randomised trials and the approach adopted for estimating such requirements can lead to improved recommendations. Such data indicate that vitamin D intakes of between 10 and about 30 µg/d may be required to avoid deficiency and ensure adequacy in adolescents, considerably greater than the current recommendations of 10-15 µg/d. Finally this review will consider the implications of this on public health policy, in terms of future refinements of vitamin D requirement recommendations and prioritisation of public health strategies to help prevent vitamin D deficiency.

Genetic and Racial Differences in the Vitamin D Endocrine System

Twin studies indicate that genetic factors may explain about 50% of the variation of serum 25-hydroxyvitamin D (25OHD). Polymorphisms of 3 genes, delta-7-sterol-reductase, CYP2R1, and DBP/GC (and maybe CYP24A1) combined, can explain about 5% to 10% of the variation in serum 25OHD. These polymorphisms are found in nearly all populations. The variation in serum 25OHD found in different areas and populations in the world is mainly due to environmental and lifestyle factors, not truly dependent on racial differences. One genetic variant of DBP, (GC2), is associated with a modest (∼10%) decrease in serum DBP and 25OHD concentrations for unexplained reasons.

Regulation of Immune Function by Vitamin D and Its Use in Diseases of Immunity

Evidence exists for a role for vitamin D and its active metabolites in modulating immune functions. In animal models, vitamin D deficiency is associated with a higher risk for autoimmunity in genetically predisposed subjects and increases in susceptibility to infections. In addition, high-dose vitamin D can improve immune health, prevent autoimmunity, and improve defense against infections. In humans, evidence exists on associations between vitamin D deficiency and impaired immune function, leading to autoimmunity in genetically predisposed people and increased risk for infections; data on therapeutic immune effects of vitamin D supplementation when vitamin D levels are already sufficient are lacking.

Vitamin D in adolescents: Are current recommendations enough?

Vitamin D is essential for bone development during adolescence and low vitamin D status during this critical period of growth may impact bone mineralization, potentially reducing peak bone mass and consequently increasing the risk of osteoporosis in adulthood. Therefore, the high prevalence of vitamin D inadequacy and deficiency in adolescent populations is of great concern. However, there is currently a lack of consensus on the 25-hydroxyvitamin D [25(OH)D] concentration, the widely accepted biomarker of vitamin D status, that defines adequacy, and the vitamin D intake requirements to maintain various 25(OH)D thresholds are not well established. While the current intake recommendations of 10-15μg/day may be sufficient to prevent vitamin D deficiency (25(OH)D<25-30nmol/l), greater intakes may be needed to achieve the higher threshold levels proposed to represent adequacy (25(OH)D>50nmol/l). This review will address these concerns and consider if the current dietary recommendations for vitamin D in adolescents are sufficient.

Vitamin D metabolites in captivity? Should we measure free or total 25(OH)D to assess vitamin D status?

There is general consensus that serum 25(OH)D is the best biochemical marker for nutritional vitamin D status. Whether free 25(OH)D would be a better marker than total 25(OH)D is so far unclear. Free 25(OH)D can either be calculated based on the measurement of the serum concentrations of total 25(OH)D, vitamin D-binding protein (DBP), albumin, and the affinity between 25(OH)D and its binding proteins in physiological situations. Free 25(OH)D can also be measured directly by equilibrium dialysis, ultrafitration or immunoassays. During the vitamin D workshop held in Boston in March 2016, a debate was organized about the measurements and clinical value of free 25(OH)D, and this debate is summarized in the present manuscript. Overall there is consensus that most cells apart from the renal tubular cells are exposed to free rather than to total 25(OH)D. Therefore free 25(OH)D may be highly relevant for the local production and action of 1,25(OH)₂D. During the debate it became clear that there is a need for standardization of measurements of serum DBP and of direct measurements of free 25(OH)D. There seems to be very limited genetic or racial differences in DBP concentrations or (probably) in the affinity of DBP for its major ligands. Therefore, free 25(OH)D is strongly correlated to total 25(OH)D in most normal populations. Appropriate studies are needed to define the clinical implications of free rather than total 25(OH)D in normal subjects and in disease states. Special attention is needed for such studies in cases of abnormal DBP concentrations or when one could expect changes in its affinity for its ligands.

Vitamin D, a modulator of musculoskeletal health in chronic kidney disease

The spectrum of activity of vitamin D goes beyond calcium and bone homeostasis, and growing evidence suggests that vitamin D contributes to maintain musculoskeletal health in healthy subjects as well as in patients with chronic kidney disease (CKD), who display the combination of bone metabolism disorder, muscle wasting, and weakness. Here, we review how vitamin D represents a pathway in which bone and muscle may interact. In vitro studies have confirmed that the vitamin D receptor is present on muscle, describing the mechanisms whereby vitamin D directly affects skeletal muscle. These include genomic and non-genomic (rapid) effects, regulating cellular differentiation and proliferation. Observational studies have shown that circulating 25-hydroxyvitamin D levels correlate with the clinical symptoms and muscle morphological changes observed in CKD patients. Vitamin D deficiency has been linked to low bone formation rate and bone mineral density, with an increased risk of skeletal fractures. The impact of low vitamin D status on skeletal muscle may also affect muscle metabolic pathways, including its sensitivity to insulin. Although some interventional studies have shown that vitamin D may improve physical performance and protect against the development of histological and radiological signs of hyperparathyroidism, evidence is still insufficient to draw definitive conclusions.

Vitamin D: Musculoskeletal health

Perhaps the role of Vitamin D supplementation has been most exhaustively studied in calcium absorption, skeletal wellbeing, muscular potency, balance and risk of falling. Nonetheless, new data has emerged and the recent research on sarcopenia makes the topic increasingly interesting. Given the socioeconomic burden of the musculoskeletal consequences of hypovitaminosis D it is vital to keep abreast with the latest literature in the field. The recommended Vitamin D supplementation dose should suffice to increase the serum 25 hydroxyvitamin D level to 30 ng/mL (75 nmol/L) and this level should be optimally maintained with a maintenance dose, particularly for those diagnosed with osteoporosis.

Vitamin D in the Spectrum of Prediabetes and Cardiovascular Autonomic Dysfunction

Vitamin D is a fat-soluble secosteroid hormone with pleiotropic effects. 1,25-Dihydroxyvitamin D coordinates the biosynthesis of neurotransmitters in the central nervous system, which regulate cardiovascular autonomic function and may explain its putative role in the development of cardiovascular autonomic neuropathy (CAN). CAN is an independent risk factor for mortality in patients with diabetes and prediabetes and is associated with an increased risk of developing type 2 diabetes and cardiovascular disease. Accumulating data indicate the presence of peripheral nerve injury at these early stages of dysglycemia and its multifactorial pathogenesis. Prediabetes is associated with vitamin D insufficiency. Vitamin D is proposed to prevent the progression of glucose intolerance. The putative underlying mechanisms include maintenance of the intracellular calcium concentration, direct stimulation of insulin receptor expression, and enhancement of the insulin response to glucose transporters. Vitamin D exerts a protective effect on peripheral nerve fibers by decreasing the demyelination process and inducing axonal regeneration. The effects of vitamin D supplementation on glucose tolerance and related autonomic nerve dysfunction have been a recent focus of scientific interest. Although well-designed observational studies are available, the causative relation between vitamin D deficiency, glucose intolerance, and CAN is still debatable. One reason might be that interventional studies are unpersuasive with regard to the beneficial clinical effects of vitamin D supplementation. Because of its favorable side effect profile, vitamin D supplementation might represent an attractive therapeutic option for treating the pandemic prevalence of prediabetes and vitamin D deficiency. Vitamin D supplementation can improve glucose tolerance and cardiovascular autonomic function and can thus reduce cardiovascular mortality among subjects with different stages of glucose intolerance and autonomic dysfunction. However, more patient-centered trials on the use of vitamin D supplementation in different conditions are needed.

Vitamin D status and insulin resistance among young obese Saudi females

Objectives:

To evaluate the association of vitamin D level with insulin resistance, among healthy student’s obese women, and to identify factors that may elucidate this association.

Methods:

One hundred and forty-seven female students between the age group of 18 and 25 years were included in this cross-sectional study, and the related socio-demographic and anthropometric data were obtained. They were selected randomly from Aljouf University, Sakaka, Saudi Arabia between November 2013 and June 2014. Serum 25-hydroxy vitamin D (25[OH]D), glucose, insulin was measured and insulin resistance was calculated using the insulin resistance index (HOMA-IR).

Results:

The results showed the percentage of 25[OH]D concentration in female students was 21.3% sufficient, 59.6% mild deficiency, and 19.3% moderate deficiency. The percentage of waist circumferences (WC) were 41.3% (>88 cm) and 58.7% (<88 cm), body mass index (BMI) was 13.6% (obese) and 31.8% (over weight), blood pressure (BP) was 65.7% (<130/85 mm Hg), and 33.2% (>130/85 mm Hg). Based on the cut-off point of 25[OH]D, 17.4% of females had 25[OH]D deficiency, 27.3% insufficient, and 55.3% sufficient. When the females were classified according to the BMI category, the serum 25[OH]D concentrations for obese was the lowest value (54.6%) when compared with the overweight (31.8%) and normal weight (0.9%). 25[OH]D was inversely associated with BMI, fat%, and HOMA-IR.

Conclusion:

Our results suggest that vitamin D deficiency is prevalent in women of Saudi who are university students especially in those who are obese. Preventive interventions in order to reduce the tendency of deficiency among college students should focus on the awareness of the essentiality of vitamin D promotion of direct exposure to sunlight (vitamin D3) and consumption of vitamin D fortified food as a part of Saudi diets.

Comparative analysis of nutritional guidelines for vitamin D

Vitamin D is essential for calcium and bone homeostasis. Humans are largely dependent on UVB-radiation-induced photosynthesis of vitamin D, as few foods contain vitamin D. However, the same radiation that produces vitamin D is also carcinogenic, albeit with a long lag time, and causes DNA damage. In view of the increasing life expectancy, avoiding excessive sun exposure is prudent. Several groups of people have a shortfall between their requirements for vitamin D and their combined endogenous synthesis and intake from natural foods, and therefore need vitamin D supplementation. Governments and scientific societies are regularly updating their recommendations for intake of vitamin D, especially for groups that should (infants) or prefer to (especially elderly individuals) avoid direct sunlight. An overview of such guidelines is presented in this Review. A fairly large consensus exists that all infants should receive 400 international units (IU) (10 μg) daily during their first year of life and that elderly individuals should have access to vitamin D supplementation (at recommended dosages varying from 400 IU to 800 IU daily in most governmental guidelines but at higher dosages in other guidelines). All guidelines unanimously agree that serum levels of 25-hydroxyvitamin D (25OHD) <25 nmol/l (10 ng/ml) should be avoided at all ages. Children and adults who have limited sun exposure should receive vitamin D supplementation, but the recommended doses vary widely (from 200 IU to 2,000 IU daily), in line with disagreement regarding the minimal desirable serum concentration of 25OHD (which varies from 25 nmol/l to >100 nmol/l).

The Association between Vitamin D Insufficiency and Nonalcoholic Fatty Liver Disease: A Population-Based Study

Previous studies have shown inconsistent results regarding the association between vitamin D insufficiency and nonalcoholic fatty liver disease (NAFLD). We attempted to demonstrate this relationship using population-based data. Vitamin D insufficiency was defined as a 25(OH)D level ≤20 ng/mL. Hepatic steatosis index was calculated to define NAFLD. Significant fibrosis was assessed using Body mass index, AST/ALT Ratio, Diabetes (BARD) score. Logistic regression analyses were performed to determine the relationship between vitamin D insufficiency and NAFLD. Among 1812 participants, 409 (22.6%) had NAFLD. Patients with nonalcoholic fatty liver disease were more likely to be male (56.7%), had higher body mass index (28.1 kg/m²), and had more metabolic syndrome (57.2%). The proportion of vitamin D insufficiency did not differ between NAFLD and non-NAFLD (77.5% vs. 77.4%). Logistic regression analyses showed that BMI, diabetes, and triglyceride level were significantly associated with NAFLD, whereas vitamin D insufficiency was not related. Subgroup analyses involving non-obese participants, male participants, and participants without metabolic syndrome showed similar results. The BARD score and the proportion of significant fibrosis by BARD score did not differ according to vitamin D status. Vitamin D insufficiency was not associated with the presence of NAFLD as assessed by validated noninvasive prediction models.

Pharmacological treatment of osteoporosis in the oldest old

The incidence of osteoporotic fractures increases with age. Consequently, the global prevalence of osteoporotic fractures will increase with the aging of the population. In old age, osteoporosis is associated with a substantial burden in terms of morbidity and mortality. Nevertheless, osteoporosis in old age continues to be underdiagnosed and undertreated. This may, at least partly, be explained by the fact that evidence of the antifracture efficacy of osteoporosis treatments comes mainly from randomized controlled trials in postmenopausal women with a mean age of 70-75 years. However, in the last years, subgroup analyses of these landmark trials have been published investigating the efficacy and safety of osteoporosis treatment in the very elderly. Based on this evidence, this narrative review discusses the pharmacological management of osteoporosis in the oldest old (≥80 years). Because of the high prevalence of calcium and/or vitamin D deficiency in old age, these supplements are essential in the management of osteoporosis in the elderly people. Adding antiresorptive or anabolic treatments or combinations, thereof, reduces the risk of vertebral fractures even more, at least in the elderly with documented osteoporosis. The reduction of hip fracture risk by antiresorptive treatments is less convincing, which may be explained by insufficient statistical power in some subanalyses and/or a higher impact of nonskeletal risk factors in the occurrence of hip fractures. Compared with younger individuals, a larger absolute risk reduction is observed in the elderly because of the higher baseline fracture risk. Therefore, the elderly will benefit more of treatment. In addition, current osteoporosis therapies also appear to be safe in the elderly. Although more research is required to further clarify the effect of osteoporosis drugs in the elderly, especially with respect to hip fractures, there is currently sufficient evidence to initiate appropriate treatment in the elderly with osteoporosis and osteoporotic fractures.

Skeletal involvement in type 1 Gaucher disease: Not just bone mineral density

Gaucher disease is characterized by multi-organ infiltration of phospholipid-laden macrophages. Bone involvement is characterized by typical deformities, osteopenia/osteoporosis, pathological fractures, and bone marrow infiltration (avascular osteonecrosis, infarction). Estimation of skeletal disease includes bone quality that contributes substantially to bone strength. We studied 23 type 1 Gaucher patients (median age 22years, range 3-73) on Enzyme Replacement Therapy from 2months to 26years (median 7years); 4 patients had pathological fractures, 10 bone infarctions, 6 avascular osteonecrosis. We noninvasively assessed bone quality by trabecular microarchitecture and macroscopic geometry, using two innovative dual-energy X-ray absorptiometry tools: Trabecular Bone Score (TBS) and Hip Structural Analysis (HSA). Bone quality parameters distinguished the patients with skeletal complications. TBS was significantly lower in patients with avascular osteonecrosis (p=0.049) and pathological fractures (p=0.024), while it could not identify those with bone infarctions. Among HSA parameters, the Cross Sectional Area of the intertrochanteric region and the Buckling Ratio of the narrow neck allowed the distinction of patients with avascular osteonecrosis. BMD was low in 11 patients (50%); neither BMD nor HSA were associated with pathological fractures. The combined evaluation of bone quality and bone quantity is useful to identify GD patients with more severe skeletal involvement.

Nutritional Vitamin D in Renal Transplant Patients: Speculations and Reality

Reduced levels of nutritional vitamin D are commonly observed in most chronic kidney disease (CKD) patients and particularly in patients who have received a kidney transplant (KTx). In the complex clinical scenario characterizing the recipients of a renal graft, nutritional vitamin D deficiency has been put in relation not only to the changes of mineral and bone metabolism (MBM) after KTx, but also to most of the medical complications which burden KTx patients. In fact, referring to its alleged pleiotropic (non-MBM related) activities, vitamin D has been claimed to play some role in the occurrence of cardiovascular, metabolic, immunologic, neoplastic and infectious complications commonly observed in KTx recipients. Furthermore, low nutritional vitamin D levels have also been connected with graft dysfunction occurrence and progression. In this review, we will discuss the purported and the demonstrated effects of native vitamin D deficiency/insufficiency in most of the above mentioned fields, dealing separately with the MBM-related and the pleiotropic effects.

Development of an Improved Standard Reference Material for Vitamin D Metabolites in Human Serum

The National Institute of Standards and Technology (NIST) has developed Standard Reference Material (SRM) 972a Vitamin D Metabolites in Frozen Human Serum as a replacement for SRM 972, which is no longer available. SRM 972a was developed in collaboration with the National Institutes of Health's Office of Dietary Supplements. In contrast to the previous reference material, three of the four levels of SRM 972a are composed of unmodified human serum. This SRM has certified and reference values for the following 25-hydroxyvitamin D [25(OH)D] species: 25(OH)D2, 25(OH)D3, and 3-epi-25(OH)D3. The value assignment and certification process included three isotope-dilution mass spectrometry approaches, with measurements performed at NIST and at the Centers for Disease Control and Prevention (CDC). The value assignment methods employed have been modified from those utilized for the previous SRM, and all three approaches now incorporate chromatographic resolution of the stereoisomers, 25(OH)D3 and 3-epi-25(OH)D3.