A randomized controlled trial of vitamin D supplementation on preventing postmenopausal bone loss and modifying bone metabolism using identical twin pairs

Effect of vitamin D supplementation or fortification on bone turnover markers in women: a systematic review and meta-analysis

Vitamin D is a vital indicator of musculoskeletal health, as it plays an important role through the regulation of bone and mineral metabolism. This meta-analysis was performed to investigate the effects of vitamin D supplementation/fortification on bone turnover markers in women. All human randomised clinical trials reported changes in bone resorption markers (serum C-terminal telopeptide of type-I collagen (sCTX) and urinary type I collagen cross-linked N-telopeptide (uNTX)) or bone formation factors (osteocalcin (OC), bone alkaline phosphatase (BALP) and procollagen type-1 intact N-terminal propeptide (P1NP)) following vitamin D administration in women (aged ≥ 18 years) were considered. Mean differences (MD) and their respective 95 % CI were calculated based on fixed or random effects models according to the heterogeneity status. Subgroup analyses, meta-regression models, sensitivity analysis, risk of bias, publication bias and the quality of the included studies were also evaluated. We found that vitamin D supplementation had considerable effect on sCTX (MD: -0·038, n 22) and OC (MD: -0·610, n 24) with high heterogeneity and uNTX (MD: -8·188, n 6) without heterogeneity. Our results showed that age, sample size, dose, duration, baseline vitamin D level, study region and quality of studies might be sources of heterogeneity in this meta-analysis. Subgroup analysis also revealed significant reductions in P1NP level in dose less than 600 μg/d and larger study sample size (>100 participants). Moreover, no significant change was found in BALP level. Vitamin D supplementation/fortification significantly reduced bone resorption markers in women. However, results were inconsistent for bone formation markers.

Modulation of the vitamin D receptor by traditional Chinese medicines and bioactive compounds: potential therapeutic applications in VDR-dependent diseases

The Vitamin D receptor (VDR) is a crucial nuclear receptor that plays a vital role in various physiological functions. To a larger extent, the genomic effects of VDR maintain general wellbeing, and its modulation holds implications for multiple diseases. Current evidence regarding using vitamin D or its synthetic analogs to treat non-communicable diseases is insufficient, though observational studies suggest potential benefits. Traditional Chinese medicines (TCMs) and bioactive compounds derived from natural sources have garnered increasing attention. Interestingly, TCM formulae and TCM-derived bioactive compounds have shown promise in modulating VDR activities. This review explores the intriguing potential of TCM and bioactive compounds in modulating VDR activity. We first emphasize the latest information on the genetic expression, function, and structure of VDR, providing a comprehensive understanding of this crucial receptor. Following this, we review several TCM formulae and herbs known to influence VDR alongside the mechanisms underpinning their action. Similarly, we also discuss TCM-based bioactive compounds that target VDR, offering insights into their roles and modes of action.

Impact of vitamin D supplementation on markers of bone turnover: Systematic review and meta-analysis of randomised controlled trials

AIM

The effects of vitamin D administration on bone turnover markers (BTMs) in adults are controversial. Thus, we carried out a meta-analysis of available randomised controlled trials (RCTs) to examine the impact of vitamin D supplementation on BTMs.

METHODS

To identify relevant RCTs, we searched the PubMed/MEDLINE, Web of Science, Scopus, Cochrane Library and Embase databases for manuscripts published up to July 2022. The present study was conducted in agreement with the PRISMA guidelines. Weighed mean difference (WMD) and 95% confidence intervals (CI) were used to calculate the magnitude of the effect of the intervention.

RESULTS

A total of 42 RCTs were included in the meta-analysis. The age of the participants enrolled in the RCTs ranged from 19.4 to 84 years. The pooled results depicted a decrease in deoxypyridinoline (DPD) concentrations (WMD: -1.58 nmol/mmol, 95% CI: -2.55, -.61, p = .001) following vitamin D supplementation. In addition, subgroup analyses demonstrated that vitamin D administration notably reduced procollagen type I N-terminal propeptide (PINP) levels in individuals aged >50 years and led to a pronounced decrease in alkaline phosphatase (ALP) values when the intervention lasted >12 weeks. No significant effect was observed on other BTMs, for example, collagen type 1 cross-linked C-telopeptide (CTX) and osteocalcin (OC) levels.

CONCLUSION

Vitamin D administration decreases DPD, PINP and ALP levels, indicating a reduced bone turnover following the intervention. Other BTMs, for example, CTX or OC values, were not affected by vitamin D prescription. Vitamin D supplementation may exert a positive effect on some important BTMs.

Effect of supplemental vitamin D3 on bone mineral density: a systematic review and meta-analysis

Context

There is still controversy over the effect of vitamin D3 supplementation on bone health.

Objective

The effects of vitamin D3 supplementation on bone mineral density (BMD) and markers of bone turnover, as well as the dose-response relationship between vitamin D3 and bone health in adults, were evaluated.

Data Sources

The PubMed, Scopus, Cochrane, Web of Science, and AGRIS databases were searched for articles published through April 30, 2022. Thirty-nine of the 6409 records identified met the inclusion criteria

Data Extraction

Data were extracted from articles by 2 authors, and data extraction was cross-checked independently. A random-effects model was used to estimate the pooled effect size and the associated 95%CI for the effect of vitamin D3 for each outcome. A one-stage random-effects dose-response model was used to estimate the dose-response relationship between vitamin D3 supplementation and BMD.

Data Analysis

Results of meta-analysis showed a beneficial effect of vitamin D3 at the lumbar spine (standardized mean difference [SMD] = 0.06; 95%CI, 0.01–0.12) and femoral neck (SMD = 0.25; 95%CI, 0.09–0.41). Dose-response analysis revealed a linear relationship between vitamin D3 supplementation doses and BMD at the femoral neck, lumbar spine, and total hip sites. No significant effect of vitamin D3 supplementation on whole-body or total hip BMD was observed (P > 0.05). Vitamin D3 supplementation significantly decreased BMD at both proximal and distal forearm (SMD = −0.16; 95%CI, −0.26 to −0.06). The variables of ethnicity, age, baseline 25-hydroxyvitamin D (25[OH]D), menopause status, vitamin D3 dosing frequency, and bone health status (P interaction = 0.02) altered the effect of vitamin D3 supplementation on BMD. Additionally, a nonlinear relationship between vitamin D3 supplement doses and markers of bone turnover was found.

Conclusion

A protective effect of vitamin D3 supplementation on BMD of the lumbar spine, femoral neck, and total hip is implicated.

Systematic Review Registration

PROSPERO registration number CRD42017054132.

Efficacy of a digital cognitive behavioral therapy for insomnia in people with low back pain: a feasibility randomized co-twin and singleton-controlled trial

Background

Digital cognitive behavioral therapy for insomnia (CBT-i) in people with low back pain (LBP) may be efficacious in improving both sleep and pain; and twin trial designs provide greater precision of treatment effects by accounting for genetic and early environmental factors. We aimed to determine the feasibility of a trial investigating the efficacy of a digital CBT-i program in people with comorbid symptoms of insomnia and LBP, in twins and people from the general community (singletons).

Methods

Thirty-two twins (16 pairs) and 66 singletons with comorbid symptoms of insomnia and LBP (> 6 weeks duration) were randomized to digital CBT-i (intervention) or educational program (control) for 6 weeks. The digital CBT-I, Sleepio (developed by Big Health Inc.), was an online interactive, automated, personalized course comprising of six sessions, once a week. The education program was six emails with general sleep information, once a week. Participants were blinded to their group allocation and offered the alternative intervention at the completion of the study. Feasibility outcomes included recruitment and follow-up rates, data collection and outcome measure completion, contamination (communication about trial interventions), acceptability (adherence), credibility, and participants’ experience of the intervention.

Results

Sixteen out of 722 contacted twin pairs were recruited (recruitment rate = 2.2%). Twins were recruited between September 2015 and August 2018 (35 months) and singletons between October 2017 and Aug 2018 (10 months). Follow-up rates for post-intervention and 3-month follow-up were 81% and 72% for twins and 82% and 78% for singletons respectively. Adherence rates (percentage of sessions completed out of six) for the digital CBT-i were 63% for twins and 55% for singletons. Contamination (speaking about the study to each other) was present in two twin pairs (13%). Written or verbal feedback (n = 21) regarding the digital CBT-i intervention from participants were positive (n = 11), neutral (n = 5), or negative (n = 6).

Conclusions

Online CBT-i was received favorably with people with comorbid symptoms of insomnia and LBP. While the online data collection was successful, strategies need to be implemented to improve adherence, follow-up, control group credibility (for digital CBT-i), and twin recruitment rates (for twin trials).

Trial registration

Australian New Zealand Clinical Trials Registry (ACTRN12615000672550). Registered 29 June 2015

Supplementary Information

The online version contains supplementary material available at 10.1186/s40814-022-01087-z.

Nutrition, Physical Activity, and Dietary Supplementation to Prevent Bone Mineral Density Loss: A Food Pyramid

Bone is a nutritionally modulated tissue. Given this background, aim of this review is to evaluate the latest data regarding ideal dietary approach in order to reduce bone mineral density loss and to construct a food pyramid that allows osteopenia/osteoporosis patients to easily figure out what to eat. The pyramid shows that carbohydrates should be consumed every day (3 portions of whole grains), together with fruits and vegetables (5 portions; orange-colored fruits and vegetables and green leafy vegetables are to be preferred), light yogurt (125 mL), skim milk (200 mL,) extra virgin olive oil (almost 20 mg/day), and calcium water (almost 1 l/day); weekly portions should include fish (4 portions), white meat (3 portions), legumes (2 portions), eggs (2 portions), cheeses (2 portions), and red or processed meats (once/week). At the top of the pyramid, there are two pennants: one green means that osteopenia/osteoporosis subjects need some personalized supplementation (if daily requirements cannot be satisfied through diet, calcium, vitamin D, boron, omega 3, and isoflavones supplementation could be an effective strategy with a great benefit/cost ratio), and one red means that there are some foods that are banned (salt, sugar, inorganic phosphate additives). Finally, three to four times per week of 30-40 min of aerobic and resistance exercises must be performed.

Environmental Factors That Affect Parathyroid Hormone and Calcitonin Levels

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

Efficacy of risedronate with cholecalciferol on bone mineral density in Korean patients with osteoporosis

The efficacy of once-weekly risedronate with and without cholecalciferol in bone mineral density (BMD) in Korean patients with osteoporosis was compared. After 12 months, both spine and hip BMD increased significantly in both groups, but there was no significant difference between two groups.

INTRODUCTION

This study investigated the efficacy and safety of once-weekly risedronate with and without cholecalciferol in BMD in Korean patients with osteoporosis.

METHODS

This was a prospective, 12-month, randomized, open-labeled, actively controlled trial involving 41 hospitals. A total of 841 subjects with osteoporosis were randomized to once-weekly risedronate (35 mg) and cholecalciferol (5600 IU) in a single pill (RSD+, n = 642) or once-weekly risedronate (35 mg) alone (RSD, n = 199). BMD was measured via dual-energy X-ray absorptiometry at the lumbar spine and hip, and the serum levels of 25-hydroxy vitamin D (25(OH) D), parathyroid hormone (PTH), and alkaline phosphatase (ALP) were assayed at baseline and after 12 months of treatment.

RESULTS

After 12 months, the lumbar spine, femoral neck, and total hip BMD increased significantly in both groups; there was no significant difference between two groups. Women in the RSD+ group exhibited significantly increased lumbar spine BMD, and subjects with previous fracture history in the RSD+ group had significantly increased total hip BMD compared with the RSD group. The serum 25(OH) D level increased significantly in the RSD+ group. The serum PTH level decreased in the RSD+ group but increased in the RSD group. The serum ALP level significantly decreased in both groups; there was no significant difference between two groups.

CONCLUSIONS

A once-weekly pill containing risedronate and cholecalciferol had the equivalent antiresorptive efficacy on BMD compared with risedronate alone and improved 25(OH) D serum levels after 12 months of treatment without significant adverse events in Korean patients with osteoporosis.

A placebo-controlled trial of folic acid and betaine in identical twins with Angelman syndrome

Background

Angelman syndrome (AS) is a neurodevelopmental disorder that is caused by maternal genetic deficiency of a gene that encodes E6-AP ubiquitin-protein ligase (gene symbol UBE3A) mapping to chromosome 15q11-q13. AS leads to stiff and jerky gait, excess laughter, seizures, and severe intellectual disability. In some parts of the brain, the paternally inherited UBE3A gene is subject to genomic imprinting by the action of the UBE3A-antisense transcript (UBE3A-ATS) on the paternally inherited allele. Consequently, only the maternally inherited UBE3A gene is expressed in mature neurons. AS occurs due to deletions of the maternal 15q11 − 13 region, paternal uniparental disomy (UPD), imprinting center defects, mutations in the maternal UBE3A gene, or other unknown genetic malfunctions that result in a silenced maternal UBE3A gene in the specific imprinted regions of the brain.

Results

A potential treatment strategy for AS is to increase methylation of UBE3A-ATS to promote expression of the paternal UBE3A gene and thus ameliorate the clinical phenotypes of AS. We treated two sets of male identical twins with class I deletions with a 1 year treatment trial of either betaine and folic acid versus placebo. We found no statistically significant changes in the clinical parameters tested at the end of the 1 year trial, nor did we find any significant adverse events.

Conclusions

This study tested the hypothesis that by increasing the methylation of the UBE3A-antisense transcript in Angelman syndrome to promote expression of the silenced paternal UBE3A gene we may ameliorate the clinical phenotypes of AS. We treated two sets of identical twins with placebo versus betaine and folic acid. Although this study represented a novel approach to treating Angelman syndrome, the differences in the developmental testing results was not significant. This paper also discusses the value of monozygotic twin studies in minimizing confounding variables and its utility in conducting small treatment studies.

Trial registration

NCT00348933. Registered 6 July 2006.

Effects of vitamin D supplementation on musculoskeletal health: a systematic review, meta-analysis, and trial sequential analysis

BACKGROUND

The effects of vitamin D on fractures, falls, and bone mineral density are uncertain, particularly for high vitamin D doses. We aimed to determine the effect of vitamin D supplementation on fractures, falls, and bone density.

METHODS

In this systematic review, random-effects meta-analysis, and trial sequential analysis, we used findings from literature searches in previously published meta-analyses. We updated these findings by searching PubMed, Embase, and Cochrane Central on Sept 14, 2017, and Feb 26, 2018, using the search term "vitamin D" and additional keywords, without any language restrictions. We assessed randomised controlled trials of adults (>18 years) that compared vitamin D with untreated controls, placebo, or lower-dose vitamin D supplements. Trials with multiple interventions (eg, co-administered calcium and vitamin D) were eligible if the study groups differed only by use of vitamin D. We excluded trials of hydroxylated vitamin D analogues. Eligible studies included outcome data for total or hip fractures, falls, or bone mineral density measured at the lumbar spine, total hip, femoral neck, total body, or forearm. We extracted data about participant characteristics, study design, interventions, outcomes, funding sources, and conflicts of interest. The co-primary endpoints were participants with at least one fracture, at least one hip fracture, or at least one fall; we compared data for fractures and falls using relative risks with an intention-to-treat analysis using all available data. The secondary endpoints were the percentage change in bone mineral density from baseline at lumbar spine, total hip, femoral neck, total body, and forearm.

FINDINGS

We identified 81 randomised controlled trials (n=53 537 participants) that reported fracture (n=42), falls (n=37), or bone mineral density (n=41). In pooled analyses, vitamin D had no effect on total fracture (36 trials; n=44 790, relative risk 1·00, 95% CI 0·93-1·07), hip fracture (20 trials; n=36 655, 1·11, 0·97-1·26), or falls (37 trials; n=34 144, 0·97, 0·93-1·02). Results were similar in randomised controlled trials of high-dose versus low-dose vitamin D and in subgroup analyses of randomised controlled trials using doses greater than 800 IU per day. In pooled analyses, there were no clinically relevant between-group differences in bone mineral density at any site (range -0·16% to 0·76% over 1-5 years). For total fracture and falls, the effect estimate lay within the futility boundary for relative risks of 15%, 10%, 7·5%, and 5% (total fracture only), suggesting that vitamin D supplementation does not reduce fractures or falls by these amounts. For hip fracture, at a 15% relative risk, the effect estimate lay between the futility boundary and the inferior boundary, meaning there is reliable evidence that vitamin D supplementation does not reduce hip fractures by this amount, but uncertainty remains as to whether it might increase hip fractures. The effect estimate lay within the futility boundary at thresholds of 0·5% for total hip, forearm, and total body bone mineral density, and 1·0% for lumbar spine and femoral neck, providing reliable evidence that vitamin D does not alter these outcomes by these amounts.

INTERPRETATION

Our findings suggest that vitamin D supplementation does not prevent fractures or falls, or have clinically meaningful effects on bone mineral density. There were no differences between the effects of higher and lower doses of vitamin D. There is little justification to use vitamin D supplements to maintain or improve musculoskeletal health. This conclusion should be reflected in clinical guidelines.

FUNDING

Health Research Council of New Zealand.

The levels of bone turnover markers 25(OH)D and PTH and their relationship with bone mineral density in postmenopausal women in a suburban district in China

This study evaluated the levels of bone turnover markers (BTMs) and investigated relationships between them and bone mineral density (BMD) in postmenopausal women in China suburban district. The prevalence of osteoporosis was 25.03 % at lumbar spine and 6.23 % at femoral neck, and BTMs were negatively correlated with BMDs.

INTRODUCTION

The aims of this study were to evaluate the levels of bone turnover markers (BTMs), including serum N-terminal procollagen of type I collagen (P1NP), beta C-terminal cross-linked of type I collagen (β-CTX), 25-hydroxyvitamin D [25(OH)D], and parathyroid hormone (PTH), and to investigate relationships between these markers and bone mineral density (BMD) as well the prevalence of osteoporosis in postmenopausal women of suburban district.

METHODS

A population of 4822 postmenopausal women aged 55-69 years old (62.22 ± 6.75) from the suburban district was recruited voluntarily. BMD was measured at the lumbar spine, femoral neck, and total hip using dual-energy X-ray absorptiometry; 2251 women in this group had the serum BTMs 25(OH)D and PTH tested.

RESULTS

The prevalence of osteoporosis was 25.03 % at lumbar spine and 6.23 % at femoral neck. The median (interquartile range) values of serum P1NP, β-CTX, 25(OH)D, and PTH were 59.3 ng/mL (44.7-75.52), 0.370 ng/mL (0.280-0.490), 23.0 ng/mL (17.1-30.5), and 31.4 pg/mL (24.9-39.7), respectively. Serum P1NP and β-CTX levels presented significantly negative correlations with BMDs at the all the sites (Beta_std = -0.098 to -0.208, respectively, P < 0.001), whereas PTH levels were negatively correlated with BMDs of the femoral neck and total hip (Beta_std = -0.062 and -0.054, P < 0.01, respectively). Serum 25(OH)D had positive associations with BMDs at total hip (Beta_std = 0.051, P < 0.01).

CONCLUSIONS

The BMD of postmenopausal women in China suburban area is higher than that in downtown area, and over 60 % of the participants had their serum 25(OH)D level over 20 ng/mL. BTMs were negatively correlated with BMDs, suggesting that BTMs are reliable factors for early declines in BMD.

Efficacy of a Sleep Quality Intervention in People With Low Back Pain: Protocol for a Feasibility Randomized Co-Twin Controlled Trial

Poor sleep quality is highly prevalent in patients with low back pain (LBP) and is associated with high levels of pain, psychological distress, and physical disability. Studies have reported a bidirectional relationship between sleep problems and intensity of LBP. Accordingly, effective management of LBP should address sleep quality. In addition, genetics has been found to significantly affect the prevalence of both LBP and insomnia. Our study aims to establish the feasibility of a trial exploring the efficacy of a web-based sleep quality intervention in people with LBP, with the genetic influences being controlled for. 30 twins (15 complete pairs) with subacute or chronic LBP (>6 weeks) will be recruited from the Australian Twin Registry. Participants will be randomly assigned to one of the two groups with each twin within a pair receiving either an interactive web-based sleep intervention based on cognitive behavioral therapy principles (intervention) or a web-based education program (control) for 6 weeks. The feasibility of the trial will be investigated with regard to recruitment rate, feasibility of data collection and outcome measure completion, contamination of intervention, acceptability and experience of intervention, and sample size requirement for the full trial. Patient outcomes will be collected electronically at baseline, immediately post-treatment, and at 3-months' follow-up post-randomization. This trial employs a robust design that will effectively control for the influence of genetics on treatment effect. Additionally, this study addresses sleep quality, a significant but under-explored issue in LBP. Results will inform the design and implementation of the definitive trial.

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

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

Building healthy bones throughout life: an evidence-informed strategy to prevent osteoporosis in Australia

Osteoporosis imposes a tremendous burden on Australia: 1.2 million Australians have osteoporosis and 6.3 million have osteopenia. In the 2007–08 financial year, 82 000 Australians suffered fragility fractures, of which > 17 000 were hip fractures. In the 2000–01 financial year, direct costs were estimated at $1.9 billion per year and an additional $5.6 billion on indirect costs. Osteoporosis was designated a National Health Priority Area in 2002; however, implementation of national plans has not yet matched the rhetoric in terms of urgency. Building healthy bones throughout life, the Osteoporosis Australia strategy to prevent osteoporosis throughout the life cycle, presents an evidence-informed set of recommendations for consumers, health care professionals and policymakers. The strategy was adopted by consensus at the Osteoporosis Australia Summit in Sydney, 20 October 2011. Primary objectives throughout the life cycle are: to maximise peak bone mass during childhood and adolescence to prevent premature bone loss and improve or maintain muscle mass, strength and functional capacity in healthy adults to prevent and treat osteoporosis in order to minimise the risk of suffering fragility fractures, and reduce falls risk, in older people. The recommendations focus on three affordable and important interventions — to ensure people have adequate calcium intake, vitamin D levels and appropriate physical activity throughout their lives. Recommendations relevant to all stages of life include: daily dietary calcium intakes should be consistent with Australian and New Zealand guidelines serum levels of vitamin D in the general population should be above 50nmol/L in winter or early spring for optimal bone health regular weight-bearing physical activity, muscle strengthening exercises and challenging balance/mobility activities should be conducted in a safe environment.

Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men

BACKGROUND

Vitamin D and related compounds have been used to prevent osteoporotic fractures in older people. This is the third update of a Cochrane review first published in 1996.

OBJECTIVES

To determine the effects of vitamin D or related compounds, with or without calcium, for preventing fractures in post-menopausal women and older men.

SEARCH METHODS

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to December 2012), the Cochrane Central Register of Controlled Trials (2012, Issue 12), MEDLINE (1966 to November Week 3 2012), EMBASE (1980 to 2012 Week 50), CINAHL (1982 to December 2012), BIOSIS (1985 to 3 January 2013), Current Controlled Trials (December 2012) and reference lists of articles.

SELECTION CRITERIA

Randomised or quasi-randomised trials that compared vitamin D or related compounds, alone or with calcium, against placebo, no intervention or calcium alone, and that reported fracture outcomes in older people. The primary outcome was hip fracture.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial risk of selection bias and aspects of methodological quality, and extracted data. Data were pooled, where possible, using the fixed-effect model, or the random-effects model when heterogeneity between studies appeared substantial.

MAIN RESULTS

We included 53 trials with a total of 91,791 participants. Thirty-one trials, with sample sizes ranging from 70 to 36,282 participants, examined vitamin D (including 25-hydroxy vitamin D) with or without calcium in the prevention of fractures in community, nursing home or hospital inpatient populations. Twelve of these 31 trials had participants with a mean or median age of 80 years or over.Another group of 22 smaller trials examined calcitriol or alfacalcidol (1-alphahydroxyvitamin D3), mostly with participants who had established osteoporosis. These trials were carried out in the setting of institutional referral clinics or hospitals.In the assessment of risk of bias for random sequence generation, 21 trials (40%) were deemed to be at low risk, 28 trials (53%) at unclear risk and four trials at high risk (8%). For allocation concealment, 22 trials were at low risk (42%), 29 trials were at unclear risk (55%) and two trials were at high risk (4%).There is high quality evidence that vitamin D alone, in the formats and doses tested, is unlikely to be effective in preventing hip fracture (11 trials, 27,693 participants; risk ratio (RR) 1.12, 95% confidence intervals (CI) 0.98 to 1.29) or any new fracture (15 trials, 28,271 participants; RR 1.03, 95% CI 0.96 to 1.11).There is high quality evidence that vitamin D plus calcium results in a small reduction in hip fracture risk (nine trials, 49,853 participants; RR 0.84, 95% confidence interval (CI) 0.74 to 0.96; P value 0.01). In low-risk populations (residents in the community: with an estimated eight hip fractures per 1000 per year), this equates to one fewer hip fracture per 1000 older adults per year (95% CI 0 to 2). In high risk populations (residents in institutions: with an estimated 54 hip fractures per 1000 per year), this equates to nine fewer hip fractures per 1000 older adults per year (95% CI 2 to 14). There is high quality evidence that vitamin D plus calcium is associated with a statistically significant reduction in incidence of new non-vertebral fractures. However, there is only moderate quality evidence of an absence of a statistically significant preventive effect on clinical vertebral fractures. There is high quality evidence that vitamin D plus calcium reduces the risk of any type of fracture (10 trials, 49,976 participants; RR 0.95, 95% CI 0.90 to 0.99).In terms of the results for adverse effects: mortality was not adversely affected by either vitamin D or vitamin D plus calcium supplementation (29 trials, 71,032 participants, RR 0.97, 95% CI 0.93 to 1.01). Hypercalcaemia, which was usually mild (2.6 to 2.8 mmol/L), was more common in people receiving vitamin D or an analogue, with or without calcium (21 trials, 17,124 participants, RR 2.28, 95% CI 1.57 to 3.31), especially for calcitriol (four trials, 988 participants, RR 4.41, 95% CI 2.14 to 9.09), than in people receiving placebo or control. There was also a small increased risk of gastrointestinal symptoms (15 trials, 47,761 participants, RR 1.04, 95% CI 1.00 to 1.08), especially for calcium plus vitamin D (four trials, 40,524 participants, RR 1.05, 95% CI 1.01 to 1.09), and a significant increase in renal disease (11 trials, 46,548 participants, RR 1.16, 95% CI 1.02 to 1.33). Other systematic reviews have found an increased association of myocardial infarction with supplemental calcium; and evidence of increased myocardial infarction and stroke, but decreased cancer, with supplemental calcium plus vitamin D, without an overall effect on mortality.

AUTHORS' CONCLUSIONS

Vitamin D alone is unlikely to prevent fractures in the doses and formulations tested so far in older people. Supplements of vitamin D and calcium may prevent hip or any type of fracture. There was a small but significant increase in gastrointestinal symptoms and renal disease associated with vitamin D and calcium. This review found that there was no increased risk of death from taking calcium and vitamin D.

Effects of vitamin D supplements on bone mineral density: a systematic review and meta-analysis

BACKGROUND

Findings from recent meta-analyses of vitamin D supplementation without co-administration of calcium have not shown fracture prevention, possibly because of insufficient power or inappropriate doses, or because the intervention was not targeted to deficient populations. Despite these data, almost half of older adults (older than 50 years) continue to use these supplements. Bone mineral density can be used to detect biologically significant effects in much smaller cohorts. We investigated whether vitamin D supplementation affects bone mineral density.

METHODS

We searched Web of Science, Embase, and the Cochrane Database, from inception to July 8, 2012, for trials assessing the effects of vitamin D (D3 or D2, but not vitamin D metabolites) on bone mineral density. We included all randomised trials comparing interventions that differed only in vitamin D content, and which included adults (average age >20 years) without other metabolic bone diseases. We pooled data with a random effects meta-analysis with weighted mean differences and 95% CIs reported. To assess heterogeneity in results of individual studies, we used Cochran's Q statistic and the I(2) statistic. The primary endpoint was the percentage change in bone mineral density from baseline.

FINDINGS

Of 3930 citations identified by the search strategy, 23 studies (mean duration 23·5 months, comprising 4082 participants, 92% women, average age 59 years) met the inclusion criteria. 19 studies had mainly white populations. Mean baseline serum 25-hydroxyvitamin D concentration was less than 50 nmol/L in eight studies (n=1791). In ten studies (n=2294), individuals were given vitamin D doses less than 800 IU per day. Bone mineral density was measured at one to five sites (lumbar spine, femoral neck, total hip, trochanter, total body, or forearm) in each study, so 70 tests of statistical significance were done across the studies. There were six findings of significant benefit, two of significant detriment, and the rest were non-significant. Only one study showed benefit at more than one site. Results of our meta-analysis showed a small benefit at the femoral neck (weighted mean difference 0·8%, 95% CI 0·2-1·4) with heterogeneity among trials (I(2)=67%, p<0·00027). No effect at any other site was reported, including the total hip. We recorded a bias toward positive results at the femoral neck and total hip.

INTERPRETATION

Continuing widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems to be inappropriate.

FUNDING

Health Research Council of New Zealand.

Vitamin D supplementation for prevention of mortality in adults

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Serum 25(OH)D response to vitamin D3 supplementation: a meta-regression analysis

OBJECTIVE

The aim of this study was to review factors that influence serum 25(OH)D when patients are given vitamin D supplements.

METHODS

From a comprehensive search of all randomized controlled clinical trials with vitamin D3 supplementation available on PubMed up to November 2011, we selected 33 with 43 treatment arms that included at least 30 adult participants. The achieved pooled mean difference (PMD) and 95% confidence intervals (CIs) were calculated using the random-effects models. Meta-regression and subgroup analyses were performed for prespecified factors, including dose, duration, baseline serum 25(OH)D, and age.

RESULTS

With a mean baseline serum 25(OH)D of 50.4 nmol/L, PMD was 37 nmol/L (95% CI, 33-41) with significant heterogeneity among studies. Dose (slope: 0.006; P < 0.001), trial duration (slope: 0.21; P < 0.001), baseline serum 25(OH)D (slope: -0.19; P < 0.001), and age (slope: 0.42; P < 0.001) independently influenced vitamin D response. Similar results were found in studies with a mean baseline serum 25(OH)D <50 nmol/L. In subgroup analyses, the PMD was higher with doses ≥800 IU/d (39.3 nmol/L) after 6 to 12 mo (41.7 nmol/L), with baseline 25(OH)D <50 nmol/L (39.6 nmol/L), and in adults aged >80 y (40.5 nmol/L).

CONCLUSION

This meta regression indicates that a higher increase in serum levels of 25(OH)D in adults is found with a dose of ≥800 IU/d, after at least 6 to 12 mo, and even when baseline 25(OH)D is low and in adults >80 y.

Vitamin D dose response is underestimated by Endocrine Society's Clinical Practice Guideline

OBJECTIVE

The recommended daily intakes of vitamin D according to the recent Clinical Practice Guideline (CPG) of the Endocrine Society are three- to fivefold higher than the Institute of Medicine (IOM) report. We speculated that these differences could be explained by different mathematical approaches to the vitamin D dose response.

METHODS

Studies were selected if the daily dose was ≤2000 IU/day, the duration exceeded 3 months, and 25-hydroxyvitamin D (25OHD) concentrations were measured at baseline and post-therapy. The rate constant was estimated according to the CPG approach. The achieved 25OHD result was estimated according to the following: i) the regression equation approach of the IOM; ii) the regression approach of the Vitamin D Supplementation in Older Subjects (ViDOS) study; and iii) the CPG approach using a rate constant of 2.5 (CPG2.5) and a rate constant of 5.0 (CPG5.0). The difference between the expected and the observed 25OHD result was expressed as a percentage of observed and analyzed for significance against a value of 0% for the four groups.

RESULTS

Forty-one studies were analyzed. The mean (95% CI) rate constant was 5.3 (4.4-6.2) nmol/l per 100 IU per day, on average twofold higher than the CPG rate constant. The mean (95% CI) for the difference between the expected and observed expressed as a percentage of observed was as follows: i) IOM, -7 (-16,+2)% (t=1.64, P=0.110); ii) ViDOS, +2 (-8,+12)% (t=0.40, P=0.69); iii) CPG2.5, -21 (-27,-15)% (t=7.2, P<0.0001); and iv) CPG5.0+3 (-4,+10)% (t=0.91, P=0.366).

CONCLUSION

The CPG 'rule of thumb' should be doubled to 5.0 nmol/l (2.0 ng/ml) per 100 IU per day, adopting a more risk-averse position.

Skeletal effects of vitamin D supplementation in postmenopausal black women

Black women have lower serum 25-hydroxyvitamin D (25[OH]D) levels and higher parathyroid hormone (PTH) levels than white peers but lower bone turnover, suggesting skeletal resistance to PTH. Our objective was to determine if vitamin D supplementation (1,000 IU/day) would prevent bone loss and whether vitamin D receptor (VDR) polymorphisms modify the response. We performed a 2-year randomized, controlled, double-blind study of 1,000 IU vitamin D(3) vs. placebo in postmenopausal black women with serum 25(OH)D levels <20 ng/mL (n = 103). Measurements of 25(OH)D, PTH, and bone turnover were evaluated at baseline and 3, 6, 12, 18, and 24 months. DNA was extracted from peripheral blood leukocytes, and genotyping was conducted using standard techniques. Spine and hip bone mineral density (BMD) was measured at baseline and every 6 months. Serum 25(OH)D increased 11 ng/mL with vitamin D supplementation (p < 0.001), with no change in the placebo group. Vitamin D supplementation produced a significant decline in PTH at 3 months only, with no differences in bone turnover between placebo and vitamin D at any time point. Two-year changes in BMD were not significantly different between placebo- and vitamin D-treated black women at any skeletal site. Despite similar elevations in 25(OH)D, femoral neck BMD was only responsive to vitamin D supplementation in FF subjects (n = 47), not Ff/ff subjects (n = 31). Vitamin D supplementation does not appear to influence bone loss in black women. However, in the FF polymorphism of the VDR gene group, vitamin D supplementation may retard the higher rate of bone loss.

Efficacy of optimization of vitamin D in preventing osteoporosis and osteoporotic fractures: A systematic review

Increased intake or supplementation of vitamin D is often recommended for normal bone health; however, its preventive effect on osteoporosis has not been fully evaluated. The aim of this review is to gather evidence of the efficacy of the optimization of vitamin D nutrition in preventing osteoporosis and osteoporotic fractures. PubMed was used for searching the relevant literature using the MeSH terms "Bone Density (limited to "human", "female", and "English" literature)" or "Fractures (limited to "human", "age ≥45 years", and "English" literature)", and "Vitamin D". The searches yielded 19 randomized controlled trials (RCTs), nine cohort studies, 19 case-control studies, 19 cross-sectional studies, and one meta-analysis. We attempted to answer three questions: 1) does increased vitamin D intake prevent bone loss in peri- and postmenopausal women?, 2) does increased vitamin D intake prevent osteoporotic fractures in the elderly?, and 3) does increased vitamin D in take positively affect peak bone mass attainment in young women? The answer to questions 1 and 2 is that a vitamin D intake of 10-17.5 μg/day (400-700 IU/day) or more is effective in preventing bone loss in late postmenopausal women and an intake of 17.5-20 μg/day (700-800 IU/day) or more together with a calcium supplement reduces the risk of osteoporotic fractures. For question 3, some lines of evidence support the negative effect of low vitamin D nutrition on the attainment of peak bone mass in young women. Further studies are needed to clarify the effect of vitamin D in this age group.

The levels of bone turnover markers in Chinese postmenopausal women: Peking Vertebral Fracture study

OBJECTIVE

The aim of this study was to evaluate serum N-aminoterminal propeptide of type I collagen (P1NP), C-terminal telopeptide of type I collagen (β-CTX), and vitamin D status in healthy Chinese postmenopausal women. The study was also designed to investigate their possible relationships with osteoporosis phenotypes.

METHODS

A community-based population of 1,724 postmenopausal women in Beijing was randomly selected. Serum bone turnover markers and 25-hydroxyvitamin D [25(OH)D] were tested by an automated Roche electrochemiluminescence system. Dual-energy x-ray absorptiometry was used to measure bone mineral density (BMD).

RESULTS

The mean (SD) values of serum β-CTX and P1NP were 0.439 (0.210) and 56.7 (27.9) ng/mL, respectively. The 25(OH)D level of postmenopausal women in Beijing was remarkably low (13.2 ± 5.4 ng/mL). Serum β-CTX and P1NP levels were negatively correlated with BMDs of lumbar spine, femoral neck, and total hip (all P < 0.01). The cubic regression model better fitted the relationships of BMD and bone turnover markers. Serum β-CTX levels were significantly higher in women with sustained osteoporotic fracture or vertebral fracture (P = 0.006 and 0.012, respectively). No association between P1NP and fracture or vertebral fracture was detected. The same situation applied to 25(OH)D. 25(OH)D was negatively correlated with β-CTX and P1NP (r = -0.073 and -0.088, P = 0.002 and <0.001, respectively).

CONCLUSIONS

Serum β-CTX and P1NP levels were negatively correlated with BMD. β-CTX was significantly higher in postmenopausal women with sustained fracture or vertebral fracture. Vitamin D deficiency was highly prevalent in postmenopausal women in Beijing.

Effect of vitamin D therapy on bone turnover markers in postmenopausal women with osteoporosis and osteopenia

OBJECTIVE

To (1) assess the rate of reduction in bone turnover with vitamin D and bisphosphonate therapies and (2) evaluate the clinical utility of bone-specific alkaline phosphatase (BSAP) in monitoring treatment response.

METHODS

We retrospectively reviewed medical records of patients with newly diagnosed osteopenia and osteoporosis from 2002 to 2009 at Loyola University Medical Center. A cohort of postmenopausal women with hip or spine T-scores of less than -1, normal serum creatinine, and no prior vitamin D or bisphosphonate therapy was divided into vitamin D-deficient (n = 29) and vitamin D-sufficient (n = 13) groups. Vitamin D-deficient patients received high-dose vitamin D, whereas vitamin D-sufficient patients received orally administered bisphosphonates. BSAP levels at baseline and 1 year were compared.

RESULTS

Vitamin D therapy in the group with vitamin D deficiency led to a 26.7% decrease in BSAP (P<.01). Bisphosphonate therapy in the vitamin D-sufficient group led to a 32.7% decrease in BSAP (P = .01). The magnitude of BSAP change in the 2 study groups (6.74 ± 6.48 μg/L and 8.72 ± 9.94 μg/L) did not differ significantly (P = .45).

CONCLUSION

The results of this study suggest that correction of vitamin D deficiency in patients with osteopenia and osteoporosis can lead to a decrease in bone turnover as measured by BSAP and that the magnitude of this reduction is similar to that achieved with orally administered bisphosphonates.

Calcium and vitamin D supplementation through fortified dairy products counterbalances seasonal variations of bone metabolism indices: the Postmenopausal Health Study

PURPOSE

To assess the effectiveness of a dietary intervention combined with fortified dairy products on bone metabolism and bone mass indices in postmenopausal women.

METHODS

Forty postmenopausal women (55-65 years old) were equally randomized into a dietary group (DG), receiving daily and for 30 months, 1,200 mg of calcium and 7.5 μg of vitamin D(3) for the first 12 months that increased to 22.5 μg for the remaining 18 months of intervention through fortified dairy products; and a control group (CG). Differences in the changes of bone metabolism and bone mass indices were examined with repeated measures ANOVA.

RESULTS

A significant increase was observed for PTH levels only in the CG during the first six winter months of intervention (p = 0.049). After 30 months of intervention, during winter, serum 25(OH)D significantly decreased in the CG while remained in the same high levels as in the summer period in the DG. Serum RANKL levels decreased significantly in the DG compared with the increase in the CG during the 30-month intervention period (p = 0.005). Serum CTx decreased significantly in the DG after six (-0.08; -0.12 to -0.03) and 12 (-0.03; -0.08 to -0.02) months of intervention. Finally, the DG had more favorable changes in total body BMD than the CG (p < 0.001).

CONCLUSIONS

Increasing dietary intake of calcium and vitamin D in osteopenic postmenopausal women appears to be effective in producing favorable changes in several bone metabolism and bone mass indices and in counterbalancing seasonal variations in hormonal and biochemical molecules.

Vitamin D and bone health: potential mechanisms

Osteoporosis is associated with increased morbidity, mortality and significant economic and health costs. Vitamin D is a secosteriod hormone essential for calcium absorption and bone mineralization which is positively associated with bone mineral density [BMD]. It is well-established that prolonged and severe vitamin D deficiency leads to rickets in children and osteomalacia in adults. Sub-optimal vitamin D status has been reported in many populations but it is a particular concern in older people; thus there is clearly a need for effective strategies to optimise bone health. A number of recent studies have suggested that the role of vitamin D in preventing fractures may be via its mediating effects on muscle function (a defect in muscle function is one of the classical signs of rickets) and inflammation. Studies have demonstrated that vitamin D supplementation can improve muscle strength which in turn contributes to a decrease in incidence of falls, one of the largest contributors to fracture incidence. Osteoporosis is often considered to be an inflammatory condition and pro-inflammatory cytokines have been associated with increased bone metabolism. The immunoregulatory mechanisms of vitamin D may thus modulate the effect of these cytokines on bone health and subsequent fracture risk. Vitamin D, therefore, may influence fracture risk via a number of different mechanisms.

The effects of a 30-month dietary intervention on bone mineral density: The Postmenopausal Health Study

Low dietary Ca intake and vitamin D insufficiency have been implicated as part of the aetiology leading to osteoporosis. The aim of the present study was to examine the effects of a 30-month dietary intervention that combined supplementation of dairy products fortified with Ca and vitamin D3 and lifestyle and nutrition counselling sessions on bone mineral density (BMD) of postmenopausal women. Sixty-six postmenopausal women (aged 55–65 years) were randomised into a dietary group (DG; n 35), receiving daily and for the first 12 months 1200 mg Ca and 7·5 μg vitamin D3, while for the next 18 months of intervention 1200 mg Ca and 22·5 μg vitamin D3 through fortified dairy products, and a control group (CG; n 31) receiving neither counselling nor dairy products. The DG was found to have more favourable changes in arms (P < 0·001), total spine (P = 0·001) and total body BMD (P < 0·001) compared with the CG. Furthermore, a significant increase was observed for the DG in lumbar spine BMD (0·056; 95 % CI 0·009, 0·103), which was not found to differentiate significantly compared with the change observed in the CG (P = 0·075). In conclusion, the present study showed that intakes of vitamin D of about 22·5 μg/d and of Ca close to the recommended level of 1200 mg from fortified dairy foods for 30 months, with compliance ensured by lifestyle and nutrition counselling sessions, can induce favourable changes in arms, total spine and total body BMD of postmenopausal women.

Cholecalciferol supplementation throughout winter does not affect markers of bone turnover in healthy young and elderly adults

Although there have been several studies of the effect of vitamin D status on bone turnover in the elderly, the findings are unclear, and, furthermore, to date very few have investigated this in young adults. The objective of these randomized, placebo-controlled, double-blind, 2-center intervention studies was to investigate the effect of cholecalciferol supplementation (0, 5, 10, and 15 microg cholecalciferol/d) throughout winter time on indices of vitamin D status and bone turnover in young (aged 20-40 y; n = 215) and elderly (aged > or = 64 y; n = 204) adults, with relatively high mean calcium intakes of 976 and 874 mg/d, respectively. Fasting serum concentrations of 25-hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH), osteocalcin, bone-specific alkaline phosphatase, and carboxyterminal collagen crosslinks were measured by enzyme immunoassays at baseline and endpoint. Fok I and Taq I vitamin D receptor (VDR) genotypes were determined by real-time PCR. Endpoint serum 25(OH)D increased (P < 0.0001) in a dose-related manner with increasing supplemental cholecalciferol (up to 15 microg/d) in 20-40-y olds and up to 10 microg/d in > or = 64-y olds. Endpoint serum PTH was lower (P < 0.05) in the 3 cholecalciferol-supplemented groups compared with that in the placebo group in > or = 64-y olds, but cholecalciferol supplementation did not affect other markers in either cohort and there was no significant interaction with VDR genotype. In conclusion, cholecalciferol supplementation alone throughout winter did not affect bone turnover markers in apparently healthy young and elderly adults, even when stratified by VDR genotype.

Vitamin D receptor gene polymorphisms modulate the skeletal response to vitamin D supplementation in healthy girls

OBJECTIVES

Vitamin D receptor (VDR) gene plays an important role in bone mass regulation. We have previously shown a beneficial effect of vitamin D supplementation on bone mass in girls. This study investigated whether the musculo-skeletal response to Vitamin D was modulated by polymorphisms in VDR gene.

DESIGN

Randomized placebo-controlled trial.

METHODS

179 girls (10-17 years), were randomly assigned to placebo or Vitamin D3 for one year. VDR genotypes were determined in 167 girls using BsmI, TaqI and ApaI restriction enzymes. Bone mass at the spine, hip, forearm and total body, and lean mass were measured by DXA at baseline and at one year.

RESULTS

After one year, VDR gene polymorphisms using Bsm1 and TaqI restriction enzymes were associated with percent changes in bone area, BMC and BMD at multiple skeletal sites in the Vitamin D3 group but not in the placebo group. The least increments were observed in the BB and tt genotypes. No similar effect was observed with ApaI enzyme. This relationship between VDR genotypes and changes in BMD and BMC remained significant after adjustment for puberty, changes in lean mass, height and bone area.

CONCLUSION

VDR gene polymorphisms influence the skeletal response to vitamin D supplementation in healthy adolescent girls.

Existing and potentially novel functional markers of vitamin D status: a systematic review

BACKGROUND

Although serum 25-hydroxyvitamin D [25(OH)D] is the currently accepted vitamin D status marker of choice, use of other biomarkers or functional endpoints have been suggested.

OBJECTIVE

The objective was to systematically review the effectiveness of 25(OH)D, parathyroid hormone (PTH), bone turnover markers, bone mineral density (BMD), and calcium absorption as biomarkers of vitamin D status.

DESIGN

Methods included a structured search on Ovid MEDLINE, EMBASE (Ovid), and Cochrane CENTRAL; rigorous inclusion/exclusion criteria; data extraction; quality assessment; meta-analysis; and meta-regression.

RESULTS

Thirty-six vitamin D supplementation randomized controlled trials (RCTs) and 4 before-after studies were included. Vitamin D supplementation significantly raised circulating 25(OH)D in all but one RCT, but the response was highly heterogeneous [weighted mean difference (WMD): 34.1 nmol/L; 95% CI: 28.9, 39.2; 32 RCTs; I2 = 97%). Vitamin D supplementation (without calcium) significantly lowered circulating PTH (WMD: -0.29 pmol/L; 95% CI: -0.56, -0.02; 11 RCTs; I2 = 29%), but this was not apparent in the presence of calcium supplementation. There was a suggestion that whole-body or lumbar spine BMD may be a useful biomarker in older people but not in adolescents. Bone turnover markers were not useful biomarkers of vitamin D status, but 4 before-after studies suggested that intestinal calcium absorption may respond to vitamin D status.

CONCLUSIONS

This systematic review confirmed that circulating 25(OH)D is a robust and reliable marker of vitamin D status. Further research is needed to clarify which population subgroups show responses of PTH, BMD, and/or calcium absorption in response to changes in vitamin D status.

Update on the pharmacogenetics of the vitamin D receptor and osteoporosis

Vitamin D and calcium are essential for normal skeletal growth and for maintaining the mechanical and structural integrity of the skeleton. Reduced intake of calcium and vitamin D may be associated with reduced bone mass and osteoporosis while a chronic and severe vitamin D deficiency may lead to osteomalacia. Given the importance of vitamin D in bone homeostasis, common polymorphisms in the vitamin D receptor gene were the first to be investigated as possible determinants of bone mass and fracture risk. Even though results are still conflicting and the molecular mechanisms by which these polymorphisms influence receptor activity remain in part to be investigated, an additional important issue is represented by their potential pharmacogenomic and pharmacogenetic implications. This review analyzes major pharmacogenetic studies of polymorphisms in the vitamin D receptor gene and osteoporosis.

Vitamin D and vitamin D analogues for preventing fractures associated with involutional and post-menopausal osteoporosis

BACKGROUND

Vitamin D and related compounds have been used to prevent osteoporotic fractures in older people.

OBJECTIVES

To determine the effects of vitamin D or related compounds, with or without calcium, for preventing fractures in older people.

SEARCH STRATEGY

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, the Cochrane Central Register of Controlled Trials (The Cochrane Library 2007, Issue 3), MEDLINE, EMBASE, CINAHL, and reference lists of articles. Most recent search: October 2007.

SELECTION CRITERIA

Randomised or quasi-randomised trials comparing vitamin D or related compounds, alone or with calcium, against placebo, no intervention, or calcium alone, reporting fracture outcomes in older people.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, and extracted data. Data were pooled, where admissible, using the fixed-effect model, or random-effects model if heterogeneity between studies appeared high.

MAIN RESULTS

Forty-five trials were included. Vitamin D alone appears unlikely to be effective in preventing hip fracture (nine trials, 24,749 participants, RR 1.15, 95% CI 0.99 to 1.33), vertebral fracture (five trials, 9138 participants, RR 0.90, 95% CI 0.42 to 1.92) or any new fracture (10 trials, 25,016 participants, RR 1.01, 95% CI 0.93 to 1.09).Vitamin D with calcium reduces hip fractures (eight trials, 46,658 participants, RR 0.84, 95% CI 0.73 to 0.96). Although subgroup analysis by residential status showed a significant reduction in hip fractures in people in institutional care, the difference between this and the community-dwelling subgroup was not significant (P = 0.15).Overall hypercalcaemia is significantly more common in people receiving vitamin D or an analogue, with or without calcium (18 trials, 11,346 participants, RR 2.35, 95% CI 1.59 to 3.47); this is especially true of calcitriol (four trials, 988 participants, RR 4.41, 95% CI 2.14 to 9.09). There is a modest increase in gastrointestinal symptoms (11 trials, 47,042 participants, RR 1.04, 95% CI 1.00 to 1.08, P = 0.04) and a small but significant increase in renal disease (11 trials, 46,537 participants, RR 1.16, 95% CI 1.02 to 1.33).

AUTHORS' CONCLUSIONS

Frail older people confined to institutions may sustain fewer hip fractures if given vitamin D with calcium. Vitamin D alone is unlikely to prevent fracture. Overall there is a small but significant increase in gastrointestinal symptoms and renal disease associated with vitamin D or its analogues. Calcitriol is associated with an increased incidence of hypercalcaemia.

Pharmacogenetics of bone treatments: the VDR and ERalpha gene story

Osteoporosis is a common skeletal disease with a strong genetic component characterized by reduced bone mass and increased risk of fragility fractures. Although osteoporosis is a worldwide problem, there are many differences in human ethnics regarding both disease morbidity and drug treatment efficacy. Polymorphisms of vitamin D receptor (VDR) and estrogen receptor-alpha (ERalpha) loci are proposed as genetic determinants of bone quality, skeletal geometry and bone turnover markers. Furthermore, varying responsiveness to vitamin D and estrogen-based treatments may reflect allele variation in their signaling pathway genes (e.g., VDR or ERalpha). Because of their specific ethnic distribution, VDR and ERalpha polymorphisms may be involved in reported human differences of osteoporosis treatment responses.

Effects of calcium and vitamin D supplementation on hip bone mineral density and calcium-related analytes in elderly ambulatory Australian women: a five-year randomized controlled trial

CONTEXT

Effects of long-term calcium, with or without vitamin D, on hip bone mineral density (BMD) and bone turnover in sunny climates have not been reported.

OBJECTIVE

The aim was to evaluate the effect of vitamin D added to calcium supplementation on hip dual-energy x-ray absorptiometry BMD and calcium-related analytes.

DESIGN, SETTING, AND PARTICIPANTS

The study was a 5-yr randomized, controlled, double-blind trial of 120 community-dwelling women aged 70-80 yr.

INTERVENTIONS

The interventions were 1200 mg/d calcium with placebo vitamin D (Ca group) or with 1000 IU/d vitamin D2 (CaD group), or double placebo (control).

MAIN OUTCOME MEASURES

Hip BMD, plasma 25-hydroxyvitamin D, biomarkers of bone turnover, PTH, and intestinal calcium absorption were measured.

RESULTS

Hip BMD was preserved in CaD (-0.17%) and Ca (0.19%) groups but not controls (-1.27%) at yr 1 and maintained in the CaD group only at yr 3 and 5. The beneficial effects were mainly in those with baseline 25-hydroxyvitamin D levels below the median (68 nmol/liter). At yr 1, compared with controls, the Ca and CaD groups had 6.8 and 11.3% lower plasma alkaline phosphatase, respectively (P<or=0.02), and 28.7 and 34.5% lower urinary deoxypyridinoline to creatinine ratio, respectively (P<or=0.05). At 5 yr, this suppression was maintained only in the CaD group. CaD reduced PTH at 3 and 5 yr cf. controls (27.8 and 31.3%, P<or=0.005) in those with baseline PTH levels above the median (3.6 pmol/liter). Therapy did not affect intestinal calcium absorption at high carrier loads.

CONCLUSIONS

Addition of vitamin D to calcium has long-term beneficial effects on bone density in elderly women living in a sunny climate, probably mediated by a long-term reduction in bone turnover rate.

Responses of parathyroid hormone to vitamin D supplementation: a systematic review of clinical trials

The beneficial bone effects of vitamin D supplementation have been attributed to suppression of secondary hyperparathyroidism by 25-hydroxyvitamin D (25-OHD) levels at least 50nmol/l. In this systematic review, we have analyzed the results of 52 clinical trials, including 72 intervention groups and 6290 patients, on vitamin D supplementation in order to evaluate the experimental evidence and the effects of age and chronic immobility on responses of parathyroid hormone (PTH). The papers for this systematic review were selected through a search in PubMed and through a review of the reference lists of articles. Negative logarithmic (R(2)=0.318, p<0.001) and linear (R(2)=0.294, p<0.001) correlations were found between 25-OHD and PTH levels, when all pre- and post-trial values were scattered. Negative linear (R(2)=0.385, p<0.001) and logarithmic (R(2)=0.406, p<0.001) correlations were also found between the changes in 25-OHD and PTH levels. Age correlated negatively with changes in PTH (r=-0.476, p<0.001). The vitamin D supplementation of the chronically immobile patients resulted in a smaller decrease in PTH levels (-8.4 vs. -17.4%, p<0.001) despite a larger increase in 25-OHD levels (187.2% vs. 109.8%, p<0.001). According to the multiple regression analysis the changes in PTH were independently predicted by pre-trial PTH, changes in 25-OHD, age and chronic immobility, explaining 53.2% (R(2)=0.532) of the variation. This meta-analysis shows that responses of PTH to vitamin D supplementation are not only determined by the baseline PTH levels and changes in vitamin D status, but also by age and mobility of the patients. Our results also suggest that PTH decreases quite linearly during vitamin D supplementation at any given 25-OHD level. Longitudinal vitamin D supplementation studies on populations with wide range of mobility and age are needed to further elucidate their confounding effects. In determining the sufficient doses of vitamin D supplementation and adequate 25-OHD levels, these confounding effects and the inter-individual variation in responses of PTH to vitamin D supplementation should be taken into account.

Recent development in pharmacogenomics: from candidate genes to genome-wide association studies

Genetic diversity, most notably through single nucleotide polymorphisms and copy-number variation, together with specific environmental exposures, contributes to both disease susceptibility and drug response variability. It has proved difficult to isolate disease genes that confer susceptibility to complex disorders, and as a consequence, even fewer genetic variants that influence clinical drug responsiveness have been uncovered. As such, the candidate gene approach has largely failed to deliver and, although the family-based linkage approach has certain theoretical advantages in dealing with common/complex disorders, progress has been slower than was hoped. More recently, genome-wide association studies have gained increasing popularity, as they enable scientists to robustly associate specific variants with the predisposition for complex disease, such as age-related macular degeneration, Type 2 diabetes, inflammatory bowel disease, obesity, autism and leukemia. This relatively new methodology has stirred new hope for the mapping of genes that regulate drug response related to these conditions. Collectively, these studies support the notion that modern high-throughput single nucleotide polymorphism genotyping technologies, when applied to large and comprehensively phenotyped patient cohorts, will readily reveal the most clinically relevant disease-modifying and drug response genes. This review addresses both recent advances in the genotyping field and highlights from genome-wide association studies, which have conclusively uncovered variants that underlie disease susceptibility and/or variability in drug response in common disorders.

Efficacy of daily and monthly high-dose calciferol in vitamin D-deficient nulliparous and lactating women

BACKGROUND

We previously found a high prevalence of vitamin D deficiency and low medication regimen compliance in Arab and East Indian women residing in the United Arab Emirates (UAE). The appropriate dosing regimen for improving vitamin D status in this population is not known.

OBJECTIVE

We aimed to determine the efficacy of daily and monthly supplementation with vitamin D2, the only high-dose calciferol available in the UAE, in lactating and nulliparous women.

DESIGN

Healthy lactating (n = 90) and nulliparous (n = 88) women were randomly assigned to consume 2000 IU vitamin D2/d or 60,000 IU vitamin D2/mo for 3 mo. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured by radioimmunoassay at baseline and every month.

RESULTS

Most women had vitamin D deficiency [ie, 25(OH)D < 50 nmol/L] at study entry. Mean +/- SD 25(OH)D concentrations at 3 mo were significantly higher than baseline in both lactating (39.8 +/- 12.4 and 25.2 +/- 10.7 nmol/L, respectively) and nulliparous (40.4 +/- 23.4 and 19.3 +/- 12.2 nmol/L, respectively) women (P < 0.001 for both). In total, vitamin D supplementation was effective in achieving serum 25(OH)D concentrations of >or=50 nmol/L in 21 (30%) of 71 women at endpoint.

CONCLUSIONS

Oral vitamin D2 supplementation with 2000 IU/d or 60,000 IU/mo for 3 mo was safe, and it increased serum 25(OH)D concentrations significantly; however, only a small proportion of the women studied achieved concentrations of >or=50 nmol/L. This suggests that, when sunlight exposure is limited, doses of vitamin D2 higher than those currently studied may be needed. Monthly dosing appears to be a safe and effective alternative to daily dosing.

Steroid hormone receptor gene polymorphisms and osteoporosis: a pharmacogenomic review

Osteoporosis is a common skeletal disorder with a strong genetic component. In recent years, significant progress has been made in understanding the genetic basis of osteoporosis. Given the biological significance of signalling through steroid hormone receptors, bone biology and calcium homeostasis, alleles of steroid hormone receptor genes have been postulated to contribute to the well-documented genetic predisposition to osteoporosis; and in different studies, these alleles have been associated with variation in bone mass and fracture risk. Even though results are still conflicting and the molecular mechanisms by which these polymorphisms influence receptor activity remain, in part, to be investigated, an additional important issue is represented by potential pharmacogenomic (the investigation of variations of DNA or RNA characteristics as related to drug response) or pharmacogenetic (the influence of variations of DNA sequence on drug response) implications. In fact, steroid hormone receptors actually mediate the action of several compounds known to positively or negatively affect bone homeostasis, such as vitamin D, estrogen and glucocorticoids. This review analyses major pharmacogenetic studies of polymorphisms in steroid hormone receptor genes.

Skeletal site-dependent response of bone mineral density and quantitative ultrasound parameters following a 12-month dietary intervention using dairy products fortified with calcium and vitamin D: the Postmenopausal Health Study

The aim of the current study was to examine whether calcium supplementation could prevent bone loss in postmenopausal women or more favourable outcomes could be obtained via the consumption of dairy products fortified with calcium and vitamin D3. For this purpose changes in bone mineral density (BMD) at different skeletal sites, assessed by dual-energy X-ray absorptiometry, as well as in quantitative ultrasound (QUS) parameters of the calcaneus over 12 months were estimated. A population of 101 postmenopausal women (55–65 years old) was randomized into a dairy group (DG: n 39), receiving approximately 1200 mg calcium/d and 7·5 μg vitamin D3/d through fortified dairy products; a calcium-supplemented group (CaG: n 26) provided with a calcium supplement of 600 mg/d; and a control group (CG: n 36). Over the intervention period the DG was found to have more favourable changes in pelvis (P = 0·040), total spine (P < 0·001) and total body BMD (P < 0·001) than the other groups. A significant increase was also observed for DG in lumbar spine BMD (2·0 %; 95 % CI 0·5, 3·5) although it did not differentiate significantly compared to the other groups. No significant differences were observed with respect to the changes in QUS parameters. The current study revealed that recommended intakes of vitamin D3 and calcium via fortified dairy products for 12 months can induce favourable changes in pelvis, total spine and total body BMD in postmenopausal women but not in QUS parameters. No such favourable changes were observed via supplementation of calcium alone.

Associations of vitamin D status with bone mineral density, bone turnover, bone loss and fracture risk in healthy postmenopausal women. The OFELY study

INTRODUCTION

Vitamin D status is considered as an important determinant of bone health but supplementation trials with vitamin D(3) have yielded conflicting results. The aim of this study was to investigate the associations between serum 25-hydroxyvitamin D (25-OH D), bone turnover markers, bone mineral density (BMD), radius bone loss and incidence of fracture in postmenopausal women.

METHODS

669 postmenopausal women (mean age: 62.2 years) belonging to a population-based cohort were followed prospectively for a median of 11.2 years. At baseline, 25-OH D levels, BMD, bone turnover markers and clinical risk factors of osteoporosis were assessed. BMD loss at the radius was estimated by annual measurements of BMD and all incident fractures which occurred in 134 women were confirmed by radiographs.

RESULTS

73% and 35% of women had serum 25-OH D levels below 75 and 50 nmol/l which correspond respectively to the median and lowest optimal values recently proposed for fracture prevention. 11% of women had levels below 30 nmol/l. Serum 25-OH D correlated modestly with intact PTH (r(2)=0.023, p<0.0001), but not with bone turnover markers or BMD at the hip and radius after adjustment for age. When levels of 25-OH D were considered as a continuous variable, there was no significant association between 25-OH D levels and radius BMD loss or fracture risk. After adjustment for age, there was no significant difference in incidence of fracture, BMD, radius BMD loss, bone turnover markers, grip strength and the percentage of fallers in the previous year between women with 25-OH D levels below or above 75, 50 or 30 nmol/l.

CONCLUSIONS

In a population of home-dwelling healthy postmenopausal women with few of them with severe vitamin D deficiency, vitamin D status may not be an important determinant of bone health.

How much vitamin D3 do the elderly need?

BACKGROUND

Vitamin D insufficiency poses a problem in many parts of the world, the elderly being an especially vulnerable group. This insufficiency results from an inadequate amount of sunshine and a low dietary intake of vitamin D. Typically, insufficiency is accompanied with high intact parathyroid hormone, (S-iPTH) concentrations.

AIMS OF THE STUDY

We studied how serum 25-hydroxy vitamin D (S-25-OHD) concentrations respond to different doses of vitamin D3 supplementation. Secondly to determine the smallest efficient dose to maintain serum 25-OHD concentration above the insufficiency level. We also studied which dose would be efficient in decreasing S-iPTH concentration in these subjects.

SUBJECTS AND METHODS

Forty-nine 65- to 85-year-old women participated. The women were randomly assigned into one of four groups receiving 0 (placebo), 5, 10 or 20 microg of vitamin D3 daily for 12 weeks. Fasting morning blood was drawn at the beginning of the study, and thereafter every second week. Calciotropic variables were assessed from serum and urine samples.

RESULTS

The S-25-OHD concentration increased significantly (p < 0.001) in all supplemented groups [5 microg: by 10.9 (8.5) nmol/L, 10 microg: by 14.4 (6.9) nmol/L, 20 microg: by 23.7 (11.9) nmol/L], whereas it decreased in the placebo group by 8.3 (13.2) nmol/L. Equilibrium in S-25-OHD concentration was reached in all groups after 6 weeks of supplementation at 57.7 (8.9) nmol/L, 59.9 (8.9) nmol/L and 70.9 (8.9) nmol/L in the groups with increasing vitamin D supplementation. The dose-response to supplementation decreased with increasing vitamin D status at baseline, r = -0.513, p = 0.002. S-iPTH tended to decrease in those with highest dose response to supplementation.

CONCLUSIONS

A clear dose response was noted in S-25-OHD to different doses of vitamin D3. The recommended dietary intake of 15 microg is adequate to maintain the S-25-OHD concentration around 40-55 nmol/L during winter, but if the optimal S-25-OHD is higher than that even higher vitamin D intakes are needed. Interestingly, subjects with lower vitamin D status at baseline responded more efficiently to supplementation than those with more adequate status.

The positive effect of dietary vitamin D intake on bone mineral density in men is modulated by the polyadenosine repeat polymorphism of the vitamin D receptor

INTRODUCTION

Few studies have considered the dietary influence of vitamin D intake on bone mineral density (BMD). Numerous studies have examined the association between VDR polymorphism and BMD, but no previous study has examined the joint influence of dietary vitamin D intake and VDR polymorphism on BMD.

METHODS

We therefore conducted a study in 230 men aged 41-76 years of age. BMD was measured with DXA. A second bone scan was performed on average 2.7 years after the first investigation. Dietary habits were assessed by 14 dietary 24-h recall interviews. The polyadenosine (A) VDR genotypes were determined.

RESULTS

Dietary vitamin D intake was associated with BMD at all sites, also after multivariate adjustment. Those in the highest quintile of intake had 9% higher femoral neck BMD (p = 0.004), 6% higher BMD at the lumbar spine (p = 0.06) and 5% higher total body BMD (p = 0.003) compared to men in the lowest quintile of dietary vitamin D intake. However, the positive association between vitamin D intake and BMD was especially apparent among those with the L/L polyadenosine (A) VDR genotype explaining between 10 and 15% of the variability in BMD depending on site (p < 0.004). There was furthermore a trend, in the lumbar spine, of less reduction in BMD with increasing vitamin D intake (p = 0.07) but not at the other sites. Calcium intake conferred no association with BMD.

CONCLUSIONS

Our results indicate that the extent of positive association between dietary vitamin D intake and BMD in men is dependent on VDR polymorphism, a novel conceivable important gene-environmental interaction.

Vitamin D insufficiency in congestive heart failure: why and what to do about it?

This article gives an overview of the current knowledge on vitamin D status in patients with congestive heart failure (CHF). A serum 25-hydroxyvitamin D level below 50 nmol/l (20 ng/ml) is generally regarded as insufficient. Available data indicate that the majority of CHF patients have 25-hydroxyvitamin D levels in the insufficiency range. Skin synthesis of vitamin D after solar ultraviolet B exposure is the most important vitamin D source for humans. However, CHF patients have relatively low outdoor activities. Consequently, a disease-related sedentary lifestyle is an important cause for the insufficient vitamin D status in CHF patients. There is also evidence from a recently performed case-controlled study that indicators of ultraviolet B exposure are already reduced in CHF patients during childhood, adolescence, and early adulthood compared to healthy controls. We present results indicating that an insufficient vitamin D status may contribute to the etiology/pathogenesis of CHF. Data include a vitamin D-mediated reduction of elevated blood pressure as well as a vitamin D-mediated prevention of enhanced parathyroid hormone levels, a pathophysiological state that contributes to cardiovascular disease. Based on population attributable risks, hypertension and cardiovascular disease have a high impact, accounting for the majority of CHF events.Theoretically, vitamin D status can be improved by adequate skin synthesis of vitamin D and/or adequate oral vitamin D intake. At present, daily oral intake of 50-100 microg vitamin D seems to be the most effective way to improve vitamin D status in CHF patients.

A positive dose-response effect of vitamin D supplementation on site-specific bone mineral augmentation in adolescent girls: a double-blinded randomized placebo-controlled 1-year intervention

The effect of vitamin D supplementation on bone mineral augmentation in 212 adolescent girls with adequate calcium intake was studied in a randomized placebo-controlled setting. Bone mineral augmentation determined by DXA increased with supplementation both in the femur and the lumbar vertebrae in a dose-responsive manner. Supplementation decreased the urinary excretion of resorption markers, but had no impact on formation markers.

INTRODUCTION

Adequate vitamin D intake protects the elderly against osteoporosis, but there exists no indisputable evidence that vitamin D supplementation would benefit bone mineral augmentation. The aim of this 1-year study was to determine in a randomized double-blinded trial the effect of 5 and 10 microg vitamin D3 supplementation on bone mineral augmentation in adolescent girls with adequate dietary calcium intake.

MATERIALS AND METHODS

Altogether, 228 girls (mean age, 11.4 +/- 0.4 years) participated. Their BMC was measured by DXA from the femur and lumbar spine. Serum 25-hydroxyvitamin D [S-25(OH)D], intact PTH (S-iPTH), osteocalcin (S-OC), and urinary pyridinoline (U-Pyr) and deoxypyridinoline (U-Dpyr) were measured. Statistical analysis was performed both with the intention-to-treat (IT) and compliance-based (CB) method.

RESULTS

In the CB analysis, vitamin D supplementation increased femoral BMC augmentation by 14.3% with 5 microg and by 17.2% with 10 microg compared with the placebo group (ANCOVA, p = 0.012). A dose-response effect was observed in the vertebrae (ANCOVA, p = 0.039), although only with the highest dose. The mean concentration of S-25(OH)D increased (p < 0.001) in the 5-microg group by 5.7 +/- 15.7 nM and in the 10-microg group by 12.4 +/- 13.7 nM, whereas it decreased by 6.7 +/- 11.3 nM in the placebo group. Supplementation had no effect on S-iPTH or S-OC, but it decreased U-DPyr (p = 0.042).

CONCLUSIONS

Bone mineral augmentation in the femur was 14.3% and 17.2% higher in the groups receiving 5 and 10 microg of vitamin D, respectively, compared with the placebo group, but only 10 mug increased lumbar spine BMC augmentation significantly. Vitamin D supplementation decreased the concentration of bone resorption markers, but had no impact on bone formation markers, thus explaining increased bone mineral augmentation. However, the positive effects were noted with the CB method but not with IT.